07-07-2008, 10:19 PM
A 26-year-old man is evaluated for a 3-day history of frequent and urgent urination. His temperature is 38.4 ºC (101.3 ºF); microscopic urinalysis shows erythrocytes and leukocytes. A 10-day course of trimethoprim“sulfamethoxazol is begun and within 3 days the fever and symptoms resolve.
One week after having completed the antibiotic therapy, the patient develops pruritus, fatigue, nausea, and anorexia and returns for evaluation.
On physical examination, the temperature is 37 ºC (98.6 ºF), pulse rate 76/min, and blood pressure 126/80 mmHg; he has a confluent macular, papular erythematous rash on the inner aspects of the arms and thighs.
Laboratory Studies
Hematocrit 42%
Leukocyte count 7400/μL
Serum electrolytes
Sodium 142 meq/L
Chloride 100 meq/L
Potassium 4.5 meq/L
Bicarbonate 21 meq/L
Blood urea nitrogen 46 mg/dL
Serum creatinine 4.0 mg/dL (1.0 mg/dL 10 months ago)
Urine pH 5, specific gravity 1.015, 2+ blood, 1+ protein. Microscopic: 10-15 erythrocytes and 20-25 leukocytes per high-power field; 3-4 leukocyte casts. Eosinophils are present. No bacteria. Urine culture is negative.
Renal ultrasonography No hydronephrosis or stones; right kidney 10.7 cm; left 10.5 cm
Which of the following is the most likely diagnosis?
( A ) Urinary tract infection with obstruction
( B ) Acute interstitial nephritis
( C ) Acute glomerulonephritis
( D ) Reflux nephropathy
( E ) IgA nephropathy