Bilateral ureteropelvic junction obstruction with ureteric stone in a female Nigerian infant: the necessity for renal and urinary tract ultrasound in acute kidney injury running head: bilateral ureteropelvic junction obstruction

Ureteropelvic junction obstruction (UPJO) also known as pelvicureteric junction obstruction (PUJO), is defined as an obstruction of the flow of urine from the renal pelvis to the proximal ureter.1 UPJO is the most common cause of obstructive uropathy (OU) in children and is second only to transient, physiologic nonpathologic hydronephrosis as the most common cause of antenatal hydronephrosis.2 Its anatomic basis is from either an intrinsic or an extrinsic cause. The intrinsic obstruction result from luminal narrowing of the UPJ, with or without kinking, and is characterized by excessive connective tissue and decreased smooth muscle content of the ureteral wall.3 Extrinsic obstruction is by compression of the ureter by anomalous renal vasculature and is commoner in older children and adults.4 The incidence of UPJO is estimated to be 1 in 1500, with a male-to-female ratio of 2:1.5 The left side is commoner with a left-to-right ratio of 1.5:1.6 Bilateral cases of UPJO are also seen in 10% to 40% of neonatal hydronephrosis.2