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

Is cortical transit time a parameter to prove relief of obstruction after pyeloplasty in antenatally diagnosed ureteropelvic junction obstruction

PURPOSE

The study aims to determine the possible improvement in cortical transit time (CTT) after surgery in infants with antenatally diagnosed ureteropelvic junction obstruction (UPJO), and investigate the correlation of CTT with preoperative renal function and parenchymal thickness.

PATIENTS AND METHODS

Medical charts of 32 antenatally diagnosed children with UPJO operated on between 2014 and 2021 were reviewed. Patients' demographics, preoperative and postoperative anteroposterior diameter (APD), parenchymal thickness (PT) ratio, differential renal function (DF), drainage patterns and CTT were compared to determine operative benefit. Preoperative CTT of each patient was also grouped as severely delayed (> 6 min) and moderately delayed (3-5 min) and compared. The correlation between the preoperative CTT and preoperative DF and PT ratio was investigated.

RESULTS

The median age of the patients was 8.8 months (1-24 months). The CTT (mean: 6.8 ± 3.0 min) was prolonged before surgery and was significantly improved (mean 4.6 ± 1.0 min) after the operation (p < 0.001). A significant negative correlation was detected between the CTT and preoperative DF and between the CTT and preoperative PT ratio. Preoperative DF was found significantly impaired in patients within the severely prolonged CTT group compared to those within the moderately prolonged CTT group. Significant improvement in DF was detected in patients in the severely prolonged CTT group after surgery.

CONCLUSION

CTT is a parameter to prove relief of obstruction in patients with antenatally diagnosed UPJO after surgery. CTT is negatively correlated with preoperative DF and PT ratio. Severely prolonged CTT may be considered to be an indication of early surgical intervention.

Nuclear medicine and pediatric nephro-urology: a long-lasting successful partnership

Congenital anomalies of the kidney and urinary tract, as well as urinary infections, are very frequent in children. After the clinical and laboratory evaluation, the first imaging procedure to be done is a renal and bladder ultrasound, but afterwards, a main contribution comes from nuclear medicine. Through minimally invasive and sedation-free procedures, nuclear medicine allows the evaluation of the functional anatomy of the urinary tract, and the quantification of renal function and drainage. If pediatric dosage cards provided by scientific societies are used, radiation exposure can also be low. In the pediatric conditions previously mentioned, nuclear medicine is used both for initial diagnosis and follow-up, mostly in cases of suspicion of ureteropelvic or ureterovesical junction syndromes, as well as vesicoureteral reflux or renal scars of febrile infectious episodes. Pediatric nephro-urology constitutes a significant workload of pediatric nuclear medicine departments. The following paragraphs are a revision of the renal radiopharmaceuticals, as well as the nuclear nephro-urology procedures - dynamic and static renal scintigraphy, and direct and indirect radionuclide cystography. A summary of the techniques, main indications, interpretation criteria and pitfalls will be provided. Some future directions for the field are also pointed out, among which the most relevant is the need for nuclear medicine professionals to use standardized protocols and integrate multidisciplinary teams with other pediatric and adult health professionals that manage these life-long pediatric pathologies, which are recognized as an important cause of adult chronic kidney disease.

Expression of tissue fibrosis genes in congenitally obstructed pyeloureteral junction and biomarkers of renal damage

Introduction

The aim of this study was to investigate the expression of fibrosis-related genes in obstructed ureteral tissue and determine its relationship with biomarkers of renal damage and preoperative renal scan findings.

Material and methods

In all cases, bladder urine and blood samples were collected preoperatively. They were analysed for serum cystatin C, urinary albumin, urinary beta 2 microglobulin, and urinary neutrophil gelatinase-associated lipocalin concentrations, as well as their concentrations standardised by urine creatinine. Pyeloureteral junction obstruction tissue specimens were frozen in liquid nitrogen upon harvesting. RNA was extracted from the samples using TRIzol reagent. qPCR was performed, and the relative expressions of TGFβ1, MMP1, TIMP1, PAI1, CTGF, and VEGFA in stenotic ureteral tissue were calculated. Spearman's rank correlation test was used to calculate the correlation between the relative expression of investigated genes, urine, and blood biomarkers of renal damage and preoperative renal scan findings.

Results

A total of 20 pyeloureteral junctions of 20 patients were harvested at the time of dismembered pyeloplasty. The median age of the patients at the time of the operation was 15.2 [9.07, 66.2] months. There was a significant negative correlation between urinary albumin concentration and relative TGFβ1 expression in pyeloureteral junction tissue (rho = -0.45, p = 0.047), as well as between uAlb and relative VEGFA expression (rho = -0.575, p = 0.008). No correlation with other urine biomarkers of renal damage or renal scan findings was found.

Conclusions

Expression of fibrosis-related genes in the obstructive tissue of the pyeloureteral junction have no direct correlation with biomarkers of renal damage.

Determination of tissue tracer transit of Technetium-99m-mercaptoacetyltriglycine diuretic renography in infants with suspected ureteropelvic junction obstruction - A multicenter prospective observational study

INTRODUCTION

There is an ongoing controversy regarding management of ureteropelvic junction obstruction in infants, with a shift towards a non-operative approach. However, precise predictors of outcome are lacking. Recent studies postulated a high prognostic value of Technetium-99m-mercaptoacetyltriglycine tissue tracer transit with regard to the development of an impaired differential renal function and its potential improvement following pyeloplasty.

OBJECTIVE

To evaluate the prognostic value of Technetium-99m-mercaptoacetyltriglycine tissue tracer transit for the occurrence of changes in differential renal function in infants with suspected unilateral ureteropelvic junction obstruction in a prospective observational multicenter study.

STUDY DESIGN

Infants below 3 months of age with a unilateral isolated hydronephrosis ≥ grade 3 received ultrasound and Technetium-99m-mercaptoacetyltriglycine diuretic renography at two different time points (timepoint 1 and timepoint 2). Data were analyzed at local centers and at the study center and were collected in an internet-based database system. Tissue tracer transit was determined for each diuretic renography, inter-observer variation for tissue tracer transit and standard parameters for judgement of differential renal function development were assessed.

RESULTS

Thirty-seven patients were analyzed. Median age was 11 weeks (7-15) at timepoint 1 and 26 weeks (19-33) at timepoint 2. A delayed tissue tracer transit at timepoint 1 was not associated with deterioration of differential renal function at timepoint 2 in both, locally (10/37 cases) and centrally (4/37) analyzed cases. However, sensitivity and specificity were poor. The intraclass correlation coefficient comparing local and central findings of tissue tracer transit and renal drainage demonstrated poor or fair agreement. Analysis of standard parameters for differential renal function development revealed a prognostic value only for the dichotomized anteroposterior renal pelvic diameter (APD, p = 0.03, 95%-CI 1.2-22.2).

DISCUSSION

Regarding the primary endpoint of our study, we could not confirm the hypothesis that delayed tissue tracer transit reliably predicts a subsequent decline in differential renal function in the cohort of patients studied. Whether the low age of the patients, technical problems in the correct assessment of tissue tracer transit by the investigator in early infancy, the study design, or the parameter itself played a role is debated.

CONCLUSION

In the presented setting tissue tracer transit was not useful as a predictive parameter for deterioration of differential renal function in infants with suspected unilateral ureteropelvic junction obstruction. Sensitivity and specificity of tissue tracer transit were not sufficient for risk stratification. Improved utility of tissue tracer transit as a marker might be achieved using a different study setting.

Management dilemma in pelvi-ureteric junction obstruction: is transit time the answer?

PURPOSE

Pelvi-ureteric junction obstruction (PUJO) is the leading cause for hydronephrosis in children. Diuretic renography used in the pre- and post-operative evaluation of pyeloplasty may not be reliable in predicting the outcome.

METHODS

A prospective study was conducted from October 2018 to November 2020, including all children with unilateral PUJO undergoing Pyeloplasty. Renal diuretic renography scans done in the pre and post operative periods were assessed for transit time. The time taken for the isotope to reach the renal pelvis was noted by a single observer as the transit time, from the dynamic frames of the diuretic renogram.

RESULTS

Of the 65 children, 74% were boys. The transit time (median) in the preoperative renography was 10 min, whereas the same was 4 min 45 s in the postoperative period, the decrease was statistically significant. On evaluation of transit time with ROC (receiver operating characteristics) curve, a cut-off of 4 min and 25 s was arrived at, which could identify the delayed drainage reliably.

CONCLUSION

Improvement in transit time is a reliable predictor of renal function improvement after pyeloplasty, comparing favorably in relation to split renal function.

Pediatric Nephro-Urology: Overview and Updates in Diuretic Renal Scans and Renal Cortical Scintigraphy

Nuclear medicine offers several diagnostic scans for the evaluation of congenital and acquired conditions of the kidneys and urinary track in children. Tc-99m-MAG 3 diuretic renal scans are most commonly used in the evaluation and follow up of urinary track dilatations. They provide functional information on the differential renal function and on drainage quality which is allows distinction between obstructed and non-obstructed kidneys and the need for surgical correction vs conservative management in kidneys with impaired drainage. Standardized imaging and processing protocols are essential for correct interpretation and for meaningful comparisons between follow up scans. Different approaches and conceptions led to some contradicting recommendations between SNMMI and EANM guidelines on diuretic renography in children which caused confusion and to the emergence of self-made institutional protocols. In Late 2018 the two societies published joint procedural guidelines on diuretic renography in infants and children which hopefully will end the confusion. Tc-99m DMSA scans provide important information about the function of the renal cortex allowing detection of acute pyelonephritis, renal scars dysplasia and ectopy as well as accurate determination of the differential renal function. They are commonly used in the evaluation of children with urinary tract infections and affect clinical management. A standardized imaging and processing protocol improves the diagnostic accuracy of these studies. SPECT or pinhole images should be a routine part of the imaging protocol. This is one of the recommendations in the new EANM and SNMMI procedural guidelines for renal cortical scintigraphy in children available online on the SNMMI website and is under publication. This article provides an overview on the clinical role of diuretic renography and cortical scintigraphy in children and describes the imaging protocols focusing on the new recommendations in the procedural guidelines.