enteric duplications ( eds ) are uncommon anomalies that can occur at any point of the gastrointestinal tract . the small intestine is the most common location ; retroperitoneum is an extremely rare site . in general , diagnosed in the neonatal period or during infancy , they are increasingly diagnosed prenatally ; early prenatal detection is possible . , there have been seven reported cases of retroperitoneal ed cyst in the english literature . a female newborn , vaginally born at 39 weeks of gestation from a 32-year - old mother , gravid 3 , para 3 . prenatal ultrasound at 22 weeks of gestation objectified an abdominal cystic mass located in the left upper abdominal quadrant , associated with fetal pyelectasis . birth weight was 4000 g , length was 51 cm , and head circumference was 35 cm . postnatal ultrasound found a retroperitoneal para - aortic liquid - filled mass measuring 60 mm  33 mm  22 mm . magnetic resonance imaging ( mri ) confirmed the presence of a retroperitoneal cyst occupying the upper left retroperitoneal space ; with mass effect displacing the left kidney down [ figure 1 ] . peroperative finding was a retroperitoneal cyst above the left adrenal , displacing the left kidney down , measuring 70 mm  30 mm ; with no communication with any portion of the alimentary tract . histopathologic examination revealed an ed cyst lined by small intestinal epithelium , with no ectopic gastric mucosa . the postoperative period was uneventful ; the patient was discharged on the 5 postoperative day . magnetic resonance imaging showing retroperitoneal cyst occupying the upper left retroperitoneal space ; with mass effect displacing the left kidney intraabdominal duplications account for two - thirds of localization , among them , jejunoileal duplications account for 65% . eds occur early in intrauterine life ; their pathogenesis remains unclear ; several hypotheses have been proposed . reported 38 cases of ed cysts ; only one was retroperitoneal communicating with a nonfunctioning right kidney . eds are a part of fetal intraabdominal cysts which evoke several differential diagnoses including ovarian cysts , renal cysts , choledochal cysts , hepatic cysts , and mesenteric cysts . marchitelli et al . found high concordance between prenatal and postnatal findings in fetal intra - abdominal cystic lesions ( 90.4% ) . double - wall  sign and peristaltism are suggestive of ed and help to differentiate it of differential diagnosis . postnatal ultrasound helps diagnosis showing an anechoic fluid - filled mass , rarely an echogenic mass is found due to complication ( hemorrhage , necrosis ) . more serious complications may occur : ulceration , perforation , severe hemorrhage , and malignant changes associated with the presence of ectopic gastric mucosa .
retroperitoneum is a very uncommon site of enteric duplication ( ed ) . 
 we report a new case of retroperitoneal ed cyst suspected in utero . 
 prenatal ultrasound showed an abdominal cystic mass . 
 noncommunicating retroperitoneal ed cyst measuring 70 mm  30 mm was resected . 
 histopathologic examination confirmed the diagnosis .