no urine output after a sore throat

A 21 year old presents to the office two weeks after a sore throat. The rapid strep test came back positive as well as cultures showing group A beta-hemolytic strepococcus. He finished his course of antibiotics and came back to the office two weeks later with the main complaint of swelling in his feet. He also noticed he's not urinating as frequently and the urine he does make is smoky-brown.  His vital signs were significant for an elevated blood pressure of 150/80. What is the most likely diagnosis?
A) Wegener's granulomatosis
B) Goodpasture's syndrome
C) Alport's syndrome
D) IgA Nephropathy
E) Postinfectious glomerulonephritis
What additional lab tests can be ordered?
A) c-ANCA
B) serum C3
C) ASO titer
D) fat pad biopsy

Answer: This patient most likely has postinfectious glomerulonephritis, an immune complex nephritic syndrome. A serum C3 would be decreased and an ASO titer would be positive.

Source:
1. Le, Tao. First Aid for the USMLE Step 2 CK. 5th. New York: McGraw-Hill, 2006.
First Aid for the USMLE Step 2 CK (First Aid for the USMLE Step 2: Clinical Knowledge)