CBC with differential, CMP, LDH, urinalysis, urine culture
EKG- to evaluate for arrhythmia
CT with IV contrast (preferred study)
Renal ultrasound - less senstive
MRI with gadolinium (contraindicated with severe renal impairment due to risk of nephrogenic systemic fibrosis)
Radioisotope scan - not commonly used
Renal infarction
Vascular
Renal abscess
Abdominal aortic aneurysm
Pyelonephritis
Renal artery embolism
Renal trauma
Renal vein thrombosis