CT Abdomen Normal Bowel Vs Small Bowel Obstruction | Adhesions, Volvulus, Hernia & Other Causes

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CT Abdomen Normal Bowel Vs Small Bowel Obstruction | Adhesions, Volvulus, Hernia & Other Causes

Small Bowel Adhesion:
A small bowel adhesion is a band of fibrous scar tissue that forms between loops of the small intestine or between the small intestine and other structures (e.g., abdominal wall, omentum, or organs). Adhesions can restrict the normal movement of the small bowel and are a common cause of small bowel obstruction (SBO). Its most common cause is abdominal surgery.

Normal Bowel:
Diameter: Less than 2.5 cm
Bowel Wall Thickness: Less than 3 mm
Mesenteric Fat: Appears hypodense
Jejunum: Located predominantly in the left upper quadrant, has a thicker wall and more prominent folds.
Ileum: Located predominantly in the right lower quadrant, with a thinner wall and fewer folds.

Small Bowel Obstruction:
Dilated bowel loops (Diameter greater than 2.5 cm)
If no other cause is found (hernia, volvulus, tumor, bezoar or foreign body), then the cause of the obstruction is most likely an adhesion.
Prominent intestinal folds (Valvulae conniventes)

Transition Point:
A Critical finding on CT in patients with small bowel obstruction (SBO). It represents the anatomical site where dilated bowel loops (proximal to the obstruction) transition abruptly to collapsed bowel loops (distal to the obstruction). Pinpoints the site and cause of obstruction.
Can occur anywhere in the small bowel, depending on the underlying cause of the obstruction (e.g., adhesions, hernia, mass, volvulus).
Abrupt Change in Bowel Caliber:
Proximal Bowel: Dilated loops (greater than 2.5-3 cm).
Distal Bowel: Collapsed loops (Less than 1.5 cm).
The site of caliber change indicates the level of obstruction.

Small Bowel Feces Sign:
Small bowel lumen contains heterogeneous material that mimics the appearance of feces in the colon.
This material includes:
Soft-tissue density (fluid and particulate matter).
Gas bubbles interspersed throughout (black dots in small bowel).
Location:
Found in dilated small bowel loops proximal to the site of obstruction.
Typically absent distal to the obstruction, where the bowel is collapsed.

Closed Loop Obstruction
The bowel is obstructed at 2 different points
Affected bowel forms a C-shaped or U-shaped loop due to obstruction at two points.

Whirl Sign:
Associated with midgut volvulus
Anticlockwise rotation of mesenteric fat and superior mesenteric vein around the superior mesenteric artery.

Strangulating Obstruction:
Dilated bowel loops
Thickened bowel wall
Increased density in the mesenteric fat indicates congestion and is a sign of bowel ischemia