Utility of biphasic multi-detector computed tomography in suspected acute mesenteric ischemia in the emergency department.

PURPOSE: To retrospectively evaluate the utility of biphasic multi-detector computed tomography (MDCT) with arterial and portal venous phases for the detection of suspected acute mesenteric ischemia (AMI) in emergency department (ED) patients compared to limited surgical confirmation.

METHODS: A research ethics board (REB)-approved retrospective review of all consecutive adult patients who underwent an emergency biphasic 64-MDCT examination of the abdomen and pelvis due to clinical suspicion for AMI over a 5-year period at a single tertiary-care institution was performed. Patients who underwent biphasic 64-MDCT scans performed for any clinical concern other than suspected acute mesenteric ischemia were excluded. Specifically, reported vascular and bowel findings were used to establish occlusive arterial, venous, and non-occlusive MDCT findings of AMI. Correlation was made with surgical findings in operatively managed patients and with serum lactate values preceding imaging assessment. Diagnostic yield and positive predictive value calculations were performed.

RESULTS: Two hundred and twenty-five patients underwent MDCT for suspected occlusive AMI between 10 Jan 2011 and 31Jul 2016. Of these, 200 patients were negative for AMI and 25 patients (mean age 73.5 years; age range 48 to 94 years; 13 men and 12 women) had MDCT findings positive for bowel ischemia (yield of 11.1%). On MDCT, 18/25 (72%) had an occlusive arterial etiology for AMI, 2/25 (8%) had an occlusive venous etiology, and 5/25 (20%) had non-occlusive AMI. Twenty of 25 (80%) patients with positive MDCT findings of AMI also had an elevated serum lactate level, including 14/18 (77.8%) patients with arterial occlusive AMI on MDCT, 2/2 (100%) with venous-occlusive AMI on MDCT, and 4/5 (80%) with non-occlusive AMI on MDCT. Correlation with surgical findings led to a positive predictive value (PPV) of biphasic MDCT for surgically proven all-cause occlusive ischemia of 92.9%. Further substratification revealed PPVs of arterial and venous-occlusive ischemia of 85.7% and 7.1%, respectively. Of the 225 patients MDCT-positive for AMI, 213 had pre-imaging serum lactate assessments. Of 188 patients MDCT-negative for AMI, 85 patients had elevated serum lactate (45.2%). Twenty of the 25 patients with positive MDCT findings of AMI (80%) also had an elevated serum lactate level, including 14/18 (77.8%) patients with arterial occlusive AMI on MDCT, 2/2 (100%) with venous-occlusive AMI on MDCT, and 4/5 (80%) with non-occlusive AMI on MDCT.

CONCLUSION: Emergent biphasic MDCT demonstrated low but non-trivial yield (11.1%) for the depiction of suspected acute mesenteric ischemia but was particularly low for occlusive venous AMI (0.9%). The relationship between serum lactate elevation and positive MDCT findings of AMI in our study conforms to prior work and cautiously suggests value in routine serum lactate assessment preceding imaging for patient prioritization.