An 8-year-old boy and his father visit the pediatrician's office with reports of a sudden onset of abdominal pain and reddish-brown urine. A urinalysis shows 4+ protein. On taking the boy’s health history, the nurse learns that he had strep throat a little over a week ago. Which condition should the nurse suspect?

Choice A reason: Acute post-streptococcal glomerulonephritis (APSGN) is a classic sequela of a recent streptococcal infection, typically occurring 1–2 weeks after a throat or skin infection. The hallmark signs include hematuria (which may appear as reddish-brown urine), proteinuria, and abdominal or flank pain due to renal inflammation. The presence of 4+ protein and recent strep throat strongly support this diagnosis. APSGN is an immune-mediated condition where antigen-antibody complexes deposit in the glomeruli, triggering inflammation and impaired filtration. Choice B reason: Kidney agenesis refers to the congenital absence of one or both kidneys. It does not present acutely and would not cause sudden abdominal pain or reddish-brown urine. It is typically diagnosed in infancy or prenatally via imaging. This choice does not fit the clinical scenario. Choice C reason: A urinary tract infection may cause abdominal pain and hematuria, but it is less likely to cause significant proteinuria (4+) and is not typically associated with a recent streptococcal infection. UTIs are more common in females and usually present with dysuria, frequency, and urgency rather than systemic signs of glomerular damage. Choice D reason: Polycystic kidney disease is a genetic disorder that leads to the development of multiple renal cysts over time. It is usually diagnosed through imaging and presents with hypertension, flank pain, and progressive renal dysfunction. It does not present acutely with reddish-brown urine and is not triggered by a recent infection.