Congenital anomalies of the kidney and urinary tract: Viva

Branch 1: Classification and embryology

The candidate should define CAKUT as the spectrum of congenital structural malformations of the kidney and urinary tract that arise from errors in embryological development. A strong candidate classifies the spectrum into three anatomical groups: the kidney and parenchymal anomalies including renal agenesis, hypoplasia, dysplasia, and the multicystic dysplastic kidney, the ureteric and collecting system anomalies including vesicoureteral reflux, megaureter, ureterocele, and duplex systems, and the bladder and urethral anomalies including posterior urethral valves, prune belly syndrome, and neurogenic bladder. ^[1]

If the examiner presses on the embryology, the candidate should describe the ureteric bud and the metanephric mesenchyme interaction. The ureteric bud grows from the Wolffian duct and invades the metanephric mesenchyme, branching to form the collecting system while the mesenchyme forms the nephron. The GDNF-RET pathway is the master regulator, and disruption produces agenesis, dysplasia, or ureteric anomalies depending on the stage and the nature of the disruption. A strong candidate names the Weigert-Meyer rule for duplex systems, in which the upper-pole ureter inserts ectopically and distally. ^[1]