What are the clinical guidelines for CT scans in elderly patients with impaired renal function?

From the Guidelines

Elderly patients with suspected acute left colonic diverticulitis should undergo a CT scan with IV-contrast to confirm the diagnosis and distinguish complicated from non-complicated diverticulitis, regardless of their renal function, as the benefits of prompt diagnosis and treatment outweigh the risks of contrast-induced acute kidney injury (CI-AKI) 1.

Clinical Guidelines for CT Scans in Elderly Patients

The clinical guidelines for CT scans in elderly patients with impaired renal function prioritize the use of CT scans with IV-contrast for diagnosing acute left colonic diverticulitis.

• The WSES guidelines suggest the use of CT-scan with IV-contrast in all elderly patients with suspected diverticulitis to confirm the diagnosis and to distinguish complicated from non-complicated diverticulitis 1.
• In patients who cannot undergo CT-scan with IV-contrast, alternative diagnostic approaches such as US, MRI, or CT-scan without IV-contrast may be used, although they are less accurate 1.

Considerations for Renal Function

When considering the use of CT scans with IV-contrast in elderly patients with impaired renal function, the following points should be taken into account:

• The high prevalence of chronic kidney disease among elderly patients should not discourage CT scan execution with IV-contrast, as prompt diagnosis and treatment may justify the risk of CI-AKI 1.
• Recent studies have shown that the risk of CI-AKI after CT-scan in patients with chronic kidney disease may be lower than previously thought 1.
• Modifiable factors related to the procedure, such as contrast media volume, route of contrast administration, and type of contrast media, may play a role in the occurrence of CI-AKI 1.

Alternative Diagnostic Approaches

Alternative diagnostic approaches, such as US, MRI, or CT-scan without IV-contrast, may be considered in elderly patients who cannot undergo CT-scan with IV-contrast.

• US may be a useful alternative in the initial evaluation of patients, although its sensitivity and specificity are lower than those of CT scans 1.
• MRI may be considered, although its reported sensitivity and specificity for ALCD are 0.98 and 0.70-0.78, respectively, and it is rarely a feasible imaging modality in an urgent setting 1.
• Unenhanced CT may be an alternative, although the evidence is insufficient to recommend it as the first-choice examination, and it has significantly lower sensitivity for the detection of complications 1.

From the Research

Clinical Guidelines for CT Scans in Elderly Patients with Impaired Renal Function

• The use of contrast-enhanced computed tomography (CT) in elderly patients with impaired renal function requires careful consideration of the risk of contrast-induced nephropathy (CIN) 2, 3, 4, 5.
• According to a study published in Radiologia, no incidents of CIN were detected in 202 patients undergoing CT examination with intravenous iodinated contrast material, including 12.9% with impaired renal function (MDRD4 < 60 ml/min/1.73 m2) 2.
• A meta-analysis of randomized controlled trials published in International Urology and Nephrology found that prophylactic administration of N-acetylcysteine (NAC) in patients with serum creatinine above 1.2 mg/dL undergoing contrast-enhanced CT reduced the risk of CIN 3.
• A review article published in Cancer Imaging recommends preventing CIN in cancer patients undergoing CT examinations by using hydration, NAC, and avoiding nephrotoxic chemotherapeutic drugs 4.
• Another study published in European Radiology found that the risk of CIN from contrast-enhanced multidetector CT in patients with renal insufficiency appeared to be low, with an incidence of 6.1% 5.

Prevention of Contrast-Induced Nephropathy

• Hydration is recommended to prevent CIN in patients with impaired renal function undergoing contrast-enhanced CT 4, 5.
• NAC may be effective in preventing CIN in patients with serum creatinine above 1.2 mg/dL undergoing contrast-enhanced CT 3.
• The use of low-dose contrast agents and avoiding nephrotoxic chemotherapeutic drugs may also help prevent CIN 2, 4.

Radiation Safety in CT Scans

• The use of CT scans in elderly patients requires careful consideration of radiation safety, with efforts to minimize radiation dose while maintaining diagnostic image quality 6.
• The American College of Radiology Dose Index Registry initiatives and radiation awareness campaigns such as Image Gently and Image Wisely can help promote radiation safety in CT scans 6.