To the Editor:
Anatomical variations of the biliary tree are not uncommon but isolated agenesis of the gallbladder is rare,^[1] with a reported incidence of 0.013%-0.075%.^[2] This variation remains undiagnosed since the patient is often asymptomatic. In spite of available diagnostic modalities, preoperative diagnosis is sometimes difficult.
A 28-year-old woman presented with symptoms of dyspepsia and upper abdominal discomfort. Routine biochemical and hematological investigations demonstrated no abnormalities. With a shrunken gallbladder with an acoustic shadow shown by sonography, the patient was hospitalized for laparoscopic cholecystectomy. Intraoperatively, no gallbladder was observed in its normal position. The whole supraduodenal part of the common bile duct was explored but no evidence of the gallbladder or cystic duct was found. Other abnormal locations, including the retrohepatic on the left side, falciform ligament, and lesser omentum were also excluded. The procedure was terminated at this stage. In the postoperative period, magnetic resonance cholangiopancreatography was carried out to confirm the diagnosis of gallbladder agenesis (Fig.). Associated congenital anomalies like annular pancreas and lumbar hernia were also re-examined intra- and post-operatively, but nothing was found. The patient was put on proton pump inhibitors and responded well.
In the 3rd week of fetal life, ventral thickening of the endoderm at the distal end of the foregut forms the liver. The caudal end of this endoderm proliferates to form the gallbladder and cystic duct. Gallbladder or cystic duct agenesis is a rare condition, about 450 cases have been reported.^[1-8] It is difficult to diagnose gallbladder agenesis preoperatively. Annular pancreas and lumbar hernia are other anomalies associated with gallbladder agenesis.^{[9, 10]} In the present case, there was no other associated anomaly.
If the gallbladder is not found at its normal or abnormal locations on laparoscopy, open exploration of the extrahepatic biliary system can be avoided. Newer imaging modalities are relatively non-invasive and can provide good information on biliary tract anatomy preoperatively. All patients with gallbladder agenesis undergoing abdominal exploration pose a challenge to the surgeon to correctly identify the anomaly and avoid injury to the bile duct.^[11]