Ultralow-contrast stepping digital subtraction angiography for whole-limb arterial evaluation: A case report

Stepping digital subtraction angiography (DSA) enables whole-limb arterial assessment with a single contrast injection, and diluted contrast medium may further reduce iodine exposure. A patient in their 80s with an abdominal aortic aneurysm and bilateral common iliac artery aneurysms was scheduled for staged internal iliac artery embolization before endovascular aneurysm repair (EVAR). Due to a mural thrombus in the left common iliac artery aneurysm, right internal iliac artery embolization was performed via an ipsilateral approach. Severe right external iliac artery stenosis prompted stepping DSA before and after embolization to evaluate distal embolization. Sevenfold- and tenfold-diluted stepping DSA examinations were performed before and after embolization, respectively, using identical injection parameters (3 mL/s; 30 mL). These required 4.29 and 3.0 mL of undiluted contrast medium, respectively. Although pedal artery enhancement was reduced with tenfold dilution, image quality remained acceptable, and no obvious distal embolization was identified in the visualized arteries; however, small emboli in poorly opacified pedal branches could not be excluded with tenfold dilution. Because internal iliac artery embolization was not expected to significantly alter lower-extremity arterial perfusion, the observed difference in image quality was considered to primarily reflect the difference between the two dilution protocols rather than changes in arterial hemodynamics. Ultralow-contrast stepping DSA may be a contrast-saving technique in selected cases when repeated whole-limb arterial evaluation is required.