Bowel and mesenteric trauma can result from blunt force, penetrating and iatrogenic trauma. CT is the gold standard imaging modality but CT findings are nonspecific ¹².

Epidemiology

The bowel and mesentery are injured in ~2.5% (range 0.3-5%) of blunt force abdominal trauma ^1,3,5,8. However not surprisingly, bowel and mesenteric injuries are more frequent after penetrating trauma ⁸. Bowel injury has consistently been found to be the most common traumatic abdominopelvic injury missed on CT ¹¹.

Pathology

Etiology

Gunshot wounds (~75%) and stabbings (~20%) are the leading causes of bowel and mesenteric injury from penetrating trauma ⁸. Motor vehicle collisions are the most common cause of blunt trauma followed by falls, assaults and sports-related trauma ^4,6.

Types

From most to least common sites of bowel injury ^1,4,6:

• jejunum (near ligament of Treitz/D-J flexure)

• ileum (near ileocecal valve)

• colon (cecum, transverse colon, sigmoid colon)

• rectum

• duodenum (D2 and D3 segments)

• stomach (greater curvature)

The mechanism of bowel injury include crush/compression type, shearing type (from fixed point of mesentery) and burst type (from increased intra-luminal pressure) and can include ⁴:

• perforation

• mural hematoma or edema

• active hemorrhage

• serosal tear

• degloving (very rare)

Mesenteric injuries can include:

• active bleeding from a laceration

• mesenteric hematoma

• mesenteric lacerations (e.g. bucket handle tears) which can create a site for acute or remote internal herniation of bowel

Grading schemes

Several grading schemes (RAPTOR and BIPS) using a variety of clincial parameters and CT findings have been validated and correlate with operative findings and the need for surgical intervention.

Radiographic features

Radiography

The erect chest x-ray may show free subdiaphragmatic gas due to traumatic bowel injury but radiographs indicated in the setting of trauma are almost always performed as a supine projection which reduces the sensitivity of pneumoperitoneum. Abdominal radiography is not indicated in trauma when CT is readily available.

CT

Bowel injury

• definitive signs:

  • visible bowel wall discontinuity ⁷

  • perforation

    • in blunt trauma, the presence of extra-luminal oral contrast media (if used) or bowel contents; extra-luminal free gas (especially in the absence of pneumothorax/pneumomediastinum) ²

    • in penetrating trauma, extra-luminal free gas is not specific to bowel perforation; extra-luminal contrast media/bowel contents leak and a wound track extending to bowel is considered the most sensitive; wall thickening/mesenteric contusion is less sensitive ²

• suggestive signs ⁷

  • mural hematoma: discontinuity in the bowel wall with mural thickening (>3-4 mm); may be complete (i.e. perforated) or incomplete ^2,4

  • moderate/large volume of free fluid without solid organ injury ^2-3

  • intermesenteric (interloop) fluid, often forming triangles

  • abnormal bowel wall enhancement: decreased due to mesenteric vascular interruption and small bowel ischemia, or increased due to vascular permeability secondary to hypoperfusion ⁷

  • positive seatbelt sign increases the likelihood of traumatic bowel injuries ⁹

  • feacalisation ¹²

Mesenteric injury

• definitive signs:

  • active extravasation of contrast media is indicative of active bleeding and a significant mesenteric injury ³

  • intermesenteric (interloop) free fluid, often forming triangles ⁷

  • beading and termination of mesenteric vessels ^{4, 7}

  • abrupt termination of the mesenteric vessels ⁷

  • accumulation ('pooling') of contrast on multiphase imaging

• suggestive signs ⁷

  • mesenteric infilatration: haziness and fat stranding

  • mesenteric hematoma

  • bowel wall thickening

Treatment and prognosis

Even with increasing non-operative management of traumatic abdominal organs (e.g. liver or spleen laceration), traumatic bowel and mesenteric injuries such as perforation or active mesenteric bleeding still require operative management ³.

Differential diagnosis

• shock bowel: diffuse bowel wall thickening (from edema) that is hyperenhancing