Simple columnar epithelium with no muscularis mucosae or submucosa
Expansion
Gallbladder wall
- Mucosa: simple columnar epithelium with microvilli, thrown into folds when empty. No goblet cells normally
- Lamina propria
- No muscularis mucosae and no submucosa, unlike the rest of the gut
- Muscularis (irregularly arranged smooth muscle)
- Perimuscular connective tissue, and serosa except where it abuts the liver
The absence of the submucosa means tumour reaches the perimuscular tissue and the liver early, which is one reason gallbladder carcinoma has such a poor prognosis, and why its staging system differs.
Rokitansky-Aschoff sinuses are outpouchings of mucosa herniating through the muscle layer, seen in chronic cholecystitis and reflecting raised intraluminal pressure.
Chronic cholecystitis shows these sinuses, mucosal flattening, fibrosis and a lymphocytic infiltrate; extensive calcification gives a porcelain gallbladder, which carries a malignancy risk.
The bile ducts are lined by simple columnar epithelium, and their progressive destruction with granulomas characterises primary biliary cholangitis, while periductal onion skin fibrosis characterises primary sclerosing cholangitis.