Ultrasonography of the abdomen and pelvis is appropriate for this patient with chronic kidney disease (CKD). She requires imaging studies to evaluate her kidneys and genitourinary tract in order to rule out a structural lesion or tumor as the source of gross hematuria. Ultrasonography is an appropriate initial screening test because it can provide necessary information without exposure to the risks associated with the administration of contrast agents in patients with severe CKD who are at increased risk of contrast-induced nephropathy (CIN) and gadolinium-induced nephrogenic systemic fibrosis (NSF).

This patient has risk factors for CIN (older age, elevated serum creatinine, diabetes mellitus); therefore, a contrast-enhanced CT to evaluate for lesions of the kidneys and genitourinary tract as a cause of her hematuria should be performed only if similar information cannot be obtained from tests that entail less risk to the patient.

The use of gadolinium in MRI studies is relatively contraindicated in patients with an estimated glomerular filtration rate of less than 30 mL/min/1.73 m² due to the increased risk of NSF. Although most NSF cases have occurred in patients with end-stage kidney disease, there have been isolated case reports occurring in patients with stage G4 CKD. Gadolinium-enhanced MRI is therefore contraindicated in these patients unless there is a compelling clinical indication and the patient is fully informed of the risk of NSF.

Radiography of the abdomen and pelvis may be a reasonable test to rule out nephrolithiasis. However, the patient does not have symptoms suggestive of nephrolithiasis, and a plain radiograph would not provide information to determine whether there are structural lesions in the kidneys or genitourinary tract.