Obstructive nephropathy: comparison between parenchymal transit time index and frusemide diuresis

Renal cortical transit time in the evaluation of prenatally detected presumed pelvi ureteric junction like obstruction: A systematic review

Introduction

Differentiating nonobstructive from obstructive dilatation of the kidney is a clinical dilemma in prenatally detected hydronephrosis. Many radionuclide renogram parameters have been used to differentiate obstructed from non-obstructed units, including cortical transit time (CTT). We evaluate the role of CTT in identifying obstruction through a systematic review.

Methods

A literature search of the MEDLINE, MEDLINE In-Process, and MEDLINE Epub Ahead of Print, EMBASE, Google scholar, Pub Med, and Cochrane Library was done using key words - radionuclide renogram, CTT, parenchymal transit time, cortical transit, renography to identify articles on the subject. The identified articles were assessed for appropriateness and reviewed.

Results

The initial search yielded a total of 1583 articles, after adding the articles from references and applying the inclusion and exclusion criteria a total of 28 articles were selected. CTT showed good inter observer agreement in identifying obstruction. The use of CTT as a single parameter for determining the need for surgery and to identify those kidneys which will have functional improvement after surgery has been evaluated and has been found to be useful. CTT is best used in conjunction with ultrasonography to make clinical decisions.

Conclusion

The commonly used visual method of estimating the CTT, is a promising parameter for the evaluation of prenatally detected pelviureteric junction obstruction. Further well-designed multicenter prospective studies are needed to establish it as the most specific parameter to differentiate obstructive from nonobstructive dilatation of the pelvicalyceal system.

Predictors of Renal Functional Improvement After Pyeloplasty in Ureteropelvic Junction Obstruction: Clinical Value of Visually Assessed Renal Tissue Tracer Transit in 99mTc-mercaptoacetyltriglycine Renography

OBJECTIVE

To determine the clinical value of visually assessed renal tissue transit time (TTT) in ^99mTc-mercaptoacetyltriglycine (^99mTc-MAG3) renography for patients undergoing pyeloplasty.

MATERIALS AND METHODS

Medical records of 164 patients who underwent dismembered pyeloplasty were retrospectively reviewed. Baseline and postoperative renal ultrasonography and ^99mTc-MAG3 renography were performed. Two urologists blinded to clinical data evaluated the renography and classified TTT as timely or delayed based on visualization of the tracer in the kidney pelvis between 2 and 10 minutes. Renal functional change after pyeloplasty was compared between patients in the timely and delayed groups.

RESULTS

A total of 126 patients (median age, 9 months) were evaluated after excluding patients with bilateral ureteropelvic junction obstruction, a single functioning kidney, duplicated ureter, or <3 months of follow-up. There were no differences between 89 patients with timely TTT and 37 patients with delayed TTT in mean preoperative hydronephrosis grade (3.7 vs 3.8) and pelvic diameter (3.1 cm vs 3.4 cm). Although the pre- and postoperative mean values of differential renal function (DRF) were significantly higher in the timely group than in the delayed group (47.2% vs 38.3% and 47.9% vs 44.6%), DRF change was greater in the delayed group (6.3% vs 0.6%). In multivariate analysis, delayed TTT was the only significant predictor of >5% improvement in renal function after pyeloplasty.

CONCLUSION

Delayed TTT in ^99mTc-MAG3 renography was a significant predictor of renal functional improvement after pyeloplasty in ureteropelvic junction obstruction. Because substantial improvement of renal function is anticipated, we recommend immediate pyeloplasty in patients with delayed TTT and decreased DRF.

Interobserver agreement on cortical tracer transit in 99mTc-MAG3 renography applied to congenital hydronephrosis

OBJECTIVE

This study aims to evaluate interobserver agreement on visual analysis of technetium-99m mercaptoacetyltriglycine (Tc-MAG3) renal tissue transit used for the evaluation of antenatal hydronephrosis.

MATERIALS AND METHODS

Thirty-eight Tc-MAG3 diuretic renograms were retrospectively collected between 1 and 31 December 2015. The 1-min reframed images were presented to four nuclear medicine consultants and to two nuclear medicine residents, one in the first year of the training program and the others in their fourth and final year. These observers were asked to classify the radiotracer cortical transit (normal/delayed) based solely on visual assessment of the images. For the interobserver agreement, modified Fleiss' kappa (κ) analysis for multiple raters was carried out. For both groups, percentages of agreement were also calculated.

RESULTS

A total of 69 kidneys were evaluated. All four nuclear medicine consultants agreed on the classification of 88.4% of the kidneys. When the agreement of at least three of the four observers was considered, the percentage of agreement reached 98.6%. The two nuclear medicine residents agreed on the classification of 69.6% of the kidneys. The modified Fleiss' κ-value was 0.88 (95% confidence interval: 0.79-0.95) for the group of nuclear medicine consultants, indicating almost perfect agreement. For the residents, it was 0.39 (95% confidence interval: 0.16-0.59), suggesting fair agreement.

CONCLUSION

Our results seem to indicate that there is an almost perfect agreement in the qualitative identification of delayed cortical transit among physicians with experience at observing renographic images.

Diuretic renography in hydronephrosis: delayed tissue tracer transit accompanies both functional decline and tissue reorganization

The significance of delayed tissue tracer transit (TTT) of (99m)Tc-mercaptoacetyltriglycine ((99m)Tc-MAG3) has not been systematically evaluated in hydronephrosis. We sought to demonstrate that delayed TTT accompanies both functional decline and histomorphologic restructuring.

METHODS

Twenty 2- to 3-mo-old piglets with surgically induced partial unilateral ureteral stenosis were examined with magnetic resonance urography (MRU) to evaluate morphology and with (99m)Tc-MAG3 diuretic renography (DR) to determine single-kidney function (SKF), evaluate the response to furosemide stimulation (RFS), and assess TTT. All animals had DR and MRU before and after surgery and a third DR after surgery. Piglets were sacrificed after the final DR for renal histology. A total histologic score (THS) was generated.

RESULTS

Preoperative DR demonstrated nonobstructive RFS, timely TTT, and balanced SKF in all 20 kidneys. After ureteral ligature, MRU demonstrated pelvic dilatation in all piglets. The postoperative DRs revealed 12 kidneys with delayed TTT in one or both follow-ups. In these 12 kidneys, the SKF declined from 51% +/- 4% to 18% +/- 14%, and the THS was 9.0 +/- 4.0. Three kidneys always had timely TTT, balanced SKF, and a THS of 1.8 +/- 0.3. The contralateral, nonoperated kidneys had timely TTT and a THS of 1.2 +/- 0.9. Postoperative scintigrams showed that 3 of 8 kidneys (38%) with an obstructive RFS had timely TTT, which demonstrates that TTT and RFS are not equivalent.

CONCLUSION

In hydronephrosis, a delayed TTT of (99m)Tc-MAG3 accompanies both functional decline and histomorphologic restructuring in obstruction. According to the literature, a delayed TTT is determined by the filtration fraction of the kidneys and appears to identify an obstruction-mediated upregulated renin-angiotensin system.

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.

Multi-detector row CT urography of normal urinary collecting system: furosemide versus saline as adjunct to contrast medium

PURPOSE

To retrospectively evaluate whether intravenous furosemide, either alone or in addition to intravenous saline, improved depiction of the normal urinary collecting system at multi-detector row computed tomographic (CT) urography.

MATERIALS AND METHODS

Institutional review board approval for review of patient images and medical records was obtained; informed consent was not required for this HIPAA-compliant study. Excretory phase images from multi-detector row CT urography in 87 patients (44 women, 43 men; age range, 21-83 years; mean, 53 years) were reviewed. Examinations were performed with, in addition to intravenous contrast medium, 250 mL of intravenous normal saline alone (n = 35), both 250 mL of normal saline and 10 mg of intravenous furosemide (n = 26), or 10 mg of furosemide alone (n = 26). Three readers, blinded to the imaging technique used, individually assigned opacification scores to each of six urinary collecting system segments. Urinary distention was assessed by one reader by measuring transverse widths of the proximal, middle, and distal ureteral segments. Mean opacification scores for each segment and mean ureteral width measurements for each technique were compared by using the Student t test.

RESULTS

Mean opacification scores achieved with furosemide were significantly higher than those achieved with saline for the middle (P </= .008) and distal (P < .001) ureteral segments. Similarly, mean ureteral widths were significantly higher with furosemide than with saline for the middle (P </= .04) and distal segments (P = .01). There was no overall benefit of administering both saline and furosemide.

CONCLUSION

To optimize opacification and distention of the normal urinary collecting system, contrast material-enhanced multi-detector row CT urography may be supplemented with intravenous furosemide alone.

The estimation of renal transit using renography--our opinion

Renal transit estimation using renography has been employed for decades. A variety of methods have been developed, ranging from simple quantitative to more sophisticated techniques. In this review, the methods are discussed in perspective of their advantages and drawbacks. Finally, the most robust methods for estimation of renal transit are proposed.

Renal transit time with MR urography in children

PURPOSE

To prospectively evaluate use of dynamic contrast material-enhanced magnetic resonance (MR) urography for measurement of renal transit time (RTT) of a contrast agent through the kidney and collecting system so as to identify obstructive uropathy in children.

MATERIALS AND METHODS

One hundred twenty-six children suspected of having hydronephrosis were hydrated prior to undergoing both conventional and dynamic contrast-enhanced MR urography of the kidneys and urinary tract. A three-dimensional sequence was used to track passage of contrast agent through the kidneys. Time between the appearance of contrast material in the kidney and its appearance in the ureter at or below the level of the lower pole of the kidney was defined as RTT. Bland-Altman plots were used to quantify intra- and interobserver performance. In 30 children, a nuclear medicine renogram was also obtained, and the half-life of renal signal decay after furosemide administration was derived and compared with the MR imaging RTT by using receiver operating characteristic curves.

RESULTS

On the basis of RTT, kidneys were classified as normal (RTT </= 245 seconds), equivocal (245 seconds > RTT </= 490 seconds), or obstructed (RTT > 490 seconds). Inter- and intraobserver agreement indicated that the technique is both robust and reproducible. Receiver operating characteristic analysis for comparison of results of MR imaging and diuretic renal scintigraphy showed good agreement between the modalities, with a mean area under the curve of 0.90.

CONCLUSION

When used in conjunction with morphologic images obtained in the same examination, RTT generally allowed normal kidneys to be differentiated from obstructed and partially obstructed kidneys.

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.

UK audit and analysis of quantitative parameters obtained from gamma camera renography

The purpose of this study was to perform an audit of quantitative values obtained from gamma camera renography in the UK. Ten patient image sequences representing normal and pathological renal function were obtained from archived studies and distributed to hospitals in the UK. Hospitals were asked to measure five parameters: relative function, renogram time-to-peak (left and right), and whole kidney mean transit time (left and right). Details of methodology, software used and operator experience were requested. This allowed the influence of operational factors on variations in reported values to be examined. A total of 180 responses from 81 hospitals were received. Values reported for the parameters, together with other details supplied, were entered into Excel and SPSS for statistical analysis. Histograms representing the distribution of values were produced for each parameter. The largest variations were found for mean transit time and occasionally for time-to-peak. The effect of factors was assessed using nonparametric statistical tests applied independently to each renogram. For all the parameters, the hospital, UK region, supplier, computer and software version influenced variations in the reported values. Algorithm and site of background region were influencing factors for relative function, the background subtraction method influenced time-to-peak, and curve smoothing influenced mean transit time.

Diagnosis of kidney transplant obstruction using Mag3 diuretic renography

Kidney transplant obstruction (KTO) following renal transplantation remains an important reversible cause of allograft dysfunction, requiring prompt diagnosis to prevent long-term graft damage. Although ultrasound can accurately diagnose renal transplant hydronephrosis, it cannot be used to assess its functional significance. We prospectively assessed the utility of technetium-99m mercaptoacetyltriglycine (Tc99m MAG3) diuretic renography for the diagnosis of allograft KTO, using standard visual and quantitative parameters, as well as calculated renal output efficiency (OE), which has been postulated to improve diagnostic yield. From a cohort of 45 renal transplant patients, two subgroups were formed. The first group of transplant recipients (n = 21) with stable function and no obstruction was used to derive normal values for Tc99m MAG3 scans. A second group of transplant recipients with acute renal dysfunction in whom KTO was clinically suspected was used to test the diagnostic utility of these derived values (n = 43 scans). KTO was diagnosed independently of the MAG3 scans by a fall in the serum creatinine in response to renal pelvis urinary drainage. OE in 12 renal allografts with KTO was significantly reduced compared with 31 Tc99m MAG3 scans without KTO (59.6 +/- 18.9 vs. 81.6 +/- 5.4%, p < 0.001). In KTO, the mean time of isotope appearance in the bladder (time to bladder [TTB]) was extended compared with unobstructed allografts (7.9 +/- 4.1 vs. 3.6 +/- 1.5 min, p < 0.001). Measurement of OE significantly improved the accuracy of diuretic MAG3 renography in the diagnosis of renal allograft KTO, especially when supplemented by the TTB, parenchymal transit time and shape of the renogram curve. Ureteric obstruction of the kidney transplant can be diagnosed with an OE reduced to < 75% (sensitivity 92%, specificity 87%) and confirmed by isotope hold-up in the pelvicalyceal system. A normal or slowly declining renogram curve effectively excluded KTO (sensitivity of 96%, negative predictive value of 84%). A parenchymal transit time of > 5 min and a TTB of > 7 min both yielded a sensitvity of 92% and a specificity of 81%. In conclusion, MAG3 renography is a clinically useful investigation for the diagnosis of KTO.

Renal transit time of 99mTc-diethylenetriaminepentacetic acid (DTPA) in normal dogs

The transit time of 99mTc-DTPA in the kidneys is an indicator of renal function that has been used in humans for the diagnosis of renal obstruction, renal artery stenosis, and rejection of renal transplants. Its use, however, has not been reported in the dog. 99mTc-DTPA scintigraphy was performed in 8 normal dogs and the time of peak was calculated as the time between the injection and the maximum renal uptake. Deconvolution analysis was performed to estimate the renal retention function using 3 different techniques, i.e. the matrix method, the fast Fourier transform (FFT) method, and the constrained least square method. The parenchymal and whole kidney mean transit times were calculated from the deconvolved renogram using alternatively the thorax and the aorta as the input function. Average mean transit times ranged from 137 to 184 seconds. Parenchymal mean transit time was significantly shorter than whole kidney mean transit time (P<0.03). Mean transit time calculated with the thorax as the input function was significantly longer than mean transit time calculated with the aorta (P<0.001). No differences were observed between mean transit time calculated with the matrix, FFT and constrained least square methods.

Report of the Radionuclides in Nephrourology Committee for evaluation of transplanted kidney (review of techniques)

Comprehensive evaluation of renal transplants has been important in differential diagnosis of medical and surgical complications in the early post-transplantation period and in the long-term follow-up. If performed well, it yields excellent functional and good anatomic information about the graft that can be effectively used in the patient. That includes selection of patients for biopsy and for various drug regimens. This is true especially in patients with anuric acute tubular necrosis (ATN) and in patients with developing chronic rejection. Improving indices of renal function (effective renal plasma flow, uptake of tubular tracers) can indicate resolution of tubular injury (ATN) while there is still no improvement in plasma creatinine. In patients with chronic rejection, plasma creatinine increases only after approximately 30% of renal function is lost due to graft fibrosis. Early recognition of this condition could permit treatment and delay of retransplantation. The protocol recommended at the Copenhagen meeting includes a flow study, scintigram of the kidneys, prevoid and postvoid bladder image, injection site image (quality control), time/activity curves of the graft and bladder, and quantitative data of perfusion, function, and tracer transit. The flow study obtained during the initial transit of the bolus through the graft could be performed either with 99mTc mercaptoacetyltriglycine, or 99mTc diethylenetriaminepentaacetate (DTPA). Quantitative analysis of perfusion facilitates interpretation of the study during the early post-transplantation period. ATN, common in cadaver transplants, typically shows adequate perfusion. The function phase should include images and time/activity curves. Images alone are insufficient. Quantitative data such as clearance or other indices of function and indices of tracer transit are essential for correct interpretation of the results. Normal images and normal graft function reliably exclude clinically important complications. A single scintigram demonstrating prolonged tracer transit with decreased function cannot separate acute rejection and ATN. On serial studies, decline in function and poor perfusion are indicative of acute rejection. A normally appearing scintigram without cortical retention, but with low function, is consistent with chronic rejection. Pharmacological intervention to exclude obstruction (diuretic renogram) or hemodynamically significant renal artery stenosis (angiotensin converting enzyme challenge) should be used whenever indicated.

A control systems approach for the simulation of renal dynamic software phantoms for nuclear medicine

For renal dynamic studies, the COST B2 hybrid phantom is an example of an artificially created software phantom. Although this phantom is useful, it is not possible to implement the phantom in a self-consistent fashion to produce, for example, a collection of tracer in the bladder which is related to the flow from the kidneys. In this study control systems are used to provide a self-consistent model. A feed-forward control system was designed for the transport of DTPA in the human body using SIMULINK. The system is based on a three-compartment model described by a set of differential equations with flow rates which may be set by the operator. The differential uptake in the kidneys may also be specified, while the flow of tracer through the renal parenchyma and collecting system of each kidney is determined using two-parameter retention functions. Curves corresponding to normal or pathological conditions may be simulated for plasma, parenchyma, collecting system and bladder by appropriate selection of parameters. The system is user-friendly and can be used to simulate almost all conditions seen in patient studies. The next stage of using this information to design dynamic image simulations is in progress.

Clinical renography: 25 years on

Renal radionuclide studies have progressed from the probe to the gamma camera and sophisticated hard- and software, yet the principles remain the same. Many of the problems were identified and the solutions proposed 25 years ago, but these solutions are still not applied in practice. This survey charts the evolution of renography during this period.

Technetium-99m-L,L-ethylenedicysteine scintigraphy in patients with renal disorders

Technetium-99m-L,L-ethylenedicysteine (99mTc-L,L-EC), a new renal imaging agent, was introduced as an alternative to 99mTc-mercaptoacetyltriglycine (MAG3). This radiopharmaceutical can be easily labelled at room temperature and has high radiochemical purity and long stability. The aim of this study was to gain clinical experience in using 99mTc-L,L-EC in normal volunteers and patients. The clearance of this radiopharmaceutical was compared with that of iodine-131 ortho-iodohippurate (OIH) in five healthy volunteers. In addition, conventional renogram and whole-body distribution of 99mTc-L,L-EC (40 min and 3 h post-injection) were evaluated in these subjects. Subsequently, ten patients with suspected obstructive nephropathy, four with renovascular disorders and two in acute renal failure were imaged. In five patients with impaired renal function both 99mTc-MAG3 and 99mTc-L,L-EC studies were performed. In each case the scintigraphic images and time/activity curves were evaluated and various semiquantitative parameters calculated and compared. No adverse effects were noted during and after 99mTc-L,L-EC scintigraphy. The mean clearance values for 99mTc-L,L-EC and 131I-OIH in volunteers were 504 and 663 ml/min respectively. The total plasma clearance of 99mTc-L,L-EC was about 75.8% of the 131I-OIH value. In volunteers the parenchymal transit time index, whole kidney transit time index and mean parenchymal transit time for 99mTc-L,L-EC were 63 s, 124 s and 175 s respectively. The mean time to peak activity was 235 s and the time from peak to 50% of peak activity was 402 s.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

An anatomical and physiological model of the renal parenchyma--model development and parametric identification

Renal function is often characterized by the activity/time curves obtained by imaging the aorta and kidney. Non-parametric deconvolution of the activity/time curves is clinically useful as a diagnostic tool in determining renal transit times. Typically non-parametric deconvolution is performed using a technique that does not require a priori information, e.g. matrix-based and Fourier-transform methods. Using data filtering and conservation of mass constraints, non-parametric deconvolution continues to exhibit noise in the deconvolved curves. This noise hampers the identification of renal transit times. Given the shortcomings of non-parametric deconvolution, a parametric model of the renal response has been developed. Our model is shown to be anatomically and physiologically plausible. In this paper, the parametric model structure is used, in conjunction with experimental data, to estimate renal physiological parameters. These parameters include the filtration fraction, renal blood transit time and urine transit times. The model parameters are then related to the minimum transit time (MinTT), mean transit time (MTT), glomerular filtration rate (GFR) and parenchymal transit time index (PTTI). As deconvolution techniques often produce negative artifacts, Fine et al developed a technique to determine an aorta background to minimize this effect. In this paper this work is extended to determine a reasonable renal background from aorta activity/time curves. Non-parametric deconvolution is used to provide initial estimates of model parameters. The model is then fitted to twelve healthy background-corrected kidneys by an iterative parameter-estimation technique. The normal values correspond to those reported in the literature. These normal values are then used to identify renal arterial stenosis in two renal hypertensive patients. The results suggest that parametric identification, based on a renal-retention-function model, may provide additional anatomical and physiological information that is not provided by conventional non-parametric methods.

Measurement of renal transit of gadopentetate dimeglumine with echo-planar MR imaging

Times of peak gadolinium concentration ([Gd]) after intravenous (IV) and left ventricular (LV) bolus injection of gadopentetate dimeglumine were determined in renal cortex and medulla in normal rabbits and in rabbits after saline load (overhydration) or hemorrhage (dehydration). Magnetic resonance images were obtained with echo-planar inversion-recovery sequences, and signal intensity-versus-time curves in cortical and medullary regions of interest were converted to [Gd]-versus-time curves. Cortical perfusion measured with microspheres demonstrated that the three physiologic states were significantly different. There were three separate [Gd] peaks in both the cortex and medulla as the bolus moved from one anatomic compartment to the next. The first cortical peak occurred sooner after LV than after IV bolus injection (P < .05) and later in dehydrated than in normal and overhydrated rabbits (P < .05). The first medullary peak always followed the first cortical peak by about 6-10 seconds and mirrored the cortical patterns. The second and third cortical peaks were consistent with proximal and distal tubular transit. These peaks similarly showed faster response to LV than IV injection and were delayed by hemorrhage. The authors conclude that quantitative physiologic information can be obtained with dynamic contrast-enhanced MR imaging of the kidney.

Is retrograde ureterography indicated in pelviureteric junction obstruction?

The role of retrograde ureterography in the management of pelviureteric junction (PUJ) obstruction remains controversial and it has recently been reiterated that visualisation of the entire ureter on the affected side is mandatory owing to the high incidence of other ureteric abnormalities. In a review of 119 consecutive adult pyeloplasties carried out over a 9-year period, only 2 ureteric abnormalities were found in association with PUJ obstruction (duplex ureter/3-cm proximal stricture). Other anatomical abnormalities included aberrant vessels, fascial bands and renal anomalies. Most secondary abnormalities were undiagnosed prior to surgery and all were easily dealt with per-operatively.

The F-15 diuresis renogram in suspected obstruction of the upper urinary tract

The results are presented of the first long-term follow-up study of patients with suspected obstruction of the upper urinary tract investigated by a modified form of diuresis renography (F - 15 renography). The incidence of equivocal results from diuresis renography is significantly reduced by the use of the F - 15 renogram. F - 15 renography provides a reliable assessment of the upper urinary tract in patients with suspected obstruction and is recommended in the investigation of equivocal upper urinary tract dilatation.

Nuclear medicine

Images

Renal parenchymal function evaluated by scintillation camera renography before and after pyeloplasty for hydronephrosis

Scintillation camera renography with Tc-DTPA was performed before and after pyeloplasty on 16 kidneys with urographic signs of pelviureteric obstruction causing hydronephrosis. Regional parenchymal renograms were generated, and the passage of Tc-DTPA through the parenchyma was measured and correlated to the change in separate glomerular filtration rate. Preoperative parenchymal passage of DTPA was significantly slower (p = 0.02) in kidneys with improved glomerular filtration rate after pyeloplasty than in those without such improvement. Postoperative passage of DTPA in parenchyma was almost identical with that in a reference series. This method seems to be clinically useful for evaluating cases of hydronephrosis and for predicting the outcome of pyeloplasty.

A clinical application of iodine quantitation using digital fluorography

A preliminary clinical study of 20 patients is described in which a method of iodine quantitation in vitro using digital fluoroscopy was applied to the intravenous urogram. It was possible to quantitate iodine levels, in terms of mass thickness, in both the renal parenchyma and collecting system in 38 of 40 kidneys studied (20 patients). In the two kidneys on which measurements could not be made, the cause of failure was subtraction artefact due to movement of bowel gas, compounded in one case by poor renal opacification. The variations of iodine mass thickness against time were plotted and their forms were similar to dynamic computed tomography and magnetic resonance imaging studies of transplanted kidneys. Potential clinical applications of this method, in particular the functional assessment of the dilated upper urinary tract, are suggested based on its ability to offer quantitative information in addition to anatomical images.

99mTc DTPA diuretic renography in the evaluation of surgery in chronic schistosomal and non-schistosomal obstructive uropathy

The selection of patients with chronic obstructive uropathy for surgery is difficult because of problems in identifying true obstruction in a grossly dilated urinary tract. This is especially so in schistosomal (bilharzial) obstructive uropathy. A prospective study of 90 patients (68 with chronic schistosomal and 22 with non-bilharzial obstructive uropathy) was carried out. All patients underwent pre-operative and post-operative radionuclide 99mTc DTPA diuretic renography (RDR). The aims were to assess the value of RDR in the pre- and post-operative management of these patients and whether it could predict the outcome of surgery. Distinctive renogram patterns were identified in patients who required surgical management. These were found useful in monitoring the results and in predicting the outcome of surgery.

Clinical experience with 99mTc-MAG3, mercaptoacetyltriglycine, and a comparison with 99mTc-DTPA

The preparation, application and clinical usage of 99mTc-mercaptoacetyltriglycine, MAG3, a tubular secreted compound, is described in the first 225 patients in a phase III study. Image quality, relative renal function, and renal transit times were compared with a 4 fold greater administered activity of 99mTc-DTPA in 11 patients. Correlation coefficients of 0.94 for relative function, 0.83 for parenchymal transit time index and 0.82 for whole kidney transit time index were found. Frusemide responses were similar. 99mTc-MAG3 is an efficacious radiopharmaceutical for routine renal radionuclide studies, giving excellent image quality in patients with hypertension, poor renal function, obstructive nephropathy or a renal transplant.

Pelviureteric junction obstruction. The value of a post-micturition view in 99mTc DTPA diuretic renography

Eighty-one 99mTc DTPA renograms were performed in 31 children who had previously undergone pyeloplasty for pelviureteric junction obstruction (PUJ). A post-micturition image following a diuretic stimulus excluded obstruction in 50% of the patients in whom the frusemide T75 was abnormally prolonged beyond 10 min. Evaluating the 99mTc DTPA renogram and the response to a diuretic without both changing the patient's position and ensuring an empty bladder may lead to incorrect diagnosis of PUJ obstruction.