An abscess is a pocket of pus under the skin which occurs when bacteria, which reside on the skin or teeth, enter the body via a puncture wound, most often by a bite during a cat fight.
An inflammatory response occurs, drawing huge amounts of white blood cells to the area and increasing regional blood flow. Pus forms, which is an accumulation of fluid, toxins, living and dead white blood cells, dead tissue and bacteria. A thin membrane (pyogenic membrane) surrounds the abscess. This area begins to grow, creating tension under the skin and further inflammation of the surrounding tissues. As the abscess grows, the skin thins and weakens, eventually causing the abscess to rupture and the pus drains out.
An abscess can form in any part of the body including under the skin, in the mouth (dental abscess) and in organs such as the liver and pancreas. This article relates to abscesses under the skin. The most common bacteria involved are staphylococci and streptococci.
How does an abscess occur?
The most common cause of skin abscesses is a puncture wound which introduces bacteria under the skin. The skin is remarkable in its ability to heal quickly, so the overlying skin heals from the puncture wound, the introduced bacteria remain trapped underneath the skin in a warm, moist environment.
The most common cause of a penetrating puncture leading to an abscess is from a cat bite. The oral cavity, including the teeth, harbour a great number of bacteria which are injected into the skin during penetration. Abscesses are seen more often in un-neutered male cats who are allowed to free roam as they are more territorial and therefore become involved in cat fights with local cats. There is an increase in cats presenting with abscesses in spring as this is cat mating season.
Other causes of abscesses include scratches and any penetrating object such as a thorn, splinter, grass seed or glass shard.
Abscesses occur most often around the head, neck, limbs and back and base of the tail. Not all cats will display symptoms.
By the time you find the abscess, the skin may be sufficiently thin resulting in the abscess draining (this is known as ‘pointing‘ and usually occurs when the abscess is close to the skin). If it has drained you may notice a thick, yellow and foul smelling discharge and a hole in the skin (see image). If the abscess is deep under the skin, you may notice an indentation (or a ‘pit‘) when pressure is applied to the area of swelling.
The goal of treatment is to lance, clean, and debride the area to promote healing.
The fur around the abscess is clipped and cleaned, the abscess is lanced and the pus drained, the area is flushed with sterile saline and dead tissue will be removed (debrided). This procedure will be under heavy sedation or general anaesthetic. The cat may need to stay in hospital for a day or two while he recovers.
Treatment is much the same as above, minus lancing. The area is clipped and cleaned, the wound is flushed with sterile saline any dead tissue is removed.
If the abscess is large, your veterinarian will insert a surgical drain to assist with the removal of pus. Flush daily with antiseptics.
A long-acting antibiotic injection or oral antibiotics will be given.
Follow your veterinarian’s instructions carefully and administer any antibiotics as prescribed.
It may be necessary for your cat to wear an Elizabethan collar, especially if he has a drain. This will prevent him from pulling it out.
A warm compress applied several times a day can increase blood flow to the area and speed healing.
Keep your cat indoors while he heals.
Watch for signs of infection including redness, oozing, and swelling of the affected area.
Follow up with your veterinarian if required.
The best way to avoid abscesses in cats is to spay and neuter cats and prevent them from free roaming.
See your veterinarian if you notice any lumps, signs of pain or fever. Do not treat an abscess at home as it can rupture into the bloodstream causing septicemia (bacteria in the blood), which can be fatal.
People can develop abscesses too and it is not uncommon for veterinarians and vet nurses to develop one. If a cat does bite or scratch you, clean the wound and keep watch for for signs of an abscess or infection. If you do think you have one, seek medical attention immediately.