Diagnostic imaging of pancreatitis

Biliary tract changes in pancreatitis

Both acute and chronic inflammatory processes in the pancreas (pancreatitis) can extend to surrounding tissues. This leads to the formation of an inflammatory infiltrate or local fibrosis, ultimately causing biliary strictures.

• Cholangiography: provides detailed visualization of the narrowing. Pancreatitis-related strictures are typically characterized by smooth contours. They are tapered (gradually narrowing) and usually extend over several centimeters.
• MRCP: magnetic resonance cholangiopancreatography is an essential modality in chronic pancreatitis. Tomograms show a characteristic smooth, elongated, and incomplete stricture in the lower common bile duct. Meanwhile, the contour of the pancreatic duct itself appears irregular.

Differential diagnosis: cholangiopathies and cholangitis

When evaluating the biliopancreatic region, it is important to differentiate changes caused by pancreatitis from other inflammatory processes.

AIDS-related cholangiopathy (AIDS cholangiopathy) typically develops in patients with a CD4+ T-lymphocyte count below 100/mm³. The etiology involves opportunistic infections, most commonly Cryptosporidium and cytomegalovirus (CMV).

• Ultrasound has high sensitivity and helps exclude other causes of pain and cholestasis.
• Radiological signs: thickening and contrast enhancement of the bile duct wall, focal intra- and extrahepatic strictures (resembling primary sclerosing cholangitis), ductal dilatation (sometimes due to stenosis of the major duodenal papilla), and concurrent gallbladder wall thickening. Management may require endoscopic drainage.

Acute bacterial cholangitis (Acute Bacterial Cholangitis) is almost always associated with partial obstruction (most commonly secondary to choledocholithiasis). It is caused by polymicrobial flora (gram-negative enteric bacteria). Clinically, it manifests with Charcot's triad (Charcot triad): fever, right upper quadrant abdominal pain, and jaundice.

• Imaging: ultrasound and CT are used (especially when liver abscesses are suspected). MRCP identifies the cause of obstruction. If choledocholithiasis is highly likely, urgent ERCP and sphincterotomy are required. Treatment includes intravenous broad-spectrum antibiotics and adequate drainage (endoscopic or percutaneous).

Recurrent pyogenic cholangitis (Recurrent Pyogenic Cholangitis) occurs predominantly in Southeast Asia or among immigrants from this region. It is characterized by recurrent cholangitis, dilatation, strictures, and the formation of multiple intrahepatic calcium bilirubinate stones. Enteric bacteria and parasites (e.g., Clonorchis sinensis) are thought to play a role in the pathogenesis.

• On CT, stones are frequently visible as high-density structures within dilated ducts.
• On Ultrasound, stones may not produce acoustic shadowing.
• Cross-sectional imaging (CT/MRI) demonstrates a segmental distribution of involvement, complications (abscesses, left hepatic lobe atrophy), and disproportionate dilatation of extrahepatic and central intrahepatic ducts with normal peripheral ducts. Long-term complications include hepatic fibrosis, portal hypertension, and cholangiocarcinoma. Treatment is combined: surgical, endoscopic, and percutaneous.

Parasitic infections of the biliary tract

Parasites can also cause biliary obstruction, cholangitis, cholecystitis, and pancreatitis.

1. Ascariasis (Ascaris lumbricoides): a parasitic roundworm 20–30 cm in length and about 5 mm in diameter. It can migrate into the bile duct through the duodenal ampulla. On ultrasound or cholangiography, the worm is visualized as a characteristic tubular structure.
2. Hydatid disease (Hydatid): a small proportion of hepatic hydatid cysts can rupture into the biliary tree, causing obstruction. Ruptured cyst membranes appear as curvilinear structures on ultrasound or cholangiography. Communication between the cyst and the ducts is identified using ERCP or CT intravenous cholangiography (CT-IVC).
3. Fascioliasis (Fascioliasis): caused by the liver fluke Fasciola hepatica (leaf-shaped, 1–2 mm in size). The infection proceeds in two stages. The hepatic stage leads to the formation of multiple small abscesses and subcapsular hemorrhages. The biliary stage is accompanied by thickening of the bile duct walls; sometimes the flukes themselves are visualized inside the bile ducts or gallbladder.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• The role of ERCP and sphincterotomy in choledocholithiasis
• CT appearance of liver abscesses in bacterial cholangitis
• Differential diagnosis of strictures in PSC vs. AIDS cholangiopathy
• Complications of pyogenic cholangitis: portal hypertension and cholangiocarcinoma
• CT intravenous cholangiography (CT-IVC) in hydatid disease

Other topics in the section "Diagnostic Radiology of the Abdominal Organs"

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