What is the most common cause of congenital hydronephrosis?

Uretero-pelvic junction (UPJ) obstruction is indeed the most common cause of congenital hydronephrosis. This condition occurs when there is a blockage at the junction where the ureter meets the kidney, impeding the normal flow of urine from the kidney to the ureter. When this obstruction occurs, urine can accumulate in the kidney, leading to hydronephrosis, which is the dilation and swelling of the kidney due to the buildup of urine.

Congenital hydronephrosis can have significant implications for kidney function and may require medical intervention or surgical treatment, particularly if the obstruction is severe. The prevalence of UPJ obstruction in the general population and among infants is well-documented, making it a key focus in neonatal care and assessment processes.

The other options represent conditions that can cause urinary obstruction, but they are less frequent in the context of congenital hydronephrosis. Ureteral strictures, while a possible cause of obstruction, are not commonly seen at birth and often arise from scarring or injury. Posterior urethral valves can lead to obstruction and hydronephrosis, particularly in males, but is less common overall. Prostatitis is an inflammatory condition of the prostate usually affecting older males and is