rossed renal ectopia is a rare type of renal ectopia with estimated oc- currence of 1 in 1,000 live births. 1 In crossed renal ectopia, both kid- neys are located on the same side with two separate ureters inserting into the bladder on opposite sides. 2 Kidneys can be fused or not. The num- ber reports of antenatally diagnosed crossed renal ectopia is very limited in literature despite the advances in antenatal sonography. Absence of amni- Turkiye Klinikleri J Gynecol Obst 2014;24(4) 257 A Rare Type of Ectopic Kidney; Crossed Ectopy with Fusion: Case Report İbrahim Halil KALELİOĞLU, a Burçin KARAMUSTAFAOĞLU BALCI, a Ercan BAŞTU, a Tayfun OKTAR, b Recep HAS, a Orhan ZİYLAN, b Atıl YÜKSEL a Departments of a Gynecology and Obstetrics, b Urology, İstanbul University İstanbul Faculty of Medicine, İstanbul Geliş Tarihi/Received: 25.09.2013 Kabul Tarihi/Accepted: 20.12.2013 Yazışma Adresi/Correspondence: Burçin KARAMUSTAFAOĞLU BALCI İstanbul University İstanbul Faculty of Medicine, Department of Gynecology and Obstetrics, İstanbul, TÜRKİYE/TURKEY burcinkaramustafaoglu@yahoo.com Copyright © 2014 by Türkiye Klinikleri OLGU SUNUMU ABSTRACT We herein report a case of prenatally diagnosed crossed renal ectopia with fusion. Crossed renal ectopia is a rare type of renal ectopia with an estimated occurrence of 1 in 1,000 live births. Crossed fused renal ectopia is a more rare type of ectopia, with a prevalence of 1/2000 in au- topsy series. The number of reported antenatally diagnosed crossed renal ectopia is very limited in literature despite the advances in antenatal sonography. A 30-year-old, gravida 1, para 0 Caucasian woman was referred to our perinatology clinic at 36 weeks of gestation due to the difficulty in sono- graphic visualization of the right kidney. Ultrasound scan showed that renal parenchyma was not visible in the right renal fossa and in the right hemipelvis. In contralateral side, both renal pelvises were identifiable. Doppler ultrasonography showed two renal arteries in contralateral side, one arising from aorta, while the other one arising from left common iliac artery. Continuity between both renal parenchyma was observed; thus, the diagnosis was crossed ectopy with fusion. We want to present our case, emphasize the importance of prenatal diagnosis and summarize the difficulties and key points in prenatal diagnosis of this abnormality. Key Words: Prenatal diagnosis; kidney pelvis; urogenital abnormalities ÖZET Bu makalede prenatal dönemde tanısı koyulmuş çapraz kaynaşmış renal ektopi olgusunu sunmaktayız. Çapraz renal ektopi renal ektopinin seyrek görülen bir türüdür. Sıklığı canlı doğum- larda 1/1000 olarak bildirilmektedir. Çapraz kaynaşmış renal ektopi ise ektopinin daha seyrek bir türüdür ve otopsi serilerinde prevalansı 1/2000’dir. Antenatal ultrasonografideki ilerlemelere ra- ğmen antenatal dönemde tanı konmuş çapraz renal ektopi olgu sayısı oldukça azdır. Olgumuz, 30 yaşında, gravida 1, para 0, Kafkas kökenli hasta, 36. gebelik haftasında sağ böbreğin ultrasonogra- fide görülememesi üzerine kliniğimize refere edilmişti. Ultrason ile incelemede sağ renal fossada ve sağ hemipelviste renal parankim izlenmedi. Her iki renal pelvis karşı tarafta izlendi. Doppler ult- rason incelemesinde karşı tarafta, biri aortadan diğeri sol ana iliak arterden köken alan iki renal arter izlendi. Her iki renal parankim birbiriyle devam etmekteydi; böylece çapraz kaynaşmış renal ektopi olarak tanı kondu. Yazımızda olgumuzu sunmak, prenatal tanının önemini vurgulamak ve bu anomalinin prenatal tanısındaki zorluklar ile anahtar noktaları özetlemek istedik. Anahtar Kelimeler: Prenatal tanı; renal pelvis; ürogenital anomaliler Turkiye Klinikleri J Gynecol Obst 2014;24(4):257-60