Microvascular Free Tissue Transfer
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Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

A free flap is a piece of tissue, usually skin or muscle that is transplanted from one area of the body to a wound that needs to be repaired

The blood supply of the tissue flap is reconnected to small blood vessels adjacent to the wound so that the flap stays alive

This type of surgery is an excellent treatment option for complex wounds in dogs

Indications for free tissue transfer

  • Microvascular free tissue transfer is used for wounds that are caused by
    • traumatic accidents
    • oncological surgery (tumor removal) - see example below
    • radiation therapy burns
    • thermal burns
    • chemical burns
    • vesicant burns - injected medications such as chemotherapeutic medications or some injectable anesthetics
  • The procedure has the advantage of requiring only one surgery to achieve a cosmetic result.

Types of free flaps that are used to repair wounds

  • Skin flaps are used for wounds that have a relatively good blood supply
  • Muscle flaps are used for wounds that do not have a good blood supply with exposed bone.  Muscle has a phenomenal capability to remove infection and heal the wound.  A skin graft is placed over the muscle. 

Surgical procedure

  • A normal segment of skin along with its nutrient artery and vein are removed from the donor site (inner thigh or side of shoulder). The blood vessels of the skin flap are surgically reconnected (with the aide of an operating microscope to visualize the vessels) to the blood vessels adjacent to the wound thereby allowing the skin flap to survive in its new location.

Case example - Medial Saphenous Fasciocutaneous Microvascular Free Flap

  • EstherEsther presented with a mast cell tumor located over the front of the wrist (called the carpus). Treatment options were amputation of the limb or excision of the tumor followed by radiation therapy. Because the tumor was fairly sizeable, a large section of skin needed to be removed in the process. A microvascular free flap is ideal in such cases, as this provides a durable covering over the wound that can withstand radiation therapy.


  • In this video, a free flap is harvested from the inner thigh. The blood vessels that feed this portion of skin are also harvested with the flap and will be disconnected from the limb. A dog will function just fine without these saphenous vessels.
  • In this video the artery of the skin flap is being sutured to an artery adjacent to the recipient wound. The artery pumps blood into the skin flap.
  • In this video the vein of the skin flap is reconnected to a vein adjacent to the recipient wound. The vein drains blood out of the skin flap.
  • congested flapEsther's flap turned a purple color in the postop period. The photo right was taken on the third day after surgery. An instrument (doppler) used to test the blood flow in the flap indicated that the artery was still pumping blood in the flap. The problem was that blood was not flowing out of the flap very well due to swelling of the tissue which was compressing the veins. This uncommon complication can result in death of the flap unless appropriate treatment is provided.
  • We therefore elected to use leech therapy to relieve the venous congestion. This entails placing the leeches directly on the flap (using a syringe casing) or pricking the skin with a needle and directly applying the leeches to the flap.
  • After the leeches release themselves from the flap, the bite sites will continue to bleed which relieves congestion of the flap. Don't be alarmed if the bandage is soaked with blood when it is changed (see photo right). Your doctor will monitor your pet for anemia if multiple leech therapy sessions are needed.


bloody bandage

  • Esther's flap survived completely and the leeches helped it along. In the photo right, 13 days after surgery, the flap is healing well with the congestion and swelling ameliorated.
flap 13 days postop

Success rate

  • About 90 to 95 % of free tissue flaps survive transplantation.

Potential complications

  • There is an inherent risk of anesthetic death with any procedure requiring anesthesia, however, this is very small.
  • A blood clot could develop in the artery or vein of the flap at the site where they have been reconnected, which may lead to death of the entire flap.
  • Venous congestion may occur due to swelling of the tissues which partially occludes the vein of the flap. In most cases this is reversible once the swelling starts to come down, however, in some cases some sutures may need to be removed to relieve compression of the tissues and blood vessels. Leech therapy may also be recommended in some cases.
  • During the healing process the surgery site may become itchy and the dog may lick or chew at the site.  If this occurs the vessels could become damaged and the flap may die. 
  • The site where the flap was collected from may break open if the dog is too active or is allowed to lick and chew at the region.
  • A pooling of fluid under the area where the skin flap was removed can occur in a small percentage of patients undergoing this procedure, however the fluid will become absorbed over time.
  • It is possible that the hair of the skin graft might grow in a different color or direction than the native hair coat around the region to be reconstructed.

Postop care

  • Starting the evening prior to surgery, aspirin should be given to help reduce the risk of blood clot formation in the vessels of the flap. The dose of aspirin is 2 mg/kg twice daily for four days (equates to about one 81 mg tablet for an 80 pound dog).
  • Bandage changes initially will be done daily to check the health of the flap; it is common that bandages are changed by the owners; bandages must not be put on tight as this could compress the blood vessels that feed the flap.
  • It is imperative that the patient is prevented from self-mutilating the flap with the aid of bandages and/or Elizabethan collars for up to 6 weeks.
  • Follow up checkups with your veterinarian are necessary to evaluate the progress of the skin flap.


  1. Miller JM, Lanz OI, Degner DA. Rectus abdominis free muscle flap for reconstruction in nine dogs. Vet Surgery 36:259-265, 2007.
  2. Degner, DA, Walshaw, R., Fowler, J.D. et al: Surgical Approaches to Recipient Vessels of the Fore and Hindlimbs for Microvascular Free Tissue Transfer in Dogs. Vet. Surg. 34 (4), 297–309, 2005.
  3. Degner, DA, Walshaw, R., Fowler, J.D. et al: Surgical Approaches to Recipient Vessels of the Head and Neck for Microvascular Free Tissue Transfer in Dogs. Vet. Surg. 33:200-208, 2004.
  4. Jackson AH, Degner DA, Myiawaki T, Jackson IT, Silverberg: The deep circumflex iliac free flap in cats. Vet Surg. 32 (4), 341–349, 2003.
  5. Myiawaki T, Degner DA, Eleszar H, Barakat K, Jackson IT: Easy tissue expansion of prelaminated mucosal-lined flaps for cheek reconstruction in a canine model.  Plast Reconst Surg 109:1978-85, 2002.
  6. Calfee EF, Lanz OI, Degner DA, Peterson SL, Duncan RB, Broadstone RV, Martin RA, Austin B:  Microvascular free tissue transfer of the rectus abdominis muscle in dogs. Vet Surg 31:32-43, 2002.
  7. Lanz OI, Broadstone RV, Martin RA, Degner DA: Effects of epidural anesthesia on microcirculatory blood flow in free medial saphenous fasciocutaneous flaps in dogs. Vet Surg 30:374-9, 2001.
  8. Bebchuk TN, Degner DA, Walshaw R, Brourman JD, Arnoczky SP: Evaluation of a free vascularized medial tibial bone graft in dogs. Vet Surg 29: 128-44, 2000.
  9. Robertson H, Degner DA, Walshaw R: Replantation of a partially amputated paw in a dog. Vet Comp Ortho Trauma 12:40-42, 1999.
  10. Fowler JD, Degner DA, Walshaw R: Microvascular free tissue transfer: Results in 57 consecutive cases. Vet Surg 27:406-412, 1998.
  11. Degner DA, Walshaw R: Medial saphenous fasciocutaneous and myocutaneous free flap transfer in eight dogs. Vet Surg 26:20-25, 1996.
  12. Degner DA, Lanz OI, Walshaw R: Myoperitoneal microvascular free flaps in the dogs: an anatomical study and clinical case report. Vet Surg 25:463-70, 1996.
  13. Degner DA, Walshaw R, Lanz OI, et al: The medial saphenous fasciocutaneous free flap in the dog. Vet Surg 25:105-113, 1996.
  14. Degner DA, Walshaw R, Arnoczky SP, Smith RJ, Degner LA, Hamaide A: Evaluation of the cranial rectus abdominis muscle pedicle flap as a blood supply for the caudal superficial epigastric skin flap. Vet Surg 25:292-299, 1996.
  15. Degner DA, Walshaw R, Kerstetter KK: Vascular anomaly of the prescapular branch of the superficial cervical artery and vein of an omocervical free skin flap in a dog. Vet Comp Ortho Trauma 8:102-106, 1995.
  16. Degner DA, Bauer MS, Steyn PF, Toombs W, Orton CE: The cranial rectus abdominis muscle pedicle flap in the dog. Vet Comp Ortho Trauma 7:21-24, 1994.
  17. Degner DA, Bauer MS, Steyn PF, Toombs W, Orton CE: The cranial epigastric skin flap in the dog. Vet Comp Ortho Trauma 7:18-20, 1994.
  18. Degner DA, Bauer MS, Cozens M: Reverse saphenous conduit flap: a case report in a cat. Vet Comp Ortho Trauma 6:175-177, 1993.

Frequently Asked Questions After Surgery

When should my dog have the first bowel movement after surgery?

  • Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
  • Reasons that a dog will not have regular bowel movements after surgery include:
    • The dog has been fasted prior to surgery
    • Dogs do not eat well during the hospital stay
    • They frequently do not eat well when they go home
    • They are fed highly digestible food that produces little stool
    • Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
  • If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
    • Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable

My pet had surgery and will not eat.  What can be done?

  • Dogs
    • Most pets will not eat their regular dog food after surgery, especially if it is kibble.
    • Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source.  The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked).   The carbohydrate can be pasta, potato or white rice.
    • Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- MugTM or Beef-in-a-MugTM products)
    • Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
    • Try Hill's A/D diet available at most veterinary hospitals
    • Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
    • Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
    • Remember that most pets will not eat the first day or two after they get home from surgery
  • Cats
    • Offer smelly foods that contain fish such as tuna or smelly cat foods
    • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
    • Hand feeding:  with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
    • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
    • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
    • Petting and stroking your cat frequently will help to stimulate appetite
    • Remember that most pets will not eat the first day or two after they get home from surgery
    • Appetite stimulants such as cyproheptadine may be helpful
    • If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My pet is vomiting.  What can be done?

  • The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled.  Usually the regurgited material will be clear or brown colored fluid. 
  • Next is to identify the cause of the vomiting or regurgitation.
  • Causes and treatment of vomiting after surgery
    • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
    • Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery.  In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
    • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
    • An uncommon cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
    • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
    • Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days.  In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days.  Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats.  You should always consult a veterinary healthcare professional before administering medication.
  • Causes and treatment of regurgitation after surgery
    • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis.  This results in poor motility of the esophagus, therefore water and food will accumulate in this structure.  In most cases, esphagitis is self-eliminating and will resolve within two or three days. 
    • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week.  This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
    • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other).  Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my dog is in pain following surgery?

  • Signs of pain include
    • crying
    • biting if you get near the surgical site
    • grimacing (lips are pulled back and the the dog looks anxious)
    • tragic facial expression
    • panting
    • restlessness and unable to sleep; pacing
    • if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
    • the worst pain will be for the first 2 to 3 days after surgery

What can I do to control my dog's pain?

  • Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
  • Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
  • If an orthopedic surgery has been done cold packing the surgical site may be helpful
    • A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack.  An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern.  Cooling the surgical site helps to numb the area.

How do I know that my cat is in pain following surgery?

  • Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
  • Signs of pain in a cat include the following:
    • biting if you get near the surgical site
    • growling or deep cry
    • not wanting to eat
    • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

  • Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
  • Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
  • Anti-inflammatories can be used, but the dose is much less than dogs

Is it okay for my pet to lick the incision?

  • If a dog licks the incision, the healing process may be delayed.
  • Licking can remove stitches and cause the incision to open
  • Licking can become a severe habit that is difficult to break
  • Licking can cause infection as the mouth has many bacteria
  • Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
  • To stop your pet from licking the following can be tried:
    • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
    • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
    • A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
    • A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
    • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
    • Bitter Apple and Liquid HeetTM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
    • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

  • Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

  • Experience in the development of new surgical treatments

  • Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

  • Assurance that a veterinarian is a surgical specialist

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