Mesenteric and Small Bowel Trauma

Published on 19/07/2015 by admin

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Last modified 19/07/2015

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 Polygonal fluid collections between folds of mesentery, bowel loops

image Indicates bowel &/or mesenteric injury
• Active bleeding = isodense with enhanced vessels
• Extraluminal gas: Intra- or retroperitoneal air

image May be absent even with transmural lacerations
• Seat belt sign: Infiltration or hematoma in subcutaneous fat of lower anterior abdominal wall
• Free fluid without an apparent solid organ injury

image Larger amounts, especially of blood attenuation (> 35 HU) are due to trauma
image Look carefully for mesenteric, bowel, or solid visceral injury

TOP DIFFERENTIAL DIAGNOSES

• “Shock bowel”
• Coagulopathy (intramural hematoma)
• Vasculitis

PATHOLOGY

CLINICAL ISSUES

• Bowel and mesenteric injuries are found in 2-5% of patients taken to surgery after abdominal trauma
• Active mesenteric bleeding requires surgery
• Use of seat belt restraints has decreased mortality from motor vehicle crash

image Incidence of bowel and mesenteric injuries has increased

DIAGNOSTIC CHECKLIST

• Check for mechanism of injury
• Don’t succumb to satisfaction of search
• Solid visceral injuries are often more obvious, but less important than injuries to bowel or mesentery
• CT is much more accurate in diagnosis of bowel injury from blunt trauma as opposed to penetrating trauma (e.g., stab wound to the abdomen)
image
(Left) Axial CECT in a 24-year-old man injured in a motor vehicle crash (MVC) shows a sentinel clot image, adjacent to thick-walled jejunum, and active bleeding, as evidenced by the contrast extravasation image. All characteristic findings in intestinal trauma.

image
(Right) Coronal CECT in the same patient shows an injured branch of the superior mesenteric artery with a large focus of contrast extravasation image. The mesenteric injury was surgically repaired and a segment of small intestine was resected.
image
(Left) Axial CECT in a 28-year-old man who was injured in an MVC demonstrates ectopic gas image adjacent to a thick-walled jejunal segment image, indicative of transmural laceration or perforation.

image
(Right) Axial CECT in the same patient demonstrates mesenteric stranding image, a characteristic finding in the setting of intestinal trauma.

TERMINOLOGY

Definitions

• Injury to mesentery &/or small intestine

IMAGING

General Features

• Best diagnostic clue

image Bowel wall thickening, mesenteric infiltration, intraperitoneal blood, ± extravasation of enteric or vascular contrast medium
• Location

image Duodenum and proximal jejunum are most common sites

Radiographic Findings

• Radiography

image Flank stripe sign: Increased density zone separates vertical colon segments from properitoneal fat and peritoneal reflection
image Dog’s ear sign: Pelvic fluid collections displace bowel from urinary bladder

Fluoroscopic Findings

• Water-soluble contrast study

image Fold thickening, luminal narrowing, extravasation
image Mainly for duodenal hematoma or laceration

CT Findings

• Must view at abdominal and lung windows
• Bowel wall thickening > 3 mm (sensitivity of 75%)
• Bowel wall enhancement hyperdense to psoas muscle or isodense to blood vessels

image Wall enhancement + thickening + free fluid strongly suggests perforation
• Mesenteric infiltration (“stranding”)

image Small hemorrhages: Streaky soft tissue infiltration of mesenteric fat
image Sentinel clot sign: Localized > 60 HU mesenteric hematoma at site of bleeding
• Intra-/retroperitoneal free fluid: Hemoperitoneum or bowel contents

image Hemoperitoneum: Present is essentially all bowel or mesenteric injuries
image Polygonal fluid collections between folds of mesentery, bowel loops

– Indicates bowel &/or mesenteric injury
– Does not result from injury to solid viscera
image Hematoma (> 60 HU), liquefied blood (35-50 HU)
image Bowel content, extravasated enteric contrast (10-30 HU)
image Active bleeding = isodense with enhanced vessels
image Bowel rupture at sites of oral contrast extravasation
• Extraluminal air: Intra- or retroperitoneal air

image Not diagnostic of bowel perforation (also seen in barotrauma and mechanical ventilation)

– Often seen in subphrenic spaces
– Between mesenteric leaves, omental interstices
– May be absent even with transmural lacerations
• Intramural air and extraluminal air and interloop free fluid

image Indicates full thickness tear
• Bowel discontinuity: Diagnostic of transmural laceration, but rare finding
• Extraluminal oral contrast material: Rare, but specific for perforation
• Seat belt sign: infiltration or hematoma in subcutaneous fat of lower anterior abdominal wall

image Highly predictive of injury to bowel and mesentery
• Chance fracture: Transverse plane fracture through vertebral body and posterior elements

image Highly associated with bowel and mesenteric injuries
• Free fluid without apparent solid organ injury

image Normal in young woman (physiological)
image Small amounts in pelvis of near-water attenuation in men may be due to overhydration
image Larger amounts, especially of blood attenuation (> 35 HU), are due to trauma

– Look carefully for mesenteric, bowel, or solid visceral injury
– Alert clinical team of need for close and repeated monitoring if surgery is to be delayed

Ultrasonographic Findings

• Grayscale ultrasound

image Free fluid in abdomen and pelvis
image Focused abdominal sonography for trauma (FAST exam)

– Never shows bowel injury; only nonspecific free intraperitoneal fluid

Angiographic Findings

• Conventional

image Vascular transection, laceration, pseudoaneurysm, arteriovenous fistula

Imaging Recommendations

• Best imaging tool

image Multiplanar CECT
• Protocol advice

image IV contrast bolus at 3 mL/sec
image Oral contrast use is safe, but uncommonly indicated

DIFFERENTIAL DIAGNOSIS

Shock Bowel

• Intense mucosal enhancement, submucosal edema (not blood)
• With diffuse mesenteric edema, signs of hypovolemia 

image Collapsed IVC, hyperenhancement of kidneys ± adrenals, etc.
• Reversible sign of recent hypotension
• Resolves quickly with fluid resuscitation

Coagulopathy

• May result in intramural hematoma of bowel
• Usually due to anticoagulant treatment
• Spontaneous etiologies: Idiopathic thrombocytopenic purpura, leukemia, hemophilia
• Barium studies, CT of SB

image Segmental, extensive, or localized changes
image Uniform, regular thickening of valvulae conniventes with symmetric, spike-like configuration, decreased luminal diameter simulating “stack of coins”
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