Disorders of the Anal Sac in Dogs

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It’s all fun and games in the clinic until we have anal sac in dogs expression day, correct? Most veterinarians and veterinary technicians are not fond of diseases in dogs affecting the anal glands probably because of the foul smell while dealing with them.

But there are quite a few situations when anal gland expression isn’t the solution to a problem that requires a more detailed and professional approach.  That’s why owners are advised not to perform anal sac expression at home and consult a vet when a problem occurs.

About the Anal Sac in Dogs

anal sac in dogs

Dogs have anal sacs situated between the inner and outer anal sphincter on both sides (positions 4 and 8 o’clock). The anal sacs produce a nasty-smelling fluid which is considered to have territory marking characteristics.

The most common condition regarding the anal sacs is probably the impaction of fluid inside the anal sacs and some breeds more predisposed to it than others are Chihuahuas, Toy Poodles, Miniature Poodles, and German Shepherds.

Less frequently vet professionals come across inflammation of the anal sacs, abscesses of the sacks, or tumors. While being quite common in dogs, anal sacs disorders in cats rarely occur.

Canine Anal Sac Impaction

If you notice your dog chasing its tail, licking and biting the area around the anus, itching, and scratching, having difficulties defecating and scooting around, you can suspect a problem with the anal sacs and visit your vet as soon as possible.

The exact causes of anal sacs impaction are unclear, but some predisposing factors include excessive secretion, chronic or recent onset of diarrhea, soft feces, poor muscle tone, etc.

The veterinarian will ask tons of questions about any obvious symptoms, history of diseases, any particular incidents and will make a complete physical examination of the dog.

Just to rule out any other more serious diseases, the vet might also suggest performing a complete blood count, serum biochemical profile, electrolyte status, and urinalysis.

The first obvious sign is enlarged anal sacs which can be easily palpated. In cases of impaction, the fluid coming out the glands will have a thick and brown to dark yellow appearance, aside from the normal pale look. When there is a forming of abscesses the exudates contain red to brown colors.

In cases with minor changes, it’s enough to just express the anal sac contents and also apply some antiseptic solutions. The problem tends to be recurrent once apparent, so your vet will schedule frequent follow-up appointments to maintain control of the situation.

Anal Sac Inflammation in Dogs

foxterrier dragging butt across tiles

This is a progressed stage of the impaction when the anal sacs become inflamed due to a number of reasons like soft stool, reduced physical activity, perineal fistulae, chronic colitis, etc.

The anal sac ducts are quite narrow so inflammation can be due to other conditions in the perineal region that potentially causes pressure and blocks the ducts.

The symptoms are generally the same as with anal sac impaction but they tend to be more severe and more painful.

The treatment protocol starts with anal sac expression. When the content of the glands and the ducts is too thick and hard it should be flushed with saline. Afterward, an antiseptic solution (Chlorhexidine or povidone-iodine) is applied in order to wash the sacs and the ducts.

In the end, an antibiotic topical solution is used with or without a corticosteroid component.

Anal Sac Perineal Fistulas

Perineal fistulas are drainage sites the pathological process naturally creates in order to evacuate accumulated content. The fistulas appear ventrolaterally to the anus after serious anal sac inflammation and abscess. The cause of perineal fistulas isn’t always the result of an anal sac disorder but frequently this is the main factor.

In this case, again the anal glands are expressed, thoroughly washed and the fistulas are drained. The dog starts with systemic antibiotic therapy for a period of 14-21 days. If during this period the fistulas remain open the vet will probably suggest a surgical extraction of the anal glands (saculectomy).

Canine Anal Sac Saculectomy

Two types of procedures exist, a closed surgical procedure and an open surgical procedure. With the closed surgical procedure, the lumen of the anal sac remains intact. The procedure starts with filling the lumen with wax and separating the gland from the surrounding tissue, tying the ducts and reconstructing the surgical site.

With the open procedure, the lumen is opened and the gland is extracted along with the duct.

The most common post-surgical complication is fecal incontinence as a result of damage done to the anal sphincters and the caudal rectal nerve. Cases of persistent perineal fistulas after a saculectomy have been reported when some parts of the sac tissue remained inside the anus.

Anal Sac Tumors in Dogs

The most common type of tumor affecting the anal glands in dogs is adenocarcinoma which tends to metastasize to the regional lymph nodes. More cases have been reported in female dogs rather than male dogs. Except for the regional lymph nodes, the tumor often metastasizes to the lungs.

The main symptoms include enlargement and swollen subcutaneous mass in the perineal region and troubles with defecation. With digitorectal examination, the vet will notice a unilateral enlargement where the affected anal sac is situated.

The electrolyte profile in these patients shows hypercalcemia and hypophosphatemia. This is due to the tumor excreting a matter similar to the parathormone. Some dogs with paraneoplastic syndrome experience polyuria and polydipsia, muscle weakness and episodes of vomiting.           

The disorder is surgically treated, but before the surgical procedure starts, patients with electrolyte imbalance need to be treated with isotonic IV solutions to regulate hypercalcemia.

The procedure is the same with anal sac saculectomy. Extraction of affected regional lymph nodes is sometimes performed in cases of regional metastasis.

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