Microscopic and ultrastructural lesions of the ureter and renal pelvis in sows with regard to Actinobaculum suis infection.

Tissues from ureter and renal pelvis of 18 sows naturally (n = 15) and experimentally (n = 3) infected with Actinobaculum suis (former Actinomyces, Eubacterium suis) were studied using light and scanning as well as transmission electron microscopy. The results were compared with the findings from 11 clinically healthy sows as controls. The lesions in both the ureter and renal pelvis of naturally and experimentally infected animals were similar. In severe cases there were necrotizing ureteritis and pyelitis with accumulation of bacterial colonies in some cases. Several superficial epithelial cells were found phagocytosing necrotic debris. In mild cases the main lesions included epithelial cell hyperplasia, desquamation of the superficial epithelial cells and goblet cell metaplasia with intraepithelial cyst formation. The goblet cells were found in the superficial as well as in the intermediate cell layers. Generally, it was observed that severe purulent ureteritis and pyelitis/ pyelonephritis in sows were to be expected only in mixed infection of A. suis with other bacteria. The findings were compared and discussed with the changes in the infected urinary bladder of sows and the alterations induced by urinary tract infection in man.