Anatomic predisposition to perianal fistulae formation in the German shepherd dog.

Gross and microanatomic features which may predispose the German Shepherd Dog to perianal fistulae formation were studied in 2 groups of clinically healthy dogs: a predisposed group (German Shepherd Dogs) and a control group comprising breeds not ordinarily affected by perianal fistulae. The dimensions of the anal crypts (depth, base width, and length), measured and compared statistically between samples, identified no significant variation between groups (P greater than 0.05). Major tissue components of the anal canal were measured microscopically and were similarly evaluated: epithelial height in each zone, thickness of the lamina propria in each zone, thickness of the internal and external anal sphincter muscles, and density of the circumanal, sebaceous, and apocrine sweat glands. The only significant finding was an increase in density of apocrine sweat glands in the zona cutanea in the pre-disposed dog group. In a semiquantitative analysis of the inflammatory responses frequently seen in the anal glands, more mature fibroplasia was seen in the German Shepherd Dogs, indicating that inflammation was more longstanding in this group.