choledochal cysts are congenitally malformed thin walled , dilated , intrahepatic or extrahepatic bile ducts . these cysts offer a major challenge for diagnosis and treatment during pregnancy because of the altered physiology associated with it . there has to be fine balance between the benefits as well as the risks associated with the treatment . it is secondary to raised intracystic pressure because of distal stricture or stones [ 4 , 5 ] . spontaneous rupture of the choledochal cyst during immediate post partum has rarely been reported [ 7 , 8 ] . here we describe a young female who presented to us with choledochal cyst with cholangitis during pregnancy . but unfortunately she presented in the immediate post partum with peritonitis secondary to spontaneous rupture of the cyst . the rarity of this presentation in post partum poses a diagnostic dilemma in the minds of treating clinician . this complication should be kept in mind while treating a known patient of choledochal cyst who presents to the emergency with peritonitis . a 27-year - old primigravida presented to surgical emergency with obstructive jaundice and grade ii cholangitis at 6 months of pregnancy . she was evaluated and was found to have a choledochal cyst on ultrasound and this was subsequently confirmed as type iv ( fig . 1 ) on magnetic resonance cholangiopancreatography ( mrcp ) . for these complaints , she underwent ercp and a biliary stent was placed so as to tide over the situation . an endobiliary stent could be placed and she was being managed conservatively but had pain abdomen , fever and vomiting 1 week after stenting . tachycardia ( pr : 120/min ) was present and there was generalized guarding and rigidity on abdominal examination . a contrast - enhanced ct scan was done that revealed the rupture of the suprapancreatic part of the choledochal cyst with free fluid in the abdominal cavity ( fig . 2 ) . after optimization , this patient underwent cyst excision with roux - en - y hepaticojejunostomy . histopathology of this excised cyst confirmed the choledochal cyst rupture without any evidence of dysplasia ( fig . the patient did well in the postoperative period and was discharged on the 10th postoperative day . with recent advances in medical science , choledochal cyst is diagnosed 25% of the times during adulthood and rarely during pregnancy [ 9 , 10 ] . it is associated with multiple complications during pregnancy like cholangitis , preterm labor , abortion and even rupture . the cumulative risk of spontaneous choledochal cyst rupture varies between 1.8% and 2.8% [ 11 - 13 ] . rupture is more common during childhood and rare during post partum period of the pregnancy . weakness of the dilated cyst wall with raised intracystic pressure because of stones / strictures , trauma due to multiple interventions , regurgitation of the amylase rich fluid in the bile duct and association of the anomalous pancreatobiliary junction are the commonly reported in literature [ 14 - 18 ] . multiple ercp and stent placement secondary to cholangitis causing the cbd weakness is the most probable cause of rupture in the present case . ercp is associated with increased risk of radiation exposure and subsequent malformations in the fetus . many studies have proved the efficacy of ercp during pregnancy particularly when the radiation dose to the fetus is calculated . ercp when indicated should be done with utmost care and in controlled conditions to prevent fetal damage . . however , pregnancy along with increased pressure during childbirth puts these patients at risk for cyst rupture and fetal loss . we tided over the complications of the cyst with minimally invasive techniques but repeated interventions for the same might have triggered the rupture . there is no consensus on the management of the ruptured choledochal cyst due to the rarity of the condition . friability of the cyst wall , hemodynamic instability , inflammation and edematous bowel mandate the drainage of the cbd either with a t - tube or percutaneous transhepatic drain [ 2 , 3 ] . alternatively , single stage operation of cyst excision with bilioenteric drainage can be performed provided the intraoperative conditions are favorable . this patient had normal bowel with minimal inflammation of the bile duct so single stage operation was contemplated . cyst rupture should be kept as a differential diagnosis whenever a known patient harboring choledochal cyst presents with peritonitis . pregnancy with choledochal cyst rupture puts the maternal as well as fetal life at risk . cyst rupture should be kept as a differential diagnosis whenever a known patient harboring choledochal cyst presents with peritonitis . pregnancy with choledochal cyst rupture puts the maternal as well as fetal life at risk . ag , kc and lk were involved in writing , editing and approval of the manuscript .