Interdigital cysts and their God-forsaken therapies

Written by:

Patty Khuly, DVM
Published: February 25, 2009

Have you ever spied a fleshy protuberance between your dog’s toes that looked like...

a) a fleshy welt

b) an ulcerated sore

c) a hairless bump, or

d) all of the above?

If so, you more than likely ran (fast!) to your veterinarian’s place only to be told your pet probably has a “simple” interdigital cyst — more correctly termed an “interdigital furuncle.” Your veterinarian may or may not have inserted a needle to extract some cells to send off for cytology (to ensure it didn’t scream “cancer”!), cultured the lesion (to identify the kind of bacteria present), and/or scraped the area to investigate for the presence of demodex mites (which are sometimes involved). Then you spent the next month or three either...

a) plying your pet with antibiotics and/or steroids and/or mite killers

b) managing an E-collar-enabled dog about the house

c) soaking her feet in Epsom salts twice daily

d) testing her for allergies

e) testing for thyroid disease

f) attempting a food trial (in case of food allergies)

g) shampooing her feet

h) whittling down her weight

i) wiping between her toes with medicated cloths

j) seeing the veterinary dermatologist, or

k) all of the above

Or perhaps your veterinarian got fed up (or you did) and you elected to have the sucker biopsied, either by completely removing the thing — just in case — or by sticking a sharp punch right over the swelling and extracting a 6 to 8 mm-sized core of flesh to send off to the histopathologist.

According to the Merck Veterinary Manual (which every pet owner should own, IMO):

"Interdigital furuncles, often incorrectly referred to as 'interdigital cysts,' are painful nodular lesions located in the interdigital webs of dogs. Histologically, these lesions represent areas of nodular pyogranulomatous inflammation –– they are almost never cystic."

The cause of these lesions is multifactorial, which is veterinarese for “we’re not always sure but we think it’s the result of a bunch of things.” (e.g., allergies, excess weight, poor foot conformation, mites, ingrown hairs or other foreign bodies, yeast infections, etc.)

The most common interdigital cyst/furuncle breeds affected include Labs, Bulldogs, other short-haired or allergy prone canines, and overweight/obese dogs. But, truth be told, any pet can get one of these interdigital cysts/furuncles. For example, my colleague is currently treating a two year old German Shepherd. The dog’s in great shape, small for his breed, and has no short hair, evidence of allergic skin disease or any other obvious predisposing factors.

These painful, limp-provoking, nasty-looking lesions are stressful enough without the E-collar (to prevent further self-trauma to the area), the frequent ministrations, and the potential side-effects of the drugs your veterinarian/dermatologist may have prescribed.

Many pet owners get discouraged, especially when treatment may go on for six to twelve (or more) weeks, and seek alternative (or more invasive) therapies. Here’s where you’re better off not trying one of Dr. Fox’s crazy essential oil treatments. And you’re almost always better off not opting for invasive, exploratory surgery to locate the source of the infection — not unless you’re willing to concede to the possibility of what’s called a “fusion podoplasty.”

A fusion podoplasty is a surgical technique to remove the entire web between the toes. Here’s where the interdigital cyst (furuncle) lies. And sure, removing it surgically has its benefits (usually quicker healing time), but it also has its downsides — especially if you approach this alternative as a "quick fix" that doesn’t address the underlying problem.

By removing the webbing between your dog’s toes, we may find that we predispose the foot to more troubles. Not only is the healing after this surgery a typically difficult and delayed process, it also means your dog will never have the same foot integrity as before. The webbing is there for a reason, after all. Foot pad overgrowths, future orthopedic issues, and a predisposition to more interdigital cysts are only a couple of problems we encounter as a result of the confrmational changes in the foot's new positioning.

All of that said, your veterinarian does understand that interdigital cysts (furuncles) aren't so "simple." But they are always treatable — just as long as you get to the right diagnosis as soon as possible, limit all offending factors, and give medical treatment a good solid try before embarking on more drastic cures.

Ever had a pet with one of these? How long did it take to treat? Did you opt for surgery?

Dr. Patty Khuly