protocol: CT angiography for GI bleed

No oral contrast

Section thickness 1 mm
Reconstruction interval 0.8 mm

Unenhanced low dose CT (to show pre-existing intraluminal hyperattenuation)

100–125 mL I.V contrast 4 mL/sec, followed by 50 mL of saline solution at 4 mL/sec

Arterial phase - triggering at proximal abdominal aorta (150 HU)

Portal venous phase at 70 seconds

Reference:
Marti M et al. Acute Lower Intestinal Bleeding: Feasibility and Diagnostic Performance of CT Angiography, January 2012 Radiology, 262, 109-116.

Understanding Intestinal rotation, non-rotation and malrotation

Nonrotation:  

Prone for midgut volvulus  

Duodenojejunal junction does not lie inferior and left of SMA

Cecum does not lie in the right lower quadrant. 

 

Incomplete rotation:   

Prone for duodenal obstruction, midgut volvulus, internal herniation (right mesocolic i.e. paraduodenal hernia.)

Peritoneal bands from misplaced cecum to mesentery compress D3.

Incomplete fixation: 

Mesentery of right and left colon and duodenum do not get fixed retroperitoneally

If descending mesocolon (between IMV & posterior parietal attachment) remains unfixed, small intestine migrates to left upper quadrant = left mesocolic hernia 

If the cecum remains unfixed, it may lead to volulus of terminal ileum, cecum, or proximal ascending colon 

 

CT:

Large bowel predominantly on left side and small bowel predominantly on right side

SMA on right and SMV on left, or SMV anterior to SMA