Pediatr Nephrol (2001) 16:581–585
© IPNA 2001
O R I G I N A L A RT I C L E
Raj K. Sharma · Ajay P. Sharma · Rakesh Kapoor Amit Gupta
Prognostic significance of distal renal tubular acidosis in posterior urethral valve
Received: 29 September 1999 / Revised: 25 January 2001 / Accepted: 25 January 2001
Abstract The prognostic significance of distal renal tubular acidosis (DRTA) in the development of overt nephropathy (ON) in children with posterior urethral valves (PUV) is not clear. This condition was studied prospectively in 22 children with posterior urethral valve (PUV), with normal renal function. Prior to surgery, the children with ON had a higher incidence of bilateral reflux (P=0.006), but the difference was not significant for age at surgery (P=0.31), duration of voiding symptoms prior to surgery (P=0.30), presence of DRTA (P=0.35) and bladder abnormalities (P=0.27), with none of these factors being significant on logistic regression analysis. At the end of the follow-up, after surgery, age at surgery (P≤0.0001), duration of voiding symptoms prior to surgery (P≤0.0003), persistent DRTA (P=0.0001) and persistent bladder dysfunction (P=0.02) after surgery were significantly higher in children with ON. On univariate logistic regression analysis, age at surgery (P=0.009), duration of voiding symptoms prior to surgery (P=0.01), persistent DRTA (P=0.002) and persistent bladder abnormalities (P=0.03) after surgery were significant for ON after surgery, but on stepwise multivariate logistic regression analysis only persistent DRTA (P=0.002) turned out to be significant. We conclude that persistent DRTA after surgery can predict overt nephropathy in children with PUV after surgery. Keywords PUV · Overt nephropathy · DRTA · Bladder abnormalities
R.K. Sharma · A.P. Sharma (✉) · A. Gupta Department of Nephrology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Rae Bareli Road, Lucknow, India e-mail:
[email protected] Tel.: +91-0522-4400059, Ext 2121, Fax: +91-0522-440017, 440973 R. Kapoor Department of Urology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Rae Bareli Road, Lucknow, India
Introduction Lower urinary tract obstruction of prolonged duration in children may have deleterious renal effects, including distal renal tubular acidosis [1,2,3] and overt nephropathy [4, 5,6]. PUV is the most common cause of obstructive uropathy in children, and these children are known to develop renal failure even after fulguration of the valves. A few risk factors such as age at diagnosis [5,7,8], nadir serum creatinine at 1 year of age [8,9], presence of bilateral vesicoureteral reflux (VUR) [5,10] and presence of urinary renal incontinence after 5 years of age [5] have been correlated with development of renal insufficiency after surgery in these children. The prognostic significance of DRTA for development of overt nephropathy in children with PUV is not clear. Therefore, we prospectively studied boys with PUV with normal serum creatinine at surgery, with the objective of studying the prognostic significance of DRTA, urodynamic bladder abnormalities and other risk factors such as age at surgery and presence of bilateral reflux, on the development of ON prior to surgery. The prognostic significance of these factors along with persistent DRTA and persistent bladder abnormalities after surgery on the prevalence of ON after surgery was also examined.
Materials and methods A prospective study was conducted in consecutive children with PUV operated on between January 1995 and March 1997 at our centre. Our study group included children with serum creatinine within the normal limit for that particular age. Children with renal insufficiency were excluded. Renal insufficiency was defined if serum creatinine was persistently (at least three readings over a span of 2 weeks) above the upper limit of the normal range for that particular age after taking care of any acute factor (dehydration, sepsis, obstruction) [11]. At presentation, after confirming the diagnosis of PUV, all the children were evaluated for demographic profile, duration of voiding symptoms prior to surgery, presence of ON, bilateral vesicoureteral reflux, DRTA, and bladder dysfunction.
582 The diagnosis of PUV was established by the presence of voiding symptoms, ultrasound, and micturating cystourethrography (MCU). MCU provided additional information regarding the degree and presence of bilateral reflux. Overt nephropathy was diagnosed in cases where 24-h urinary protein excretion was greater than the upper limit of the normal range for that age [12]. Twentyfour-hour urine collections were done before surgery by urethral catheterization in all children. The evaluation for DRTA was done after excluding urinary tract infection (UTI) and ensuring adequate hydration. In cases where UTI was detected, investigations were postponed until at least 3 weeks after resolution of UTI. DRTA was diagnosed, if urine pH (by pH meter) was greater than 5.5 despite adequate systemic acidaemia (arterial blood pH
