An abscess is a collection of pus that results from skin and deep tissue damage and local bacterial infection. Fight abscesses are extremely common in cats that spend time outdoors or fight with housemates. The small puncture holes quickly seal, and the closed wound pocket is an ideal incubator for bacterial infection. Fight wounds can occur anywhere on the cat's body but are most common on the face, limbs, rear end, and tail. Abscesses may become large and extremely painful. A bite abscess usually heals in 10-14 days. Any abscess that does not heal is further investigated for feline immunodeficiency virus, feline leukemia, and mycobacteria infection.2 Painful abscesses on the neck or in the mouth may be caused by an infection with Actinobacillus lignieresii bacterium and usually result from contamination of injury. The pus is usually white or green and odorless with yellow granules.7 Abscesses are often seen in cats with dermatophilosis.
Treatment consists of opening and draining the abscess (often requiring anesthesia) and flushing the wound. It is safest to have a veterinarian to do this. After cleaning, the abscess must be kept open until it heals from the inside. Never be tempted to lance a bump yourself. Blood-filled bruises called hematomas may look like abscesses, but if they are lanced, a cat may bleed to death.
The most common antibiotics used in treating cat abscesses are clindamycin and penicillin; doxycycline and enrofloxacin may be effective for abscesses resistant to other antibiotics. Antibiotic therapy alone is likely to fail in cases when the wound is not drained.4,5,6 Warm compresses are useful to promote drainage, maintain cleanliness of the area, improve blood circulation, and speed up healing.3 Bite wound infections that are not cleared by penicillin may be due to Mycobacterium, the cause of tuberculosis. In cats, its signs may include abscesses of unknown origin, particularly around the eyes, weight loss, low-grade fever, decreased appetite, dehydration, vomiting, and diarrhea. The lymph nodes may be enlarged and can contain abscesses.8
Abscesses can form in the liver through a variety of ways. In kittens, bacterial infection of the umbilical cord can travel directly into the liver. Older cats may acquire bacterial infection from other areas of the body, such as infected bile ducts, or liver itself. Bacteria are always present to some extent in the liver as it cleans and filters the blood received from the stomach and intestines. Any weakening of the liver's defenses can easily lead to bacterial infection and abscess formation. Cats with liver abscesses usually experience vomiting, fever and are lethargic.1