title: The halo sign and peripancreatic fluid: useful CT signs of hypovolaemic shock complex in adults.
abstract: OBJECTIVE
  To report two new, useful computed tomography (CT) signs of the hypovolaemic shock complex (HSC) in adults admitted after blunt abdominal trauma: the halo sign (ring of fluid around a collapsed intra-hepatic inferior vena cava (IVC)), and peripancreatic retroperitoneal fluid.
  
  
  METHODS
  CT images of 498 consecutive patients admitted after blunt abdominal trauma were reviewed, of which 27 had CT signs of the HSC. The CT images of these 27 patients were analysed. A control group of 101 patients examined using CT for suspected blunt abdominal trauma who did not have the HSC were chosen for comparison.
  
  
  RESULTS
  The most common features involved the vascular compartment: diminished IVC diameter n = 27 a positive halo sign n = 21 diminished anteroposterior diameter of the aorta n = 13 and abnormal vascular enhancement n = 10. Peripancreatic retroperitoneal fluid in the absence of pancreatic injury, pancreatitis or pancreatic disease was observed in eight patients. Hollow visceral abnormalities included: diffuse increased mucosal enhancement of both the small and large bowel n = 19 diffuse thickening of the small bowel wall n =11 and small bowel dilatation n = 7. Solid visceral abnormalities included both decreased and or increased enhancement. Several concomitant intra- and extra-abdominal injuries were also identified.
  
  
  CONCLUSIONS
  In the setting of blunt abdominal trauma, early abdominal CT can show diffuse abnormalities due to the HSC, which occasionally may alert clinicians of unsuspected shock. Recognition of these signs as distinguished from injured viscera is important in order to avoid unnecessary laparotomy. Two new signs are described: the halo sign and peripancreatic retroperitoneal fluid.
authors.affiliation: Department of Medical Imaging, Sunnybrook and Women's College Health Sciences Centre, University of Toronto, Ont., Canada. max.ryan@utoronto.ca
authors.forename: M F
authors.initials: MF
authors.lastname: Ryan
authors.forename: P A
authors.initials: PA
authors.lastname: Hamilton
authors.forename: J
authors.initials: J
authors.lastname: Sarrazin
authors.forename: P
authors.initials: P
authors.lastname: Chu
authors.forename: O
authors.initials: O
authors.lastname: Benjaminov
authors.forename: K
authors.initials: K
authors.lastname: Lam
mesh_terms: D000007:Abdominal Injuries / Q000150:complications / Q000000981:diagnostic imaging*; D000063:Accidents, Traffic; D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D005122:Exudates and Transudates / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000000981:diagnostic imaging*; D017678:Sex Distribution; D012769:Shock / Q000000981:diagnostic imaging* / Q000209:etiology; D014057:Tomography, X-Ray Computed; D014949:Wounds, Nonpenetrating / Q000150:complications / Q000000981:diagnostic imaging*