Lower extremity CT angiograms and their effect on kidney function in orthopedic trauma patients

To evaluate the frequency of unindicated CT Angiograms (CTAs) obtained at our institution and the association between contrast-induced nephropathy (CIN) and decreased glomerular filtration rate (GFR).

Retrospective case series SETTING: Academic Level 1 trauma center PATIENTS/PARTICIPANTS: Patients aged 18 years and older with CTAs following lower-extremity (LE) trauma between 2010-2018.

CTAs performed in 257 LEs and corresponding pre- and post-contrast renal function labs in these LE trauma patients.

The primary outcome was vascular injury requiring intervention. Secondary outcomes were CIN and the association of CIN with decreased GFR and injury severity score (ISS).

There was no indication (no hard signs of vascular injury, ABI>0.9) for CTA in 121 patients (61%) of the total 199 patients. Of the 78 patients with signs of vascular injury or ABI<0.9, 35 (45%) had positive CTAs and 15 (19.2%) required vascular intervention. Of the 121 unindicated patients, 26 (21%) had positive CTAs and 1 (0.008%), a knee dislocation, required vascular intervention. In 155 patients with renal function labs, initial GFR<60ml/min was a risk factor for CIN as compared to GFR>60ml/min (p=0.001). Rate of CIN did not correlate with Injury Severity Score (ISS).

CTAs are obtained more often than indicated and initial GFR<60ml/min is a risk factor for developing CIN, irrespective of the trauma burden. CTAs should be reserved for when hard signs of vascular injury or ABI<0.9, especially in those patients with decreased renal function.

Level IV.