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Suspected Obstructive Uropathy

Date: May 16, 2012
Result type: Resources

Indication Overview

Obstructive uropathy can be defined as any blockage of urine drainage from the kidney (renal calyces or renal pelvis), ureter, or bladder.1 As a result of the blockage, urine backs up into the kidneys, causing dilatation of the ureter, renal pelvis, and renal calyces, which can damage the kidney if it is not treated. The appearance of dilated or enlarged renal pelvis and calyces is referred to as hydronephrosis and is a symptom of obstructive uropathy.2 Obstructive uropathy can be a long-term disease (chronic) or occur suddenly (acute). As well, it can occur in one kidney (unilateral) or both kidneys (bilateral).2 Symptoms may include nausea, vomiting, excessive sweating (diaphoresis), and abdominal or groin pain.3

There are many causes of obstructive uropathy; however, the most common causes include stones in kidneys (nephrolithiasis),4 ureter (ureterolithiasis) or anywhere in the urinary tract (urolithiasis).5,6 Other causes of obstructive uropathy include health conditions such as pregnancy, prostate cancer,2 retroperitoneal fibrosis,7 spinal cord injury,8,9 ureteral stricture,6 and congenital anomalies (e.g., ureteropelvic junction obstruction [UJO]),5,10 which is most common in children but also occurs in adults.6 The gold standard to assess urinary obstruction is unclear;11-13 therefore, several imaging modalities are often used.8

Population: Adults and children with chronic and acute urinary obstruction presenting with symptoms including renal colic, suspected urinary obstruction symptoms (e.g., evidence of hydronephrosis), impaired renal function.

Intervention: Renal scintigraphy (renal scan). Synonyms for renal scan in the literature and in clinical practice include diuresis renography, renal flow studies, radioisotope renography,8 Lasix renography (Patrick Au, Acute and Emergency Services Branch, Saskatchewan Ministry of Health: unpublished data, 2011), and nuclear medicine renogram.14 The terms renal scintigraphy and renal scan will be used throughout this report.

Renal scanning begins with intravenous (IV) administration of a radiotracer immediately followed by acquisition of images for 20 to 30 minutes.15 An external gamma camera detects emission of gamma rays emitted by the radiotracer, which is reflective of the distribution of radiotracer in the patient. Radiotracers currently used in Canada include technetium-99m-labelled mercaptoacetyl trigylcine (99mTc-MAG3), technetium-99m-labelled- diethylenetriamine pentaacetic acid acid (99mTc-DTPA), or technetium-99m-labelled-dimercaptosuccinic acid (99mTc-DMSA).

99mTc-MAG3 and 99mTc-DTPA are rapidly taken up by the kidney and then excreted through the urinary tract. Their mechanism of renal uptake and imaging characteristics, however, differ —99mTc-DTPA is taken up by the kidney through glomerular filtration and is not secreted or reabsorbed by the renal tubules, whereas 99mTc-MAG3 is mostly taken up by the proximal renal tubules and its high plasma protein binding prevents it from being filtered through the glomerular membrane. Once 99mTc-DTPA reaches the kidney, it is then excreted by filtration. Hence, the glomerular filtration rate (GFR) quantifies the amount of filtrate formed per minute (normal GFR: ~ 120 mL/min in adults). Conversely, clearance of 99mTc-MAG3 is expressed as the effective renal plasma flow (ERPF) — an approximation of renal plasma flow (normal ERPF: ~ 600 mL/min in adults). 99mTc-DMSA remains in the renal parenchyma for an extended period and is used for static renal scintigraphy. 99mTc-DMSA accumulates in the functioning renal cortex, and impaired renal cortex and space-occupying lesions are depicted as hypoactive areas.16

The diuretic, furosemide (Lasix), is then administered by IV, and a second series of images is acquired for an additional 20 to 30 minutes while the bladder empties.15 The images gathered as the bladder empties help to calculate a filtration rate that provides information regarding how well the kidney is functioning and if there is an obstruction.17 These images are used to calculate the clearance rate of the radiotracer, which is measured by the following outcomes: renal transit time (RTT),14 and washout half-time (T1/2).18,19 If the patient has problems emptying his or her bladder, a urinary catheter may be used.16

Comparators: For this report, the following diagnostic tests are considered as alternatives to renal scintigraphy:

  • Magnetic Resonance Urography (MRU): MRU requires a magnetic resonance (MR) scanner. Patients undergoing MRU are given fluids to hydrate the body. A sedative may be administered (usually in children) at this point, and a catheter (usually in children) may also be given to the patient so that the flow of urine can be observed without the patient having to go to the washroom during the procedure. A diuretic, typically furosemide (Lasix) is administered and images are taken with the MRI machine. A contrast agent (gadolinium [Gd]) is also administered, usually 15 minutes after the diuretic, and more images are taken to measure the volume of the kidney and how the urine accumulates, in order to calculate measurements that determine the renal function.12,14,20
  • Ultrasound (U/S): During a U/S, a transducer is placed over the organ of interest. The transducer produces sound waves that pass through the body. As the sound waves pass through the body, they produce echoes that are analyzed by a computer to produce images of the body part being analyzed.21 When there is a presence of obstruction in the renal tract, obstruction is diagnosed primarily by the appearance of hydronephrosis (expert opinion — Martin Reed). Obstruction in the kidney may also cause a decrease in blood flow that can be measured as an increase in vascular resistance (arterial resistance),17,18 referred to as the renal resistive index (RI). Generally, an RI less than or equal to 0.70 means kidney function is normal,9,17 while an RI greater than 0.70 suggests an obstructed kidney.22 In children younger than six months, an RI greater than 0.9 is borderline obstructive hydronephrosis.18 Doppler ultrasound, which is a type of ultrasound that shows images in colour, can distinguish between obstructive and non-obstructive pyelocaliectasis17 and show a wave-like (peristaltic)23 inflow into the bladder (ureterovesical or urinary jet). If a urinary jet is absent, this can also be indicative of obstruction.17,19 Relative jet frequency is the measure used to diagnosis presence of jets indicative of obstruction.19

Other possible comparators could include the Whitaker test, which has been largely replaced by computed tomography (CT) and U/S (expert opinion — Martin Reed and Eric Turcotte). Retrograde pyelography is a surgical technique and is used primarily for cancer diagnosis rather than obstruction assessment (expert opinion — Martin Reed and Eric Turcotte). Both of these comparators were excluded from this report. Renal scan with 123I-orthoiodohippurate (123I-OIH) uses the same approach as the 99mTc-based renal scan.24 No information regarding 123I-OIH renal scan related to the criteria was identified in the literature. (Note: 123I-OIH is not currently available on the Canadian market and when it was, the T1/2 of 13 hours limited its availability; expert opinion —Gilbert Matte.)

Outcomes: Eleven outcomes (referred to as criteria) are considered in this report:

  • Criterion 1: Size of the affected population
  • Criterion 2 : Timeliness and urgency of test results in planning patient management
  • Criterion 3: Impact of not performing a diagnostic imaging test on mortality related to the underlying condition
  • Criterion 4: Impact of not performing a diagnostic imaging test on morbidity or quality of life related to the underlying condition
  • Criterion 5: Relative impact on health disparities
  • Criterion 6: Relative acceptability of the test to patients
  • Criterion 7: Relative diagnostic accuracy of the test
  • Criterion 8: Relative risks associated with the test
  • Criterion 9: Relative availability of personnel with expertise and experience required for the test
  • Criterion 10: Accessibility of alternative tests (equipment and wait times)
  • Criterion 11: Relative cost of the test.

Definitions of the criteria are in Appendix 1.

Methods

The literature search was performed by an information specialist using a peer-reviewed search strategy.

Published literature was identified by searching the following bibliographic databases: MEDLINE with In-Process records via Ovid; The Cochrane Library (2011, Issue 1) via Wiley; PubMed; and University of York Centre for Reviews and Dissemination (CRD) databases. The search strategy was comprised of both controlled vocabulary, such as the National Library of Medicine's MeSH (Medical Subject Headings), and keywords. The main search concepts were radionuclide imaging and obstructive uropathy.

Methodological filters were applied to limit retrieval to health technology assessments, systematic reviews, meta-analyses (HTA/SR/MA), randomized controlled trials, and non-randomized studies, including diagnostic accuracy studies. No date or human limits were applied to the HTA/SR/MA search. For primary studies, the retrieval was limited to documents published between January 1, 2001 and April 1, 2011, and the human population. Both searches were also limited to English language documents. Regular alerts were established to update the search until October 2011. Detailed search strategies are located in Appendix 2.

Grey literature (literature that is not commercially published) was identified by searching relevant sections of the CADTH Grey Matters checklist. Google was used to search for additional web-based materials. The searches were supplemented by reviewing the bibliographies of key papers. See Appendix 2 for more information on the grey literature search strategy.

Targeted searches were done as required for the criteria, using the aforementioned databases and Internet search engines. When no literature was identified that addressed specific criteria, experts were consulted.

Search Results

The literature search identified 34 HTA/SR/MA and 816 primary studies. From the HTA/SR/MA, 13 potential articles underwent full-text screening. From the primary studies, 142 articles underwent full-text screening.

No applicable HTA/SR/MA were identified with information to address Criterion 7 on the relative diagnostic accuracy of tests. Eight applicable primary studies were identified for this criterion (three relevant for adult population and five relevant for children), and 32 articles reported information for the following criteria: 1) Size of the affected population; 2) Timeliness and urgency of test results in planning patient management; 3) Impact of not performing a diagnostic imaging test on mortality related to the underlying condition; 4) Impact of not performing a diagnostic imaging test on morbidity or quality of life related to the underlying condition; 5) Relative impact on health disparities; 6) Relative patient acceptability of test; 8) Relative risks associated with the test; and 9) Relative availability of expertise and experience required for the test.

The remaining citations were either articles found through searching the grey literature, articles from targeted searches, or articles from the reference lists.

Summary table

Table 1: Summary of Criterion Evidence

Domain 1: Criteria Related to the Underlying Health Condition
Criterion Synthesized Information
1 Size of the affected population Adult

The prevalence of obstructive uropathy ranges from 5 in 10,000 to 5 in 1,000, depending on the type of obstructive uropathy.4,5,25,26

Pediatric

The most common cause of obstructive uropathy in children is due to UJO and it occurs in 1 in 1,500 children.10

Assuming the incidence rate in Canada is similar to that in the United States, the size of the affected population is more than 1 in 10,000 (0.01%) and less than or equal 1 in 1,000 (0.1%) in both the adult and pediatric populations.
2 Timeliness and urgency of test results in planning patient management According to the Saskatchewan Ministry of Health, the priority for renal scan for the evaluation of hydronephrosis is two to seven days, and eight to 30 days for GFR and ERPF measures for suspected urinary tract obstruction and impaired renal function (Patrick Au, Acute and Emergency Services Branch, Saskatchewan Ministry of Health: unpublished data, 2011).

Adult

Acute bilateral obstruction symptoms will disappear within hours or days if the disease is detected and treated promptly.4 In chronic cases of obstruction, immediate interventions are not necessary, except in cases where an infection needs to be drained or there is a solitary kidney.27

Pediatric

No pediatric-specific urgency classification for suspected obstructive uropathy was listed (Patrick Au, Acute and Emergency Services Branch, Saskatchewan Ministry of Health: unpublished data, 2011); however, based on possible morbidities associated with a delay in diagnosis, the target time frame would be at a minimum similar to that of adults. UJO in children may resolve spontaneously within the first 18 months of life.10,28

The target time frame for performing the 99mTc-based test is between 8 and 30 days, and obtaining the test results in the appropriate timely manner for the underlying condition has moderate impact on the management of the condition or the effective use of heath care resources.
3 Impact of not performing a diagnostic imaging test on mortality related to the underlying condition According to Statistics Canada, 52 patients died from obstructive uropathy (1.6 per million people) and 39 due to urolithiasis (1.2 per million) in 2007 (ages not specified).29

Diagnostic imaging results have no impact on mortality.
4 Impact of not performing a diagnostic imaging test on morbidity or quality of life related to the underlying condition Adult

Renal obstruction longer than one week can cause permanent renal damage but with recovery in renal function.7 Complete obstruction of more than 12 weeks can cause irreversible damage to the renal system7 and, potentially, chronic kidney failure.30 Other potential comorbidities from renal obstruction include chronic tubulointerstitial disease,7 urinary retention,26 chronic/recurrent UTI,5 incontinence,26 and complications from long-term catheter use.26

In chronic bilateral obstruction, once the blockage is cleared, patients may experience "post-obstructive" diuresis, which can be life-threatening.26

Pediatric

23% of children with renal insufficiency will require transplantation.30

Diagnostic imaging test results can have a moderate impact on morbidity or quality of life.

 

Domain 2: Criteria Comparing 99mTc with an Alternative or Comparing Between Clinical Uses
Criterion Synthesized Information
5 Relative impact on health disparities To be scored locally.
6 Relative acceptability of the test to patients  Renal scintigraphy: Patients may have concerns about radiation exposure and the IV injection of a radiopharmaceutical agent. IV fluids might be required if the adequacy of hydration is a concern.16 Because a full bladder may slow drainage of the radiopharmaceutical from the upper part of urinary tract, the bladder should be emptied frequently. Bladder catheterization may be required, especially in pediatric patients. In particular in children, catheterization may be associated with some discomfort.31

MRU: MRU is an MRI technique. Because of the closed space of an MRI, patients may experience feelings of claustrophobia, as well as being bothered by the noise. This may be less of a problem with new MRI machines, if available (Medical Isotopes and Imaging Modalities Advisory Committee [MIIMAC] expert opinion). It has been reported that up to 30% of patients experience apprehension and 5% to 10% endure some severe psychological distress, panic, or claustrophobia.32,33 Patients are not exposed to radiation during an MRI scan, which may be more acceptable to some.

Children may require sedation and catheterization for the duration of the MRU procedure.14 Patients may also have difficulties accepting the contrast dye, if required.33,34

U/S: This test may be preferred in pediatric patients, as there is no radiation and does not require sedation of children.

Renal scintigraphy using 99mTc-radiolabelled isotopes:
  • is minimally less acceptable than MRU in adult patients
  • is moderately more acceptable than MRU in pediatric patients
  • is minimally less acceptable than U/S in both adult and pediatric patients.
7 Relative diagnostic accuracy of the test

Adult

The review of the current literature yielded three primary studies that compared renal scan with various comparators in the diagnosis of renal obstructive uropathy in adults.8,35,36

Diagnostic Accuracy of Imaging Tests in Adults
Test Sensitivity (%) Specificity (%)
MRU 70 to100 N/A
U/S 96 90

MRU = magnetic resonance urography; N/A = not available; U/S = ultrasound.

Pediatric

Five primary studies evaluated diagnostic accuracy of MRU and U/S compared with renal scan in a pediatric population with renal obstructive uropathy.12,14,18-20

Diagnostic Accuracy of Imaging Tests in Pediatrics
Test Correlation Coefficient (R)* Sensitivity (%), Specificity (%) Accuracy
MRU 0.96-0.98 N/A N/A 0.90
U/S N/A 87 96.4 N/A

CT = computed tomography; MRU = magnetic resonance urography; N/A= Not available; U/S = ultrasound
*Between test and renal scan.

Based on the available evidence, in both adults and children, the diagnostic accuracy of renal scintigraphy with 99mTc radiolabelled tracers is:

  • moderately better than MRU in both adult and pediatric patients
  • moderately better than U/S in both adult and pediatric patients.
8 Relative risks associated with the test

Non–radiation-related Risks

Renal scan: Adverse events from renal scintigraphy are rare but may include reaction to the radiopharmaceutical, rash, fever, or chills.37 There is also a relative contraindication in the administration of captopril in patients with a solitary kidney, as it may precipitate transient acute renal failure if the kidneys have physiologically significant renal artery stenosis (MIIMAC expert opinion).

MRU: MRI is often used in conjunction with the contrast agent Gd. Gd is contraindicated in patients with renal failure or end-stage renal disease, as they are at risk of NSF. The frequency of severe, life-threatening reactions with Gd is extremely rare (0.001% to 0.01%) and the frequency of moderate reactions range are also rare (0.004% to 0.7%).38 Children may require sedation.

Radiation-related Risks

Effective Doses of Radiation39-41
Diagnostic Study Average Radiation Dose (mSv)
Adult Pediatric
Renal scan — 99mTc-DMSA N/A 0.03939
Renal scan — 99mTc-MAG3 1 to 1040 0.015,39 0.3 to 340
Renal scan — 99mTc-DTPA N/A 0.01239
MRI 040 039
U/S 040 039
Average background dose of radiation per year 1 to 3.042-44

MRI = magnetic resonance imaging; MRU = magnetic resonance urography; mSv = millisievert; N/A = not applicable; 99mTc-DMSA = technetium-99m-labelled-dimercaptosuccinic acid;  99mTc-DTPA = technetium-99m-labelled-diethylenetriamine pentaacetic acid; 99mTc-MAG3 = technetium-99m-labelled mercaptoacetyl triglycine; U/S = ultrasound.

There is some concern from physicians that, in patients with poor functioning kidneys, exposure to a radioisotope may further compromise their function.8

Overall, renal scintigraphy using 99mTc radiolabelled isotopes is:

  • minimally less safe than MRU in adults patients
  • minimally more safe than MRU in pediatric patients
  • minimally less safe than U/S in both adult and pediatric patients.
9 Relative availability of personnel with expertise and experience required for the test As radionuclide uptake is different in children, as compared to adults, and reader disagreement is more common for younger children, expertise in pediatric imaging is required for renal scintigraphy. In addition, expertise in pediatric MRU is limited.

Assuming the necessary equipment is available, if 99mTc imaging using renal scintigraphy is not available, it is assumed that:
  • fewer than 25% of the procedures for both adult and pediatric patients can be performed in a timely manner using MRU
  • more than 95% of the procedures for both adult and pediatric patients can be performed in a timely manner using U/S.
10 Accessibility of alternative tests (equipment and wait times) No nuclear medicine cameras are available in the Yukon, Northwest Territories, or Nunavut.45

No MRI scanners are available in the Yukon, Northwest Territories, or Nunavut.46 Across Canada, the average wait time is 9.8 weeks.47

U/S machines are widely available across the country. According to the Fraser Institute, the average wait time for U/S in 2010 was 4.5 weeks.47

Assuming the necessary expertise is available, if 99mTc imaging using renal scintigraphy is not available, it is assumed that:
  • 25% to 74% of the procedures in both adult and pediatric patients can be performed in a timely manner using MRU
  • more than 95% of the procedures in both adult and pediatric patients can be performed in a timely manner using U/S.
11 Relative cost of the test

According to our estimates, the cost of scintigraphy with 99mTc-based radioisotopes to establish whether obstruction is present is $310.45. U/S is a minimally less costly alternative. MRU is a moderately more costly imaging test.

Relative Costs
Test Total Costs ($) Cost of Test Relative to 99mTc-based Test ($)
Renal scintigraphy 310.45 Reference
MRU 670.15 +359.70
U/S 88.25 –222.20

 

ERPF = effective renal plasma flow; GFR = glomerular filtration rate; Gd = gadolinium; IV = intravenous; IVP = intravenous pyelogram; MRI = magnetic resonance imaging; MRU = magnetic resonance urography; N/A = not applicable; NSF = nephrogenic systemic fibrosis; RCIN = radiocontrast-induced nephropathy; 99mTc = technetium-99m; UJO = ureteropelvic junction obstruction; U/S = ultrasound; UTI = urinary tract infection.  

Criterion 1: Size of affected population (link to definition)

Adult
The prevalence of obstructive uropathy ranges from five in 10,000 to five in 1,000, depending on the type of obstructive uropathy.4,5,25,26 Chronic unilateral obstructive uropathy occurs in five in 1,000 people,5 while acute unilateral and chronic bilateral obstructive uropathy occurs in one in 1,000 people.25,26 Acute bilateral obstructive uropathy occurs in five in 10,000 people.4 The incidence of kidney stones occurs in 2% to 12%48-52 of the population.

Pediatric
The most common cause of obstructive uropathy in children is due to UJO and it occurs in one in 1,500 children.10 Pediatric urolithiasis occurs in 1% to 5% of children of developed nations,52 although the incidence is higher in children with Down syndrome (ranging from 3 to 21.4%).53,54

Return to Summary Table.

Criterion 2: Timeliness and urgency of test results in planning patient management (link to definition)

According to the Saskatchewan Ministry of Health, the priority for renal scan for the evaluation of hydronephrosis is two to seven days, and eight to 30 days for GFR and ERFP measures for suspected urinary tract obstruction and impaired renal function (Patrick Au, Acute and Emergency Services Branch, Saskatchewan Ministry of Health: unpublished data, 2011). Prompt diagnosis is imperative, as an undiagnosed and untreated obstruction can result in significant morbidity including infection and permanent renal damage,1,7,30

Adult
Acute bilateral obstruction symptoms will disappear within hours or days if the disease is detected and treated promptly.4 In chronic cases of obstruction, immediate interventions are not necessary except in cases where an infection needs to be drained or there is a solitary kidney.27

Pediatric
No pediatric-specific urgency classification for suspected obstructive uropathy was listed (Patrick Au, Acute and Emergency Services Branch, Saskatchewan Ministry of Health: unpublished data, 2011); however, based on possible morbidities associated with a delay in diagnosis, the target time frame would be at a minimum similar to that of adults. UJO in children may resolve spontaneously within the first 18 months of life.10,28

Return to Summary Table.

Criterion 3: Impact of not performing a diagnostic imaging test on mortality related to the underlying condition (link to definition)

According to Statistics Canada, 52 patients died from obstructive uropathy (1.6 per million people) and 39 due to urolithiasis (1.2 per million) in 2007 (ages not specified).29 A 1999 study conducted by DeVivo et al. in patients with spinal cord injury reported that urinary complications accounted for 3.8% of deaths during the first year after injury and 2.3% of deaths beyond the first year after the injury has occurred.55

Return to Summary Table.

Criterion 4: Impact of not performing a diagnostic imaging test on morbidity or quality of life related to the underlying condition (link to definition)

Adult
Renal obstruction for greater than one week may cause some permanent renal damage, but with recovery in renal function, while complete obstruction for greater than 12 weeks may cause irreversible damage to the renal system with no recovery of renal function.7 In acute bilateral obstruction, symptoms will disappear within hours or days if the disease is detected and treated quickly. In chronic cases of obstruction, immediate interventions are not necessary, except in cases where an infection needs to be drained or the patient has one kidney.27

Cases of chronic obstruction may result in chronic tubulointerstitial disease7 and can result in a decrease in renal blood flow,7 glomerular filtration rate,7,30 impaired renal function,5,7,26 acidosis, and nephrogenic diabetes.30 In acute unilateral obstruction, renal damage may occur, but it is rare, as the other kidney usually functions to compensate for the one that is impaired.25

Patients treated for obstruction or who clear a stone on their own may experience a life-threatening condition called post-obstructive diuresis,26 which can be described as a loss of key electrolytes through the purged urine7 after a blockage has been cleared.26

Pediatric
It is important to note that, in children, UJO may resolve spontaneously within the first 18 months of life. If symptoms persist past this time period, then intervention may be necessary.10,28

In pediatric cases, 23% of children with renal insufficiency will require transplantation.30

For both adults and children, complications associated with prolonged renal obstruction include long-term incontinence or urinary retention, and formation of urethral or kidney stones26 and chronic/recurrent urinary tract infection (UTI).5

Return to Summary Table.

Criterion 5: Relative impact on health disparities (link to definition)

Adult
Kidney stones occur in 2% to 12%of the population, but are twice as likely to occur in Caucasian populations compared to Asian populations.48-52 The incidence of stone disease peaks between the ages of 20 through 50, and occurs more often in men than in women as a ratio of 3:1.48

Women who are pregnant4 or have undergone female circumcision56 may also be at a greater risk of developing urinary obstruction. However, renal scans would not be the procedure of choice in pregnant women because of the radiation (expert opinion — Martin Reed). Other populations that may be at a greater risk of developing urinary obstruction include individuals with prostate cancer,2 retroperitoneal fibrosis,7 spinal cord injury,8,9 ureteral stricture,6 and congenital anomalies (e.g., UJO),5,10 which is most common in children but also found in adults.6

Pediatric
Children with Down's syndrome are more likely to have urinary obstruction (e.g., hydronephrosis [180 per 10,000 population], UJO [2.6 per 10,000 population], anterior urethral obstruction [2.6 per 10,000 population]) than children without Down's syndrome (obstruction of the urethra [0.3 per 10,000 children]).54 However, nuclear imaging tests are not likely to be used in this patient population (expert opinion — Martin Reed).

Return to Summary Table.

Criterion 6: Relative acceptability of the test to patients (link to definition)

Renal scintigraphy
Overall, renal scan is reported to be well-tolerated.57 However, patients may have concerns about radiation exposure and the IV injection of a radiopharmaceutical agent. IV fluids might be required if the adequacy of hydration is a concern.16 Because a full bladder may slow drainage of the radiopharmaceutical from the upper part of the urinary tract, the bladder should be emptied frequently. Bladder catheterization may be required, especially in pediatric patients. In particular in children, catheterization may be associated with some discomfort.31

MRU
Because of the closed space of an MRI, patients may experience feelings of claustrophobia, as well as being bothered by the noise. This may be less of a problem with new MRI machines, if available (Medical Isotopes and Imaging Modalities Advisory Committee [MIIMAC] expert opinion). It has been reported that up to 30% of patients experience apprehension and 5% to 10% endure some severe psychological distress, panic, or claustrophobia.32,33 Patients are not exposed to radiation during an MRI scan, which may be more acceptable to some.

U/S
This test may be preferred in pediatric patients, as there is no exposure to ionizing radiation   and the test does not require sedation.

Return to Summary Table

Criterion 7: Relative diagnostic accuracy of the test (link to definition)

Adult
No meta-analyses or systematic reviews with information regarding the diagnostic accuracy specific to an adult population was found; however, three primary studies8,35,36 were identified that compared U/S, MRU, or CT to renal scans using 99mTc-MAG3 or 99mTc-DTPA. Only those studies that evaluated patients for an initial diagnosis of obstruction were included. Studies that evaluated obstruction after surgery or intervention for clearance of obstruction were not included. The main outcomes that were reported for diagnostic accuracy were the correlation coefficient of the renal scan compared with the alternative imaging test and, in some cases, sensitivity and specificity were reported (Appendix 4).

Results of the accuracy of diagnosis of hydronephrosis by renal scan and U/S are summarized in Table 2.

Renal scintigraphy versus MRU

Abou El-Ghar et al.35 assessed the role of MRU and renal scintigraphy for the anatomical and functional evaluation of obstructed kidneys. A total of 96 patients (59 males, 37 female) with compromised renal function were included in the study (mean age = 52.5 ±14 years). All included patients underwent Gd-enhanced MRI and 99mTc-DTPA renal scan. Diagnosis of obstruction was confirmed by ureterogram or endoscopy and/or open surgery (gold standard). Anatomically, MRI detected the cause of the obstruction in all kidneys with non-calcular obstruction (100% sensitivity) and in 21 kidneys with calcular obstruction (70% sensitivity). When combined with abdominal X-ray and ultrasonography, the sensitivity of MRI in detection of cause of obstruction was 97%. Functionally, a comparison between Gd-enhanced MRI and 99mTc-DTPA renal scan showed a good correlation (r = 0.79, P < 0.0001); the mean GFR value for the compromised kidneys was 14.6 ± 6 mL/min for the MRU and 18 ± 4.9ml min-1 for the renal scan. The authors concluded that the MRU is as accurate as renal scan in assessing renal function and could be used as a single modality for diagnosing obstruction in cases where patients would not be compromised due to renal function contraindications.35

El-Nahas et al.36 evaluated the diagnostic accuracy of MRU in comparison with renal scan in 46 patients with pelvic-UJO (22 males, 24 females; mean age 31.6 years). All patients underwent 99mTc-MAG3 renal renography, while renal U/S or intravenous urography were also conducted for morphological changes. The clearance of the agents as assessed by both MRU and renal scan were calculated and compared using a correlation coefficient. The mean value of the MRU clearance was 32.8 mL/min, while the renal scan was 31.6 mL/min. The difference between the two tests was not statistically significant (P = 0.19); however, the correlation between the two values was (r = 0.82; P < 0.001). The authors concluded that there is a strong correlation between MRU and renal scan clearance, which can be attributed to the high accuracy of MRU in calculating renal clearance and diagnosing obstructive uropathy.36

Renal scintigraphy versus U/S

A 2001 study by Tsai et al.8 evaluated the diagnostic accuracy of U/S and renal scan in the detection of hydronephrosis in patients with spinal cord injury (SCI) using intravenous pyelogram as the gold standard.8 A total of 109 patients with SCI and hydronephrosis were evaluated over a three-year period from 1993 to 1996 at a rehabilitation hospital in Taiwan. The mean age of the group was 33.7 years and the main outcome measure was the ERPF using the radiopharmaceutical 99mTc-MAG3. Of analyzed kidneys, U/S correctly excluded the presence the hydronephrosis in 173 of 192 non-obstructed kidneys and positively identified 41 of 43 kidneys with documented hydronephrosis. The renal scan correctly excluded 161 non-obstructed kidneys and correctly identified 39 of 43 kidneys with hydronephrosis.8 The corresponding sensitivity of U/S was 0.96, with a specificity of 0.91. Renal scan reached a sensitivity of 0.91 with a specificity of 0.84. The authors conclude that U/S was more accurate than renal scintigraphy for the detection of hydronephrosis in patients with SCI, although they add that renal scintigraphy can provide valuable information regarding total and individual renal function, which cannot be obtained by U/S alone.8

Table 2 presents a summary of diagnostic accuracy measures of imaging tests in adults with renal obstructive uropathy.

Table 2: Summary of Diagnostic Accuracy Measures of Tests in Adult Renal Obstructive Uropathy8,35,36

Test Correlation
Coefficient (R)*
Sensitivity (%) Specificity (%)
MRU 0.79-0.82 70 to 100 N/A
U/S* N/A 96 90

MRU = magnetic resonance urography; N/A= Not available; U/S = ultrasound.
*Between test and renal scan.

Pediatric

No meta-analyses or systematic reviews with information regarding the diagnostic accuracy specific to a pediatric population was found; however, five12,14,18-20 primary studies were found that evaluated diagnostic accuracy of MRU and U/S in comparison with a radioisotope renal scan in a pediatric population of renal obstructive uropathy. Studies that included a population of children with renal obstructive uropathy that were diagnosed via U/S in the womb and were being evaluated after birth for a confirmation of diagnosis prior to surgical intervention were excluded.

Renal scintigraphy versus MRU

Jones et al.14

A study conducted by Jones and colleagues between November 2001 and September 2003 involved a total of 137 children in order to diagnose obstructive uropathy. MRU and renal scan with 99mTc DTPA (hence calculation of GFR) or 99mTc MAG3 (hence ERFP) were conducted on all the participants. The majority of the patient population involved boys (61%) with a mean age of 3.5 ± 4.5 years (range: 0.02 to 15.2 years) and girls (39%) with a mean age of 4.1±4.9 (range: 0.2 to 16.5). The renal transit time and split renal function were calculated as outcomes for the MRU to determine obstruction. Diagnosis of obstruction for renal scan was decided if the T1/2 washout time was greater than 20 minutes after the administration of the diuretic. In final, data from 30 patients was included and a total of 59 kidneys evaluated. An receiver operating characteristic (roc) curve was generated, and the area under the curve (AUC) was calculated to be 0.90. This value means that the accuracy of MRU was 90% in comparison to renal scan as a gold standard (100%).14

Perez-Brayfield et al.20

Perez-Bayerfield and colleagues conducted a study to evaluate the role of dynamic enhanced MRI in order to compare it with other imaging modalities in the diagnosis of pediatric hydronephroisis. A total of 96 children (mean age four years) were involved in the study and a total of 100 dynamic contrast MRIs were done along with U/S and renal scan using 99mTc-MAG3 (n=71), 99mTc-DTPA (n=39) or 99mTc-DMSA (n=3). The SRF for nuclear imaging and MRI was compared in 71 of the 100 cases and the correlation coefficient was calculated to be r2=0.93 which yields and r value of 0.96.

Grattan-Smith et al.12

Grattan-Smith and colleagues conducted a study to evaluate the role of dynamic enhanced MRI compared with other imaging modalities in the diagnosis of 40 children (mean age 1.4 years) with pediatric hydronephrosis.  MRIs were done along with renal scan using 99mTc-MAG3 (n=22), 99mTc-DTPA (n=15) or 99mTc-DMSA (n=2). The SRF for renal scan and MRI was calculated and compared in all 40 cases. The correlation coefficient was calculated to be r=0.98. In conclusion, the authors summarized that in regards to the anatomical function, MRU was superior to renal scan, however, SRF outcomes between MRI and renal scan are equivalent.

Renal scintigraphy versus U/S

de Bessa Junior et al.19

A study conducted by de Bessa Junior et al. evaluated the diagnostic accuracy of U/S compared to renal scan to identify cases of urinary obstructions. A total of 54 patients were eligible for the study between September 2005 and October 2006; the median age of patients was four years (age range: 3 months to 14 years). All patients underwent U/S and renal scan using 99mTc-DTPA within a maximum of two weeks. For U/S, obstruction was diagnosed if the ureterovesical jet frequency was less than or equal to 25%. Renal scan was the reference test, and obstruction was diagnosed as a measure of differential renal function less than 40%. The sensitivity and specificity for U/S in comparison to renal scan were calculated to be 87% (95% CI; 78.9% to 98.2%) and 96.4% (95% CI; 87% to 99%), respectively. The positive likelihood ratio and negative likelihood ratio were 24.3 and 0.1 respectively. The authors' conclude that a relative jet frequency value of less than or equal to 25% was a good indicator of obstructive uropathy and could be used as a non-invasive alternative to renal scan, but the authors state that further research is needed.19

Table 3: Summary of Diagnostic Accuracy Measures of the Tests in Pediatric Renal Obstructive Uropathy12,14,18-20

Test Correlation Coefficient (R)* Sensitivity (%), Specificity (%) Accuracy
MRU 0.96-0.98 N/A N/A 0.90
U/S N/A 87 96.4 N/A

CT = computed tomography; MRU = magnetic resonance urography; N/A= Not available; U/S = ultrasound
*Between test and renal scan.

Return to Summary Table.

Criterion 8: Relative risks associated with the test (link to definition)

Non–radiation-related Risks

Renal scan
Adverse events from renal scintigraphy are rare but may include reaction to the radiopharmaceutical, rash, fever, or chills.37 There is also a relative contraindication in the administration of captopril in patients with a solitary kidney, as it may precipitate transient acute renal failure if the kidneys have physiologically significant renal artery stenosis (MIIMAC expert opinion).

MRU
MRI is contraindicated in patients with metallic implants including pacemakers.58 MRI is often used in conjunction with the contrast agent Gd. Some patients may experience an allergic reaction to the contrast agent (if required), which may worsen with repeated exposure.59 Side effects of Gd include headaches, nausea, and metallic taste. Gd is contraindicated in patients with renal failure or end-stage renal disease, as they are at risk of nephrogenic systemic fibrosis. According to the American College of Radiology Manual on Contrast Media38 the frequency of severe, life-threatening reactions with Gd are extremely rare (0.001% to 0.01%). Moderate reactions resembling an allergic response (i.e., rash, hives, urticaria) are also very unusual and range in frequency from 0.004% to 0.7%.38 Children may require sedation.

U/S
There are no reported risks associated with U/S in the literature that was reviewed.

Radiation-related Risks

Among the modalities to diagnose obstructive uropathy, renal scintigraphy exposes the patient to ionizing radiation. The average effective dose of radiation delivered with each of these procedures can be found in Tables 4 and 5.

Table 4: Effective Radiation Doses for Various Imaging Tests in Adults

Test Effective Radiation Dose (mSv)
99mTc-DTPA renal scan 1.844
99mTc-MAG3 renal scan 2.644
MRU 0
U/S 0
Average background dose of radiation per year 1-3.042-44

MRU = magnetic resonance urography; mSv = millisievert; 99mTc-MAG3 = technetium-99m-labelled  mercaptoacetyl triglycine; 99mTc-DTPA = technetium-99m-labelled- diethylenetriamine pentaacetic acid; U/S = ultrasound.

Table 5: Comparison of Radiation Exposure Levels of Different Imaging Tests in Pediatric Patients

Diagnostic Study Average Radiation Dose (mSv)*
Renal scan with 99mTc-DMSA 0.03939
Renal scan with 99mTc-GH 0.02460
Renal scan with 99mTc-MAG3 0.01539
Renal scan with 99mTc-DTPA 0.01239
U/S 039
MRI 039
Average background dose of radiation per year 1-3.042-44

MRI = magnetic resonance imaging; mSv = millisievert; 99mTc-MAG3 = technetium-99m-mercaptoacetyl triglycine; 99mTc-DTPA = technetium-99m-diethylenetriamine pentaacetic acid; 99mTc-GH = technetium-99m-glucoheptonate;  99mTc-MAG3 = technetium-99m-labelled mercaptoacetyltrigylcine; U/S = ultrasound.

Return to Summary Table.

Criterion 9: Relative availability of personnel with expertise and experience required for the test (link to definition)

The personnel required for the performance of the imaging tests to evaluate suspected obstructive uropathy are presented by imaging modality. A summary of the availability of personnel required for renal scintigraphy or any of the alternative imaging modalities is provided in Table 6.

Renal scintigraphy
In Canada, physicians involved in the performance, supervision, and interpretation of renal scans should be nuclear medicine physicians or diagnostic radiologists with training/expertise in nuclear imaging. Physicians should have a Fellowship of Certification in Nuclear Medicine or Diagnostic Radiology with the Royal College of Physicians and Surgeons of Canada and/or the Collège des médecins du Québec. Nuclear medicine technologists are required to conduct renal scans. Technologists must be certified by the Canadian Association of Medical Radiation Technologists (CAMRT) or an equivalent licensing body.

All alternative imaging modalities
In Canada, physicians involved in the performance, supervision, and interpretation of diagnostic MRI and U/S should be diagnostic radiologists45 and must have a Fellowship or Certification in Diagnostic Radiology with the Royal College of Physicians and Surgeons of Canada and/or the Collège des médecins du Québec. Foreign-trained radiologists also are qualified if they are certified by a recognized certifying body and hold a valid provincial license.61

Service engineers are needed for system installation, calibration, and preventive maintenance of the imaging equipment at regularly scheduled intervals. The service engineer's qualification will be ensured by the corporation responsible for service and the manufacturer of the equipment used at the site.

Qualified medical physicists (on site or contracted-part time) should be available for the installation, testing, and ongoing quality control of MRI scanners and nuclear medicine equipment.61

MRU
MRU is an MRI-based test. For the performance of MRI, medical technologists must have CAMRT certification in magnetic resonance or be certified by an equivalent licensing body recognized by CAMRT.

U/S
Sonographers (or ultrasonographers) should be graduates of an accredited school of sonography or have obtained certification by the Canadian Association of Registered Diagnostic Ultrasound Professionals. They should be members of their national or provincial professional organization. Sonography specialties include general sonography, vascular sonography, and cardiac sonography.45 In Quebec, sonographers and medical radiation technologists are grouped together; in the rest of Canada, sonographers are considered a distinct professional group.45

Table 6: Medical Imaging Professionals in Canada45

Jurisdiction Diagnostic Radiology Physicians Nuclear Medicine Physicians MRTs Nuclear Medicine Technologists Sonographers Medical Physicists
NL 46 3 263 15 NR NR
NS 71 5 403 71 NR NR
NB 47 3 387 55 NR NR
PEI 7 0 57 3 NR 0
QC 522 90 3,342 460 NR NR
ON 754 69 4,336 693 NR NR
MB 58 8 501 42 NR NR
SK 61 4 359 36 NR NR
AB 227 18 1,229 193 NR NR
BC 241 21 1,352 212 NR NR
YT 0 0 NR 0
NT 0 0 26 1 NR 0
NU 0 0 NR 0
Total 2,034 221 12,255 1,781 2,900* 322*

AB = Alberta; BC = British Columbia; MB = Manitoba; MRT = medical radiation technologist; ON = Ontario; NB = New Brunswick; NL = Newfoundland and Labrador; NR = not reported by jurisdiction; NS = Nova Scotia; NT= Northwest Territories; NU = Nunavut; PEI= Prince Edward Island; QC = Quebec; YT = Yukon.
* This represents a total for all of the jurisdictions.

Return to Summary Table.

Criterion 10: Accessibility of alternative tests (equipment and wait times) (link to definition)

There are notable variations in the availability of medical imaging technologies within hospitals across Canada. Nuclear medicine cameras are not available in the Yukon, the Northwest Territories, and Nunavut. Table 7 provides an overview of the availability of equipment required to diagnose obstructive uropathy. Data for nuclear medicine cameras (including SPECT) are current to January 1, 2007. The number of MRI and SPECT/CT scanners is current to January 1, 2010. Data were not available for U/S.

Table 7: Diagnostic Imaging Equipment in Canada45,46

  Nuclear Medicine Cameras MRI Scanners SPECT/CT Scanners
Number of devices 60345 21846 9646
Average number of hours of operation per week (2006-2007)45 40 71 n/a
Provinces and Territories with no devices available YT, NT, NU YT, NT, NU PE, YT, NT, NU

MRI = magnetic resonance imaging; NT = Northwest Territories; NU = Nunavut; PEI = Prince Edward Island; SPECT/CT = single-photon emission computed tomography/computed tomography; YT = Yukon.

Renal scintigraphy
For renal scans, nuclear medicine facilities with gamma cameras (including SPECT) are required. Three jurisdictions — the Yukon, the Northwest Territories, and Nunavut — do not have any nuclear medicine equipment.45 In 2007, the latest year for which data are available, the average time for renal scintigraphy in McGill University Health Centre (MUHC) hospitals was 13 days. However, the wait times were reported to be less than one day for emergency cases.62

MRI
There are no MRI scanners available in the Yukon, Northwest Territories, or Nunavut.45  According to the Canadian Institute for Health Information's National Survey of Selected Medical Imaging Equipment database, the average number of hours of operation per week for MRI scanners in 2006–2007 ranged from 40 hours in PEI to 99 hours in Ontario, with a national average of 71 hours.45 In 2010, the average wait time for MRI in Canada was 9.8 weeks.47

U/S
U/S machines are widely available across the country. According to the Fraser Institute, the average wait time for U/S in 2010 was 4.5 weeks.47

Return to Summary Table

Criterion 11: Relative cost of the test (link to definition)

Fee codes from the Ontario Schedule of Benefits were used to estimate the relative costs of Lasix-enhanced renal scintigraphy and its alternatives. Technical fees are intended to cover costs incurred by the hospital (i.e., radiopharmaceutical costs, medical/surgical supplies, and non-physician salaries). Maintenance fees are not billed to OHIP — estimates here were provided by St. Michael's Hospital in Toronto. Certain procedures (i.e., PET scan, CT scan, MRI scan) are paid for, in part, out of the hospital's global budget; these estimates were provided by The Ottawa Hospital. It is understood that the relative costs of imaging will vary from one institution to the next.

According to our estimates (Table 8), the cost of scintigraphy with 99mTc-based radioisotopes to establish whether obstruction is present is $310.45. U/S is a minimally less costly alternative. MRU is a moderately more costly imaging test.

Table 8: Cost Estimates Based on the Ontario Schedule of Benefits for Physician Services Under the Health Insurance Act (September 2011)63

Fee Code Description Tech. Fees ($) Prof. Fees ($) Total Costs ($)
Renal scintigraphy
J835 Computer-assessed renal function — includes first transit 135.10 73.00 208.10
J880 Computer-assessed renal function — repeat after pharmacological intervention 46.00 22.50 68.50
Maintenance fees — from global budget 33.85   33.85
TOTAL 214.95 95.50 310.45 
MRU
X451C MRU — abdomen — multislice sequence   77.20 77.20
X455C ×3 Repeat (another plane, different pulse sequence; to a maximum of 3 repeats)   38.65 (×3) = 115.95 115.95
X487C When Gd is used   38.60 38.60
X499C 3-D MRI acquisition sequence, including post-processing (minimum of 60 slices; maximum 1 per patient per day)   65.40 65.40
Technical cost — from global budget 300.00   300.00
Maintenance fees — from global budget 73.00   73.00
TOTAL 373.00 297.15 670.15
U/S
J135 Abdominal scan — complete 50.00 34.95 84.95
Maintenance fees — from global budget 3.30   3.30
TOTAL 53.30 34.95 88.25

3-D = three-dimensional; Gd = gadolinium; MRI = magnetic resonance imaging; MRU = magnetic resonance urography; Prof. = professional; Tech. = technical; U/S = ultrasound.

Return to Summary Table.

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  65. Campbell C. What is the major function of the calyx? [Internet]. Bellevue (WA): eHow; 2011. [cited 2011 Dec 22]. Available from: http://www.ehow.com/about_6068054_major-function-calyx_.html#ixzz1Z5b7m3dZ

 

Appendix 1: Multi-Criteria Decision Analysis Definitions

Domain 1: Criteria Related to the Underlying Health Condition
Criterion Definition
1. Size of the affected population The estimated size of the patient population that is affected by the underlying health condition and which may potentially undergo the test. The ideal measure is point prevalence, or information on how rare or common the health condition is.
2. Timeliness and urgency of test results in planning patient management The timeliness and urgency of obtaining the test results in terms of their impact on the management of the condition and the effective use of health care resources.
3. Impact of not performing a diagnostic imaging test on mortality related to the underlying condition Impact of not performing the test, in whatever way, on the expected mortality of the underlying condition. Measures could include survival curves showing survival over time, and/or survival at specific time intervals with and without the test.
4. Impact of not performing a diagnostic imaging test on morbidity or quality of life related to the underlying condition Impact of not performing the test, in whatever way, on the expected morbidity or on the quality of life reduction of the underlying condition. Measures of impact may include natural morbidity outcome measures such as events or disease severity, or might be expressed using generic or disease-specific quality of life rating scales with and without the test.
Domain 2: Criteria Comparing 99mTc with an Alternative, or Comparing between Clinical Uses
Criterion Definition
5. Relative impact on health disparities Health disparities are defined as situations where there is a disproportionate burden (e.g., incidence, prevalence, morbidity, or mortality) amongst particular population groups (e.g., gender, age, ethnicity, geography, disability, sexual orientation, socioeconomic status, and special health care needs).

Impact on health disparities is assessed by estimating the proportion of current clients of the 99mTc-based test that are in population groups with disproportionate burdens.

(Explanatory note: The implication of this definition is that, everything else being the same, it is preferable to prioritize those clinical uses that have the greatest proportion of clients in groups with disproportionate burdens.)
6. Relative acceptability of the test to patients Acceptability of the 99mTc-based test from the patient's perspective compared with alternatives. Patient acceptability considerations include discomfort associated with the administration of the test, out-of-pocket expenses or travel costs, factors that may cause great inconvenience to patients, as well as other burdens. This criterion does not include risks of adverse events but is about everything related to the experience of undergoing the test.
7. Relative diagnostic accuracy of the test Ability of the test to correctly diagnose the patients who have the condition (sensitivity) and patients who do not have the condition (specificity) compared with alternatives.
8. Relative risks associated with the test Risks associated with the test (e.g., radiation exposure, side effects, adverse events) compared with alternatives. Risks could include immediate safety concerns from a specific test or long-term cumulative safety concerns from repeat testing or exposure.
9. Relative availability of personnel with expertise and experience required for the test Availability of personnel with the appropriate expertise and experience required to proficiently conduct the test and/or interpret the test findings compared with alternatives.
10. Accessibility of alternatives (equipment and wait times) Availability (supply) of equipment and wait times for alternative tests within the geographic area. Includes consideration of the capacity of the system to accommodate increased demand for the alternatives. Excludes any limitation on accessibility related to human resources considerations.
11. Relative cost of the test Operating cost of test (e.g., consumables, heath care professional reimbursement) compared with alternatives.

 

Appendix 2: Literature Search Strategy

OVERVIEW
Interface: Ovid
Databases: Ovid MEDLINE In-Process & Other Non-Indexed Citations and Ovid MEDLINE <1948 to April 1, 2011>
Date of Search: April 4, 2011
Alerts: Weekly search updates began April 4, 2011 and ran until October 2011.
Study Types: Health technology assessments, systematic reviews, meta-analyses, randomized controlled trials, non-randomized studies, and diagnostic accuracy studies.
Limits: No date limit for systematic reviews; publication years 2001 – April 2011 for primary studies

English language

Human limit for primary studies
SYNTAX GUIDE
/ At the end of a phrase, searches the phrase as a subject heading
MeSH Medical subject heading
.fs Floating subheading
exp Explode a subject heading
* Before a word, indicates that the marked subject heading is a primary topic; or, after a word, a truncation symbol (wildcard) to retrieve plurals or varying endings
? Truncation symbol for one or no characters only
ADJ Requires words are adjacent to each other (in any order)
ADJ# Adjacency within # number of words (in any order)
.ti Title
.ab Abstract
.hw Heading word: usually includes subject headings and controlled vocabulary 
.tw Text word: searches title, abstract, captions, and full text
.mp Keyword search: includes title, abstract, name of substance word, subject heading word and other text fields
.pt Publication type
.nm Name of substance word: used to search portions of chemical names and includes words from the CAS Registry/EC Number/Name (RN) fields
.jw Journal words: searches words from journal names
/du Diagnostic use
/ri Radionuclide imaging

 

Ovid MEDLINE Strategy
Line # Search Strategy
1 Technetium/
2 exp Technetium Compounds/
3 exp Organotechnetium Compounds/
4 exp Radiopharmaceuticals/
5 radioisotope*.mp.
6 (technetium* or Tc-99* or Tc99* or Tc-99m* or Tc99m* or 99mTc* or 99m-Tc* or 99mtechnetium* or 99m-technetium*).tw,nm.
7 Radionuclide Imaging/ or Perfusion Imaging/ or Radioisotope Renography/
8 ri.fs.
9 ((radionucl* or nuclear or radiotracer* or perfusion or gamma camera*) adj2 (imag* or scan* or test* or diagnos*)).tw.
10 (SPECT or scintigraph* or scintigram* or scintiphotograph* or scintiscan*).tw.
11 Tomography, Emission-Computed, Single-Photon/
12 (single-photon adj2 emission*).tw.
13 ((renal* or kidney* or dimercapto-succinic acid* or dimercaptosuccinic acid* or dimercapto-succinate acid* or dimercaptosuccinate acid*) adj7 (imaging or perfusion* or scan*)).tw.
14 (renograp* or reno-graph* or renogram* or DMSA).tw.
15 (MAG3 or MAG-3 or Mercaptoacetyltriglycine or Mertiatide or TechneScan or Mercaptoacetylglycylglycylglycine or Mercaptoacetyl triglycine).tw.
16 (DTPA or diethylenetriaminepentaacetic acid* or diethylenetriamine penta-acetic acid*).tw.
17 125224-05-7.rn.
18 or/1-17
19 Ureteral Obstruction/
20 exp Urethral Obstruction/
21 exp Hydronephrosis/
22 exp Urinary Calculi/
23 exp Renal Insufficiency/
24 ((renal* or ureter* or urethra* or urinary*) adj3 (block* or obstruct*)).tw.
25 ((fetal* or obstructi*) adj3 (uropath* or nephropath*)).tw.
26 (hydronephros* or calculus or calculi or (urinary adj2 stone*)).ti.
27 ((kidney* or renal) adj3 (failure* or insufficienc*)).tw.
28 or/19-27
29 Meta-Analysis.pt.
30 Meta-Analysis/ or Systematic Review/ or Meta-Analysis as Topic/ or exp Technology Assessment, Biomedical/
31 ((systematic* adj3 (review* or overview*)) or (methodologic* adj3 (review* or overview*))).tw.
32 ((quantitative adj3 (review* or overview* or synthes*)) or (research adj3 (integrati* or overview*))).tw.
33 ((integrative adj3 (review* or overview*)) or (collaborative adj3 (review* or overview*)) or (pool* adj3 analy*)).tw.
34 (data synthes* or data extraction* or data abstraction*).tw.
35 (handsearch* or hand search*).tw.
36 (mantel haenszel or peto or der simonian or dersimonian or fixed effect* or latin square*).tw.
37 (met analy* or metanaly* or health technology assessment* or HTA or HTAs).tw.
38 (meta regression* or metaregression* or mega regression*).tw.
39 (meta-analy* or metaanaly* or systematic review* or biomedical technology assessment* or bio-medical technology assessment*).mp,hw.
40 (medline or Cochrane or pubmed or medlars).tw,hw.
41 (cochrane or health technology assessment or evidence report).jw.
42 or/29-41
43 exp "Sensitivity and Specificity"/
44 False Positive Reactions/
45 False Negative Reactions/
46 du.fs.
47 sensitivit*.tw.
48 (predictive adj4 value*).tw.
49 distinguish*.tw.
50 differentiat*.tw.
51 enhancement.tw.
52 identif*.tw.
53 detect*.tw.
54 diagnos*.tw.
55 accura*.tw.
56 comparison*.tw.
57 Comparative Study.pt.
58 (Validation Studies or Evaluation Studies).pt.
59 Randomized Controlled Trial.pt.
60 Controlled Clinical Trial.pt.
61 (Clinical Trial or Clinical Trial, Phase II or Clinical Trial, Phase III or Clinical Trial, Phase IV).pt.
62 Multicenter Study.pt.
63 (random* or sham or placebo*).ti.
64 ((singl* or doubl*) adj (blind* or dumm* or mask*)).ti.
65 ((tripl* or trebl*) adj (blind* or dumm* or mask*)).ti.
66 (control* adj3 (study or studies or trial*)).ti.
67 (non-random* or nonrandom* or quasi-random* or quasirandom*).ti.
68 (allocated adj "to").ti.
69 Cohort Studies/
70 Longitudinal Studies/
71 Prospective Studies/
72 Follow-Up Studies/
73 Retrospective Studies/
74 Case-Control Studies/
75 Cross-Sectional Study/
76 (observational adj3 (study or studies or design or analysis or analyses)).ti.
77 cohort.ti.
78 (prospective adj7 (study or studies or design or analysis or analyses or cohort)).ti.
79 ((follow up or followup) adj7 (study or studies or design or analysis or analyses)).ti.
80 ((longitudinal or longterm or (long adj term)) adj7 (study or studies or design or analysis or analyses or data or cohort)).ti.
81 (retrospective adj7 (study or studies or design or analysis or analyses or cohort or data or review)).ti.
82 ((case adj control) or (case adj comparison) or (case adj controlled)).ti.
83 (case-referent adj3 (study or studies or design or analysis or analyses)).ti.
84 (population adj3 (study or studies or analysis or analyses)).ti.
85 (cross adj sectional adj7 (study or studies or design or research or analysis or analyses or survey or findings)).ti.
86 or/43-85
87 Case Reports.pt.
88 86 not 87
89 18 and 28 and 42
90 limit 89 to english language
91 or/19-22,24-26
92 18 and 91 and 88
93 limit 92 to (english language and humans and yr="2001 -Current")

 

OTHER DATABASES
PubMed Same MeSH, keywords, limits, and study types used as per MEDLINE search, with appropriate syntax used.
Cochrane Library Same MeSH, keywords, and date limits used as per MEDLINE search, excluding study types and Human restrictions. Syntax adjusted for Cochrane Library databases.

 

GREY LITERATURE SEARCHING
Dates for Search: April 2011
Keywords: Included terms for radionuclide imaging and obstructive uropathy.
Limits: No limits

The following sections of the CADTH grey literature checklist, "Grey matters: a practical search tool for evidence-based medicine" (http://www.cadth.ca/en/resources/grey-matters) were searched:

  • Health Technology Assessment Agencies (selected)
  • Clinical Practice Guidelines
  • Databases (free)
  • Internet Search

 

Appendix 3: Definitions

Area under the curve (AUC): The area under the receiver operating characteristic (ROC) curve (AUC) is widely recognized as the measure of a diagnostic test's discriminatory power. The maximum value for the AUC is 1.0, thereby indicating a (theoretically) perfect test (i.e., 100% sensitive and 100% specific)64

Calculi: Is the plural of calculus, commonly called stone. A calculus is usually composed of mineral salts. These pathological concretions can occur in the kidneys, ureters, bladder, and urethra, and are usually formed of crystalling urinary salts held together by viscous organic matter.23

Calyces: Plural of calyx. A cuplike part of the urinary collecting portion of the kidney. The calyx is the method by which urine is passed from the kidney to the bladder.65

Differential Renal function: See SRF.

Diuretic: An agent that increases the secretion of urine.23

Effective renal plasma flow (ERPF): The rate at which the radioisotope is cleared by the proximal tubules, with only a small fraction cleared by the glomerulus tubules. In individuals with healthy kidneys, this clearance rate is 500 to 600 mL/min. This measure can be calculated by examining the uptake and clearance rate of a radioisotope to determine renal function.16

Glomerular filtration rate (GFR): The rate at which the radioisotope clears the glomerulus tubules of the kidney.16

Hydronephrosis: The swelling of the kidneys5 or top of the ureter,10 which can be due to an obstruction in the urinary tract.5

Nephrolithiasis: The presence of calculi in the kidney.23

Pyelocaliectasis: Dilation of the pelvis and cavities (calyces) of the kidney.23

Receiver operating characteristic (roc): The ROC curve offers a graphical illustration of these trade-offs at each "cut-off" for any diagnostic test that uses a continuous variable. Ideally, the best "cut-off" value provides both the highest sensitivity and the highest specificity, easily located on the ROC curve by finding the highest point on the vertical axis and the furthest to the left on the horizontal axis (upper-left corner).64

Renal transit time (RTT): The time it takes for the contrast material to move from the kidneys to the level of or below the lower pole of the kidney (ureter).14

Resistive Index (RI): A measure of (peak systolic velocity – peak diastolic velocity)/peak systolic velocity.

Split renal function (SRF) OR differential renal function (DRF) OR differential ureteral catherization test: Compares the areas of two kidneys; can be calculated by the accumulation of the radiotracer in the kidney after injection.19 It is used to determine various function parameters of one kidney compared with the other kidney.

Tetany: A nervous affection characterized by intermittent tonic spasms.23

Ureterolithiasis: Development of a calculus in the ureter.23

Ureterovesical jets (urinary jet): A wavelike (peristaltic)23 inflow into the bladder.19

Ureterolpelvic Junction Obstruction(UJO): A congenital anomaly prevalent in children that causes an obstruction where the ureter joins the pelvis.10

Urolithiasis: Formation of urinary calculi and the illness associated with the presence of urinary calculi in the urinary tract.23

Washout half-time (T1/2): The time it takes for 50% of the radioisotope to exit the kidneys after the injection of the diuretic (e.g., furosemide or LASIX).18,19 A diagnosis of obstruction is considered when T1/2 > 20 minutes to 30 minutes.18

 

Appendix 4: Diagnostic Accuracy

Table 9: Diagnostic Accuracy of Renal Scan and the Alternative Tests Based on the Information Presented in the Included Studies

Study Population Size, Outcome Measured, and (Mean Age) Renal Scan 99mTc X-ray U/S MRU CT
Adult
Tsai et al., 20018 109 patients with SCI, ERPF,
(33.7 years)
Sens: 91%

Spec: 84%

PPV: 56%

NPV: 98%
Reference standard N/A N/A N/A
El-Ghar et al., 200835 96 adults unilateral, bilateral chronic obstructive hydronephrosis and compromised renal function, GFR
(52.5 years)
Mean: 18 ±    4.9mL/ min-1

R= see MRU
N/A N/A Mean  14.6 ± 6ml min-1

R = 0.79
N/A
El-Nahas et al., 200736 46 patients with symptomatic pelvic UJO, GFR
(31.6 years)
Mean:

R = see MRU
N/A N/A Mean

R = 0.82
N/A
Pediatric
de Bessa Jr. et al., 200719 54 pediatric patients

Renal scan: T1/2

U/S : RJF

(4 years)
Reference standard N/A Sens 87%

Spec 96.4

PLR 24.3

NLR 0.1
N/A N/A
Jones et al., 200414   126 pediatric patients

SRF

(4.1 years)  
Reference standard N/A N/A AUC : 0.90

Acc: 90%
N/A
Perez-Brayfield et al., 200320   96 pediatric  patients

SRF

(4 years)  
R = see MRU   N/A N/A R = 0.96 N/A
Grattan-Smith et al., 200312   40 pediatric patients

SRF

(1.4 years)
R = see MRU   N/A N/A R = 0.98 N/A

AUC=area under the curve; CT= computed tomography; ERFP = effective renal plasma flow; GFR = glomerular filtration rate; MRU= magnetic resonance urography; NA = not applicable; NLR= negative likelihood ratio; NPV= negative predictive value; PLR=positive likelihood ratio; PPV=positive predictive value, R= correlation coefficient; RJF = renal jet frequency; Sens= sensitivity; Spec= specificity; SRF = split renal function; 99mTc = technetium-99m;UJO = ureteropelvic junction obstruction; U/S = ultrasound.