3. DISCUSSION
Although, COVID-19 mostly affects the respiratory system, GI-related complaints are seen in up to 38% of patients [11]. A large meta-analysis of more than 18,000 patients from around the world suggested that diarrhea was the most common (11.5%) GI symptom, followed by nausea and vomiting (6.3%), then abdominal pain (2.3%) [12]. In critically ill patients with COVID-19, GI-complications are seen in 74 to 86% which can include transaminitis, feeding intolerance, cholecystitis, pancreatitis, colonic pseudo-obstruction, and even life-threatening mesenteric ischemia [7]. AMI is the sudden onset of small intestinal hypoperfusion and patients most commonly present with acute abdominal pain requiring emergent surgical intervention.
The exact pathophysiology of bowel ischemia in critically ill patients with COVID-19 remains uncertain. Pathogenesis of thrombotic events in the context of COVID-19 include endothelial inflammation, thrombin formation, complement activation and initiation of the immune response [13,14]. Gross arterial and venous thrombosis, microvascular thrombosis and even non-occlusive mesenteric ischemia have been suspected responsible for fatal bowel wall necrosis [9]. Additionally, ICU admissions, high doses of vasopressors, hemodynamic instability, metabolic derangements, positive pressure ventilation, and viral enteritis should also be considered as contributory factors for bowel wall ischemia in COVID-19 patients [7,9].
A systematic review showed radiologically detectable arterial/venous thrombosis was not identified in more than half of patients with ischemic bowel [9]. Such patients develop mesenteric ischemia despite patent and well-perfusing proximal and mesenteric vessels on CT [7,8,15]. Likewise, CECT of our patient showed patent mesenteric vessels suggestive of non-occlusive mesenteric ischemia. Nevertheless, CECT should be considered in any cases of COVID-19 with prominent GI signs and symptoms, especially those admitted in ICU. CECT can also be helpful in detecting associated vascular findings and identifying those patients who may benefit from percutaneous endovascular thrombectomy as well [16].
The most common finding in COVID-19 associated coagulopathy is an increase in D-dimer levels. Abnormally elevated D-dimer has been found to be reported in up to 46.4% of all COVID-19 patients with prevalence higher among critically ill ICU patients (60%) than non-severe patients (43%) [17]. Various studies have reported different cutoff scores of D-dimer correlating with poor outcomes. Zhang et al. [18] examined 343 cases and showed that D-dimer levels of over 2.0 µg/mL could predict mortality with a sensitivity of 92.3% and a specificity of 83.3%. Furthermore, study by Rostami et al. [19] showed an increase in D-dimer and fibrinogen concentrations in the early stages of COVID-19 disease with a 3 to 4-fold rise linked to poor prognosis. A meta-analysis by Parisi et al., on 25,719 hospitalized COVID-19 patients showed that anticoagulant use was associated with 50% reduced in-hospital mortality risk [20]. Therefore, D-dimer and fibrinogen levels should be monitored, and all hospitalized patients should undergo thromboembolism prophylaxis with an increase in therapeutic anticoagulation in certain clinical situations [5].