The pathogenesis and management of renal scarring in children with vesicoureteric reflux and pyelonephritis

Patterns of damage observed on dimercaptosuccinic acid kidney scans and future risk of urinary tract infections or reduced kidney function

BACKGROUND

99mTc-Dimercaptosuccinic acid (DMSA) scan is highly accurate for assessing functional imaging of the kidney parenchyma. Kidney damage observed on DMSA scan is associated with future development of chronic kidney disease. This study aims to differentiate between different patterns of damage observed on DMSA scan and determine their predictive clinical value.

METHODS

We reviewed first-in-life DMSA scans performed ≥ 4 months post febrile urinary tract infection (UTI) or for suspected congenital kidney abnormalities, in a single referral center, from November 2007 to February 2011. DMSA uptake patterns were classified as normal; peripheral focal defects; diffuse inhomogeneity in tracer distribution within kidney parenchyma; and the combination of both patterns. Subsequent UTIs and estimated glomerular filtration rate (eGFR) were recorded at last follow-up.

RESULTS

One hundred five patients met inclusion criteria, and 57 (54%) were females. Median (IQR) age at scan was 2 (1.3, 5.1) years. Fourteen patients (13.3%) had focal defects, 29 (27.6%) had diffuse inhomogeneity and 9 (8.6%) had diffuse inhomogeneity with focal defects. After a mean follow-up period of 9.6 ± 3.3 years (available for 99 children), 29 (29%) patients experienced recurrent UTIs [median (IQR) episodes: 2 (1, 5)]. UTI tendency differed between groups (focal defects: 71.4%; diffuse inhomogeneity with focal defect: 44.4%; diffuse inhomogeneity only: 22.2%; normal scan: 18.3% p < 0.001). On multivariate analysis only the presence of focal defects predicted recurrent UTIs [OR (95%CI): 3.89 (1.2, 12.6), p = 0.024]. The percentage of patients with an eGFR < 75 ml/min/1.73 m2, was highest in patients with diffuse inhomogeneity with focal defects compared to patients with normal scans, focal defects only or diffuse inhomogeneity only (22% vs. 2%, 0% and 3.7% respectively, p = 0.032).

CONCLUSIONS

Focal defects on DMSA scan, likely representing post pyelonephritis scars, are a strong predictor of recurrent UTIs. Patients with diffuse inhomogeneity with focal defects on scan have the highest risk of reduced eGFR during follow-up.

Kidney involvement during the course of febrile urinary tract infection

Febrile urinary tract infections (fUTIs) are among the most common severe infections in the pediatric population, posing a significant risk to kidney health. The pathophysiology of fUTIs involves the direct bacterial invasion of kidney tissue, which triggers an inflammatory response. While this response is effective in eradicating the infection, it can also cause substantial kidney damage at multiple levels. In this review, we explore the various forms of kidney involvement in fUTIs, along with their clinical, radiological, and biochemical presentations. We also discuss the implications of these events for the long-term prognosis of kidney function. Understanding these manifestations can assist clinicians in making prompt diagnoses and initiating appropriate treatment to minimize complications such as sepsis, kidney scarring, and long-term kidney damage.

Prophylaxis Options in Children With a History of Recurrent Urinary Tract Infections: A Systematic Review

CONTEXT

The prevention of urinary tract infection recurrence (UTI) in children has been a challenge yet to be solved. Current practice in children with recurrent UTI (RUTI) suggests that antibiotic prophylaxis may prevent further episodes of UTI and future complications.

OBJECTIVE

To conduct a systematic review and meta-analysis of randomized controlled trials comparing prophylaxis options for the prevention of UTI and kidney scarring in children with a history of RUTI.

DATA SOURCES

We conducted a systematic literature search through major electronic databases (PubMed/Medline, Scopus and Cochrane Library) up to November 26th, 2023. Mean difference and SD were used for continuous outcomes and odds ratio for dichotomous outcomes.

STUDY SELECTION

Our meta-analysis included 3335 participants from 23 studies.

DATA EXTRACTION

The primary outcome was the effect of the different prophylaxis options on the incidence of symptomatic UTI in children with RUTI during prophylactic treatment.

RESULTS

Cranberry products and nitrofurantoin lead to lower odds of symptomatic UTI episodes during prophylaxis compared with the control group and control, trimethoprim-sulfamethoxazole, or trimethoprim groups accordingly. Nitrofurantoin may be the best option for UTI incidence reduction compared with all available documented interventions.

LIMITATIONS

No prophylaxis option has been shown to reduce kidney scarring.

CONCLUSIONS

Nitrofurantoin and cranberry products may decrease the incidence of symptomatic UTI episodes in pediatric patients with a history of RUTI. Future randomized control trials studying nonantibiotic prophylaxis options focusing on children with UTI recurrence and the risk for kidney scarring are needed to draw further conclusions.

The Intrarenal Reflux Diagnosed by Contrast-Enhanced Voiding Urosonography (ceVUS): A Reason for the Reclassification of Vesicoureteral Reflux and New Therapeutic Approach?

Vesicoureteral reflux (VUR) is defined as the urine backflow from the urinary bladder to the pyelo-caliceal system. In contrast, intrarenal reflux (IRR) is the backflow of urine from the renal calyces into the tubulointerstitial space. VURs, particularly those associated with IRR can result in reflux nephropathy when accompanied by urinary tract infection (UTI). The prevalence of IRR in patients with diagnosed VUR is 1-11% when using voiding cystourethrography (VCUG), while 11.9-61% when applying the contrast-enhanced voiding urosonography (ceVUS). The presence of IRR diagnosed by VCUG often correlates with parenchymal scars, when diagnosed by a 99mTc dimercaptosuccinic acid scan (DMSA scan), mostly in kidneys with high-grade VURs, and when diagnosed by ceVUS, it correlates with the wide spectrum of parenchymal changes on DMSA scan. The study performed by both ceVUS and DMSA scans showed IRRs associated with non-dilated VURs in 21% of all detected VURs. A significant difference regarding the existence of parenchymal damage was disclosed between the IRR-associated and IRR-non-associated VURs. A higher portion of parenchymal changes existed in the IRR-associated VURs, regardless of the VUR grade. That means that kidneys with IRR-associated VURs represent the high-risk group of VURs, which must be considered in the future classification of VURs. When using ceVUS, 62% of places where IRR was found were still unaffected by parenchymal changes. That was the basis for our recommendation of preventive use of long-term antibiotic prophylaxis until the IRR disappearance, regardless of the VUR grade. We propose a new classification of VURs using the ceVUS method, in which each VUR grade is subdivided based on the presence of an IRR.

The efficacy and safety of corticosteroids in pediatric kidney scar prevention after urinary tract infection: a systematic review and meta-analysis of randomized clinical trials

BACKGROUND

Acute pyelonephritis (APN) in pediatric patients may lead to kidney scarring and is one of the main causes of permanent kidney damage. The incidence of kidney scarring after one febrile urinary tract infection (UTI) is reported to range from 2.8 to 15%, with the percentage rising to 28.6% after ≥ 3 febrile UTIs. Corticosteroids may have a role in the reduction of kidney scar formation and urine cytokine levels. The possible benefit of adjuvant corticosteroid administration in the reduction of kidney scar formation in children with APN has been recently examined in randomized controlled trials (RCTs).

OBJECTIVES

The aim of this meta-analysis was to provide a summary of the current literature about the efficacy and safety of adjuvant corticosteroid administration in the reduction of kidney scar formation in children with APN.

DATA SOURCES

An extensive literature search through major databases (PubMed/MEDLINE and Scopus) was carried out for RCTs from inception until October 12, 2022, investigating the efficacy and safety of adjuvant corticosteroids in preventing kidney scarring in children with APN. A risk ratio with 95% CI was used for dichotomous outcomes.

RESULTS

In total, 5 RCTs with 918 pediatric patients with APN were included in the study. Adjuvant corticosteroid treatment revealed a statistically significant reduction in kidney scarring (95% CI 0.42-0.95, p = 0.03), without increasing the risk of adverse events like bacteremia, prolonged hospitalization, or recurrence of UTI.

LIMITATIONS

There were limitations regarding sample size (n = 498 children), different classes of corticosteroids (methylprednisolone or dexamethasone), different routes of corticosteroid administration (intravenous or oral), and different day courses (3-day or 4-day course).

CONCLUSIONS

Adjuvant corticosteroid administration seems to have a beneficial effect on kidney scar reduction in children with APN. Future studies should focus on the evaluation of the efficacy and safety of corticosteroids in kidney scarring reduction after APN to strengthen the results of our study. A higher resolution version of the Graphical abstract is available as Supplementary information.

The ureteral diameter ratio as a predictive factor in renal scarring associated with primary vesicoureteral reflux

INTRODUCTION

The ureteral diameter ratio (UDR) is reported to be effective in predicting the outcomes of vesicoureteral reflux (VUR) in several studies.

OBJECTIVE

The objective of the current study was to compare the risk of scarring in patients with VUR relative to UDR and the VUR grade. We also aimed to demonstrate other associated risk factors in scarring and investigate the long-term complications of VUR and their relationship with UDR.

STUDY DESIGN

Patients diagnosed with primary VUR were retrospectively enrolled in the study. UDR was calculated by dividing the largest ureteral diameter (UD) by the distance between L1-L3 vertebral bodies. Demographic and clinical data, laterality, VUR grade, UDR, delayed upper tract drainage on voiding cystourethrogram, recurrent urinary tract infections (UTI), and long-term complications of VUR were compared between the patients with and without renal scars.

RESULTS

A total of 127 patients and 177 renal units were included in the study. There was a significant difference between the patients with and without renal scars according to age at diagnosis, bilaterality, reflux grade, UDR, recurrent UTI, bladder bowel dysfunction, hypertension, decreased estimated glomerular filtration rate, and proteinuria. The logistic regression analysis revealed that UDR had the highest odds ratio among the factors affecting scarring in VUR.

DISCUSSION

VUR grading based on the evaluation of the upper urinary tract is one of the most important predictors for treatment options and prognosis. However, it is more likely to reflect ureterovesical junctional anatomy and function, which play a crucial role in the pathogenesis of VUR.

CONCLUSION

UDR measurement seems to be an objective method that can help clinicians predict renal scarring in patients with primary VUR.

Evaluation of renal function and scars in children with primary vesicoureteral reflux

OBJECTIVE

To evaluate growth, glomerular and tubular function, renal damage, scars in children affected by primary VUR.

METHOD

We retrospectively evaluated the clinical records of our Unit from January 2006 to September 2020. For each patient we evaluated growth, laboratoristic and scintigraphic glomerular and tubular function, renal damage and collective system urodynamics at baseline and at the last visit.

RESULT

We enrolled 41 patients affected by primary VUR and treated with continuous antibiotic prophylaxis. Glomerular function and urodynamics did not change over time. EFNa directly correlated with weight (r 0.44 p 0.004) and TRP inversely correlated with severity of reflux (r -0.32, p 0.04). Female sex was associated to nephrolithiasis (OR 17.0, p 0.02) and proteinuria (at T0 OR 5.8 p 0.03 at T1 OR 5.8, p 0.03). Daily proteinuria increased with age (r 0.66, p <0.0001 at T0 and r 0.44 p 0.004 at T1) while protein-to-creatinine ratio decreased. Renal scars at T0 inversely correlated with glomerular and tubular function at T1 but they did not correlate with severity or laterality of reflux.

CONCLUSION

Even if renal function remains stable through years, it is critical to identify the subjects with significant congenital renal damage.

Risk factors for renal scarring and clinical morbidity in children with high-grade and low-grade primary vesicoureteral reflux

INTRODUCTION

Primary vesicoureteral reflux (VUR) is associated with urinary tract infections (UTIs) and renal damage. However, the importance of early diagnosis of VUR has been questioned. Moreover, most studies have few patients with high-grade VUR. Hence, we retrospectively analyzed a large cohort of patients with primary high-grade and low-grade VUR and assessed risk factors for renal damage and clinical morbidity.

MATERIAL AND METHODS

We included patients (<18 years) at diagnosis with low-grade (1-3) or high-grade (4-5) primary VUR and noted their clinical history and presence of hypertension, low eGFR (<60ml/in/1.73 m²), renal scarring (focal or generalised) and reduced differential renal function (DRF; <45%). Risk factors were assessed (in patients and renal units) by logistic regression and generalised estimating equation.

RESULTS

Of 399 primary VUR patients, 255 (64%) had high-grade VUR. Indications for voiding cystourethrogram were recurrent UTI (38%), first UTI (28%) and antenatal hydronephrosis (17%). At diagnosis, 252 (65%) had renal scars (focal in 170 [44%], generalised in 82 [21%]), and 188 (47%) had reduced DRF. High-grade VUR patients were more likely than low-grade VUR patients to have renal scarring (75% vs. 49%, p < 0.01), low eGFR (23% vs. 13%, p = 0.04) and significant hypertension (26% vs. 13%, p = 0.02). High-grade VUR was associated with generalised scars (odds ratio [OR] 11, p < 0.001), focal scars (OR 3.1, p < 0.001) and reduced DRF (OR 2.3, p < 0.001) shown in the table. Male sex was a risk factor for generalised scars (OR 2.3, p = 0.005). Focal scars were associated with recurrent UTIs (OR = 1.8, p = 0.004) and reduced DRF (OR 1.4, p = 0.027). Patients with multiple focal scars were diagnosed at an older age (2 years [1,4] than those with single scars (1.5 years [1,4] or no scars (1 year [0, 3]), p = 0.04).

DISCUSSION

The prevalence of renal damage and clinical morbidity at VUR diagnosis was higher than other studies. High-grade VUR patients had a greater prevalence of renal damage, low eGFR and hypertension than low-grade VUR patients and was a risk factor for focal scars, generalised scars and reduced DRF. Focal scars were independently associated with recurrent UTI. Those with multiple scars were diagnosed later than those with single scars or no scars.

CONCLUSIONS

High-grade VUR was associated with renal damage and clinical morbidity. Our study highlights the importance of diagnosing VUR early to identify patients who may warrant long-term follow-up and intervention to minimize morbidity.

Renal Cortical Scarring: 68Ga-PSMA-11 PET versus 99mTc-DMSA Scan in a Case with Pyelonephritis

We previously reported ⁶⁸Ga-prostate‑specific membrane antigen (PSMA)-11 and ^99mTcdimercaptosuccinic acid (DMSA) images of the 1st case of our prospective research comparing renal PSMA PET to DMSA scan in adult patients with pyelonephritis. Here, we present renal cortical PSMA PET and DMSA images of our 2nd patient with chronic recurring pyelonephritis which demonstrated renal parenchymal defects secondary to scarring in the kidney.

Contemporary Management of Urinary Tract Infection in Children

Urinary tract infection (UTI) is common in children, and girls are at a significantly higher risk, as compared to boys, except in early infancy. Most cases are caused by Escherichia coli Collection of an uncontaminated urine specimen is essential for accurate diagnosis. Oral antibiotic therapy for 7 to 10 days is adequate for uncomplicated cases that respond well to the treatment. A renal ultrasound examination is advised in all young children with first febrile UTI and in older children with recurrent UTI. Most children with first febrile UTI do not need a voiding cystourethrogram; it may be considered after the first UTI in children with abnormal renal and bladder ultrasound examination or a UTI caused by atypical pathogen, complex clinical course, or known renal scarring. Long-term antibiotic prophylaxis is used selectively in high-risk patients. Few patients diagnosed with vesicoureteral reflux after a UTI need surgical correction. The most consequential long-term complication of acute pyelonephritis is renal scarring, which may increase the risk of hypertension or chronic kidney disease later in life. Treatment of acute pyelonephritis with an appropriate antibiotic within 48 hours of fever onset and prevention of recurrent UTI lowers the risk of renal scarring. Pathogens causing UTI are increasingly becoming resistant to commonly used antibiotics, and their indiscriminate use in doubtful cases of UTI must be discouraged.

The risk factors for recurrence of febrile urinary tract infection and renal scarring in children with functional urinary incontinence

OBJECTIVES

Functional urinary incontinence is often associated with recurrent urinary tract infection (UTI), vesicoureteral reflux (VUR), and renal scarring. This study aims to evaluate the correlations between urodynamic findings and recurrence of UTI, VUR, and renal scarring in children with functional incontinence.

METHODS

In this retrospective observational study, data on the presence of VUR, urodynamics and 99Tc-dimercaptosuccinic acid scintigraphy findings, and episodes of febrile UTI were obtained from patients' records. The patients had at least 3 years of follow-up.

RESULTS

There were significant associations between recurrence of UTI and decreased bladder capacity (hazard ratio: 1.321, P = .028). The receiver operator characteristic curve analysis showed a cutoff value for compliance of 13.25 mL/cmH₂ O for renal scarring (P = .000). There was a significant association between bladder wall thickening and VUR (odds ratio: 2.311, P = .008). The compliance had a cutoff value of 14.7 mL/cm H₂ O (P = .023) for severe VUR. The frequency of renal scarring was higher in patients with severe VUR and dysfunctional voiding (P = .001 and P = .041, respectively). The independent risk factors for renal scarring were low compliance, severe VUR, and dysfunctional voiding in children with functional incontinence, but recurrence of febrile UTI was not a risk factor for renal scarring. Decreased bladder capacity was a risk factor for recurrence of febrile UTI.

CONCLUSIONS

The present study suggests that low compliance, severe VUR, and dysfunctional voiding, but not the recurrence of febrile UTI, are the independent risk factors for renal scarring in children with functional incontinence, and decreased bladder capacity is the risk factor for the recurrence of febrile UTI.