Signs of post-traumatic hypovolemia on abdominal CT and their clinical importance: A systematic review

•In the acute setting, diagnosing hypovolemic shock clinically may be challenging due to hemodynamic compensatory mechanisms.•Imaging signs of clinically occult yet (possibly) pending hypovolemic shock can be present on contrast enhanced CT.•On CT, HSC can consist of vascular and/or visceral signs representing the true hypovolemic state and hypoperfusion, respectively.•A flat IVC on CT is a good predictor of occult shock and higher mortality, evidence regarding other signs is scarce. Our aim was to assess the findings of hypovolemia on abdominal CT that are most frequently seen in blunt abdominal trauma patients. When possible, we assessed the correlation of these CT signs with clinical outcome. MEDLINE, CENTRAL and EMBASE were systematically searched. Two reviewers independently screened and included articles and performed the data-extraction. Primary outcomes of interest were the frequency of each sign and its correlation with mortality. Secondary outcomes were need for intervention, transfusion need, intensive care unit admission rate and length of stay. A flat inferior vena cava and an inferior vena cava halo, a diminished aortic calibre, shock bowel, altered enhancement of the liver, pancreas, adrenals, kidneys, spleen and gallbladder, peripancreatic fluid and splenic volume changes have been described in the setting of hypovolemic trauma patients to constellate a CT hypovolemic shock complex. It is argued that vascular signs represent the true hypovolemic state and the visceral signs represent hypoperfusion. There is no consensus on the frequency or clinical relevance of these signs, which at least partly can be explained by the heterogeneity in study design, study population, scanning protocols and outcome parameters. Available evidence suggests a good predictive value for occult shock and a higher mortality rate when a flat inferior vena cava is present. Evidence regarding the other signs is scarce. The hypovolemic shock complex is an entity of both vascular and visceral CT signs that can be seen in blunt trauma patients. It can offer guidance to a swift primary imaging survey in the acute trauma setting, allowing the radiologist to alert the treating physicians to possible pending hypovolemic shock.