Intermittent hydronephrosis: a diagnostic challenge

Can we improve the usefulness of the diuretic renogram in the diagnosis of ureteropelvic junction obstruction (UPJO) in children? Introduction of mercaptoacetyltriglycine-suspected obstruction scoring system (MAG-SOS)

INTRODUCTION

Mercaptoacetyltriglycine (MAG-3) renogram is one of the gold standard diagnostic tools of ureteropelvic junction obstruction (UPJO); however, there is no widely agreed indications of pyeloplasty based on MAG-3 findings. In this study, we introduce a renogram scoring system that can help improve the prognostic value of MAG-3 renogram and in the decision making of pyeloplasty.

PATIENTS AND METHODS

We retrospectively reviewed consecutive pyeloplasties for antenatal hydronephrosis from 2010 to 2020. A control group was included of non-operatively managed SFU grade 3 and 4. The initial renal ultrasound and preoperative MAG-3 Lasix renogram were reviewed for differential renal function (DRF), type of renogram curve and tracer washout half-time (T1/2). A ROC curve was used to evaluate the cut-off points that can be associated with obstruction. A multivariate linear regression model was used to assess the best renogram parameter that can predict surgical intervention.

RESULTS

We included 188 patients with 209 renal units. The median age for pyeloplasty was 5.4 months. The mercaptoacetyltriglycine-Suspected Obstruction Scoring System (MAG-SOS) was associated with pyeloplasty (AUC = 0.97, P < 0.001) (Figure A). A score of 5 is 100% specific for obstruction. 78% of units required surgical intervention had a MAG-SOS score of≥5 while all units of the control group had a range of score 0-4. Using the multivariate analysis, the MAG-SOS system showed to the only independent predictor for pyeloplasty (HR = 0.03, p < 0.001).

DISCUSSION

This study has some limitations. Firstly, the retrospective nature of the cohort; however, all patients were reviewed by one investigator who was blinded to the line of management. This is a single institutional study; therefor, this MAG-SOS should be evaluated by other centers to ensure its efficiency. Lastly, the pyeloplasty decision was taken by 3 different urologists; nevertheless, all of them adopt the same indications which are similar to those of the Society for Pediatric Urology and the Canadian Urological Association guidelines.

CONCLUSION

The MAG-SOS system showed to be a useful tool that can predict pyeloplasty. A score of 5 has 100% specificity for patients having a pyeloplasty performed. Prospective studies are required to confirm the usefulness of this novel tool.

Drainage-related ultrasonography (DRUS): a novel technique for discriminating obstructive and nonobstructive hydroureters in children

BACKGROUND

Despite advances in urologic imaging, the paucity of an optimal technique that accurately clarifies obstructive and nonobstructive hydroureter exists.

OBJECTIVE

This study was conducted to introduce a novel and modified ultrasonographic technique, known as drainage-related ultrasonography (DRUS), discriminating obstructive and nonobstructive, nonrefluxing hydroureter.

MATERIALS AND METHODS

A total of 358 children (mean age, 3.7 years) with 418 nonrefluxing hydroureter were included. These children were composed of two groups of obstructive nonrefluxing (141 children with 157 dilated ureters) and nonobstructive, nonrefluxing (217 children with 261 hydroureter). The definite diagnosis regarding the subtype of hydroureter was derived from appropriate investigation. The maximum diameter of the dilated ureter, which was observed on ultrasonography, was recorded before and after 3 h of catheterization, as D1 and D2, respectively. To assess the D ratio, a formula was developed, that is, [(|D1 - D2|)/D1] × 100. Values were recorded and cutoff points were set to discriminate between subtypes.

RESULTS

Obstructive versus nonobstructive subtypes of nonrefluxing hydroureter were clarified with 78.5 % sensitivity and 83.4 % specificity, by setting a cutoff point of 22 % for the D ratio. Regardless of the cutoff point assigned to the reduction in D (D2 compared with D1), DRUS revealed 93.9 % sensitivity, 80.6 % specificity, 63.2 % positive predictive value, and 97.4 % negative predictive value in discriminating upper from lower obstruction.

CONCLUSION

DRUS affords favorable results in terms of differentiating between obstructive and nonobstructive, nonrefluxing hydroureter, as well as between upper and lower obstruction in obstructive cases. It has the potential to become an efficient imaging modality in the diagnostic algorithm of hydroureter.

Radionuclides in nephrourology, Part 2: pitfalls and diagnostic applications

Radionuclide renal scintigraphy provides important functional data to assist in the diagnosis and management of patients with a variety of suspected genitourinary tract problems, but the procedures are underutilized. Maximizing the utility of the available studies (as well as the perception of utility by referring physicians) requires a clear understanding of the clinical question, attention to quality control, acquisition of the essential elements necessary to produce an informed interpretation, and production of a report that presents a coherent impression based on data contained in the report and that specifically addresses the clinical question. To help achieve these goals, part 1 of this review addressed the available radiopharmaceuticals, quality control, and quantitative indices, including the measurement of absolute and relative renal function. Part 2 assumes familiarity with part 1 and focuses on the common clinical indications of suspected obstruction and renovascular hypertension; part 2 also summarizes the status of radionuclide renal imaging in the evaluation of the transplanted kidney and the detection of infection, discusses potential pitfalls, and concludes with suggestions for future research. The series of SAM questions accompanying parts 1 and 2 has been designed to reinforce and extend points made in the review. Although the primary focus is the adult patient, aspects of the review also apply to the pediatric population.

[Intermittent hydronephrosis in childhood]

INTRODUCTION

Intermittent pelviureteric junction obstruction, and its consequence,intermittent hydronephrosis is a difficult condition to identify. The renal collecting system is not dilated between the episodes of abdominal pain attacks and a prompt investigation is hard to carry out during the time of painful crisis. Therefore, most of the patients are initially misdiagnosed.

AIM

The aim of the study was to assess the occurrence and the clinical characteristics of this phenomenon in children operated in the Department of Urological Surgery, Heim Pál Children Hospital, Budapest, Hungary.

PATIENTS AND METHODS

Medical records of children operated for hydronephrosis between 2008 and 2012 were reviewed. The occurrence rate and clinical features of intermittent hydronephrosis were analyzed.

RESULTS

76 children were operated for pelviureteric junction obstruction, of which 10 met the criteria of intermittent hydronephrosis. The average interval between the onset of symptoms and the final diagnosis was 2 years and 4 months. In 7 patients pyeloplasty, and in 3 patients nephrectomy were performed.

CONCLUSIONS

Intermittent hydronephrosis represents a well-defined proportion among cases operated for hydronephrosis. The delay in diagnosis led to the loss of the kidney in one third of the patients, and this finding urges for the awareness of health professionals for this phenomenon. In case of recurrent abdominal pain of unknown etiology one must suspect a urological origin, even if a previous abdominal ultrasound showed normal kidneys.

Nonobstructive dilation of urinary tract and later development of obstruction: report of one case

Cases of nonobstructive dilation of the upper urinary tract subsequently becoming obstructive are rare. We report a case involving a male child approximately 2.5 years old (29 months) who presented with an obstruction of the ureterovesical junction, which had been diagnosed and treated for nonobstructive dilation at another hospital 15 months earlier. At our hospital, we found no ureteral orifice by cystoscopic examination. Exploratory surgery was performed and complete obstruction of the ureterovesical junction was observed. We resected the segment involved in the obstruction and performed an ureteroneocystostomy. Patients found to have nonobstructive dilation of the urinary tract, a common and often innocuous finding, need careful follow-up to ensure that obstructions that may develop later can be treated in a timely manner.

International Scientific Committee of Radionuclides in Nephrourology (ISCORN) consensus on renal transit time measurements

This report is the conclusion of the international consensus committee on renal transit time (subcommittee of the International Scientific Committee of Radionuclides in Nephrourology) and provides recommendations on measurement, normal values, and analysis of clinical utility. Transit time is the time that a tracer remains within the kidney or within a part of the kidney (eg, parenchymal transit time). It can be obtained from a dynamic renogram and a vascular input acquired in standardized conditions by a deconvolution process. Alternatively to transit time measurement, simpler indices were proposed, such as time of maximum, normalized residual activity or renal output efficiency. Transit time has been mainly used in urinary obstruction, renal artery stenosis, or renovascular hypertension and renal transplant. Despite a large amount of published data on obstruction, only the value of normal transit is established. The value of delayed transit remains controversial, probably due to lack of a gold standard for obstruction. Transit time measurements are useful to diagnose renovascular hypertension, as are some of the simpler indices. The committee recommends further collaborative trials.

A veno-caliceal fistula related to ureteric stricture in a kidney allograft masquerading as renal failure

We report an unusual case of veno-caliceal fistula that developed because of high ureteric pressure caused by graft ureteric stricture after kidney transplantation in a 60-year-old patient. We further confirmed its presence with radiological images. Recirculation of creatinine and other uremic toxins resulted in a biochemical picture of renal failure in the presence of normal kidney function, confirmed by normal scintigraphy findings. Drainage of the pelvi-caliceal system could not be assessed accurately by means of diuretic renogram using technetium-99m diethylenetriaminepentaacetic acid with frusemide because of the rapid clearance of tracer activity from the system in the presence of a veno-caliceal fistula. The patient's renal function improved rapidly after interrupting urine recirculation by using percutaneous drainage, confirming "pseudo renal failure" as the cause of his persistently increased serum creatinine concentration. The ureter was re-implanted later, and the veno-caliceal fistula was not seen in the nephrostogram after the operation. He remains well with stable renal function at 3 years' follow-up. Clinicians should exercise judgment when evaluating patients with allograft dysfunction, especially when the investigation and clinical findings show contradicting results.

The natural history of postoperative renal function in patients undergoing ileal conduit diversion for cancer measured using serial isotopic glomerular filtration rate and 99m technetium-mercaptoacetyltriglycine renography

PURPOSE

There is little consensus regarding long-term followup of renal function in patients who undergo urinary diversion. We established the usefulness of combined serial isotopic glomerular filtration rate measurement and diuresis renography in the early identification of patients at risk for deterioration of renal function following ileal conduit diversion.

MATERIALS AND METHODS

A total of 340 patients with ileal conduit diversion who were followed between 1990 and 2000 were identified. We analyzed data on 178 patients who had more than 4 years of followup. Renal function was assessed by serial estimation of serum creatinine, isotopic glomerular filtration rate and diuresis renographic measurements.

RESULTS

Of the patients 52 (29%) demonstrated a worsening glomerular filtration rate. Mean followup +/- SEM was 8.2 +/- 0.4 years (range 4 to 30) and 67% of patients had more than 6 years of followup. In this group we found that hypertension, recurrent urinary sepsis and an initial post-diversion glomerular filtration rate of less than 50 ml per minute per 1.73 m were prevalent risk factors. Hypertension was an independent predictor of a decreased glomerular filtration rate in this group. Of 52 patients with a deteriorating glomerular filtration rate 19 had type II or IIIb curves on followup renography, of whom 13 underwent revision surgery. Renal function subsequently stabilized or improved in this group.

CONCLUSIONS

Of patients with an ileal conduit 29% have renal function deterioration in the long term. No surgical cause for glomerular filtration rate deterioration was found in 18%. Important predisposing factors in nonobstructed cases were hypertension, recurrent urinary sepsis and a glomerular filtration rate of less than 50 ml per minute per 1.73 m. Hypertension was an independent predictor of a decreased glomerular filtration rate in the group with worsening glomerular filtration rates. In 11% of patients deterioration was due to upper tract obstruction. This was identifiable using renography and the glomerular filtration rate. A type IIIb curve was an early indicator of obstruction.

[Specificities of the treatment of abnormal pyelo-ureteral junction in children]

Pyelo-ureteral junction abnormalities in children are most frequently discovered by prenatal ultrasound investigation. Most pyeloplasties by resection-anastomosis of the pyelo-ureteral junction are performed in young infants, usually with a posterior approach, patient prone. The indication and type of urinary pyelic drain remain debated: simple nephrostomy or double J drain. Ureteral-caliceal anastomosis is an interesting approach to rare surgical reoperations, particularly with major pyelo-ureteral dilatation. Laparoscopic surgery may prove usefulness in less small children. Endopyelotomy gives good results for post-operative stenoses.

Intermittent hydronephrosis secondary to ureteropelvic junction obstruction: clinical and imaging features

OBJECTIVE

We sought to assess the clinical and imaging findings in intermittent hydronephrosis secondary to ureteropelvic junction obstruction, with particular emphasis on the characteristic ultrasonographic findings.

METHODS

This prospective, longitudinal, observational study included all children who had intermittent ureteropelvic junction obstruction and presented with abdominal pain over 6 years. Renal ultrasound was used as an initial screening tool to detect intermittent hydronephrosis. Renal ultrasonography was repeated every 1 to 2 days to record serial changes from the symptomatic to the asymptomatic stage. Their clinical manifestations and imaging findings were studied.

RESULTS

Eighteen patients (14 boys, 4 girls) were studied. Most had sharp pain that began acutely and typically lasted for <2 days. Most of the children (16 of 18) had nausea and vomiting that accompanied the pain. The acute episode generally resolved spontaneously and was followed by a pain-free interval that ranged from days to months. Factors that predisposed to an attack included increased water intake, vigorous exercise, or bladder distention. All patients had clearly demonstrable obstruction of the renal pelvis during an acute attack, a finding that diminished or resolved during the symptom-free intervals. During convalescence, all patients had renal pelvic wall thickening on ultrasonography. This finding appeared on the second or third day after a painful episode subsided, persisted for 6 to 9 days, and then disappeared in the symptom-free stage. Pyeloplasty was performed in 17 patients, none of whom had recurrent pain on follow-up. Extrinsic obstructions were found in 9 patients.

CONCLUSIONS

The keys to diagnosis are awareness of the syndrome, a detailed history, and immediate and serial imaging studies during painful crises. A thickened renal pelvic wall during convalescence is an important ultrasonic sign of intermittent hydronephrosis.

Increased intra-abdominal pressure results in both obstructive and nonobstructive types of impairments of renal pelvic excretion

An experimental study has been conducted to evaluate the effects of increased intra-abdominal pressure (IAP) on the excretion function from renal pelvis into the ureter.

METHODS

Sixteen adult male New Zealand rabbits were randomly allocated in two groups after obtaining basal scintigraphies. Group I consisted of 8 rabbits which were subjected to an increased IAP for ten day period. In Group II an other 8 rabbits were subjected to an increased IAP for 60 day period. At the end of the periods of increased IAP the post-pressure scintigraphic evaluations of both groups were carried out. Time to maximum activity (Tmax), T1/2 and T2/3 values of the radiopharmaceutical in the kidneys and down slope parameters (DS1/2, DS2/3) were calculated from the renogram curves of both right and left kidneys. Comparison of basal and post-pressure scintigrapies and the mean difference of the renogram parameters between groups were performed.

RESULTS

All basal scintigraphies were normal. Post-pressure scintigraphies revealed an obvious delay in the excretion phase in both groups. Both kidneys of a rabbit in group I revealed a non-obstructive pattern through responding well to administration of diuretic. Furthermore both kidneys of a rabbit from group II have revealed an obstructive pattern. T1/2 and T2/3 values were significantly elevated and mean DS1/2, DS2/3 were significantly decreased in post-pressure scintigraphies of the both groups without revealing a statistically significant difference between groups I and II. The mean difference of Tmax was significantly increased in group II.

CONCLUSION

The increases in IAP, through the compressive effect upon ureters together with a concomitant increase in intravesical pressure, may impair the passage of urine from renal pelvis into ureter. The impaired passage may play a role in the development of hydronephrosis which may either reveal a nonobstructive and/or obstructive pattern.

Analysis of compartmental models of type 4 nuclear renograms with calculation of flow rate parameters and instantaneous drainage rates

OBJECTIVE

To estimate the dynamic rates of arterial delivery and renal drainage in renograms with the Homsy sign, using optimized computed compartmental modelling.

METHODS

Eleven F-15 renograms and one F+15 renogram (using 99mTc-mercaptoacetyltriglycine) with the Homsy sign were studied, with 26 controls. Compartmental models were constructed for each renogram using components (blood, renal, bladder) linked by variables (arterial rate, drainage rate). Each model was optimized using the Marquadt least-squares method to numerical data from the time-activity curves (TACs). The model renal component at sample points along the TAC was minimized and the corresponding drainage rates calculated.

RESULTS

The models were optimized, with a mean (range) r2 of 0.811 (0.68-0.88). There were continuous low drainage rates for all type 4 renograms, with no quadrupling of the flow rate, as predicted by the standard model.

CONCLUSION

The standard model is unlikely to be correct and the Homsy sign is probably an artefact seen in patients with impeded urinary drainage. Computer modelling of individual renograms is feasible and can provide useful insights into the pathophysiology of renal uptake and drainage.

Standardization of the renogram technique for investigating the dilated upper urinary tract and assessing the results of surgery

OBJECTIVE

To recommend a standard technique for the renographic evaluation of the dilated upper urinary tract, and for evaluating the results of surgery.

METHODS

This review is an update of the previously recommended consensus report of the 9th International Symposium of Radionuclides in Nephrourology.

RESULTS

State-of-the-art recommendations are detailed for standardizing common radionuclide investigations.

CONCLUSIONS

Where open, laparoscopic or endourological techniques for treating pelvi-ureteric junction obstruction are under study, results can only be compared by standardizing the investigational techniques. The guidelines produced here are recommended for this purpose.

Ureteropelvic Junction Obstruction: Some new Acquisitions about Etiology, Pathophysiology and Diagnostics

The etiopathogenesis of uretero-pelvic junction obstruction (UPJO) has been the subject of many speculations and it remains, in some ways, a debatable matter. Some recently reported thorough research refer to neuro-mediated pathogenetic mechanisms rather than (or together with) myogenic ones.

Advances in US, radioisotopic functional imaging, CT and RM contribute to differentiate the obstructive conditions from the non-obstructive ones and to afford today a better assessment of renal functional damage. Particularly, diuretic renography is a non-invasive test for characterization of the renal functional abnormalities resulting from UPJO. Helical CT with angiography is a useful technique for identification of crossing vessels (pyelo-vascular tangle) which can be used for the pre-surgical planning of endopyelotomy. Endoluminal ultrasonography can be used to guide the position of the incision for endopyelotomy (US-guided endopyelotomy).

Laboratory examinations are important to determine the overall renal function (serum creatinine, acid-base balance, serum electrolytes, etc.), urinary MCP-1 and NAG (markers of tubular damage), and to rule out urinary tract infections.

The management of UPJO (watchful waiting; either open or laparoscopic dismembered pyeloplasty; endoluminal procedures) is greatly influenced by the diagnostic evaluation.

The paper aims to outline the advances in both physiopathology and diagnostics of UPJO on the basis of a review of the literature.

Antenatally detected, unilateral dilatation of the renal pelvis: a critical review. 2. postnatal non-operative treatment--long-term hazards, urgent research

BACKGROUND

Even after two decades, there is still much discussion about the postnatal treatment of antenatally detected, isolated pelvic dilatation (consistent with pyelo-ureteral junction obstruction). A recent review concluded that non-operative expectancy seemed safe - even after 17 years in certain cases. However, the final outcome, i.e. when these children have reached old age, is remote.

OBJECTIVE

This review takes stock of conceivable long-term hazards and evaluates prognosticating tools, and offers a basis for protocols for future randomized controlled trials. Long-term hazards: Symptoms in this context are generally considered ominous. In the antenatally detected cases, i.e. primarily asymptomatic, symptoms have been reported but they were not necessarily combined with renal damage. Hydronephroses, so mild, that they are written off, may deteriorate later on (indeed insidiously), although probably seldom. Urgent research: A predictor of outcome is eagerly pursued but hard to obtain, due to the difficulty in defining true obstruction in compliant systems such as the urinary one. Ordinary diagnostics offer no help, but there are promising innovations: constant pressure/flow assessment (flow necessary to keep a preset intrapelvic pressure), NAG/creatinine in pelvic urine, and TGFbeta-1 in voided urine. Renal microstructure, sometimes severely damaged early (which disagrees with the good results with expectancies) could possibly herald future deterioration.

CONCLUSION

Adverse developments should be meticulously documented and published swiftly, so policy can be changed if necessary, before it is too late. Cognizance of their existence, not necessarily frequency and statistics, is then first order. Efforts to design prognosticating tools has also high priority.

Recovery from release of ureteral obstruction in the rat: relationship to nephrogenesis

BACKGROUND

Obstructive nephropathy is a major cause of renal insufficiency in infants and children. Despite release of unilateral ureteral obstruction (UUO) in the first five days of life in the rat, renal growth is impaired, while glomerular filtration rate (GFR) is preserved at one month, but decreases markedly by one year. To test the hypothesis that renal recovery from UUO depends on the stage of nephrogenesis at the time of relief of obstruction, renal recovery from relief of five days UUO following completion of nephrogenesis (days 14 to 19) was compared with UUO during nephrogenesis (days 1 to 5).

METHODS

Rats underwent UUO or sham operation at one day of age, with relief five days later. In additional groups of neonatal rats, the operation was at 14 days, with relief at 19 days. Three months later, blood pressure, GFR, urine flow, sodium and potassium excretion, and kidney weight were measured. In addition, the number of glomeruli, glomerular maturation, glomerular diameter, tubular atrophy, and interstitial fibrosis were determined in each kidney. The effects of five-day UUO on number of glomeruli was determined also in adult rats one month following relief of obstruction.

RESULTS

Three months following relief of UUO during days 14 to 19, renal growth was decreased by 50%, compared to a 30% reduction following relief of UUO during days 1 to 5 (P < 0.05). The number of glomeruli was reduced by approximately 50% regardless of the timing of UUO, but glomerular size was reduced only in rats with UUO from days 14 to 19. Blood pressure and tubular atrophy were increased, and GFR, urine flow, sodium and potassium excretion were decreased in the postobstructed kidney of both neonatal groups. In the adult rat, the five-day UUO did not result in a decrease in the number of glomeruli.

CONCLUSIONS

In the period immediately following nephrogenesis, the kidney is particularly susceptible to long-term injury from temporary UUO. This suggests that a delay in relief of significant ureteral obstruction should be avoided if diagnosed in the perinatal or neonatal period.

[Role of scintigraphic tests in upper urinary tract dilatation in children]

The diuresis renography has an important place in the management of upper urinary tract dilatation in children. This non-aggressive and low irradiant exploration is very helpful to determine if hydronephrosis is obstructive or not and to evaluate the renal function impairment. The protocol of exam must be particularly rigorous and interpretation should take into account physiopathological factors that influence provocated diuresis. A well patient hydration and if necessary a bladder catheter are required. The MAG-3 is the radiopharmaceutical of choice especially in newborn and infants. The furosemide administration at 20 minutes after radiotracer injection is the most commonly used protocol and is generally sufficient to classify the urinary dilatation. Equivocal cases and symptomatic forms can benefit from a modified protocol in which furosemide is administered 15 minutes before radiotracer injection (F-15). False positive tests may result from a marked dilatation or renal function reduction. The place of diuresis renography in management of neonatal hydronephrosis is controversial, particularly because of the dynamic and evolving nature of this pathology.

Dismembered pyeloplasty followed by metachronous ureteropelvic junction obstruction in the contralateral kidney

Hydronephrosis due to congenital ureteropelvic junction obstruction (UPJO) is commonly diagnosed by antenatal sonography. We report the case of an infant who developed new-onset hydronephrosis in the right kidney following uneventful left-sided pyeloplasty for a congenital UPJO. The furosemide minus 15-minute diuretic renogram (F-15 DR) was used to confirm obstruction in the affected renal unit when standard diuretic renography was equivocal. The indications for surgery or observation as well as the role of the F-15 DR are discussed.

Urinary tract anomalies and dysfunctional voiding: a spectrum dictated by the influence of amniotic pressure upon fetal urodynamics

The etiologic basis of urinary tract anomalies and dysfunctional voiding largely remain unknown. However, the travel of urine from renal pelvis into the amniotic cavity under the pressures exerted by amniotic fluid satisfactorily explains the etiologic basis. Amniotic pressure is affected by the changes in maternal intraabdominal pressure. The intraabdominal pressure of the fetus is also dictated by the amniotic pressure. Amniotic pressure compresses the urethra throughout the length, and may increase both bladder leak point pressure and urethral resistance. Furthermore, the urine is propelled against amniotic pressure. These factors closely simulate outflow obstruction. Since the pressure within the bladder with minimal urine content reflects the intraabdominal pressure, intravesical pressure is also elevated during fetal life. Additionally, elevated intravesical pressures impair ureteral drainage. The compressive effect exerted by fetal intraabdominal pressure upon ureters, further elevate the pressure within the renal pelvis. While forwarding the urine against these pressures may result in anomalies of the urinary tract, the increased work load of the detrusor may act as a state of injury that forms the basis of dysfunctional voiding.

A prospective randomized trial comparing 2 diuresis renography techniques for evaluation of suspected upper urinary tract obstruction in children

PURPOSE

We compare the diagnostic impact of 2 diuresis renography techniques for evaluation of suspected upper urinary tract obstruction in children.

MATERIALS AND METHODS

A total of 72 children were randomly assigned to 1 of 2 standardized diuresis renography protocols. The protocols were identical, except for the time of furosemide (F) injection. In the F+20 scans furosemide was given 20 minutes after the 99mtechnetium pentetic acid radiopharmaceutical. With the modified F-15 scans furosemide was injected 15 minutes before renography. Hydration, bladder catheterization, urine output determination, radiopharmaceutical injection and scan acquisition were identical. Renography outcomes (obstructed, nonobstructed or equivocal) were analyzed for the investigated side(s) and for the contralateral side, which was used as a control in children with suspected unilateral obstruction. Chi-square test was used to compare the percentage of obstructed and nonobstructed scans of both protocols. Fisher's exact test was used to compare the nonobstructed scans and equivocal results of both protocols.

RESULTS

Of the 96 scans performed 8 were excluded because of technical problems. The remaining scans included 44 F+20 and 44 F-15. Of the 88 scans 10 were used to evaluate possible bilateral obstruction. A total of 48 boys and 24 girls were evaluated. Because 2 children had a solitary kidney each, the total number of renal units studied for outcome was 174. The F-15 scan showed 7 times more obstruction than the F+20 scan on the investigated side, and this difference was statistically significant. No obstruction was diagnosed on the contralateral side with either technique when used to investigate cases of suspected unilateral obstruction.

CONCLUSIONS

The timing of the furosemide injection (F-15 scan versus F+20) has a significant impact on the obstructive versus nonobstructive renography results when evaluating children with suspected upper urinary tract obstruction.

Provocative imaging. Diuretic renography

Diuretic renography remains the noninvasive functional study of choice in patients with hydronephrosis resulting from apparent UPJ obstruction. Meticulous attention to proper patient preparation, radiopharmaceutical selection, furosemide dosage and administration, and image interpretation and an awareness of potential pitfalls are essential for accurate diagnosis. For most patients, the F + 20 protocol is sufficient, however; the F-15 protocol allows clarification in cases of equivocal baseline F + 20 studies. Invasive antegrade techniques such as the Whitaker pressure/perfusion test are best reserved for patients in whom the diagnosis remains equivocal after diuretic renography, or in patients with massive hydronephrosis or renal insufficiency. New standardized protocol guidelines should help to ensure studies that are reproducible in different nuclear medicine laboratories.

The true clinical significance of renography in nephro-urology

Isotopic renography is a non-invasive technique used routinely by the clinician to provide information about kidney structure and function. Whilst there is no doubt of its value in the accurate measurement of glomerular filtration rate and in the detection of parenchymal abnormalities, its role in the diagnosis of renovascular disease (especially in patients with renal insufficiency), the exclusion of obstruction and the evaluation of the patient with either acute renal failure or renal transplant dysfunction remains unproven. In part, this reflects a failure to standardise protocols and rigorously evaluate diagnostic techniques. Recent developments in ultrasound, computerised X-ray tomography and nuclear magnetic resonance now present the clinician with rival techniques and emphasise the need for the clinical development of isotopic renography.

Prenatal hydronephrosis caused by aberrant renal vessels: a follow-up challenge. Reports of two cases

With routine use of obstetric ultrasonography, fetal low-grade hydronephrosis is commonly detected, but may resolve spontaneously after birth. Two cases are presented to illustrate that in some cases such findings can express intermittent hydronephrosis caused by aberrant renal vessels. Renal deterioration later in childhood may be a consequence.

Neonatal hydronephrosis--the controversy and the management

Neonatal hydronephrosis is being detected with increasing frequency. The majority of these cases have a tendency to resolve during infancy. Hydronephrosis is an anatomical entity that is not synonymous with obstruction. Review of the pathoembryology, the pathophysiology, the diagnostic techniques currently used and the natural history of hydronephrosis is given. The management and the controversies involved are discussed.

Renal nuclear medicine

The measurement of renal function has been a major field of interest in nuclear medicine. Many studies in the literature are still dedicated to this subject, with the aim of replacing the traditional urinary clearance methods with simpler and easier techniques. Simplified plasma clearance methods appear of sufficient accuracy to estimate global kidney function, except in very low function in which urinary clearance is still indicated. Gamma-camera methods have also been developed that, although of a lesser accuracy than the in vitro techniques, offer the important advantage of allowing renal imaging with the estimation of separate kidney function. Because of the intimate link between kidney function and structure, the diagnosis of nephrourological diseases has represented an important goal of nuclear medicine research. The functional information attainable with radionuclides is a valuable complement to the morphological information of imaging techniques such as x-ray computed tomography, ultrasonography, and magnetic resonance imaging. Recent contributions of nuclear medicine to the progress of clinical nephrology include the evaluation of renal function and the diagnostic work-up of renovascular hypertension, obstructive nephropathy, urinary tract infection, and renal transplantation.

"Well-tempered" diuresis renography: its historical development, physiological and technical pitfalls, and standardized technique protocol

Differentiating the various causes of hydronephrosis from that of obstruction can be very difficult. Diuretic renography has been adopted as a noninvasive clinical management tool to assist in this differentiation. However, the correlation of the results of diuresis renography, the Whitaker test, and the surgical results has only been between 40% and 85%. This is believed to be due to the many physiological factors and technical pitfalls of the technique. These include variable renal function, variable compliance of the collecting system, the effect of back pressure from a full bladder, the state of hydration, the choice of radiopharmaceutical, and the timing of the diuretic injection. Even the technique of measuring the clearance half-time (T 1/2) is controversial, with at least eight different methods defined. In order to diminish the effect of these variables, a standardized protocol for diuretic renography has been proposed by a consortium of members of the Society for Fetal Urology and the Pediatric Nuclear Medicine Club of the Society of Nuclear Medicine. These include a standardized hydration with a dilute glucose solution, bladder catheterization and measurement of urine output response, uniform radiopharmaceutical choice, and diuretic dose with specific timing of the diuretic injection. The various methods for T 1/2 calculation are illustrated, and various stereotypical renogram and diuresis response curves are offered as aids in the interpretation of the study. Diuresis renography is one of the most complex functional studies in nuclear medicine today. A thorough understanding of the physiological basis for diuresis renography and the pitfalls of the technique is required for its appropriate use in the management of patients suspected of urinary tract obstruction.