The time factor in the development of sterile renal scarring following high-pressure vesicoureteral reflux

Why are pediatric urologists unable to predict renal deterioration using urodynamics? A focused narrative review of the shortcomings of the literature

In this focused narrative review we set out to review the current literature addressing the utilization of UDS in patients with spina bifida (SB). We specifically analyzed 6 urodynamic parameters and their roles as predictors of upper tract deterioration in pediatric SB patients. The material available did not allow a systematic analysis or the usage of metanalysis methodology, due to the predominance of small retrospective cohorts, and high heterogeneity. We identified 10 retrospective chart reviews that met our study criteria. The results of each of these papers, as well as other studies deemed relevant to the discussion, are included in our narrative review of the literature. We summarize the current literature, offer explanations for divergences in opinion, and identify future research directions and emerging solutions with a focus on machine learning.

Intrarenal reflux in primary vesicoureteral reflux

OBJECTIVES

To elucidate the significance of intrarenal reflux.

METHODS

We retrospectively analyzed 276 patients (age <5 years) with grade III to V vesicoureteral reflux. They were divided into two groups: 55 patients with intrarenal reflux and 221 patients without intrarenal reflux (control group). All patients received low-dose antibiotic prophylaxis.

RESULTS

The most common initial presentation in both groups was febrile urinary tract infection. On dimercaptosuccinic acid scan, the rate of decreased differential renal function (<40%) was significantly higher in the intrarenal reflux group than in the control group (51% vs 33%, P < 0.05). Breakthrough urinary tract infections were observed in 26 patients (47%) in the intrarenal reflux group and 61 patients (28%) in the control group (P < 0.01). There was no statistically significant difference regarding spontaneous resolution of reflux, which occurred in nine patients (16%) in the intrarenal reflux group and 32 patients (14%) in the control group. Surgical treatment was selected more often in the intrarenal reflux group (P < 0.05) because of the high incidence of breakthrough urinary tract infection.

CONCLUSIONS

The rate of spontaneous resolution of high-grade vesicoureteral reflux is similar between patients with and without intrarenal reflux. However, those with intrarenal reflux present are more likely to present a decreased differential renal function and breakthrough urinary tract infections. Consequently, surgical treatment is considered more frequently in cases with intrarenal reflux. Although high-grade vesicoureteral reflux with intrarenal reflux can be treated conservatively, physicians should take into account the higher risk of breakthrough urinary tract infections.

The Clinical Significance of Intrarenal Reflux in Voiding Cystourethrography (VCUG)

Purpose

Intrarenal reflux (IRR) occurs in 3-10% of cases of total reflux and can lead to renal injury, which may eventually result in renal scarring. In this study, we evaluated the clinical importance of IRR detected by voiding cystourethrography and evaluated the relationship between IRR and renal scarring.

Materials and Methods

From January 2002 to May 2008, 50 patients who were diagnosed with vesicoureteral reflux (VUR) and showed IRR in voiding cystourethrography were enrolled. IRR was seen in 59 renal units in our enrolled patients. A ^99mTc 2,3-dimercaptosuccinic acid (DMSA) renal scan was performed after VUR was detected in all cases. Nine patients were conservatively treated with prophylactic antibiotics, whereas 41 patients received an anti-reflux operation. A follow-up renal scan was performed after 3 to 6 months to check for any changes in renal scarring.

Results

The average patient age was 9.2 months (range, 1-42 months). Forty-nine patients were male; only one patient was female. The mean duration until surgery was 2.9 months. Generally, the IRR sites corresponded to the sites of photon defects on DMSA renal scans (76.3%). Furthermore, the photon defects on IRR sites tended to progress to renal scarring (65.2%). The rate of change in scarring was lower in the surgery group (47.1%) than in the prophylactic antibiotic group (75%).

Conclusions

IRR sites and the sites of photon defects on DMSA renal scans showed a high correspondence, and these sites tended to progress to renal scarring. We suggest that VUR with IRR should be actively managed to decrease the chances of renal scarring.

A genome search for primary vesicoureteral reflux shows further evidence for genetic heterogeneity

Vesicoureteral reflux (VUR) is the most common disease of the urinary tract in children. In order to identify gene(s) involved in this complex disorder, we performed a genome-wide search in a selected sample of 31 patients with primary VUR from eight families originating from southern Italy. Sixteen additional families with 41 patients were included in a second stage. Nonparametric, affected-only linkage analysis identified four genomic areas on chromosomes 1, 3, and 4 (p < 0.05); the best result corresponded to the D3S3681-D3S1569 interval on chromosome 3 (nonparametric linkage score, NPL = 2.75, p = 0.008). This region was then saturated with 26 additional markers, tested in the complete group of 72 patients from 24 families (NPL = 2.01, p = 0.01). We identified a genomic area on 3q22.2-23, where 26 patients from six multiplex families shared overlapping haplotypes. However, we did not find evidence for a common ancestral haplotype. The region on chromosome 1 was delimited to 1p36.2-34.3 (D1S228-D1S255, max. NPL = 1.70, p = 0.03), after additional fine typing. Furthermore, on chromosome 22q11.22-12.3, patients from a single family showed excess allele sharing (NPL = 3.35, p = 0.015). Only the chromosome 3q region has been previously reported in the single genome-wide screening available for primary VUR. Our results suggest the presence of several novel loci for primary VUR, giving further evidence for the genetic heterogeneity of this disorder.

Therapy Insight: what nephrologists need to know about primary vesicoureteral reflux

Vesicoureteral reflux (VUR) is the abnormal, retrograde flow of urine from the bladder to the upper urinary tract. This disease affects about 1% of otherwise normal children, 30-50% of those who present with urinary tract infections, and approximately 10% with prenatally diagnosed hydronephrosis. Over the past 50 years, tremendous progress has been made in the diagnosis, treatment and management of VUR. The realization that VUR is probably a component of generalized dysfunction of the lower urinary tract (i.e. dysfunctional elimination syndrome) has further enhanced understanding of the disease. This Review covers basic pathogenesis, diagnosis, management, clinical presentation, and current controversies surrounding VUR.

Renal disease potentiates the injury caused by SWL

PURPOSE

The present study tested the hypothesis that renal disease potentiates the structural/functional changes induced by a clinical dose of shockwaves.

MATERIALS AND METHODS

Experimental pyelonephritis was induced in 6- to 8-week-old pigs before treatment with 2,000 shocks at 24 kV. These pigs were divided into two groups according to whether they were infected with a highly virulent (Group 1) or less virulent (Group 2) inoculation of E. coli. All animals were imaged by MR prior to SWL as a means of documenting the extent of pyelonephritis and immediately after SWL to examine the lesion produced by the shockwaves. The glomerular filtration rate (GFR), renal plasma flow (RPF) and para-aminohippurate (PAH) extraction were determined bilaterally on day 30 (Group 1) or day 80 (Group 2).

RESULTS

In group 2, urine flow and sodium excretion were reduced by 50% from baseline in the shocked kidneys at both 1 and 4 hours post-SWL. A sustained reduction in RPF through 4 hours post-SWL was noted in the shocked kidneys in Group 1, but RPF was significantly reduced only at the 1-hour determination in Group 2. Large, consistent reductions in GFR were evident at 1 and 4 hours post-SWL in shocked and unshocked kidneys of Group 2 and in the shocked kidneys of Group 1. No significant changes were noted in PAH extraction.

CONCLUSION

Acute pyelonephritis exaggerated the effect of a clinical dose of shockwaves on renal hemodynamics. This effect suggests that renal disease may be risk factor for SWL-induced injury.

99mtechnetium-dimercapto-succinic acid renal scanning and excretory urography in diagnosis of renal scars in children

We compared the ability of excretory urography (without tomography) and 99mtechnetium-dimercapto-succinic acid renal scanning to detect renal scars in 32 children with primary vesicoureteral reflux. These children did not have hydronephrosis, renal failure or urinary tract obstruction. In all cases both studies were conducted within a 10-month period. The findings from both modalities were in agreement for 51 of the 64 renal units evaluated (80 per cent). Evaluation of the excretory urogram indicated 6 cases of diffuse and 2 of focal scarring that were not detected by evaluation of the renal scan. The sensitivity of excretory urography to detect renal scars was 84 per cent and the specificity was 83 per cent. The 99mtechnetium-dimercapto-succinic acid renal scan showed 5 cases of focal renal scarring not detected by excretory urography. The sensitivity of the renal scan to detect renal scars was 77 per cent and the specificity was 75 per cent. We conclude that neither study alone could effectively replace the other for the detection of renal scars, and recommend that both be included in the initial evaluation and followup of patients with renal scars.

Vesicoureteral reflux and reflux nephropathy

Vesicoureteral reflux (VUR) is mainly a primary phenomenon due to incompetence of the ureterovesical junction, mostly affecting a pediatric population. During micturition cystourethrography (MCU) reflux into the kidney--intrarenal reflux (IRR)--is occasionally seen. In areas with IRR the kidney surface may subsequently be depressed and the papillae retracted (reflux nephropathy (RN]. VUR may lead to hypertension and/or end-stage renal failure. Most commonly, VUR is discovered during evaluation for urinary tract infection, but it may also be present in patients with hypertension, toxemia of pregnancy, chronic renal failure and proteinuria, and it may be found in siblings of patients with VUR. For the time being VUR is demonstrated at radiographic MCU, whereas RN is diagnosed by demonstration of focal scars and of abnormal parenchymal thickness at urography. In children with VUR and no abnormalities of calyces or parenchymal defects standardized measurement of the parenchymal thickness at three sites may identify kidneys which are likely to develop focal scars. Quantitation of focal scarring should be performed in connection with a measure of the overall kidney size. The occurrence of IRR is dependent of the papillary morphology, intrapelvic pressure and urine flow. There may be an important relationship between renal ischemia and IRR in producing a 'vicious circle of deleterious effects' which, combined with parenchymal extravasation, may lead to RN. Treatment of VUR includes medical and surgical management. Since renal scarring may occur in infancy, prevention should focus on infants and young children. Infants and young children with severe VUR may have normal urograms. Therefore a MCU should also be performed, preferably with the recommended standardized technique.