Understanding CT imaging findings based on the underlying pathophysiology in patients with small bowel ischemia

Abstract

Because acute small bowel ischemia has a high mortality rate, it requires rapid intervention to avoid unfavorable outcomes. Computed tomography (CT) examination is important for the diagnosis of bowel ischemia. Acute small bowel ischemia can be the result of small bowel obstruction or mesenteric ischemia, including mesenteric arterial occlusion, mesenteric venous thrombosis, and non-occlusive mesenteric ischemia. The clinical significance of each CT finding is unique and depends on the underlying pathophysiology. This review describes the definition and mechanism(s) of bowel ischemia, reviews CT findings suggesting bowel ischemia, details factors involved in the development of small bowel ischemia, and presents CT findings with respect to the different factors based on the underlying pathophysiology. Such knowledge is needed for accurate treatment decisions.

Small bowel transmural necrosis secondary to acute mesenteric ischemia and strangulated obstruction: CT findings of 49 patients

“…Abnormal bowel wall enhancement could manifest as a decrease or increase in the enhancement of the affected bowel walls, relative to the normal-looking bowel in other areas. This CT finding was believed to reflect perfusion status of the bowel [ 21 ]. “Small bowel dilatation” was defined as a loop having an outer transverse diameter ≥2.5 cm [ 22 ].…”

Diagnostic Role of MDCT in Acute Mesenteric Ischemia

“…MDCTA is the best imaging modality in the diagnosis of acute mesenteric ischemia with a sensitivity of 94% and a specificity of 95% [9,18,21,22].CT protocol optimal protocol includes a multiphasic examination: non-enhanced acquisition followed by biphasic contrast-enhanced phases (delay of 30 s for the arterial phase and at 60-70 s for the venous phase). Intravenous administration of nonionic iodinated contrast material at a high flow rate at a rapid injection rate of 4-5 mL/sec, followed by a saline solution flush (1.5 mL/kg ) is administered optimizing scanning times with contrast bolus tracking methods [18,23]. The delayed scan phase, at 3 minutes from contrast injection, can be considered in a case-by-base evaluation to detect delayed or decreased enhancement.…”

“…The real incidence may be underestimated because this condition occurs in critically ill patients with predisposing conditions such as heart failure, major trauma, the use of vasopressors, and cardiogenic or septic shock (Figure 6) [2,36,56], NOMI should be considered in the differential diagnosis in these patients because imaging findings may be subtle, and the distribution of affected bowel may be discontinuous or involve multiple vascular territories [56]. The pathogenetic mechanism is poorly understood it may rely on a protective reflex in which the mesenteric vessels undergo constriction or spasm to preserve blood flow to the cardiac or central nervous systems [2,3,18,36,57]. At CT, diagnosis of NOMI can be challenging because vessels are not occluded and may present only subtle luminal narrowing of SMA and its first-order branches.…”

“…In stage II, necrosis extends into the submucosal and muscularis propria layers. In stage III, transmural necrosis involves all three layers [17,18]. In this scenario, MDCTA findings are fundamental to discriminating reversible ischemia from irreversible transmural necrosis [19].…”

Automatic detection of ischemic necrotic sites in small intestinal tissue using hyperspectral imaging and transfer learning

“…It is usually caused by insufficient or obstructed blood supply to the small intestine [2]. The causes of the disease are complex and varied, including mesenteric artery embolism, mesenteric vein thrombosis, intestinal obstruction, and intestinal torsion [3,4]. Ischemia-reperfusion injury and apoptosis in small intestinal tissues also lead to tissue necrosis [5].…”