Stephen J. Birchard DVM, MS, Diplomate ACVS

Sunday, May 8, 2016

Surgical Removal of Giant Lipomas in Dogs

Lipomas are benign tumors of adipose tissue that are common in dogs. Most lipomas are small, well circumscribed, movable, and not painful. They most commonly occur in the subcutaneous space but in rare cases can form in a body cavity such as the abdomen (Fig. 1a-c), or between large muscles such as the semimembranosis and semitendonosis (1).
Fig. 1a: Lateral abdominal radiograph in a dog with an abdominal lipoma.
Note large fat density mass in the mid to caudal abdomen.
Fig. 1b: Ventrodorsal radiograph of same dog as Fig. 1a.
Fig. 1c: Operative photograph of an abdominal lipoma in same dog as the above radiographs.

Lipomas that are large and grow between fascial planes are called infiltrative lipomas. (2,3)

Simple (not infiltrative) lipomas that are small, quiescent, and not causing pain or dysfunction are usually not treated. However, in some cases because of the sheer size and location of the lipoma, surgical resection is recommended. For example, a very large lipoma of the axilla like in the dog illustrated in this article may cause serious functional problems with the front limb.(Fig.2) 
Fig. 2: Preoperative appearance of a very large lipoma of the right axilla in this Labrador retriever
Surgical resection can be performed to allow better use of the leg and relief of discomfort. Even giant lipomas, if not infiltrative, can frequently be surgically removed. However, attention to anatomic detail and meticulous surgical technique are critical to avoid complications.

Lipomas are suspected in any subcutaneous mass that is soft on palpation, movable, and well circumscribed. Fine needle aspirate samples appear grossly as oil droplets on a slide and reveal few cells microscopically. Radiographs (Fig. 1a,b) or CT scan of the mass may be indicated for very large or infiltrative lipomas that could be near or surrounding vital structures or in a body cavity.(4) 

Preoperative Considerations
Since many patients with lipomas are geriatric, appropriate preoperative evaluation would include a thorough history and physical examination, laboratory tests (CBC and serum chemistry profile) and thoracic radiographs if cardiopulmonary issues are suspected. 

Surgical Technique
After induction of general anesthesia, clip and aseptically prepare a wide field over the lipoma. Make an incision that spans the length of the lipoma. 
Fig. 3: Initial incision in the lipoma on same dog as in Fig. 2.
Using blunt and sharp dissection, define the borders of the mass and separate it from surrounding tissues. Finger dissection is usually effective in defining tissue planes and extracting the mass. When dissecting into deep tissue planes, use retractors to improve exposure and identify important structures such as large vessels and nerves. 
Fig. 4: Dissection of the lipoma in same dog as Fig. 2. The axilla artery and vein
and elements of the brachial plexus are seen at the base of the mass. 
Encapsulated lipomas will usually “peel out” well, but after removal inspect all surrounding tissues for residual lobules of lipoma. 
Fig. 5: Completed resection of the massive lipoma from the axillary space in dog from Fig. 2.
Prior to wound closure, inspect the surgical field for hemorrhage. Since removal of lipomas results in large areas of empty space in the tissues, place a closed suction drain to prevent fluid accumulation and seroma. (See Veterinary Key Points blog on the Jackson-Pratt drain.) 
Fig. 6: A closed suction drain has been placed in the Labrador in Fig. 2
and the incision closed routinely.
Close the wound routinely and place a light bandage on the animal to protect the drain tubing and reservoir. Leave the drain in place until drainage has reduced to trivial amounts. 

In the following video see dissection of a massive lipoma from the lateral cervical region of a dog. Removal of the mass exposed the trachea, carotid artery, and vagosympathetic trunk. 

Simple lipomas, even large ones, have a good prognosis since they are benign and slow growing. Postoperative recurrence is rare, but careful monitoring for development of new lipomas in other parts of the body is advised. Liposuction removal of lipomas was reportedly successful in 1 study but complications were common and recurrence of lipoma was high (28%) (5)

Infiltrative lipomas have a more guarded prognosis because they can be difficult to completely excise and recurrence is more common than with simple lipomas. Depending on the clinical study, one-third to one-half of dogs with infiltrative lipoma will develop recurrence after surgical removal. (2,3) Carefully monitor the surgical area for evidence of regrowth that can occur months or years postoperatively.

1. Thomson MJ, Withrow SJ, Dernell WS, Powers BE Intermuscular lipomas of the thigh region in dogs: 11 cases. J Am Anim Hosp Assoc. 1999 Mar-Apr;35(2):165-7.
2. McChesney AE, Stephens LC, Lebel J, Snyder S, Ferguson HR. Infiltrative lipoma in dogs.Vet Pathol. 1980 May;17(3):316-22
3.Bergman PJ1, Withrow SJ, Straw RC, Powers BE. Infiltrative lipoma in dogs: 16 cases (1981-1992) J Am Vet Med Assoc. 1994 Jul 15;205(2):322-4.
4. McEntee MC1, Thrall DE. Computed tomographic imaging of infiltrative lipoma in 22 dogs.Vet Radiol Ultrasound. 2001 May-Jun;42(3):221-5
5. Hunt GB1, Wong J, Kuan S. Liposuction for removal of lipomas in 20 dogs. J Small Anim Pract. 2011 Aug;52(8):419-25.