Among 115 necropsy cases (1952-2004) of captive Japanese cormorants that were used for UKAI-a traditional Japanese fishing method-three Japanese cormorants (Phalacrocorax capillatus) were diagnosed with gout on the basis of gross and histological findings. At necropsy, visceral serosa, especially pericardium and hepatic capsule, thickened by chalk-appearing urate were observed. Urate was also observed in the parenchyma of kidneys. Histopathologically, amorphous eosinophilic urate was heavily deposited in the thickened serosa and ureters. Severe squamous metaplasia and keratinization of the ureteral epithelium were observed, and the ureters had dilated due to the accumulation of urate and keratins along with the infiltration of the heterophils. Tophi were observed in the kidney of two severe cases. Uratic emboli and thrombi were formed in the blood vessels of the liver, lungs, kidneys, and spleen. The cause of hyperuricemia, which is indicated by uratic emboli in the vessels, is the obstruction of the ureter by squamous metaplasia and keratinization. In addition, renal uratic accumulation may promote hyperuricemia and result in heavy deposition of urates throughout the body.
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