170 DISEASES/DISORDERS
Tenesmus.
Involuntary leakage of malodorous contents from the anal sacs.
Blood-tinged exudate on feces.
Cats: excessive licking of the tail fold and tail base or perianal region.
Anal sac abscessation: malodorous, blood-tinged secretions; pain when sitting or
unwillingness to sit (Figure 10.3).
Anal sac adenocarcinomas:
May secrete a parathormone-like substance that causes pseudohyperparathy-
roidism with hypercalcemia, causing polyuria, polydipsia, weakness, lethargy,
or gastrointestinal signs (53% of cases)
Renal calcification may produce renal failure
Locally invasive
May be bilateral (14%)
Older dogs (>10 years)
High metastasis rate (47–96%).DIFFERENTIAL DIAGNOSIS
Food hypersensitivity
Atopic dermatitis
Flea bite hypersensitivity
Gastrointestinal parasites
Colitis
Tail fold pyoderma
Psychogenic (behavioral) perianal pruritus
Neoplasia
Perianal fistulae
DIAGNOSTICS
Rectal exam.
Expression of anal sacs; contents should evacuate without significant pressure or dis-
comfort to patient.
Impacted sacs may contain thick, pasty fluid; often becomes thinner with infection
and accumulation of inflammatory cells (pus).
Cytology of contents: ineffective for distinguishing between normal and affected dogs;
neutrophils and bacteria common.
Culture and sensitivity of contents or draining tract; gram-negative bacteria
predominate.
Adenocarcinoma:
CBC, serum chemistry: azotemia, hypercalcemia, hypophosphatemia
Urinalysis and sediment: hypercalciuria, urine specific gravity increased