Swollen eyes and brown urine

A 12-year-old girl is brought in by her mother, who reports dark brown urine and swelling around the daughter’s eyes. The patient may have complained about a sore throat 2 weeks prior. Which lab result would confirm the suspected diagnosis? A. Urinalysis positive for protein and red blood cells B. Serum BUN > 50 C. Serum negative for presence of anti-DNAse B antibodies D. Elevated serum C3 concentration E. Serum ASO titer > 1:330 ANSWER The suspected diagnosis is post-streptococcal glomerulonephritis. The dark brown urine suggests hematuria, and the periorbital edema suggests loss of protein. The history of pharyngitis and patient age point toward streptococcal cause, rather than one of the many other causes of hematuria and proteinuria. In the setting of a recent Group A strep infection, ASO titers (> 1:330), anti-DNAse B antibodies, and anti-hyaluronidase antibodies are frequently elevated. While UA will definitely show proteinuria and red cells, this confirms glomerulonephritis but not the specific entity. Serum C3 concentrations are usually decreased in the setting