Non-occlusive mesenteric ischaemia: CT findings, clinical outcomes and assessment of the diameter of the superior mesenteric artery

Abstract

Objective: Review of the experience of a tertiary care centre for almost 10 years in the CT diagnosis of non-occlusive mesenteric ischaemia (NOMI). Analysis of CT findings, correlation with clinical outcomes and evaluation of the usefulness of measuring the superior mesenteric artery (SMA) diameter for the diagnosis of NOMI.

Methods: 106 patients were diagnosed with NOMI in a biphasic CT examination from 2008 to 2017 in our hospital. Clinical outcomes and CT findings were reviewed. In 55 patients, the diameter of the SMA was compared with a previous CT scan where NOMI was not the diagnosis, and statistical analysis using paired t-test was performed.

Results: 81 patients (76%) had findings consistent with small bowel ischaemia and the ileum was the segment most commonly involved (47%). Lack of wall enhancement, pneumoperitoneum, pneumatosis intestinalis and portal venous gas were all considered signs of bowel necrosis and surgery was performed promptly. 70 patients had signs of vascular narrowing of the SMA branches and in the 55 cases with a previous CT scan, there were statistically significant differences regarding the SMA diameter with a mean reduction of the artery calibre and standard deviation of 1.93 ± 1.1 mm between the NOMI and non-NOMI scans (p < 0.001).

Conclusion: Acknowledgment of characteristic bowel necrosis CT findings is crucial for determining the therapeutic attitude and the use of previous CT scans to compare the SMA diameter may help the radiologist to achieve an early diagnosis of NOMI in an often critically ill patient population. Advances in knowledge: Diagnosis of NOMI can be difficult in cases of partial mural ischaemia, thus objective data (diameter of the SMA) should be useful for the radiologist to include NOMI as the first diagnostic option in the differential diagnosis.

Figure 1.

A 71-year-old female with ischaemic colitis at the sigmoid–rectal junction. (a) Contrast-enhanced MDCT image at angiographic phase shows the maximum and minimum diameters of the SMA (automated measuring using AVA application) immediately distal to the origin of its first branch, in a transverse plane of the vessel. (b) Contrast-enhanced MDCT image at angiographic phase of the same patient but in a previous CT performed to assess a liver focal lesion. Note that the maximum diameter of the SMA is greater than in (a), with a difference of 1.37 mm. AVA, advanced vessel analysis; MDCT, multidetector CT; SMA, superior mesenteric artery.

Figure 2.

An 83-year-old female with distal ileum non-occlusive mesenteric ischaemia. (a) MIP coronal contrast-enhanced MDCT image at angiographic phase shows the SMA (white arrow), narrowing of the major SMA branches (black arrow) and impaired filling of intramural vessels. (b) MIP coronal contrast-enhanced MDCT image at angiographic phase of the same patient but in a previous CT performed to rule out hepatocellular carcinoma. The SMA (white arrow) and its branches have a normal morphology, with no irregularities and distal intramural vessels are depicted. MDCT, multidetector CT; SMA, superior mesenteric artery; MIP, maximum intensity projection.

Figure 3.

Typical CT findings of small bowel ischaemia. (a) An 88-year-old female with ileum and jejunum ischaemia. Sagittal MPR contrast-enhanced MDCT image at portal venous phase demonstrates lack of wall enhancement, dilatation, mural thinning and pneumatosis intestinalis in a large segment of small bowel (white arrow). Notice the gas within the mesenteric veins and portal venous gas (black arrow). No surgery was performed and the patient died within 24 h since the symptoms onset. (b) An 82-year-old female with ileum and caecum ischaemia. Axial contrast-enhanced MDCT image at portal venous phase shows lack of wall enhancement, pneumatosis intestinalis and mural thickening (unlike image a) of a segment of ileum (white arrow). Bowel resection was performed at surgery and histological findings were consistent with mesenteric ischaemia. MDCT, multidetector CT; MPR, multiplanar reconstruction.

Figure 4.

Ischaemic colitis in watershed areas. (a) A 74-year-old female with splenic flexure ischaemic colitis. Axial contrast-enhanced MDCT image at portal venous phase shows wall thickening, fat stranding and mucosal hyperenhancement (white arrow) of the left colon splenic flexure. Colonoscopy was performed 8 days after CT and histological findings were consistent with ischaemic colitis. (b) An 84-year-old male with sigmoid–rectal ischaemic colitis. Axial contrast-enhanced MDCT image at portal venous phase depicts sigmoid–rectal junction wall thickening and fat stranding. Due to the instability of the patient, urgent surgery was performed with left hemicolectomy. Histology confirmed the diagnosis of ischaemic colitis. MDCT, multidetector CT.

Figure 5.

A 67-year-old female with right colon non-occlusive mesenteric ischaemia. (a) Axial contrast-enhanced MDCT image at portal venous phase shows a large hypodense wedge-shape area in liver segments VIII and IVA (black arrows) consistent with parenchymal infarction. Notice the portal venous gas (white arrow). (b) Axial contrast-enhanced MDCT image at angiographic phase depicts a wedge-shape area of lack of cortical enhancement in the left kidney consistent with renal infarction (white arrow). Notice the wall thinning, lack of mural enhancement and fat stranding in the right colon (white arrowhead). Surgery and histological findings confirmed the suspected diagnosis of right colon transmural ischaemia. MDCT, multidetector CT.

Figure 6.

A 69-year-old male with small and large bowel ischaemia. (a) Sagittal MPR contrast-enhanced MDCT image at portal venous phase shows patchy areas of absence of mural enhancement and pneumatosis intestinalis in the jejunum (white arrows). (b) Axial contrast-enhanced MDCT image at portal venous phase demonstrates findings consistent with an extensive mesenteric ischaemia affecting the jejunum and ileum. There is gas in the mesenteric veins, ascites and mural thickening of the right colon consistent with ischaemic colitis (white arrowhead). The patient underwent surgery, nevertheless due to the extent of the intestinal necrosis no bowel resection was performed. MDCT, multidetector CT; MPR, multiplanar reconstruction.