The luminal surface is seen at the far right, entirely replaced by gangrenous fibrinous exudate.

The exudate is composed of numerous degenerating neutrophils and smudgy chromatin.

Areas with an intact surface show neutrophils involving the epithelium and congested dilated capillaries that rupture into the lumen.

If less involved areas remain intact, nuclear irregularities compatible with reactive atypia may be found.

The gallbladder wall in acute cholecystitis is usually thickened by profound edema, seen here as stromal pallor and hypocellularity. Dissecting RBCs are found with the edema fluid.

Another image showing the extreme degree of edema.

Interstitial hemorrhage is marked, and reactive fibroblasts are seen within the altered stroma. The fibroblastic stroma is loosely arranged.

A different gallbladder again shows the interstitial hemorrhage and reactive fibroblasts in the stroma.

Gangrenous cholecystitis is a severe form of acute cholecystitis. The gallbladder becomes a green-black necrotic organ and there may be perforation as well. In a study of 200 cases of acute cholecystitis, gangrenous cholecystitis was seen in about 20% of cases (Ahmad). Histologic findings include edema of the gallbladder wall, a prominent leukocytic infiltrate, vascular congestion, abscess formation, and gangrenous necrosis.

This entity arises with increased incidence in men, in those with cardiovascular disease and WBC counts greater than 17,000 WBC/mL. Signs are similar to acute cholecystitis, and the diagnosis is not usually made prior to cholecystectomy. CT findings may include intraluminal membranes, and hemorrhage into the lumen (Merriam).

Increased morbidity is seen, with about 8% rate of intraabdominal abscess.