Elective ovariohysterectomy or castration can proceed in shelter dogs despite mild to moderate presurgical leukocytosis.

Objective: To determine whether shelter dogs presenting for elective ovariohysterectomy or castration have leukocytosis, whether leukocytes are associated with age and infection, and whether leukocytosis precludes progression to surgery.

Animals: 138 dogs (from 13 regional shelters) presented for ovariohysterectomy or castration between October 7 and December 6, 2019.

Procedures: For this prospective study, each dog underwent presurgical physical examination, CBC, and tests for Dirofilaria immitis antigen and Anaplasma phagocytophilum, Borrelia burgdorferi, and Ehrlichia canis antibodies, with additional tests performed as needed. Dogs were aged by dentition as juvenile (< 3 or ≥ 3 to ≤ 6 months) or adult (> 6 months). Leukogram results were compared across age groups with recognized infections and parasitism and with dogs' progression to surgery.

Results: There were 34 dogs < 3 months old, 22 dogs ≥ 3 to ≤ 6 months old, and 82 > 6 months old. Sixty-three of 138 (45.6%) dogs had leukocytosis (median, 16,500 cells/µL; range, 13,700 to 28,300 cells/µL). Dogs < 3 months of age had higher median leukocyte and lymphocyte counts (14,550 cells/µL and 3,700 cells/µL, respectively) than dogs > 6 months of age (12,500 cells/µL and 2,400 cells/µL, respectively). Only 1 dog had a stress leukogram. Forty-seven dogs had recognized infection, but there was no association with leukocytosis. Surgery proceeded successfully for all dogs with leukocytosis.

Clinical Relevance: Mild to moderate leukocytosis is common before elective surgery in shelter dogs, but surgery can proceed safely. A CBC should be reserved for ill-appearing dogs rather than as a screening test, and age-specific reference intervals should be considered.