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ABDOMINAL RADIOLOGY Table of Contents   
Year : 2006  |  Volume : 16  |  Issue : 3  |  Page : 359-362
Superior mesenteric artery tear with hypoperfusion syndrome


From the MD Radiology, Goa Medical College, Bambolim, Goa, India

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Keywords: SMA tear, hypoperfusion syndrome, CT

How to cite this article:
Sharma M, Kalyanpur T M, Sardessai S. Superior mesenteric artery tear with hypoperfusion syndrome. Indian J Radiol Imaging 2006;16:359-62

How to cite this URL:
Sharma M, Kalyanpur T M, Sardessai S. Superior mesenteric artery tear with hypoperfusion syndrome. Indian J Radiol Imaging [serial online] 2006 [cited 2020 Jun 6];16:359-62. Available from: http://www.ijri.org/text.asp?2006/16/3/359/29017

   Introduction Top


The primary causes of insufficient blood flow to the intestine or mesenteric ischemia are diverse and include thromboembolism, nonocclusive causes, bowel obstruction, neoplasm, vasculitis, abdominal inflammatory conditions, trauma, chemotherapy, radiation, and corrosive injury [1].

Bowel and mesenteric injuries occur in approximately 5% of blunt abdominal trauma cases and are, therefore, relatively unusual injuries. The signs on imaging are subtle and have low diagnostic specifity [2].


   Case report Top


An 18 year old girl presented to casualty early in the morning with abdominal trauma by a wooden plank that fell on her as she was sleeping. She had no external signs of injury. On examination her BP was 90/70 mm Hg with a pulse of 110 beats/min. She had generalized abdominal tenderness and rigidity. She was sent for an emergency USG. The CXR was normal with no rib fractures.

US showed significant free fluid in abdomen with internal echoes suggesting hemoperitoneum. Minimal thickening of small bowel loops was noted. An urgent contrast CT scan of abdomen was performed without oral contrast in view of free fluid with no demonstrable visceral pathology on US.

The plain scan showed increased density of free fluid at the site of tear termed the "sentinel clot sign" [Figure - 1]. Contrast CT scan shows the following ; free air and high density free fluid [Figure - 2], poor enhancement of spleen and pancreas [Figure - 3], intense contrast enhancement of kidneys and a small caliber of IVC ( < 9 mm anteroposterior diameter at renal veins) and aorta ( [Figure - 4], minimally thickened bowel loops showing more of the white pattern type of contrast enhancement [Figure - 5], and active extravasation of intravenous contrast [Figure - 6].


   Discussion Top


CT is far superior to US for detection of bowel and mesenteric injuries however high degree of suspicion with oral and IV contrast are essential prerequisites. [2].

The most specific signs of bowel injury include oral contrast extravasation, direct visualization of disrupted bowel and extraluminal gas. [2].
"Shock bowel" is a diffuse non occlusive type of ischemia of the small bowel in hypotensive adults who have sustained blunt trauma. Hypoperfusion results in increased vascular permeability to macromolecules and albumin, which leads to diffuse bowel wall thickening and increased enhancement on CT scans because of slowed perfusion and interstitial leakage of molecules of contrast material .[3],[4]. Reversal of shock bowel with successful treatment of the hypovolemia suggests that this "white attenuation pattern" represents a reversible ischemic change without clinical significance [3],[4].

Other CT manifestations of "hypoperfusion syndrome " include diminished caliber and increased enhancement of the IVC and aorta as well as intense contrast enhancement of the kidneys and mesentry. [3]. Enhancement of the spleen and pancreas is decreased due to splanchnic vasoconstriction. [5].

Absence of enhancement or decreased enhancement of the bowel wall may be the most specific finding for bowel ischemia [6] , although counterintuitive, the ischemic segment may also appear with increased enhancement, which is caused by altered vascular permeability and perfusion problems (i.e., delayed return of venous blood with subsequent slowing of the arterial supply or arteriospasm) [6],[7].

Bowel wall thickening is the most common CT finding in bowel ischemia, although it is nonspecific [8]. When the lumen is distended, normal bowel wall thickness is 1-2 mm; when the lumen is collapsed, normal thickness may be 3-4 mm. [9]. Bowel dilatation reflects the interruption of peristaltic activity in ischemic segments, it is a common but nonspecific finding. [9].

CT demonstrates intestinal wall abnormalities that can be analyzed by categorizing attenuation changes in the intestinal wall. These attenuation patterns include; white, gray, water halo sign, fat halo sign, and black. [1]

The white pattern represents avid contrast material enhancement that uniformly affects most of the thickened bowel wall. If the bowel wall is enhanced to a degree equal to or greater than that of venous opacification in the same scan, it should be classified in the "white attenuation pattern" [1].Common diagnoses with this pattern include vascular disorders. At least two pathophysiologic events likely underlie this attenuation pattern: (a) Vasodilatation and/or (b) injury to intramural vessels with accompanying interstitial leakage. [3],[4].

Other CT findings of bowel ischemia reported in the literature include;

intramural gas (intestinal pneumatosis), mesenteric or portal venous gas,

Infarction of other abdominal organs like liver, spleen, pancreas [10].

Engorgement of mesenteric veins reflects venous congestion secondary to stasis. Owing to the edema, hemorrhage or inflammation that accompanies bowel ischemia, the mesenteric fat may be abnormally increased in attenuation. [11].

Hemorrhage from the intestine or mesentery into the peritoneum may be more hyperattenuating than older hemorrhage that has diffused throughout the abdomen. [2]. This difference in attenuation is particularly likely if the hemorrhage is initially confined within a smaller portion of the peritoneal space (e.g., between the leaves of the mesentery). This appearance has been termed the "sentinel clot sign". [5]

 
   References Top

1.Jack Wittenberg, MD, Mukesh G. Harisinghani, MD, Kartik Jhaveri, MD, Jose Varghese, MD and Peter R. Mueller, MD. Algorithmic Approach to CT Diagnosis of the Abnormal Bowel Wall. Radiographics.2002; 22:1093-1107. RSNA 2002.  Back to cited text no. 1    
2.Otto chan and Loannis Vlahos. The abdomen and major trauma. Textbook of radiology and imaging, D. Sutton, Seventh edition, 2003; vol 1, 23:705-707.  Back to cited text no. 2    
3.Sivit CJ, Taylor GA, Bulas DI, Kushner DC, Potter BM, Eichelberger MR. Posttraumatic shock in children: CT findings associated with hemodynamic instability. Radiology 1992; 182:723-726.  Back to cited text no. 3  [PUBMED]  
4.Mirvis SE, Shanmuganathan K, Erb R. Diffuse small-bowel ischemia in hypotensive adults after blunt trauma (shock bowel): CT findings and clinical significance. AJR Am J Roentgenol 1994; 163:1375-1379.  Back to cited text no. 4  [PUBMED]  
5.Anne Paterson and Louise Sweeney. Paediatric gastrointestinal radiology. Grainger and Allison's, Diagnostic radiology a textbook of medical imaging, fourth edition, 2001; 54:1219  Back to cited text no. 5    
6.Chou CK. CT manifestations of bowel ischemia. AJR Am J Roentgenol 2002; 178:87-91.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]
7.Rha SE, Ha HK, Lee SH, et al. CT and MR imaging findings of bowel ischemia from various primary causes. RadioGraphics 2000; 20:29-42.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]
8.Bartnicke BJ, Balfe DM. CT appearance of intestinal ischemia and intramural hemorrhage. Radiol Clin North Am 1994; 32:845-860.  Back to cited text no. 8  [PUBMED]  
9.Balthazar EJ. CT of the gastrointestinal tract: principles and interpretation. AJR Am J Roentgenol 1991; 156:23-32  Back to cited text no. 9  [PUBMED]  
10.Taourel PG, Deneuville M, Pradel JA, et al. Acute mesenteric ischemia: diagnosis with contrast-enhanced CT. Radiology 1996; 199:632-636'  Back to cited text no. 10  [PUBMED]  
11.Lund EC, Han SY, Holley HC, et al. Intestinal ischemia: comparison of plain radiographic and computed tomographic findings. RadioGraphics 1988; 8:1083-1108  Back to cited text no. 11  [PUBMED]  

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Correspondence Address:
M Sharma
Room No217, RMO's Hostel, GMC, Bambolim, Goa
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.29017

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    Figures

[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7]



 

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    Introduction
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    References
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