Posterior Urethral Valves

Abstract

Posterior urethral valves (PUV) is the most common congenital cause of lower urinary tract obstruction (LUTO), accounting for over half (57%) of all reported cases. The large majority of patients with PUV are diagnosed soon after birth or in the first year of life following investigations for an antenatally detected hydronephrosis or urinary tract infection. After birth, an ultrasound of the urinary tract, a voiding cystourethrogram (VCUG), and a diuretic renogram will help to differentiate PUV from other causes of bladder outlet obstruction and upper urinary tract dilatation. On VCUG, the posterior urethra will typically appear dilated and elongated, ending with a U-shape at the membranous urethra. Prenatal intervention of LUTO supports the utility of a risk stratification to guide fetal intervention. Neonatal management of a newborn with suspected PUV includes a period of stabilization with adequate bladder drainage, rehydration, and electrolyte correction awaiting plateau of creatinine levels. The aim of any endoscopic treatment is to incise rather than remove the valves. Current methods of incision include cold knife incision, endoscopic electrocautery incision, and laser fulguration. Early circumcision in all PUV patients is recommended to reduce the risk of UTI. PUV-associated morbidity extends beyond infancy and childhood through adolescence into adult life, regardless of the apparent success of early valve ablation. Long-term issues in patients with PUV relate to renal, bladder, and sexual function. Vesicoureteral reflux is detected in a third of ureteral units and resolves in two-thirds after endoscopic resection of valves. The “Valve Bladder Syndrome” refers to patients with PUV that, despite a proven absence of outflow obstruction, show a persistent and progressive uretero-hydronephrosis and loss of renal function. In addition, a third of patients with PUV progress to chronic kidney disease (CKD) or ESKD during childhood or young adulthood despite active treatment. Many prognostic factors have been proposed over the years, with Nadir Creatinine >1 mg/dl (88 μmol/L) in the first year of life indicating high risk of progression to ESKD. A multidisciplinary (MDT) approach to the prenatal and postnatal management of children with LUTO should be provided to prevent severe pulmonary hypoplasia and ESKD. Future prospective randomized trials will help to standardize prenatal evaluation and management of LUTO across fetal centers and define long-term postnatal outcomes following fetal intervention.