From the Guidelines
The diagnostic approach to rule out ischemic colitis involves a combination of clinical evaluation, laboratory tests, and imaging studies, with CT scan with intravenous contrast being a crucial step, as recommended by the most recent guidelines 1. The initial assessment should include a thorough history and physical examination, focusing on risk factors such as age over 60, cardiovascular disease, and recent hypotensive episodes. Laboratory tests should include complete blood count to check for leukocytosis, comprehensive metabolic panel to assess renal function, and lactate levels which may be elevated in severe cases. Stool studies should be performed to exclude infectious causes. Imaging begins with plain abdominal radiographs to rule out perforation, followed by CT scan with intravenous contrast, which may show bowel wall thickening, "thumbprinting," or vascular occlusion, as suggested by the American College of Radiology Appropriateness Criteria 1. Colonoscopy is the gold standard diagnostic tool, typically performed within 48 hours of presentation, revealing segmental erythema, edema, ulcerations, or hemorrhagic nodules, most commonly in the watershed areas like the splenic flexure and rectosigmoid junction. Biopsies should be obtained during colonoscopy to confirm the diagnosis histologically. In cases where colonoscopy is contraindicated, CT angiography can evaluate mesenteric vessels for occlusion, as recommended by the guidelines 1. Some studies suggest that endoscopic evaluation with biopsies from at least one site is essential in acute severe colitis for diagnosis and excluding other causes of acute colitis 1. However, in immunocompromised patients, the diagnosis of acute abdomen, including ischemic colitis, requires a multidisciplinary approach and a high degree of suspicion, with contrast-enhanced CT scan being the most reliable exam to diagnose intrabdominal disease 1. Key points to consider in the diagnostic approach include:
- Clinical evaluation and risk factor assessment
- Laboratory tests, including complete blood count, comprehensive metabolic panel, and lactate levels
- Imaging studies, including plain abdominal radiographs and CT scan with intravenous contrast
- Colonoscopy as the gold standard diagnostic tool
- CT angiography as an alternative in cases where colonoscopy is contraindicated
- Multidisciplinary approach and high degree of suspicion in immunocompromised patients.
From the Research
Diagnostic Approach to Rule Out Ischemic Colitis
To diagnose ischemic colitis, a combination of clinical suspicion, radiographic, endoscopic, and histological findings are used 2. The following steps can be taken to rule out ischemic colitis:
- Clinical evaluation: Patients typically present with mild abdominal pain and tenderness over the involved segment of bowel, as well as passage of blood mixed with stool 3.
- Laboratory tests: Although laboratory tests may suggest the diagnosis, they are not specific for ischemic colitis.
- Radiographic images: Computed tomography (CT) scan may have suggestive findings, but it is not the gold standard for diagnosis 3, 4.
- Endoscopic visualization: Colonoscopy is the procedure of choice for diagnosis, and endoscopic visualization of colonic mucosa with histologic analysis of biopsies is the gold standard for identification of colonic ischemia 3, 5.
- Rectosigmoidoscopy: Emergent rectosigmoidoscopy is required for diagnosis confirmation, surgical decision, and prognosis analysis 4.
Key Considerations
- Ischemic colitis can present as a spectrum of injury, from transient self-limited ischemia to acute fulminant ischemia with transmural infarction 3.
- The diagnosis and management of ischemic colitis depend on the severity of the disease 2.
- Most cases of non-gangrenous ischemic colitis are transient and resolve spontaneously without complications, while gangrenous ischemic colitis is associated with high morbidity and mortality and requires urgent operative intervention 2.
- Surgical resection of the affected segment should be considered early to minimize adverse outcomes 5.