Canine Anal Sac Disease Study Guide

Overview and Clinical Importance

Anal sac disease encompasses a spectrum of disorders affecting the paired anal sacs located at approximately the 4 and 8 o'clock positions relative to the anus. These conditions represent one of the most common presenting complaints in small animal practice, with an estimated incidence of 12 to 16 percent in dogs and less than 1 percent in cats. The clinical spectrum ranges from simple impaction to life-threatening neoplasia, making accurate diagnosis and appropriate treatment critical for NAVLE success.

The anal sacs are invaginations of the cutaneous zone of the anal canal, positioned between the internal and external anal sphincter muscles. Each sac is lined by stratified squamous epithelium and contains both apocrine and sebaceous glands that produce a pungent secretion used for territorial marking and individual identification.

Anatomy and Physiology

Anatomic Structure

The anal sacs are paired structures positioned bilaterally at the 4 and 8 o'clock positions (or 5 and 7 o'clock) around the anus, located between the internal and external anal sphincter muscles. Each sac communicates with the cutaneous zone of the anus via a single duct that opens just lateral to the anal opening.