Five cases of bilateral ureteral obstruction after appendicectomy are presented. All five patients were boys (age range, 9 to 15 years). All of them had had severe appendicitis. Based on the urethrocystoscopy findings, edema of the posterior bladder wall appeared to be the cause of obstruction of both distal ureters. This is confirmed by the immediate recovery of renal function after installation of bilateral uretercatheters. It is known that contamination of the peritoneal cavity can occur by organisms leaking from a gangrenous or perforated appendix. This can cause localized inflammatory edema of the posterior bladder wall. It is remarkable that through ultrasound investigation, only mild to moderate dilatation of the urinary tract was observed. An explanation can be obtained from animal models, wherein acute obstruction of the ureter leads only to a transient increase in ureteral pressure, followed by a decline toward the preobstruction level. It is important to be aware that this complication can occur after appendectomy; bilateral uretercatheters can be installed, and irreversible renal damage can be avoided.