162 DISEASES/DISORDERS
Gender predisposition reports inconsistent: higher prevalence possible in male sexu-
ally intact dogs.
A genetic basis has been proposed but not proven.
CLINICAL FEATURES
Vary with the severity and extent of involvement (Figures 9.1–9.5).
Dyschezia.
Tenesmus.
Hematochezia.
Ribbon-like stool.
Constipation.
Diarrhea.
Malodorous anal discharge.
Purulent anal discharge or bleeding.
Painful tail movements.
Licking and self-mutilation.
Reluctance to sit, posturing difficulties, and personality changes.
Fecal incontinence.
Anorexia.
Weight loss.
Perianal sinus and fistulous tracts.
Tracts may interconnect.
Lesions may extend beyond the perianal tissues in severe cases (Figure 9.6).
DIFFERENTIAL DIAGNOSIS
Chronic anal sac abscess
Perianal infection
Perianal adenoma or adenocarcinoma with ulceration and drainage
Anal sac adenocarcinoma or squamous cell carcinoma
Colitis or inflammatory bowel disease
Rectal neoplasia
Rectal fistula
DIAGNOSTICS
Presumptive diagnosis: based on clinical signs and results of physical examination.
Biopsy (primarily to rule out neoplasia): epithelial-lined tracts with pleocellular infil-
trate, granulating fibrosis, and lymphoid nodules.
Probing of tracts to determine depth and extent.
Palpation of the anal sphincter and caudal rectum for thickening (fibrosis).