Septic Bursitis in an 8-Year-Old Boy

Table 1

Comparison of bursitis, septic arthritis, and osteomyelitis [11–19].

	Clinical	Labs	Microbiology	Imaging
Bursitis	(i) Localized tenderness over area of infection; (ii) Decreased range of motion of affected joint or pain with movement; (iii) Erythema or edema; (iv) History of repetitive movement of involved joint	Noninfectious; Joint fluid analysis: <2000/𝜇L—predominantly mononuclear cells; Septic; (i) Leukocyte count: mildly to moderately elevated; (ii) ESR*: mildly to moderately elevated; (iii) Joint fluid analysis: predominantly polymorphonuclear cells; (iv) WBC count: 5,000–20,000 𝜇L (possibly >70,000 𝜇L) usually less than septic arthritis; (v) Increased protein; (vi) Decreased glucose	(i) S. aureus most common (>80%); (ii) Streptococcus (5–20%)	(i) Plain radiograph and bone scans are not sensitive for bursitis; (ii) MRI, if needed, is very sensitive for bursitis
Septic Arthritis	(i) Red, warm, and immobile joint; (ii) Often has palpable effusion; (iii) Chills and fever occur secondary to bacteremia	(i) Joint fluid; yellow-green color; (ii) WBC count >50,000 𝜇L (>75% polymorphonuclear cells); (iii) ESR: elevated	(i) Staphylococcus (40%); (ii) Streptococcus (30%); (iii) Gram-negative rods (20%)	(i) Plain radiograph: periarticular soft-tissue swelling is most common finding, linear deposition of calcium pyrophosphate; (ii) US: used to dx effusions in chronically distorted joints
Osteomyelitis	(i) Swelling, warmth, and erythema over area of infection or affected bone; (ii) Painful range of motion of affected joint; (iii) Pain in area of infection; (iv) Fevers or chills	(i) WBC count: usually does not exceed 15,000 𝜇L and can be normal in chronic osteomyelitis; (ii) ESR and CRP** usually increased	(i) Blood cultures positive in only 50%; (ii) Most common cause; Staphylococcus aureus	(i) Plain radiograph: periosteal thickening or elevation; cortical thickening, sclerosis or irregularity; osteolysis; new bone formation; (ii) CT: useful for guiding needle biopsy in closed infections; (iii) MRI: gold standard; shows localized marrow abnormalities; (iv) US: fluid next to bone without soft-tissue in between usually suggests osteomyelitis; (v) Nuclear medicine: 3-phase bone scan helpful for acute stages and shows increased metabolic activity

∗ESR (normal values): males (0–15 mm/hr), females (0–20 mm/hr); ∗∗CRP (normal value): 0–10 mg/dL.