IMAGES FOR SURGEONS

Gastrointestinal symptoms such as abdominal pain comprise of around 5% of the presenting symptoms of COVID-19. We describe a COVID-19 patient presenting with a rare mesenteric abscess with secondary bowel perforation. The patient is a 33-year-old male who contracted mild COVID19 infection not requiring hospitalization in June 2020. He presented to the Emergency Department in January 2021 with 1 day onset of severe lower abdominal pain. His vital parameters were normal. Examination revealed generalized peritonitis with significant leucocytosis of 20 10 cells per litre. An erect chest X-ray had no consolidative changes to suggest active COVID-19 infection. He underwent a computed tomography scan which revealed inflammatory changes in the right upper abdomen, extraluminal free air seen in the mesentery and a defect in the small bowel (Fig. 1). He was consented and underwent an exploratory laparotomy. Intraoperatively, a segmental ileal perforation at the mesenteric border was noted with generalized purulent contamination. A segmental ileal resection with a primary anastomosis was performed. His initial SARS-CoV-2 ribonucleic acid (RNA) polymerase chain reaction (PCR) test was positive. During his inpatient stay, his PCR swabs became negative, and he was discharged 13 days postoperatively. Histopathology of the segmental ileal resection revealed an acute abscess centered in the small bowel mesentery. There were no extensive mucosal changes in the bowel wall to suggest it was the primary site of pathology, and the features were not typical of either primary ischemia or inflammatory bowel disease (Fig. 2(a) and (b)). These all suggested that the patient developed a mesenteric abscess first, prior to secondary bowel perforation. Interestingly, no other sites of infection were found. Unfortunately, no PCR tests were performed on the abscess for SARS-CoV-2. Primary mesenteric abscesses are rare, especially so in an immunocompetent patient. To date, in the absence of inflammatory bowel disease, small bowel diverticuli or tuberculosis, most of the literature concerning primary mesenteric abscesses are related mostly to suppuration from mesenteric adenitis. Given his lack of respiratory symptoms, it is likely that the patient was an intermittent shedder of SARS-CoV-2. The aetiology of his abscess is uncertain, but an infection must have reached the mesentery to initiate the inflammatory process. Given his recent COVID-19 infection, the authors wonder if there was any possible link between the two. COVID-19 infections can result in gastrointestinal symptoms including bowel perforation. However, the aetiology of these complications is usually a direct result of microvascular thrombosis and ischemia, pseudo-obstruction, or a combination of microvascular thrombosis with non-occlusive mesenteric ischemia. However, the histological assessment of the ileal perforation in our patient, was not consistent with any of the above aetiologies. The authors postulate that the mesenteric abscess may have been caused by either (1) initial COVID-19 related mesenteric adenitis, with subsequent suppuration and perforation; or (2) an immune deficiency, either acquired after his COVID-19 infection or unrelated, resulting in a primary mesenteric abscess formation, given his delayed viral shedding almost 6 months after his index COVID-19 diagnosis. Angiotensin-converting enzyme 2 (ACE2) protein, which is highly expressed in the intestinal epithelium, is the SARS-CoV-2 viral host cell receptor, and is the postulated mechanism behind gastrointestinal tract infection by SARS-CoV-2. The authors postulate that an initial COVID-19 infection of the ileum may have occurred, with resultant reactive mesenteric adenitis that underwent suppuration because of secondary bacterial infections, resulting in adjacent transmural bowel wall involvement and perforation. The other potential cause might be due to immune dysregulation. COVID-19 infections are known to result in immune dysregulation, and immunocompromised patients are known to have prolonged viral shedding. The patient may have an undiagnosed immunodeficiency, which might explain his initial mild symptoms and prolonged viral shedding. However, during his