A 28-year-old woman has had dysuria, freuency, and urgency for the past 2 days. On physical examination, her temperature is 37.6oC. A urine culture grows >100,000 colonies/mL of Escherichia coli. She is treated with antibiotic therapy. If the problem continues to recur, the patient is likely to be at greatest risk for development of which of the following renal diseases?