Case Ico-delete Highlights A 42-year-old woman presents for an evaluation of back pain. She states that she has a history of recurrent UTIs; she notes that on occasion her urine appears red. Upon physical examination, she demonstrates CVA tenderness. Her vital signs include blood pressure of 145/90 mm Hg, respiratory rate of 16 breaths/min, and heart rate of 72 bpm. Urinalysis shows leukocyte esterase 1+, protein trace, and blood 3+. The microscopic examination reveals 5-10 WBCs/hpf and 20-30 RBCs/hpf. An abdominal ultrasound demonstrates multiple, bilateral fluid collections within the kidneys.

Question
What, if any, is the most likely underlying renal pathology?