A 75-year-old man is referred to the ED after being seen in the clinic with an elevated BUN and creatinine on routine exam. The patient is not ill-appearing and has stable vital signs. A pelvic...

A 75-year-old man is referred to the ED after being seen in the clinic with an elevated BUN and creatinine on routine exam. The patient is not ill-appearing and has stable vital signs. A pelvic ultrasound from several years ago shows two normal appearing kidneys. What is the most likely cause of renal failure in this patient?

A. Kidney stone lodged in the right ureter → postrenal failure

B. Diabetes mellitus → renal insufficiency

C. Benign prostatic hypertrophy → postrenal failure

D. Sepsis → prerenal failure

E. Good pasture syndrome → intrinsic renal failure