A 4-year-old girl presents to her physician’s office with complaints of 1-week history of tea-colored urine and mild edema of the both feet. Current blood pressure is 110/70 mm Hg. Urinalysis is significant for > 10 red blood cells (RBCs)/high-power field (HPF) and 1+ protein. Her mother states that 2 weeks ago she was treated with oral antibiotics for pharyngitis that was associated with abdominal pain and sandpaper-like rash. Subsequent lab workup revealed depressed C3 levels with normal C4 levels, urine protein/creatinine ratio of 1 mg/mg, and lipid levels within normal limits for age. Of the following entities, which is the most likely explanation for this patient’s hematuria?
A. Immunoglobulin (Ig)-mediated membranoproliferative glomerulonephritis
B. Henoch-Schönlein purpura (HSP) nephritis
C. Acute poststreptococcal glomerulonephritis
Acute poststreptococcal glomerulonephritis is the most common acute postinfectious glomerulonephritis. A disease primarily of school-age children, it has been shown to follow infection with specific strains of group A β-hemolytic Streptococcus despite appropriate antibiotic treatment. Symptoms of hematuria, edema, and hypertension usually start abruptly about 1 to 2 weeks after having pharyngitis. Symptoms begin to spontaneously improve within a week of onset, with edema and hypertension resolving within 2 to 3 weeks. Urine abnormalities may take several months to years to resolve. Classic laboratory findings include low C3 levels with normal C4 levels. C3 levels usually return to normal within 12 weeks after initial symptoms. Diagnosis is confirmed when the patient has the classic complement findings, combined with a positive streptozyme assay or DNase B.
All of the other choices can cause hematuria or glomerulonephritis but have differences in complement levels. Lupus nephritis and infective carditis usually have low C3 and C4. Ig-mediated membranoproliferative glomerulonephritis is an immune complex–mediated glomerular disease that often follows an acute illness but usually presents with nephrotic syndrome (proteinuria, hypoalbuminemia, and hyperlipidemia) and low C4 levels. HSP presents as a tetrad consisting of papular purpuric rash, abdominal pain, arthralgia, and microscopic hematuria and usually has normal complement levels.
A previously healthy 7-year-old girl presents to the emergency department with a 3-day history of cough, rhinorrhea, and sore throat. Fever, with erythematous rash on bilateral cheeks, started this morning. She was seen by her primary care physician (PCP) 2 days ago and started on penicillin for upper respiratory infection symptoms. Her mother is concerned because she has not had any urine output for 9 hours despite continuing to drink well. She denies any dysuria or myalgia. Based on this history, what urine examination findings are indicative of the underlying cause of her decreased urine ...