Abdul Muhaimin Abdullah^1,, Mohamed Ashraf Mohamed Daud^{1, 2}

Background: Cases of large intra-abdominal cyst in fetus are rare and determination of its origin is challenging. A multidisciplinary approach is recommended. Case Presentation: A large intra-abdominal cystic mass was found in a 28 weeks fetus during routine ante-natal scan. The baby was born via a scheduled cesarean section and initial physical examination revealed a distended abdomen. Ultrasonography of abdomen showed a large cystic mass in which the origin was undetermined. Hence, contrast enhanced computed tomography abdomen was performed, revealed grossly dilated pelvicalyceal system due to congenital ureteropelvic junction (UPJ) obstruction. The baby underwent right open dismembered pyeloplasty at days 27 of life. Post-operative period was uneventful and serial renal function test showed no renal impairment. Baby was discharged home after 40 days of operation. Conclusion: UPJ obstruction can present antenatally as a large cystic mass and multidisciplinary team involvement should be considered to determine the pre-natal and post-natal management. These include an appropriate delivery plan including method and place of delivery.

ureteropelvic junction obstruction, large intraabdominal cystic mass, hydronephrosis