Rice Farmer with Fever, Jaundice, and Acute Kidney Injury
A 45-year-old rice farmer from Leyte presents with five days of fever, severe headache, myalgia, and calf tenderness. He reports wading through flooded rice paddies one week before symptoms began. Temperature is 39.2°C, BP 100/60 mmHg, HR 110/min. He has conjunctival suffusion and diffuse abdominal tenderness without rebound. Laboratories show WBC 14,200/µL with 82% neutrophils, platelets 110,000/µL, creatinine 2.1 mg/dL, total bilirubin 3.2 mg/dL, ALT 120 U/L, and urinalysis with 10–15 RBC/hpf and proteinuria. Dengue NS1 antigen is negative. A local clinic has started paracetamol only. The patient asks whether he needs antibiotics and whether a blood test can confirm the diagnosis. You must interpret the findings, choose empiric therapy, and explain the limitations of serologic testing in this setting.
1. What is the most likely diagnosis, and which findings argue against dengue?
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Most likely diagnosis: leptospirosis with icteric renal failure (Weil disease). The exposure to flooded rice paddies, conjunctival suffusion, calf tenderness, neutrophilic leukocytosis, thrombocytopenia, renal impairment, and bilirubin elevation out of proportion to transaminases fit leptospirosis. Dengue is less likely because NS1 is negative, the white cell count shows neutrophilia rather than leukopenia, and renal failure with hyperbilirubinemia is atypical. However, early dengue NS1 can be negative, and coinfection is possible in an endemic area, so observation and serial testing are prudent. The absence of rebound tenderness lowers concern for a surgical abdomen. This is a judgment call: exposure and organ pattern favor leptospirosis, but dengue cannot be excluded by one negative test.
2. Which diagnostic tests would you order, and how do you interpret a negative IgM ELISA on day 5?
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Order blood cultures and, if available, leptospira PCR on blood and urine early, plus IgM ELISA and a paired microscopic agglutination test. A negative IgM ELISA on day 5 does not exclude leptospirosis because antibodies often appear after the first week; PCR sensitivity is highest before antibiotics and falls thereafter. MAT requires paired acute and convalescent sera and is the reference test, but results are retrospective. Therefore, start empiric antibiotics after cultures rather than waiting for confirmation. Repeat serology in 2–4 weeks and notify public health authorities. In a dengue-endemic area, also monitor platelets and hematocrit.
3. Choose an empiric antibiotic regimen and explain why it is appropriate for this patient.
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Give intravenous ceftriaxone 1 g once daily, or IV penicillin G 1.5 million units every 6 hours. Ceftriaxone is convenient because it has broad leptospiral activity, once-daily dosing, and does not require renal dose adjustment at this creatinine. Doxycycline is an alternative for mild disease but is less ideal with significant renal impairment and must be avoided in pregnancy. Start antibiotics promptly after blood cultures; do not delay for serology. Add supportive care for acute kidney injury, monitor urine output and electrolytes, and arrange dialysis if uremia or hyperkalemia develops. Jarisch–Herxheimer reaction can occur after the first dose, so monitor temperature and blood pressure.