Posterior urethral morphology on initial voiding cystourethrogram correlates to early renal outcomes in infants with posterior urethral valves

Appearance of the bladder on initial voiding cystogram in boys with PUV and its relation to pre and postnatal findings

Introduction

Bladder profile in boys with Posterior Urethral Valves can be very varied with a spectrum going from high pressure, unstable, hypocompliant small bladders to hypercompliant, large acontractile bladders, with some being near-normal. Our question was whether appearance, specifically of the bladder, on initial VCUG was correlated to prenatal features and whether it could predict early postnatal outcome.

Method

We used a prospectively gathered database of boys with prenatally suspected PUV. We analyzed whether the appearance, specifically of the bladder, was related to date of prenatal diagnosis, presence of a megacystis on prenatal ultrasound, presence of vesico-ureteral reflux (VUR), presence of abnormal DMSA scan, nadir creatinine or presence of febrile urinary tract infection (fUTI) during the first two years of life.

Results

The database comprised 90 cystograms. 15% of bladders were judged normal/regular, 54 % were small/diverticular and 31% were large/diverticular. Bladder appearance was not associated with presence of prenatal megacystis, abnormal DMSA scan, VUR, nor rate of fUTI. The only significant associations were normal/regular bladder and early prenatal diagnosis (p = 0.04) and normal/regular bladder and elevated nadir creatinine (>75µmol/l) (p = 0.01).

Discussion

We believe that when focusing solely on the appearance of the bladder, excluding information about the urethra and presence of reflux, the cystogram alone is insufficient to inform on future bladder function. This could be used as an argument in favor of performing early urodynamics in this population.

External validation and reliability assessment of posterior urethral morphology on initial voiding cystourethrogram as a predictor for infants with posterior urethral valves

INTRODUCTION

The morphology of the bladder and posterior urethra on initial voiding cystourethrogram (VCUG) in posterior urethral valve (PUV) has been proposed as a meaningful early metric for short- and long-term kidney outcomes. Here, we seek to externally validate the proposed association and assess the reliability of PUV morphology characteristics.

MATERIALS AND METHODS

We reviewed our institutional database for patients managed for PUV between 2000 and 2022 and included those treated with primary ablation with at least 1 year of follow-up for kidney function. Each VCUG was evaluated by three independent raters for the height-width ratio of the bladder (HW-B), height-width ratio of the posterior urethra (HW-PU), and posterior-anterior urethral ratio (PA-UR), and trabeculation (none, fine, or coarse). We assessed the reliability in these with intra-class coefficient and Fleiss kappa for continuous and categorical data, respectively. We performed univariate analysis with nadir creatinine and five-year follow-up glomerular filtration rate (GFR).

RESULTS

In total, 98 patients met inclusion criteria. The median age at diagnosis and ablation was 10 and 21 days, respectively. Patients with nadir creatinine <0.8 mg/dL had higher follow-up GFR (101 vs. 20 ml/min/1.73 m2, p = 0.04), and lower risk of CKD (odds ratio 14.7, p = 0.002). The median value for HW-B was 1.4, median HW-PU was 2.1, and median PA-U was 4.7, There was significant inter-class agreement between all three measures of 0.80, 0.51, and 0.70 (p < 0.001). The inter-rater agreement for bladder trabeculation was fair (Fleiss K = 0.40, p < 0.001). There was no statistically significant correlation between HW-B, HW-PU, PU-A with nadir creatinine (p = 0.07, 0.33, 0.91) or 5-year GFR (0.27, 0.45, 0.62), respectively.

DISCUSSION

There is significant interest in determining prognostic factors and metrics in PUV. The morphological characteristics on VCUG are reliable and is available information for all boys diagnosed with PUV, resulting in an attractive metric. While we do not demonstrate correlation with kidney outcomes, VCUG features warrant further attention as prognostic factors in PUV.

CONCLUSIONS

PUV morphology on initial VCUG is a reliable metric of lower urinary tract deformity but is not associated with 5-year kidney outcomes.

Indirect signs of infravesical obstruction on voiding cystourethrography improve post-neonatal posterior urethral valves detection rate

OBJECTIVES

To identify the diagnostic performance of clinical and radiological signs (on voiding cystourethrography [VCUG]) to detect posterior urethral valves (PUV) in the post-neonatal period.

MATERIALS AND METHODS

One hundred eighteen males (median age = 0.8 years, range = 1 month-14 years, 48 toilet-trained) undergoing VCUG in a 2-year period were prospectively enrolled. Direct (dilated posterior urethra) and indirect (hypertrophied bladder neck, musculus interuretericus hypertrophy, and trabeculated appearance of the bladder wall) PUV signs on VCUG were assessed. Uroflowmetry was defined pathological by patterns suggesting infravesical obstruction.

RESULTS

Twenty-two patients with direct, 28 with indirect PUV signs on VCUG, and one with normal VCUG but persisting micturition symptoms with pathological uroflowmetry underwent urethrocystoscopy and in 43/51 a PUV diagnosis was made (n = 22, 51.2%, with direct PUV signs). In 8/28 patients with indirect signs, PUV were not confirmed. Among non-toilet-trained patients, none of the clinical signs/symptoms was associated with PUV while among toilet-trained patients only pathological uroflowmetry (odds ratio, OR = 4.0 [95% confidence interval:1.2-13.2; p = 0.02]) and pathological uroflowmetry with history of urinary tract infection (OR = infinity) were significantly associated with PUV. Significant associations with PUV of direct and indirect signs on VCUG were found both in toilet-trained and non-toilet trained patients. Direct PUV sign had 100% specificity and sensitivity while indirect PUV signs showed sensitivity = 58.1% and specificity = 89.3%. The absence of any radiological sign had a negative predictive value = 98.5%.

CONCLUSION

Only half of patients with endoscopy-confirmed PUV presents with direct sign of PUV on VCUG. Accounting for indirect PUV signs on VCUG and pathological uroflowmetry (in toilet-trained children) could improve the PUV detection rate.

CLINICAL RELEVANCE STATEMENT

Indirect radiological PUV signs should be valorized when interpreting VCUG to improve the PUV detection rate. The absence of any radiological PUV (direct and indirect) sign on VCUG excludes PUV with a very high negative predictive value.

KEY POINTS

• Worldwide agreement is that a non-dilated urethra on voiding cystourethrography excludes obstruction. • Half of patients with posterior urethral valves have non-dilated urethra on voiding cystourethrography. • Accounting for indirect signs of posterior urethral valves on voiding cystourethrography improves the diagnostic performance.

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.