Anal Sac Disease in Dogs

Anal sac impaction is caused by blockage of the ductal outflow of anal sac secretion. Anal sacculitis is an
inflammation of the anal sacs. Abscessation occurs
when the anal sacs rupture under the skin and cause
an abscess that usually forms a draining tract.
Aetiology and pathogenesis
Anal sac disease can be caused by many inflammatory factors that may cause closure of the ductal
opening, including atopic dermatitis, food allergy,
colitis, obesity, conformation, perianal fstulae,
masses, anal hyperplasia and trauma.
Clinical features
Dogs and cats scoot, lick or show pain in the area of
the affected anal sac. Pain can be intense during defecation or when the tail is raised. Enlargement of the
glands may be palpated externally or by rectal exam.
Draining tracts with purulent or haemorrhagic discharge, inflammation and cellulitis may be present
over the inflamed abscessed gland.
Differential diagnoses
• Atopic dermatitis and food allergies commonly
cause perineal pruritus, licking and scooting.
• Colitis or inflammatory bowel disease causing
chronic diarrhoea may cause anal licking and
scooting.
• Perineal fstulae cause draining tracts around
the anus and into the anal sac.
• Faecal parasites.
Diagnosis
All pets with anal sac issues should have a rectal
exam to make sure that there are no masses or other
causes of the symptoms. Palpation of an enlarged
anal sac and the resolution of symptoms by emptying the sac, are diagnostic for impaction. If painful,
sedation or anaesthesia will be needed for thorough
evaluation. Blood in the anal sacs is not a normal
fnding and indicates anal sacculitis.
1,2 An inflamed,
painful anal sac that has abscessed under the skin

with or without a draining tract is fairly characteristic, but if several draining tracts are present
consider perineal fstulae, especially in German
Shepherd dogs. Cytology of anal sac contents of
normal dogs shows neutrophils, intracellular bacteria and yeasts, and so cytology may be of limited
beneft.
3,4 Bacterial culture may be necessary if the
infection fails to respond to treatment.


Treatment:

• Underlying causes of anal sac inflammation should be looked for and treated, which may include diet trials for colitis and atopic dermatitis.
• Increased fbre diets to increase the bulk and frmness of the faeces can be tried.
• Impacted anal sacs should be carefully expressed and the underlying cause addressed. Follow-up cases to ensure that symptoms resolved after the anal sacs were expressed.
• Bloody discharge from the anal sac duct needs to be treated with anal sac lavage and instillation of medications. All cats and some dogs need sedation for this procedure. This involves cannulating the anal sac duct with a tom-cat catheter, a 22-gauge intravenous catheter (without needle) or a 5-Fr red rubber catheter, and lavaging repeatedly with saline. If lavage fluid cannot be sucked into the syringe the catheter should be withdrawn and the anal sac manually but gently expressed to remove debris. When the lavage fluid is mostly clear, the sac should be emptied completely and flled with a topical steroid/antibiotic/antifungal ear product. This process should be repeated every 10–14 days until the anal sac is no longer bloody; usually two treatments are needed. The case should be re-valuated if more than four treatments are needed. Oral antibiotics are probably not helpful in these cases.
• If the anal sac is abscessed, has formed a draining tract to the outside and is draining well, only pain medication and oral antibiotics may be needed, depending on the severity of the condition. If the abscess has not penetrated
to the outside, or if a pocket of fluid has formed below the draining tract, the animal can be anaesthetised and the abscess opened at the point area most dependent and furthest from the anal opening, to obtain a sample for bacterial
culture, and for flushing. The opening should be left open to drain and heal by second intention. These openings typically heal well with oral antibiotics and pain medications. Cases should be rechecked when less painful to ensure that there are not underlying causes for anal sac inflammation.
• Chronic anal sac disease that is painful and recurrent may warrant surgical removal of the anal sacs.
2 Bear in mind that removal of the anal sacs will not help with scooting or licking of the anus if these symptoms are due to other diseases – owners should be warned about this beforehand or they may be disappointed in the results. Faecal
incontinence, anal stricture and fstulation are possible complications.

Key point

• The underlying causes of anal sac inflammation must be addressed to prevent recurrence.