Imaging examinations serve as the primary approach for diagnosing diseases of the biliary system. Commonly used methods include:
Ultrasound Examination
Ultrasound is the first-line method for diagnosing biliary diseases, providing diagnostic accuracy rates exceeding 95% for gallbladder stones and intrahepatic bile duct stones. Diagnostic accuracy for extrahepatic bile duct stones is approximately 80% due to interference from gastrointestinal gas. Ultrasound can detect intrahepatic bile duct diameters exceeding 0.4 cm and extrahepatic bile duct diameters greater than 1.0 cm, which may indicate ductal dilation and potential obstruction sites and causes. Ultrasound is also highly accurate for diagnosing acute and chronic cholecystitis, gallbladder and bile duct tumors, and congenital biliary anomalies. Certain procedures and treatments, such as gallbladder puncture and drainage, can be performed under ultrasound guidance.
X-Ray Examination
During surgery, cholangiography conducted via puncture or catheter insertion into the cystic duct or common bile duct can provide information regarding anatomical variations in the biliary system, residual stones, bile duct strictures, and ductal patency, aiding surgical decision-making. For patients with intrahepatic or extrahepatic bile duct catheters (including T-tubes) placed for drainage, routine pre-removal cholangiography is generally performed. Abdominal X-rays have limited utility and are primarily used to differentiate biliary diseases from other intra-abdominal conditions, such as gastrointestinal perforation or bowel obstruction.
CT (Computed Tomography)
CT scans allow identification of the causes and locations of biliary obstructions. Enhanced CT plays a critical role in the diagnosis, staging, and preoperative and postoperative evaluation of biliary tumors.
MRI and Magnetic Resonance Cholangiopancreatography (MRCP)
MRI provides assessments of the resectability of biliary tumors and aids in the differential diagnosis of complex biliary system diseases. MRCP offers a clear visualization of the biliary tract structure, with a detection rate of 90%–100% for normal intrahepatic and extrahepatic bile ducts. It is valuable for identifying bile duct strictures, biliary injuries, intrahepatic and extrahepatic stones, biliary anomalies, and for locating the site of biliary obstructions.
Nuclear Scintigraphy
Single-Photon Emission Computed Tomography (SPECT) involves the intravenous injection of radioactive agents, with dynamic imaging recorded using a gamma camera or SPECT. This method aids in the differential diagnosis of jaundice and the identification of post-operative bile leakage.
Positron Emission Tomography (PET) is used for distinguishing between benign and malignant biliary lesions and for detecting recurrence or metastases of biliary tumors.
Percutaneous Transhepatic Cholangiography (PTC)
PTC involves the percutaneous insertion of a catheter into the intrahepatic bile ducts under X-ray or ultrasound guidance, followed by injection of a contrast agent to obtain rapid visualization of intrahepatic and extrahepatic bile ducts. This method is effective for identifying the location, extent, and severity of biliary lesions and for aiding the diagnosis and differential diagnosis of jaundice and characterization of biliary diseases. Common complications include bile leakage, bleeding, and biliary tract infections. This method also supports therapeutic procedures, such as percutaneous transhepatic cholangial drainage (PTCD) for jaundice reduction or bile duct stent placement.
Endoscopic Retrograde Cholangiopancreatography (ERCP)
ERCP involves the insertion of a catheter into the bile or pancreatic ducts via the duodenal papilla under direct visualization using a fiber-optic duodenoscope, enabling cholangiography. The duodenum and papilla can also be directly visualized. ERCP aids in identifying anatomical variations and lesions in the bile and pancreatic ducts while allowing for sampling of tissues or cells for pathological diagnosis. As an invasive procedure, ERCP carries risks of complications such as pancreatitis, bleeding, perforation, and biliary tract infections. For this reason, diagnostic ERCP is recommended only when non-invasive imaging modalities, such as ultrasound, CT, or MRI, fail to provide definitive diagnoses. ERCP also permits treatment of certain biliary diseases, such as endoscopic sphincterotomy for stone removal in cases of extrahepatic bile duct stones, or nasobiliary drainage for obstructive jaundice.
Cholangioscopic Examination
Intraoperative cholangioscopy can assist in diagnosis and treatment by identifying bile duct strictures, tumors, or stones. Biopsy specimens or debris can be collected using the cholangioscope, and procedures such as stone retrieval can be performed using a basket device. Postoperatively, the cholangioscope can be used for stone fragmentation, removal, flushing, balloon dilation, or hemostasis, either through a sinus tract or a preplaced jejunal Roux-en-Y loop.
Endoscopic Ultrasound (EUS)
EUS provides detailed visualization of the structural layers of the bile ducts and the duodenal wall. It is particularly valuable for assessing the nature and extent of periampullary lesions. In uncertain cases, needle biopsies can be performed under ultrasound guidance to confirm pathological diagnoses.