A 40-year-old woman presents to the emergency department with unremitting left flank pain. She denies dysuria or fever. She notes that her urine output has decreased over the last few days. On urinalysis, red blood cells are noted. All other labs are within normal range. What is the diagnosis?
a) Renal calculi
b) Pyelonephritis
c) Renal infarction
d) Renal cell carcinoma