OCT angiography characterizes time- and diameter-dependent intestinal microvascular alterations in acute mesenteric ischemia

SignificanceAcute mesenteric ischemia (AMI) is associated with high mortality, and accurate assessment of intestinal viability and the extent of ischemic injury remains challenging. Microvascular alterations may precede overt mucosal structural damage but are difficult to monitor dynamically.AimWe aim to investigate the ability of OCT/OCTA to dynamically quantify intestinal mucosal microvascular alterations during AMI and to determine their temporal and vessel-diameter-dependent associations with histological injury.ApproachAMI was induced in mice by mesenteric artery ligation. In a longitudinal cohort (n=8), OCT was performed at baseline and 0.5, 1, 2, and 4 h after ischemia to quantify vessel length and vessel perfused density (VPD) in three diameter categories (<20 μm, 20 to 50 μm, and >50 μm). In a separate cross-sectional cohort (n=40), mice were randomly assigned to sham or ischemia groups (n=8 each). OCT was also used to detect the vascular parameters of intestinal mucosal microcirculation. Histological injury was assessed by villus height, crypt depth, and Chiu’s score. Correlations between microvascular and histological parameters were analyzed. Receiver operating characteristic curve was used to assess vascular parameters for discriminating severe intestinal injury.ResultsIschemia induced time- and diameter-dependent microvascular impairment. With the prolongation of ischemia, both vessel length and VPD decreased significantly across all vessel diameter categories (P<0.05). The length and VPD of vessels >50 μm decreased significantly faster than those of vessels <20 μm (P<0.05). Notably, reductions in the vascular parameters of 20 to 50 μm and >50 μm vessels were observed as early as 0.5 h after ischemia and preceded significant elevation of Chiu’s score. Villus height and crypt depth progressively decreased, whereas Chiu’s score increased with prolonged ischemia. OCT-derived vascular parameters across all diameter categories were positively correlated with villus height and crypt depth and negatively correlated with Chiu’s score (all P<0.05). In addition, OCT-derived vascular parameters had significant diagnostic performance for severe mucosal injury (Chiu′s score≥3).ConclusionsOCT enables real-time and quantitative assessment of intestinal mucosal microvascular alterations in AMI. Diameter-dependent microvascular impairment precedes overt histological injury and is associated with the severity of mucosal damage. These findings support the potential use of OCTA for intraoperative assessment of intestinal viability and provide a basis for future identification of ischemic transition zones and optimization of bowel resection boundaries.