Evaluation of polyuria and polydipsia along with other established prognostic factors in posterior urethral valves for progression to kidney failure: experience from a developing country

Kidney disease progression in pediatric and adult posterior urethral valves (PUV) patients

BACKGROUND

Posterior urethral valves (PUV) is the most common cause of obstructive uropathy in boys; approximately 15% develop kidney failure by early adulthood. However, rates of kidney function decline are poorly defined in PUV children and adults, as is the impact of potentially modifiable chronic kidney disease (CKD) progression risk factors.

METHODS

We conducted a retrospective review of all PUV patients followed at our institution from 1995 to 2018. Inclusion criteria were estimated glomerular filtration rate (eGFR) > 20 ml/min/1.73 m2 after 1 year of age, no dialysis or kidney transplant history, and ≥ 2 yearly serum creatinine values after age 1 year. eGFRs were calculated using creatinine-based estimating formulas for children (CKID U25) or adults (CKD-EPI). The primary outcome was annualized change in eGFR, assessed with linear mixed effects models. We also examined the association of acute kidney injury (AKI), proteinuria, hypertension (HTN), and recurrent febrile urinary tract infections (UTIs) with eGFR decline.

RESULTS

Fifty-two PUV patients met the inclusion criteria. Median (interquartile range) eGFR decline was 2.6 (2.1, 3.1) ml/min/1.73 m2/year. Children (n = 35) and adults (n = 17) demonstrated progressive decline. Proteinuria and recurrent UTIs were significantly associated with faster progression; AKI and HTN were also associated but did not reach significance.

CONCLUSION

PUV patients show progressive loss of kidney function well into adulthood. Proteinuria and recurrent UTIs are associated with faster progression, suggesting potential modifiable risk factors. This is the first study to report annualized eGFR decline rates in PUV patients, which could help inform the design of clinical trials of CKD therapies.

Nadir creatinine as a predictor of renal outcomes in PUVs: A systematic review and meta-analysis

Background

Posterior urethral valves (PUVs) represent the most severe pediatric obstructive uropathy, responsible for chronic renal failure in up to 65% of cases and progression to end-stage kidney disease (ESKD) in about 8%-21% of patients. Unfortunately, renal outcomes have poorly improved over time. The key point is to identify patients at risk; thus, several prenatal and postnatal prognostic factors have been analyzed to improve clinical outcomes. Postnatal nadir creatinine seems to accurately predict long-term renal prognosis, but there is no definitive evidence to support this finding.

Objective

We performed a systematic review with meta-analysis to analyze the predictive value of nadir creatinine on long-term renal function in infants with PUVs.

Methods

We conducted this systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed and Cochrane Library were systematically searched for studies published from January 2008 to June 2022. All the articles were checked independently by two reviewers in two steps.

Results

A total of 24 articles were screened, and 13 were included for data extraction. Data from 1,731 patients with PUVs were analyzed, with a mean follow-up of 5.5 years; of these, on average, 37.9% developed chronic kidney disease (CKD) and 13.6% developed ESKD. All the articles evaluated nadir creatinine as a predictor of CKD, most using a level of 1 mg/dL, with statistical significance at the 5% level. The relative risk of developing CKD in patients with creatinine values higher than the nadir cutoff considered was 7.69 (95% CI: 2.35-25.17, I 2 = 92.20%, p < 0.001).

Conclusions

Nadir creatinine is the best prognostic factor for long-term renal function in patients affected by PUV. A value above the cutoff of 1 mg/dL should be considered a significant predictor for the risk of CKD and ESKD. Further studies are needed to define different nadir creatinine cutoffs for better stratification of the different CKD stages and for the development of reliable scores, which include the association of several variables.

Chronic Kidney Disease in Boys with Posterior Urethral Valves-Pathogenesis, Prognosis and Management

Posterior urethral valves (PUV) are the most common form of lower urinary tract obstructions (LUTO). The valves can be surgically corrected postnatally; however, the impairment of kidney and bladder development is irreversible and has lifelong implications. Chronic kidney disease (CKD) and bladder dysfunction are frequent problems. Approximately 20% of PUV patients will reach end-stage kidney disease (ESKD). The subvesical obstruction in PUV leads to muscular hypertrophy and fibrotic remodelling in the bladder, which both impair its function. Kidney development is disturbed and results in dysplasia, hypoplasia, inflammation and renal fibrosis, which are hallmarks of CKD. The prognoses of PUV patients are based on prenatal and postnatal parameters. Prenatal parameters include signs of renal hypodysplasia in the analysis of fetal urine. Postnatally, the most robust predictor of PUV is the nadir serum creatinine after valve ablation. A value that is below 0.4 mg/dl implies a very low risk for ESKD, whereas a value above 0.85 mg/dl indicates a high risk for ESKD. In addition, bladder dysfunction and renal dysplasia point towards an unbeneficial kidney outcome. Experimental urinary markers such as MCP-1 and TGF-β, as well as microalbuminuria, indicate progression to CKD. Until now, prenatal intervention may improve survival but yields no renal benefit. The management of PUV patients includes control of bladder dysfunction and CKD treatment to slow down progression by controlling hypertension, proteinuria and infections. In kidney transplantation, aggressive bladder management is essential to ensure optimal graft survival.