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 . 
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