Making an incision
Sometime during their lives, most animals have some type of surgery. Often it is a neuter or spay. Other abdominal surgeries and surgeries to repair a fracture are also common. In most cases, when an incision is made, the cut is not just made through the skin, but also through the subcutaneous layer. This layer is composed of fat and connective tissue. Under the subcutaneous layer, are the muscles. In many surgeries the incision has to be made through these, as well.
Closing an incision
To provide the best healing and most support, the three layers (muscle, subcutaneous layer, and skin) need to be closed
The threadlike material that may be used to close incisions is called "suture" material. The material is generally attached to a semicircular needle. A special instrument called a "needle holder," which is something like a long, small pliers, is used to hold the needle and push it through the tissue.
Absorbable sutures: Some suture is absorbable, meaning the body will break down the material over the course of a number of weeks. Absorbable sutures are most commonly used for the muscle and subcutaneous layers. This type of material is also used to close the incision in any organs, such as the intestine. Absorbable sutures may also be used to close the skin incision in small animals. The material is actually passed sideways through the layer of skin, so it is not visible once the closure is complete. The advantage of this "intradermal closure" is that it is more difficult for the animal to remove the stitches by licking or scratching at the site. Another advantage is that since the material is absorbable, an appointment to remove the stitches is not necessary.
Nonabsorable sutures: Nonabsorbable sutures are not broken down by the body and must be manually removed. These sutures may be made out of nylon, steel, or synthetic materials. Nonabsorbable sutures are commonly used to close an incision in the skin. Stitches made with these materials are very strong.
Staples may be used internally to permanently clamp a particular type of tissue. When used to clamp off small blood vessels, the staples are referred to as "vascular clips." Staples may also be used to close an incision in the intestine or stomach. They are most commonly used to close an incision in the skin. Staples and clips are made of metal. Those used internally will remain there for the rest of the animal's life. Those in the skin will need to be removed using a special "staple remover."
Surgical adhesive (tissue glue) may be used to close very small incisions that are made in the skin. This glue is applied to the edges of the cut skin, which are then brought together and held for several seconds. The glue binds the two skin edges together, and will eventually be removed by the body or sloughed off.
Factors affecting healing
The healing of the body is remarkable. Usually in 7-10 days the incision is strong enough to withstand considerable stretches and tension. An incision heals from side to side, not from end to end. This means that a 4-inch incision will not take 4 times as long to heal as a 1-inch incision, but both will heal in relatively the same amount of time.
Too much activity
Although sutures and staples are strong, if an animal moves in a way that puts tension on them, the tissues will take longer to heal, and the sutures may even pull out. This is similar to a piece of clothing that can be torn open at the seam if the cloth on both sides is of the seam is pulled apart. Tissue adhesives can also be torn apart. For this reason, animals should be kept quiet and usually not allowed to run or jump until the incision is healed.
Licking or scratching
Animals that lick or scratch at an incision can actually work the incision open. This most commonly occurs with sutures or tissue adhesive, though some animals have actually removed staples, too. In some instances a bandage can be placed over the incision to protect it. Elizabethan collars may be placed on the animal so he cannot reach to the incision with his mouth. Bandaging, or placing a sock on the hind foot may help reduce the risk that scratching will open up the incision. If an animal is known to have a tendency to lick or scratch at an incision, intradermal closures and stainless steel sutures in the skin are often used.
Infection or fluid accumulation
An infection at the incision site will slow down healing and cause absorbable sutures to break down more rapidly. An accumulation of fluid or pus around the incision also puts extra tension on the sutures, increasing the risk they may pull out. To prevent infection, it is important to keep incisions clean and dry.
If the area was infected prior to the incision being made (e.g., cuts in the skin due to trauma, such as being hit by a car), a drain will often be placed to allow the passage of fluid and pus out of the area, away from the incision. A latex tube is placed through the infected area. The latex tubing is placed through two small incisions above and below the main incision. The tubing keeps two openings in the skin to allow any newly formed pus to drain. The drain also provides a way to flush antiseptic solution through the area for several days, if necessary.
Reaction to the suture material
Some animals may have a reaction to the suture material, similar to a reaction to a sliver. Very small accumulations of pus may occur around the suture material. There are two scenarios depending on where the reaction is occuring.
If the suture material is in the muscle or subcutaneous layer, a small drainage area through the skin may develop. In most instances, the reaction will not cause a problem and will disappear once the sutures have been resorbed by the body. In rare cases, the incision will have to be opened and the sutures replaced with a different type of material.
If the reaction is to skin sutures, it will disappear once the sutures are removed.
Different tissues heal at different rates. Internal organs such as the urinary bladder and intestine will heal faster than skin.
Medications and health conditions
Some medications are known to slow down the healing process. The most common ones are the corticosteroids. Certain drugs used in cancer therapy, even aspirin at high doses, may also affect healing time. Certain nutritional deficiencies can slow healing. Vitamin A, Vitamin C, zinc, and protein are all necessary for healing.
Certain health conditions such as acute anemia, kidney or liver failure, protein deficiencies, diabetes, cancers, and hormonal imbalances may cause delayed healing. Age is also a factor; older animals often take longer to heal.
Incisions are usually made through multiple tissue layers and each layer is closed separately. Various methods are available to close an incision, and are chosen based on the site of the incision, animal characteristics, and other factors affecting healing. To assure proper healing, after care is very important.