PUV remains one of the common and challenging problems in Paediatric Urology. Large centres report incidence of 2 to 7 cases per year.1 We see about 12 cases per year in our unit. And about 20-25 cases in the hospital. Hanlon-Lundberg et al2 have reported an incidence of approximately 1 in 5000 to 8000 male infants. Presently there are 14 reported pairs of siblings with PUV. These include seven pairs of twins and seven pairs of non-twin siblings. The only reported case of PUV in successive generations was by Hanlon-Lundberg et al.2 They reported a case of antenatally diagnosed PUV in an infant whose father and paternal uncle were both treated for PUV in childhood.

A day 2 neonate was brought to us, as he had not passed urine since birth and on examination had a distended bladder and bilateral palpable renal lumps. He was diagnosed antenatally in another hospital as a case of PUV with bilateral hydroureteronephrosis. Investigations revealed PUV with bilateral grade V vesico-ureteral reflux (Fig. 1) and poorly functioning right kidney.

One and a half year ago, brother of this neonate was admitted with us on day 3 after birth with abdominal distension and dribbling of urine. On clinical examination he had a distended bladder and a palpable left kidney. Investigations revealed PUV with bilateral grade V vesico-ureteral reflux (Fig. 2) with left non-functioning kidney. Right ureterostomy and later left nephro-ureterectomy were done. Patient died of renal failure at the age of nine months.

Parents refused any further major intervention this time for the second child, and therefore only cystoscopy and fulguration of valves was done, in view of poor prognosis in previous sibling.

Genetic aspect of various genitourinary anomalies has been emphasized recently. Vesico-ureteral reflux, ureteral duplication, uretero-pelvic junction obstruction, renal agenesis and hypospadias have been shown to demonstrate familial tendencies.1 This observation was validated by us in non-twin siblings as described in this report. Both our neonates suffered a severe disease and succumbed during infancy similar to the literature case reports.3,4

Fig. 1 : Voiding cystourethrography 2nd sibling.	Fig. 2 : Voiding cystourethrography 1st sibling.

Davidson and Newberger first reported on posterior urethral valves in twins in 1933.5 Both children died at the age of two weeks because of sepsis and renal failure. The diagnosis of PUV was made at necropsy examination. The first report suggesting that PUV might occur in brothers was by Counseller and Menville in 1935.6 They reported a seven and half month old child who had PUV and died ten hours after placement of suprapubic cystostomy. His older brother also suffered from identical symptoms and died when he was 6 months old. The authors assume that the brother also had PUV. In 1957 Kjelberg and associates7 reported on a series of 52 PUV patients, which included three pairs of twins and one pair of non-twin siblings. Clinical information was noted only in two pairs of twins aged 8 years and one and half years. Farkas and Skinner reported on two brothers with PUV.8 A seven days old boy had urinary retention with overflow dribbling and was found to have PUV on evaluation. His older brother who was asymptomatic, when evaluated showed pyuria and radiological investigation revealed disease that was identical, mirror image to that of his brother.

Although Davidson et al described first case of twins with PUV, their monozygosity was not established. Kroovand9 was the first to report on twins with PUV with proven monozygosity. These twins had a monochorionic diamniotic placenta and possessed identical Rh and ABO blood grouping and identical HLA haplotype. Grajewski et al10 reported a pair of identical twins presenting at different age groups and different radiological findings. His findings reconfirmed the observation of Krueger11 that those who present early have more severe disease and suffer greater curtailment of linear growth. Hence they recommend early evaluation of siblings to avoid insidious long-term effects of this anomaly. Thomalla JV et al4 reported two pairs, one pair of monozygotic twin with discordance and other pair of non-twin sibling with PUV.

Doraiswami et al6 reported a pair of non-twin siblings with PUV. One presented at the age of three years and other at fourteen years. Other siblings and parents were also screened but did not reveal any urological anomalies. Crankson et al12 and Hutton et al13 reported a pair each of antenatally diagnosed PUV in siblings. In Hutton’s series of 67 cases of PUV over 10 years 14 (44%) of the 32 prenatally-diagnosed cases were identified on sonography during third trimester although earlier USG had been normal. Hutton et al recommends early scans around 18 weeks of gestation with another during third trimester.

First reported case of PUV in successive generation was by Hanlon-Lundberg et al.2 They reported a case of antenatally diagnosed PUV in a foetus whose father and parental uncle were both treated for PUV in childhood.

The occurrence of PUV in monozygotic twins suggests an inheritable trait that follows Mandelian genetics. However discordance in monozygotic twins as reported by Thomallia4 and Reule et al14 suggest that the abnormality may be secondary to random mutation or dependent on a combination of genetic or environmental factors. According to Livne et al15 many congenital genitourinary anomalies that are derivatives of the mesonephric duct are polygenetic disorders. PUV also are associated with interaction of many genes of small effect rather than caused by a chromosomal abnormality or a single mutant gene of large effect.

When a posterior urethral valves are identified in one boy, it is prudent to investigate his brother especially a twin sibling, even if asymptomatic, so that the disease may be discovered earlier and further renal damage prevented.15 We agree with Hutton that antenatal USG for renal anomalies should be repeated in the third trimester even if it is normal at 18 to 20 weeks. .