Ureteral morphology and pathology during urolithiasis in cats

Cats exhibit high susceptibility to urinary organ-related diseases. We investigated the healthy ureter morphol-ogies and compared these with ureters that were surgically resected distal to a urolithiasis obstruction in cats. Healthy ureters (total length 9.88 +/- 0.38 cm) developed adventitia composed of collagen fibers (ADCF), con-taining a longitudinal muscular layer, toward the distal segment. The healthy ureter was the smallest in the middle segment (4.71-6.90 cm from the urinary bladder) with significantly decreased luminal and submucosal areas compared to those in the proximal segment. Diseased cats exhibited a high incidence of calcium oxalate urolithiasis with renal dysfunction, regardless of age, sex, and body size. Diseased ureters showed increased perimeters, inflammation, and decreased nerves in ADCF. Collagen fibers were increased in the submucosal area, intermuscular spaces, and ADCF, particularly near the obstructed lesion. The mean resected ureter length was 5.66 +/- 0.49 cm, suggesting a high obstruction risk in the middle segment. The middle segment also increased the cross-sectional area of the ureter and ADCF, regardless of the distance from the obstructed lesion. The ureters in several cases either lacked the transitional epithelium, or exhibited transitional epithelial hyperplasia, and some of these formed the mucosal folds. In conclusion, we demonstrated the following characteristics and histo-pathological features of cat ureters: decreases in the ureter size, lumen area, and submucosa area from proximal to middle segment in healthy; ADCF changes in urolithiasis, including increased connective tissues with inflammation and decreased nerves. These data are important to understand the pathogenesis of feline ureteral obstruction.

Automated summary

Cats are highly susceptible to urinary organ-related diseases. This study investigated the morphologies of healthy ureters and compared them with surgically resected ureters affected by urolithiasis obstruction. The findings revealed that healthy ureters exhibited a decrease in size, lumen area, and submucosa area from the proximal to middle segment. Diseased ureters showed increased connective tissue, inflammation, and decreased nerves. These findings provide important insights into the pathogenesis of feline ureteral obstruction.