Small Animal Dermatology Q&A 21

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A dog was presented as an after-hours emergency for the complaint of acute rectal bleeding. Note the perianal furunculosis, erythema, and exudation. After sedation, fistulous tracts were found 1–2 cm lateral to the anus in positions between 6 and 8 o’clock.

Question	Answer		Article
What is the diagnosis?	Anal sac abscessation with rupture and perineal furunculosis.		Link to Article
How should the dog be treated?	This is a chronic problem due to extensive perianal furunculosis and cellulitis. Under general anesthesia, all of the hair from the surrounding area should be clipped. The abscesses should be incised and debrided by curettage, and the wounds should be flushed with a large volume of a dilute antibacterial solution (povidone-iodine or chlorhexidine). Appropriate analgesic treatment should be prescribed, as home care will require twice-daily hydrotherapy. Oral antibiotics (e.g. cephalexin 30 mg/kg PO q12h for 30 days) should be prescribed. Healing of the lesions will occur by granulation. There is the risk that damage to the anal sacs and/or ducts may lead to chronic fistulous tracts and recurrent infections. If this occurs, surgical removal of the anal sacs may be necessary. In this dog, the diffuse perianal furunculosis suggests that there may be an underlying pruritic trigger. Surgical excision may resolve the infections, but relapses of perianal furunculosis and inflammation will persist unless the underlying cause is found.		Link to Article
What is the source of secretions of the anal sac and what is its function?	The walls of the sac are comprised of sebaceous glands and the ducts are lined with numerous epitrichial sweat glands. The anal sac fluid is a mixture of fatty acids, serous secretions, and cellular debris. The function is unknown but is presumed to be part of scent marking/social function.		Link to Article