Comparative post-hatching histogenesis of gallbladder and extrahepatic bile ducts in chickens, ducks, and pigeons

Introduction The post-hatching development of the gallbladder and extrahepatic bile ducts play an important role in the functional maturation of the avian digestive system. However, post-hatching histogenesis is poorly characterized among species. This comparative study investigated the histogenesis of these biliary structures in chickens ( Gallus gallus domesticus), ducks ( Anas platyrhynchos ) and pigeons ( Columba livia ) from one day after hatching to eight months of age. Methods Tissue samples were examined from Forty birds ( n = 16,16,8 for each age group) of domestic chickens, ducks and pigeons at four post-hatching stages; Stage I: first day (1 dph); Stage II: one month post hatching (1 mph), Stage III: 4 months (4 mph) and Stage IV: 8 months (8 mph). The gallbladder and extrahepatic bile ducts were examined by gross morphology and light microscopy with H&E, Masson’s trichrome, Wiegert’s elastic tissue Stain, and combined PAS/Alcian blue (pH 2.5) staining. Results The gallbladder was present in chicken and duck but absent in pigeon. Morphologically it was elongated and tubular in chickens, while ovoid in ducks occupying a deep cystic fossa. Three extra-hepatic bile ducts were visualized: Hepato-cystic, Cystico-enteric and Hepato-enteric. Histologically, in ducks, the mucosal villi were consistently shorter and broader, whereas chickens exhibited taller and more elongated villi. During post-hatching development, both species showed progressive maturation of the gallbladder mucosa, characterized by increased villous complexity, progressive stromal collagenization, and lymphocytic infiltration. The lining epithelium showed strong PAS and Alcian blue positivity at all examined post-hatching stages in both species, indicating persistent mucin production and a constitutive mucosal protective barrier. Discussion This study provides baseline information on the normal post-hatching development of the avian biliary system and share in comparative anatomy, developmental biology and veterinary pathology as well as serving as a fruitful reference for future studies on avian hepatobiliary health and disease.