CT hypoperfusion complex refers to the predominantly abdominal imaging features that occur in the context of profound hypotension. Multiple abdominal organs can display atypical appearances not related to the initial trauma but reflect alterations in perfusion secondary to hypovolemia which affects the sympathetic splanchnic stimulation. The small bowel is more commonly affected than the large bowel.
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Terminology
The term CT hypoperfusion complex is now preferred over the older and less accurate term shock bowel 2,9.
Pathology
Etiology
CT hypoperfusion complex is most commonly described in the context of post-traumatic hypovolemic shock but can also occur in 1,2:
severe head or spinal injury
Radiographic features
CT
Features of CT hypoperfusion complex have been defined as (some or all of these features may be present):
small caliber abdominal aorta: AP diameter <13 mm, measured at 20 mm above and below the level of renal arteries 2; this occurs in ~30% of patients with hypovolemia and is not specific
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collapsed inferior vena cava: AP diameter <9 mm in three consecutive segments; i.e. measured at 20 mm both above and below the level of renal veins and at the perihepatic portion 2,6
sometimes not appreciated due to massive fluid resuscitation
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halo sign
low density (<20 HU) fluid surrounding the IVC 6
this occurs in ~80% of patients with severe hypovolemia 8
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enhancing, thickened bowel walls (>3 mm) 2
most commonly involves the jejunum
wall thickening is due to submucosal edema
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hyperenhancing mucosa
hyperdense to the psoas muscle on contrast enhanced images 2,13
shock pancreas: heterogeneous enhancement with peripancreatic fluid (<20 HU) 2,6; this is a controversial finding 10
hypoenhancement of the spleen (subjective) 2
decreased splenic volume 14
hypoenhancement of the liver: 25 HU less than the spleen 6
bilateral adrenal gland hyperenhancement may be a feature 7 mainly in pediatrics and is controversial in adults 10
hyperenhancing kidneys 13
ascites 13
shock thyroid: heterogenous contrast enhancement, enlargement and surrounding fluid 11,12.
The small bowel findings are the most commonly observed feature in CT hypoperfusion complex. Note that the frequency of most associated findings does not differ between trauma and non-trauma patients with CT hypoperfusion complex, except in case of a collapsed IVC which occurs in the majority of trauma patients, but in <40% of non-trauma patients with CT hypoperfusion complex 2. A follow-up study following resuscitation may demonstrate reversal of small bowel findings.
Treatment and prognosis
CT findings tend to be reversible with appropriate fluid management 3 although severe hypotension and shock have a significant mortality rate.
Differential diagnosis
The clinical context is extremely valuable for image interpretation. The differential for thickened enhancing bowel includes 4,5:
vasculitides (e.g. Henoch-Schonlein purpura)
submucosal or intramural hemorrhage (e.g. coagulopathy)
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