Gross and cytological characteristics of normal canine anal-sac secretions

A study was conducted to characterize the gross and cytological characteristics of secretions from normal canine anal sacs. Fifty dogs with no recent history of anal-sac disease were selected consecutively and their anal sacs manually expressed. Of the 47 dogs with known or estimated ages, 27 were < 1 year olds. However, these youngest dogs were not significantly different from the rest in cell counts, viscosity, or presence of dark or light solid portions of the secretions. For all dogs combined, the secretions typically contained 41 (median) corneocytes per 400x magnification microscopic field, lots of basophilic background debris, and a mixture of Gram-positive cocci (173 per field; median), Gram-positive rods (29 per field; median), and Gram-negative rods (two per field; median). Although median counts across 10 400x fields per sac indicated no leucocytes or yeasts, many of the normal dogs had an occasional 400x field with non-degenerate neutrophils and yeasts. Erythrocytes were not a feature of these anal-sac secretions, and mononuclear leucocytes were found only rarely. Extreme heterogeneity existed in gross colour, consistency and the amount of solid material. Thus, these latter parameters probably would not be valid indicators of anal-sac disease.