By Ray Arza, DVM For The Education Center
Originally published in Veterinary Practice News, April 2016 – Download as a PDF
Canine acral lick granuloma—also known as acral lick dermatitis, acral pruritic furunculosis and lick granuloma—is a self-induced dermatological condition that develops as a result of excessive and prolonged licking of one or more areas.[1-2]
With time, this intense incessant licking leads to skin inflammation and can form a plaque or nodule with a raised border. The lesion surface typically is thick, alopecic, erythematous and often eroded or ulcerated. Draining sinuses, hyperpigmentation, scaling and crusting sometimes may be present.
Acral lick granuloma is typically a single unilateral lesion, although two or more lesions occasionally have been noted. Most commonly, lick granulomas involve the anterior aspect of the carpal-metacarpal or tarsal- metatarsal areas. Other lesion locales include the flank, tail base, stifle and tibia.
Although any dog can develop acral lick granulomas, most commonly the lesions occur in older, male, large-breed dogs such as Labrador retrievers, golden retrievers, German shepherds, German shorthair pointers, Saint Bernards, Great Danes and pit bulls.[1,3]
Acral lick granuloma can be caused by numerous etiological factors, either organic or psychogenic. Organic factors include food allergy, atopic dermatitis, fungal or bacterial infections, foreign bodies, ectoparasites, painful bone and articular diseases, local trauma and hormonal imbalance. Possible psychogenic causes are long-standing anxiety, boredom, stress, attention-seeking or stereotypic behavior. Differential diagnosis includes neoplasia; bacterial, fungal or pressure point granulomas; demodicosis; and calcinosis circumscripta.[3-4]
Successful diagnosis and therapy of acral lick granuloma depend on the accurate identification of the underlying causes. Because the acral lick granuloma can be caused by a wide variety of factors, a complete diagnostic evaluation of the patient is recommended. The clinician should consider the following tests: lab blood values, T4, TSH, allergy testing, deep skin scrapes, biopsy, bacterial and fungal culture/sensitivity of the affected area, radiographs and neurological investigations.[1,3,5] The treatment strategy involves treating the lesion along with the underlying etiological factors and the infection.
Once support therapy is established, the acral lick granuloma lesion may resolve on its own. However, if the lesion is very large and ulcerated, and the veterinarian desires to expedite healing, surgical ablation with CO2 laser is indicated. In case of conventional surgical excision, skin reconstruction usually is required via direct apposition, flaps or skin grafts. Surgical excision often results in dehiscence or the development of a new lick granuloma.
CO2 laser surgery allows for ablation of all or most of the affected tissue down to a more normal layer of dermis, facilitating a much faster resolution.
A canine patient was presented for surgical ablation of a severe acral lick granuloma overlying the anterior aspect of the left carpus. The client had been dealing with this for about five years, and the lesion was very large, alopecic, firm, erythematous, irregularly shaped and non-ulcerated. X-rays revealed no arthritic changes, and a biopsy was not performed.
Appropriate preanesthetic induction followed by general anesthesia was used.
Recommended Laser Equipment, Settings
Aesculight flexible hollow waveguide CO2 laser with 0.4 mm and 3 mm laser focal spot sizes.
Resection and debulking: 10 to 15 watts continuous wave (CW) with 0.4 mm focal spot size is used to excise most of the granulation tissue, ensuring not to remove the entire thickness (Figure 2). Note that wattage may be increased for thicker, more fibrous tissue.
Ablation/vaporization: Initially vaporize the remaining excess tissue at 20 to 30 watts CW (depending on the thickness of the remaining tissue) with 3 mm focal spot size. Then progressively reduce to 10 to 12 watts (ideally in SuperPulse mode) to increase control of the speed of tissue ablation and remove down to the level of normal dermis.
The affected area is clipped and aseptically prepped for surgery. It usually is unnecessary to debulk the lesion. In the case shown in Figures 1 to 6, however, the lesion was very large, and it was much quicker to first debulk (Figure 3) and then to vaporize the remainder of granulomatous tissue. Typically, the technique involves vaporizing tissue layer by layer in a tracking linear motion over the entire surface of the lesion. It is imperative to frequently wipe away char or carbonized tissue with saline-soaked sponges. Doing so helps to ensure the optimal delivery of laser energy to the target tissue.
After each pass, the depth of ablation is evaluated in relation to the adjoining healthy dermis. The wattage selected depends on the surgeon’s preference and the thickness of the granulomatous tissue to remove. I normally set wattage very high at first (20 to 40 watts, CW, 3 mm spot size), and then progressively decrease it when getting close to completion.
The surgeon might see numerous microabscesses (Figure 3) throughout the granulation tissue, but as one gets close to normal tissue, these should disappear (Figure 4). When the laser procedure is finished, there should be no appreciable thickened tissue upon digital palpation, but there should be dermis covering the subcutaneous tissue. There should be no appreciable bleeding, and the tissue should have a more normal appearance (Figure 4).
This procedure is relatively simple but can be quite time-consuming if the lesion is large and the granulation tissue is thick. The most crucial part of the procedure involves getting a feel for how deep to go or when to stop removing tissue. It is critical not to go beyond the normal dermal margins, or bleeding and delayed healing will occur.
A thick layer of Collasate and then a Telfa pad and bandage are applied. The bandage is changed at least once a week until the surgical site is completely healed. The dog should wear an Elizabethan collar until the lesion heals. The patient is rechecked at each bandage change until complete resolution. Typically, the clinical outcome of CO2 laser treatment is fairly cosmetic and has some hair regrowth (Figure 6).
A CO2 laser gives the surgeon precise control over the amount of tissue to be removed without extensive mechanical or thermal trauma to the healthy surrounding tissues. There is virtually no bleeding intraoperatively, and laser energy effectively kills bacteria at the surgical site, thus reducing the risk of infection.
Surgical laser treatment results in uncomplicated healing and esthetic clinical outcome. It is important to remember that acral lick granulomas are caused by several underlying etiological factors, such as behavioral issues, infections, metabolic disease and osteoarthritis. The patient should be monitored for these factors in order to ensure the appropriate support therapy and to avoid possible recurrence of acral lick granuloma.
- Hedlund CS. Surgery of the integumentary system. In: Fossum TW, ed. Small animal surgery, 3rd ed, St. Louis, MO: Elseveir/Mosby, 2007;159-259.
- Spiegel IB, Seltzer JD. ALD: causes and cures: dermatologic condition remains frustrating for dogs and owners. DVM Newsmagazine. September 2007: 14S+. Health Reference Center Academic. http://go.galegroup.com. Accessed Jan. 7, 2016.
- Patel A. Acral lick dermatitis. Compan anim. May 2010;15(4):1-4.
- Denerolle P, White SD, Taylor TS, Vandenabeele SIJ. Organic diseases mimicking acral lick dermatitis in six dogs. J Am Anim Hosp Assoc. July-August 2007;43:215-20.
- Berger N, Eeg PH. Veterinary laser surgery a practical guide. Ames, Iowa: Blackwell Publishing; 2006.
Dr. Ray Arza earned his DVM at the University of Tennessee in 1979. He was a small animal general practitioner for 23 years with a special interest in surgery and dentistry. Dr. Arza started using a surgical laser in 1998, and soon thereafter became a popular lecturer at conferences, universities, and seminars on laser technologies. In 2002, he left private practice to join industry as an educator, trainer, consultant, and lecturer. He acquired laser therapy expertise in 2005, and among other positions, has served LiteCure, LLC, as its veterinary medical director. He is the co-author of both volumes of Class IV Laser Therapy Treatment of Common Conditionsand contributor to the veterinary protocols programmed in LiteCure’s veterinary lasers.
This Education Center article was underwritten by Aesculight of Woodinville, Wash., the manufacturer of the only American-made CO2 laser.