The development of anuria after appendectomy is usually related to complications associated with appendicitis or with the surgical sequelae of appendectomy. The paper reports an unusual case of anuria after appendectomy in a 13-year-old boy. The patient presented with a sudden cessation of urine output just 72 hours after appendectomy. Initially, it was suspected that the anuria was caused by the infective state or by a complication of surgery. However, an abdominal computed tomography (CT) scan revealed that pielo-ureteral stones in both kidneys had caused the anuria. Renal failure due to postrenal anuria resolved completely after stone removal.