A Rare Cause of Ureteropelvic Junction Obstruction

An 8-year-old boy was referred to Pusan National University Yangsan Hospital with left ureteropelvic junction (UPJ) obstruction. He had experienced episodes of intermittent gross hematuria that had first presented at the age of 5 years. He was otherwise healthy and had no previous medical problems. He had no history of urinary tract infections or stones. A physical examination showed no left flank pain. A complete blood count with differential and the results of renal function tests were within normal limits. Urinalysis revealed microscopic hematuria, whereas the urine culture was negative. Urine cytology showed no evidence of malignancy. Ultrasonography (USG) showed grade 3 left hydronephrosis according to the Society of Fetal Urology classification, with renal pelvis dilatation of a maximum diameter of 6.4 cm. Longitudinal USG showed a mildly echogenic mass at the dilated upper ureter (Fig. 1A). The right side was normal. The intravenous pyelogram (IVP) revealed hydronephrosis and a dilated renal pelvis that had corkscrew narrowing on the left side. Below the dilated renal pelvis, an S-shaped ureteral fold was observed, with an intraluminal nonopaque and smooth filling defect of about 3 cm in length (Fig. 1B). An obstructive pattern in the left kidney was revealed by Tc diethylenetriamine pentaacetic acid (DTPA) renography. A serial excretion film demonstrated isotope retention in the left kidney of up to 59 minutes (Fig. 1C).