Subcutaneous Abscesses and Cellulitis Emily Rothstein, DVM, DACVD

BASIC INFORMATION If the animal is seriously ill, other laboratory tests may be Description recommended to determine what effects the infection is having on A subcutaneous abscess is a collection of pus and infected mate- other organs in the body. rial within the tissues beneath the skin. Cellulitis is an infection or inflammatory reaction that has spread out within these tissues, TREATMENT AND FOLLOW-UP rather than being confined to one pocket. Causes Treatment Options The most common cause is a bacterial infection, although fun- An abscess must often be surgically opened to provide drainage, gal infections and even sterile processes can cause similar signs. and this usually requires general anesthesia or heavy sedation. Bacteria are introduced into the deeper tissues through a wound Sometimes dead tissue is removed, the cavity is flushed with an or injury or by rupture of a hair follicle. (See also the handout antiseptic solution, and a drain is left in place to allow continued for Deep Bacterial Pyoderma and Furunculosis .) Some of the drainage from the site. Cellulitis may be treated with warm, wet more common causes are cat and dog bite wounds, punctures from compresses initially. In some instances, an abscess will form (even thorns, and injuries that cause a break in the skin. with appropriate treatment) that requires surgical drainage. In both situations, antibiotics are given, usually for about 14 days. Clinical Signs Warm, wet compresses are often recommended postoperatively A painful swelling is commonly detected under the skin, and to encourage drainage and provide comfort. Additional nursing sometimes open, draining tracts or holes are seen in the skin. The and supportive care may be needed for animals that are seriously skin overlying the abscess is usually red, but over time it may die, ill from the infection. turn blue or black, and begin to slough (come off). The pet may have a fever, loss of appetite, and lethargy, and these may be the Follow-up Care only signs detected at home. In these cases, the abscess or cellulitis Complete healing of an abscess usually occurs within 2 weeks but is discovered by the veterinarian when the animal is examined. it can take longer if the cause of the deep infection (such as bite wounds, porcupine quills, or plant foreign material) is difficult to Diagnostic Tests identify and treat. If the source of infection is not adequately iden- A tentative diagnosis is based on the clinical signs described. The tified and removed, a recurrence can be expected. In some cases, diagnosis is supported by the following: signs of infection begin soon after the antibiotics are finished; in • Examination of material from the infected site under the micro- others, signs of infection may return days to months later. scope shows pus and bacteria. Prognosis • A bacterial culture of the pus can be done and sometimes shows Prognosis is often very good with adequate treatment, but some that more than one type of bacteria is present. lesions heal with a scar. Cases that are complicated by infestations • Lancing of a swollen area suspected to be infected often of maggots or by kidney, liver, or blood changes have a poorer determines whether an abscess is present. prognosis and require more intensive therapy.