## 3 Colonic Ischemia After rAAA Repair
Mortality rates in the latter meta-analysis were highly variable, with some studies reporting mortality exceeding 50% in patients with confirmed ischemia. The higher incidence of intestinal ischemia after OSR compared to EVAR is primarily due to the greater surgical trauma associated with the open technique, including direct aortic manipulation and prolonged clamping, which often compromise blood flow to the intestines. OSR is also linked to higher blood loss, longer operative times, and increased transfusion requirements, all contributing to hemodynamic instability and splanchhic hypoperfusion. Furthermore, the manipulation of the aorta can lead to microembolization, which may cause ischemia in the mesenteric branches. In contrast, patients undergoing EVAR typically have more stable clinical conditions and a favorable anatomy, while those requiring OSR are often more critical or have a complex anatomy, introducing a selection bias. Moreover, such a metanalysis, despite the methodological strength and large sample size, presents some limitations due to the heterogeneity between studies, including differences in patient characteristics, ischemia definitions, surgical techniques, and perioperative management. Additionally, the lack of a standardized definition of intestinal ischemia leads to the potential underestimation or overestimation of incidence. Lastly, some older studies included in the meta-analysis reflect outdated surgical practices and protocols; therefore, these results need to be taken with caution, and further studies are needed to evaluate them [14; 15; 16; 17]. A previous study by [PERSON] et al. and a recent systematic review by [PERSON] et al. have demonstrated a lower inflammatory response and less ischemia-reperfusion injury after EVAR compared to OSR, which may contribute to a reduction in microembolization, leading to CI [18; 19]. Additionally, in the meta-analysis by [PERSON] et al., the reintervention rate was approximately half the CI prevalence, and patients who developed bowel ischemia (BI) after ruptured AAA repair had significantly higher morbidity and mortality, even in the absence of reintervention [12]. This divergence can be attributed to the high variability in the diagnostic methods and criteria across different studies, which are not standardized. Recent studies often identify many cases of non-clinically relevant CI. On the other hand, some studies present selection bias by reporting only those cases of CI that necessitate reintervention, with a consequent failure in reporting the overall prevalence of CI. This makes it difficult to draw a unanimous conclusion from the literature. Regarding diagnostic criteria, several studies have demonstrated the high sensitivity of sigmoidoscopy in detecting CI following rAAA surgery [19; 20; 21; 22] (Figure 2). This heightened sensitivity has led to an increased incidence rate of CI, between 14% and 32%, without a corresponding increase in resection rates due to the conservative management of many mild or moderate ischemia cases. The study by [PERSON] et al. demonstrated a negative predictive value (NPV) of endoscopically normal colonic mucosa, suggesting that the absence of endoscopic lesions allows for the clinically safe exclusion of transmural ischemia. In contrast, the presence of moderate to severe endoscopic abnormalities was associated with a positive predictive value (PPV) of 73%, indicating a high likelihood of transmural damage requiring surgical intervention [23]. However, recent studies have demonstrated that the specificity of sigmoidoscopy in identifying transmural ischemia that necessitates surgical resection is lower [23; 24]. For this reason, recent European guidelines recommend considering sigmoidoscopy in case of high clinical suspicion of CI and not routinely after rAAA repair [25]. Additionally, some authors suggest the early consideration of exploratory laparotomy to optimize diagnosis and overall patient management [26; 27].