Complications: Gangrene and Perforation
The most formidable complications of acute inflammation are gangrenous cholecystitis and wall perforation. When gangrene develops, portal venous phase CT, MRI, and contrast-enhanced ultrasound (CEUS) reveal discontinuous, irregular contrast enhancement of the mucosal layer. This is a highly specific sign indicating tissue ulceration and necrosis. Additionally, intraluminal detached membranes and gas foci within the thickness of the wall are visualized.
Wall perforation occurs in 5–10% of patients. It may present as free bile leakage into the abdominal cavity, a localized pericholecystic abscess, or fistulous tract formation. Typical imaging signs include relative collapse of the gallbladder and surrounding fluid. A localized wall defect is best seen on CT, whereas CEUS demonstrates a lack of enhancement in the rupture zone.
Atypical Forms of Acute Inflammation
Emphysematous cholecystitis (Emphysematous Cholecystitis) is a rare but extremely dangerous form with high mortality. It is more common in men, and gallstones are present in less than half of the cases. Gas-forming microflora produce gas that accumulates in the wall or lumen. On ultrasound, intraluminal gas gives a characteristic bright echogenic curvilinear stripe with "dirty" acoustic shadowing, while small foci in the wall produce the "comet-tail" artifact. On MRI, gas appears as an area of complete signal dropout (signal void).
Acalculous cholecystitis (Acalculous Cholecystitis) is typical for ICU patients. Diagnosis is difficult because gallbladder distension and echogenic sludge may be the result of a critical illness rather than inflammation. In doubtful cases, percutaneous cholecystostomy is performed, which provides a rapid therapeutic effect. A debatable form of chronic accalculous cholecystitis is also distinguished, in which cholescintigraphy with cholecystokinin reveals an ejection fraction of less than 35%, confirming gallbladder dysfunction.
Chronic Processes and Differential Diagnosis
Radiological evaluation requires clear differentiation of inflammatory changes from neoplastic ones:
- Xanthogranulomatous cholecystitis: a rare chronic process mimicking cancer. It is distinguished from carcinoma by 5 key features: mucosal continuity, diffuse wall thickening, the presence of hypoattenuating nodules (hypoattenuating), and sparing of the liver and intrahepatic ducts.
- Adenomyomatous hyperplasia: benign wall thickening with the formation of Rokitansky–Aschoff sinuses. Ultrasound is characterized by the "comet-tail" artifact, while fat-suppressed MRI clearly shows intramural cystic inclusions.
- Porcelain gallbladder: complete or focal wall calcification. The condition is associated with a risk of malignancy, therefore prophylactic cholecystectomy is indicated for patients.
- Gallbladder fistulas: usually communicate with the duodenum in the setting of chronic cholelithiasis. A formidable consequence is gallstone ileus, in which CT shows aerobilia and an obstructing stone in the intestinal lumen.
Lesions: Polyps and Cancer
Gallbladder polyps are most commonly cholesterol polyps, with true adenomas being less frequent. On ultrasound, they appear as echogenic lesions fixed to the wall in the dependent portions and do not produce acoustic shadowing. They are distinguished from biliary sludge by the presence of blood flow on color Doppler mapping.
According to guidelines, surgical treatment is indicated for polyps larger than 10 mm, as well as for those measuring 6–9 mm in patients with symptoms or risk factors (age over 50 years, primary sclerosing cholangitis). Gallbladder carcinoma is a rare pathology with a poor prognosis. In late stages, it manifests as biliary obstruction and is visualized as a large mass replacing the gallbladder.
Briefly: answers to topical questions
What clinical and morphological forms of acute cholecystitis are distinguished in surgical classification?
Based on the depth of wall destruction, three main clinical and morphological forms of acute cholecystitis are distinguished.
- Catarrhal — characterized by superficial inflammation.
- Phlegmonous — represents purulent inflammation.
- Gangrenous — accompanied by wall necrosis.
In an unfavorable course and with a burdened comorbid background, the initial catarrhal process can progress to these destructive forms.
What imaging signs make up the classic Rigler's triad in gallstone ileus?
The cited sources do not explicitly mention the term "Rigler's triad". The following imaging signs are described for gallstone ileus:
- Intestinal obstruction — in more than 50% of patients, plain radiographs show signs of bowel obstruction.
- Pneumobilia / aerobilia — the presence of gas in the biliary tract; in pneumobilia, gas has a branching pattern and is more pronounced centrally, closer to the porta hepatis.
- Gallstone — usually 2–3 cm in size; identified on plain abdominal radiographs in approximately 1/3 of patients.
What risk factors and pathological conditions provoke the development of acute accalculous cholecystitis?
Acute acalculous (acalculous) cholecystitis is most commonly observed in severely ill patients in critical condition; the clinical presentation generally corresponds to sepsis.
The diagnostic algorithm specifies the presence of characteristic risk factors for acute accalculous cholecystitis, an infectious disease, or parasitosis as an initial condition.
What is the normal thickness of the gallbladder wall in millimeters on ultrasound?
According to ultrasound examination, the wall of a normal, uncontracted gallbladder is smooth, and its thickness is less than 3 mm.
For accurate evaluation, the examination is performed after a 4-hour fast, which allows the gallbladder to fill and reduces gas in the upper abdomen.
To differentiate a polyp from a small gallstone on ultrasound, remember the two "S" rule: Shiftability (a stone moves with postural changes, a polyp is fixed) and Shadow (a stone produces a thin acoustic shadow, a polyp does not).
Class and exam questions
How to reliably differentiate a gallbladder polyp from thick sludge on ultrasound?
Use color Doppler flow mapping. Internal blood flow is registered in a true polyp, whereas sludge is completely avascular.
What is the danger of a cholecystoduodenal fistula?
A large calculus can migrate through a fistula into the intestine and cause obturation obstruction of the distal small bowel — this complication is called gallstone ileus.
What is the most reliable imaging sign of gallbladder gangrene?
Discontinuous or irregular mucosal enhancement due to ulceration. This sign is well visualized on CT, MRI, and contrast-enhanced ultrasound.
What else to study on this topic
- Gallbladder Mucocele (Hydrops): Pathogenesis and Imaging Findings
- Gallstone Ileus: Imaging Diagnosis and Aerobilia
- Rokitansky–Aschoff Sinuses: Histology and MRI Visualization
- Criteria for Gallbladder Dysfunction on Cholescintigraphy
- Contrast-Enhanced Ultrasound (CEUS) in Assessing Polyp Malignancy Risk
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