Anorectal lymphadenopathy causing colic, perirectal abscesses, or both in five young horses.

Enlarged anorectal lymph nodes can cause colic in young horses by obstructing the caudal aspect of the rectum. Dyschezia and clinical signs consistent with abdominal pain were the predominant reasons for evaluation of the 5 young (3 to 15 month old) horses of this report. Digital transrectal palpation revealed a firm mass obstructing the caudal aspect of the rectum in each horse. Results of cytologic evaluation of the masses revealed a lymphoid population of cells in 4 of 5 horses. These nodes regressed over time or became abscesses and drained into the rectum. In 1 horse, detection of a mature abscess and concomitant dysuria necessitated immediate surgical drainage of the mass; however, the other 4 horses were successfully managed medically, thereby avoiding risks associated with surgery of the perirectal area. Anorectal lymphadenopathy should be considered as a differential diagnosis in young horses with colic.