患儿，男，5岁。因腹部伤后42天，腹左侧渐增肿块2天入院。查体：自动体位，腹胀壁软，腹左侧扪及18×12×12cm囊性肿块，肠管内移。B超示：左侧腹膜后16×11.6×11.2cm液性肿块。IVP示：右肾、输尿管显影正常，左肾、输尿管未显影，膀胱影正常。行囊肿穿刺，吸出2000ml尿液后肿块消失，3日后复发。拟左肾盂积水探查见：左侧腹膜后16×12× Children, male, 5 years old. 42 days after abdominal injury, abdomen on the left gradually increased mass 2 days admission. Physical examination: automatic position, abdominal distension wall soft, abdomen left palpable 18 × 12 × 12cm cystic mass, bowel movement. B ultrasound showed: left retroperitoneal 16 × 11.6 × 11.2cm liquid mass. IVP shows: the right kidney, normal ureterography, left kidney, ureter is not developed, normal bladder shadow. Line cyst puncture, sucked out 2000ml urine disappeared after the mass, 3 days after the recurrence. To be seen on the left hydronephrosis see: left retroperitoneal 16 × 12 ×