Assignment Task:
A 7-year-old boy is brought to your office by his parents with acute onset of brown-colored urine, vague malaise, and mild periorbital edema. He is otherwise healthy, with a negative medical history. His family history is negative for renal disease. His blood pressure is 130/75 mm Hg. His physical examination shows no abnormalities except for mild periorbital edema. Results of his laboratory studies immediately available include a serum sodium level of 140 mEq/L (140 mmol/L), potassium level of 4.0 mEq/L (4.0 mmol/L), and creatinine level of 0.4 mg/dL (35.4 µmol/L). His UA shows a specific gravity of 1.010, pH 6, 3þ blood, 1þ protein, and more than 100 RBCs per high-power field with few RBC casts. Which of the following is the most appropriate next step in the diagnosis of this patient?
A. A 24-hour urine collection for protein.
B. A renal biopsy.
C. C3 and C4 complement levels.
D. Genetic testing for renal disease.
E. Serum immunoglobulin A level.