A 56-year-old male presents
with pain in the lower back. The pain has a girdle like distribution beginning
in the lower back and radiating to the lower abdomen. He has not been on any
drugs. The patient is hypertensive but there are no other physical signs of
note. Investigations reveal a normocytic normochromic anaemia, raised
erythrocyte sedimentation rate and C-reactive protein. Renal function is
impaired. Ultrasound scanning reveals bilateral hydronephrosis.
Which of the following investigations is most likely to give you the diagnosis?
