c l i n i c a l
f o l i o s :
d i s c u s s i o n
Abscess
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Related narrative: Incision and Drainage of Abscess The treatment of abscess is drainage. No abscess should be treated with antibiotics. While a superficial skin abscess in many areas of the body can be safely drained under local anesthesia in an outpatient setting, abscesses near the perineum require complete exploration under regional or general anesthesia. Such exploration is not possible under local because of the pain. An incompletely drained perineal abscess, especially in a diabetic, may progress to necrotizing faciitis. In addition, such an abscess may track up into the ischiorectal space. Rectal examination under anesthesia is important to determine if there is a connection with the anal crypts where perianal and perirectal abscesses usually start. The late consequences of such a connection can be a fistula in ano. Localization of the center of an abscess may be determined by fluctuance (soft point). Fluctuance is caused by pressure necrosis and thinning of the overlying skin by the expanding abscess. In certain areas, particularly the buttocks and breast, the skin is too thick or the abscess too deep to cause fluctuance, and fluctuance can not be relied on for localization. It is important to drain such collections early before the patient becomes toxic. Needle localization is necessary in such cases. Success has been achieved recently in many cases of breast abscess with ultrasound-guided needle aspiration and antibiotic treatment. Subcutaneous septation forces the expanding abscess to form pockets or loculations. These loculations must be identified and opened at the time of drainage. Both digital exploration and careful spreading of a large clamp accomplish this purpose. An adequate opening is necessary to allow the abscess cavity to close from the bottom up before the skin opening narrows down. If the cavity does not fall open easily as in this case, it is necessary to excise a wedge of skin to ensure adequate drainage. This may also be done by making a cruciate incision and excising the corners. If there is suspicion of an anal crypt origin and the possibility of later fistula formation, the incision should be made as close to the anus as possible to minimize the length of the fistula tract. Culture of the abscess is usually an academic exercise since drainage itself is curative. It is also usually evident what the bacteriology of the pus is from its appearance. Pure staph, the common pathogen in superficial infections, is cream colored. Mixed infections are gray as in this case, and anaerobes give the pus a strong smell. The culture information may be useful if there is progression of surrounding cellulitis. Perioperative antibiotics are useful for the existing septicemia and the septicemia secondary to manipulation, especially in diabetics, patients with valvular heart disease, and patients with implanted prosthetic devices. Subsequent continued antibiotic coverage in otherwise healthy patients is usually unnecessary. If there is unusual induration, or suspicion of a secondary cause of the abscess such as malignancy, a biopsy of the abscess wall is done. The word "packing" is a misnomer. The purpose of the gauze wick is to allow free drainage of the residual abscess contents and to help keep the opening patent. A tightly packed abscess cavity hinders drainage and perpetuates bacteremia. The wick should be changed starting on the first post drainage day and replaced until the cavity is sufficiently shallow. Showering, or sitz bath in the case of perineal abscess, even while packing is being replaced, is beneficial to wash out the cavity and speed healing. References: Howerton RA and Bonello JC, in Cameron, Current Surgical Therapy (5th ed), Mosby: 224-226.
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