CT
Axial non-contrast
Axial C+ arterial phase
Axial C+ portal venous phase
Intraluminal arterial contrast extravasation is identified in the proximal sigmoid in the left iliac fossa, on background of extensive colonic diverticular disease.
The inferior mesenteric artery does opacify, however there is impression of a tight ostial stenosis due to calcific atheromatous disease of the aorta.
Conclusion
Active arterial bleeding into the lumen of the proximal sigmoid.