Acute Hot Swollen Ankle in a Patient on Multiple Medications
A 64-year-old woman with hypertension, gout, and stage 3 chronic kidney disease (eGFR 38) presents with a 2-day history of a red, hot, swollen right ankle. Temperature 38.1 degrees C, HR 104, BP 148/88. She takes hydrochlorothiazide, losartan, allopurinol 300 mg daily, and ibuprofen as needed. The ankle is diffusely tender without a clear portal of entry; there is a small fissure between the fourth and fifth toes. WBC 14,200 with 82% neutrophils; CRP 120. Joint aspiration is planned.
1. What is the differential and how do you prioritize it?
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Cellulitis, gout/pseudogout, and septic arthritis are the leading considerations. Systemic signs (fever, tachycardia, leukocytosis, elevated CRP) favor infection, but gout can mimic infection. The toe fissure is a plausible portal of entry. Septic arthritis is the most urgent concern and requires arthrocentesis before antibiotics if feasible. Crystal analysis, Gram stain, and culture of synovial fluid are essential. Consider DVT if swelling is unilateral.
2. How does her medication list and renal function affect treatment choices?
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Ibuprofen is nephrotoxic and should be stopped, especially with eGFR 38 and possible infection. Hydrochlorothiazide can raise uric acid and worsen gout; discuss alternatives. Allopurinol should not be started or dose-adjusted during an acute flare without guidance; continue if already stable, but review dosing in CKD. Antibiotics require renal dose adjustment. Avoid NSAIDs for pain; use acetaminophen with caution and consider short-course opioids if needed.
3. What findings on joint aspiration would change management, and what empiric therapy is reasonable pending results?
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Cloudy synovial fluid with WBC >50,000 and positive Gram stain suggests septic arthritis, requiring urgent IV antibiotics and orthopedic consultation for drainage. Negative Gram stain but monosodium urate crystals confirms gout; treat with intra-articular or systemic corticosteroids, avoiding NSAIDs given CKD. If aspiration is dry or equivocal, treat empirically for cellulitis with a renal-adjusted antibiotic covering skin flora (e.g., cephalexin or clindamycin if penicillin-allergic) and reassess in 24-48 hours. Blood cultures if systemically ill.