Prenatal diagnosis of choledochal cyst using ultrasound and magnetic resonance imaging.

Abstract

A 25-year-old primigravid woman was referred at 30 weeks' gestation to evaluate a fetal intra-abdominal cystic mass. Sonographic examinations revealed a singleton fetus with biometry consistent with 30 weeks of gestation. An intra-abdominal cystic mass measuring 22 × 12 mm was noted. The amniotic fluid volume was normal. Color Doppler ultrasound revealed no flow within the mass. The cyst connected via the cystic duct to the gallbladder, raising the suspicion of a choledochal cyst (Figure 1). Ultrafast magnetic resonance imaging (MRI) scans further depicted a detailed anatomical relationship of the choledochal cyst to the liver, gallbladder and biliary tract (Figure 2). The choledochal cyst consisted of a cystic dilation of the common bile duct without dilation of the gallbladder and intrahepatic bile ducts. A diagnosis of Type IA choledochal cyst was thus made. The size of the cyst remained unchanged during follow-up ultrasound examinations. Sonographic image of a choledochal cyst at 30 weeks' gestation. The choledochal cyst (CC) connects with the gallbladder (GB). Ultrafast magnetic resonance imaging scan of a Type IA choledochal cyst at 30 weeks' gestation. IHD, intrahepatic duct. At 39 weeks' gestation a female infant was born by vaginal delivery with Apgar scores of 10 and 10 at 1 and 5 min, respectively. The postnatal ultrasound and biochemical examinations confirmed the presence of a choledochal cyst. At 7 days of age the cyst was excised and a Roux-en-Y hepaticojejunostomy was performed. At surgery a Type IA choledochal cyst was noted. The histopathological features were consistent with the diagnosis of a choledochal cyst. The infant was discharged 8 days after the operation and was progressing well at 1 month of age. Choledochal cysts are rare anomalies that appear as cystic or fusiform dilations of the extra- or intrahepatic biliary tree or both. Five types of choledochal cysts have been described1. Type I cysts consist of a cystic dilation of the common bile duct (Type IA), a focal segmental dilation of the distal common bile duct (Type IB), or a fusiform dilation of both the common hepatic duct and the common bile duct (Type IC). Type II cysts are true diverticula of the common bile duct. Type III cysts, or choledochoceles, are cystic dilations involving only the intraduodenal portion of the common bile duct. Type IV cysts consist of multiple intra- and extrahepatic cysts (Type IVA) or multiple extrahepatic cysts only (Type IVB). Type V cysts comprise single or multiple cystic dilation of the intrahepatic bile ducts. The differential diagnosis of choledochal cysts includes simple hepatic cysts, biliary atresia, ovarian, omental or mesenteric cysts, duodenal or gallbladder duplications, adrenal cysts, renal cysts, dilated loops of bowel, hydronephrotic renal pelvis and situs inversus. Prenatal diagnosis of choledochal cysts with ultrasound has been well described in the literature2-5. In the preoperative assessment of choledochal cysts, MRI, MR cholangiography, and MR cholangiopancreatography have been used to accurately demonstrate the presence, extent and types of the cysts6-12. Additionally, MRI has the advantages of rapid delineation of tissue borders and easy selection of imaging planes. However, the role of MRI in the prenatal investigation of choledochal cysts remains unclear. MacKenzie et al.13 previously reported the prenatal ultrafast MRI finding of a choledochal cyst in a fetus at 16 weeks' gestation. In their case, the MRI image of the choledochal cyst was presented as a simple intra-abdominal cyst that was not different from that obtained by prenatal ultrasound. In contrast, the present case provides evidence that, in the third trimester, MRI is able to present more precise information than ultrasound in delineating the anatomical relationship of the cyst to the liver, gallbladder and biliary tract. We suggest that ultrafast MRI is a useful tool in the third-trimester investigation of choledochal cysts in addition to prenatal ultrasonography. C.-P. Chen* , S.-J. Cheng?, T.-Y. Chang*, L.-F. Yeh*, Y.-H. Lin*, W. Wang , * Department of Obstetrics and Gynecology, Mackay Memorial Hospital, 92, Section 2, Chung-Shan North Road, Taipei, Taiwan, Republic of China, Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan, Republic of China, Department of Nursing, National Yang-Ming University, Taipei, Taiwan, Republic of China, ? Department of Radiology, Mackay Memorial Hospital, Taipei, Taiwan, Republic of China