Bursae are small sac-like cavities that contain fluid and are lined by a synovial membrane. They are located subcutaneously between bony prominences and tendons or in deeper fascial tissue between bone and muscle, essentially serving to reduce friction between these structures. Inflammation of bursae (ie, bursitis) can be caused by infection, particularly when the superficial subcutaneously located bursae are involved. These infections are typically secondary to local trauma and rarely attributable to hematog-enous seeding. In addition to prior history of trauma to superficial bursae, other predisposing factors may include prior rheumatoid arthritis or gouty involvement of the bursae, alcoholism, diabetes mellitus, renal insufficiency, intravenous drug use, and other forms of immunosuppression [65,66]. Trauma often is occupationally associated, favoring situations that place pressure on the olecranon, prepatellar, and superficial infrapatellar bursae, the most common sites of septic bursitis [67,68].
Peribursal cellulitis, warmth, and erythema are common. Close inspection of the skin also may reveal lacerations, abrasions, and ecchymoses . Fever and pain with movement of the associated joint also is characteristic of superficial bursitis. Interestingly, Smith and colleagues  have reported that in septic olecranon bursitis, a temperature of greater than or equal to 2.2° C between the affected and unaffected olecranon processes was 100% sensitive in distinguishing septic from nonseptic bursitis.
Like many other inflammatory conditions, a peripheral leukocytosis, an elevated C-reactive protein, and an elevated erythrocyte sedimentation rate are often present. Although radiographic evaluation may reveal abnormal accumulations of fluid, the presence of a foreign body, and the extent of infection, the diagnosis of septic bursitis requires sampling of the bursal fluid. The range of leukocytosis per mm3 is broad and the absolute number usually is less than is present in septic arthritis. In one series of 32 patients with septic bursitis, the bursal fluid leukocyte count averaged 23,350/mm3 with a standard deviation of 22,065/mm3; more than 10% of patients had fewer than 2000 leukocytes/mm3 . Gram stain is positive in 50% or less of all cases . Sensitivity of culture may be increased by directly inoculating bursa-associated fluid into liquid media versus direct culture methods . Blood cultures also may be helpful in identifying the microbi-ologic cause of infection in deeper and more severe forms of septic bursitis . More than 75% of septic bursitis cases are attributable to S aureus; other causes include streptococci, Staphylococcus epidermidis, enterococci, diphtheroids, and, rarely, Gram-negative bacilli . Subacute and chronic infectious bursitis can be attributable to other organisms such as, Brucella, mycobacteria, Prototheca, and Aspergillus.
Treatment typically requires drainage and antibiotics. Initial antibiotics are dictated by Gram-stain evaluation of bursal fluid. If the Gram stain is negative, antistaphylococcal therapy is initiated with intravenous cefazolin, nafcillin or oxacillin, or vancomycin. Subsequent treatment then is dictated by culture and susceptibility results. Daily percutaneous drainage procedures are performed until sterility is attained and antibiotics usually are administered for at least 2 to 3 weeks. Indications for surgery include inadequate needle drainage of bursa, inability of needle to access bursa for drainage, necrosis, presence of foreign body, and refractory infection .
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