In 2020, serving at the Papa Giovanni XXIII Hospital in Bergamo (the Italian District most affected by the "first wave" of the SARS-CoV2 Pandemic) and, subsequently, at the Fatebenefratelli Hospital in Milan (the Italian District most affected by the "second wave"), I got to know and treat many people hospitalized for COVID-19.
As both COVID-Unit Doctor and Surgeon on call, I saw that, beyond the most well-known respiratory manifestations, SARS-CoV2 disease is often an intestinal infection which, among other things, can be present even in the absence of manifest signs of pneumonia.
This intestinal infection most frequently presents with non-specific symptoms such as diarrhea, nausea and abdominal cramps, and in some cases may be complicated by bleeding, pain and abdominal distension that are associated with a sudden deterioration in the condition of patients: this deterioration cannot be explained only by visiting the patient, because at clinical examination of the abdomen the appreciable signs are often weak.
Usually performing a bowel ultrasound when the clinical visit alone is not enough for me to understand what is happening in the abdomen of my patients, I have started to do it regularly in all the COVID-19 patients I visited for abdominal symptoms.
And so, in the patients that showed a significant clinical worsening, I soon observed the presence of marked thickening of the walls of their colon, affecting single tracts or almost all of its length, associated with the presence of hypoechogenicity of the walls (darker aspect) as observed in ischemic colitis (where the blood supply to the walls is reduced and a marked inflammatory reaction is present).
In these patients I then requested a contrast-enhanced CT scan of the abdomen, to integrate the ultrasound findings and exclude microperforative signs, eventually followed by a colonoscopy. The findings at colonoscopy were inevitably suggestive of diffuse or segmental ischemic colitis, with markedly thickened walls of the colon and submucosal haemorrhages.
I therefore began to write down all these observations and to collect several images, trying to understand the mechanism of this intestinal damage. Talking with the Pathologist, who observed microthrombosis of the pulmonary vessels in the lungs of patients who died of COVID-19 (with lesions more similar to those of pulmonary embolism), I figured out that the same thing could happen in the walls of the bowel.
I studied the receptor mechanisms of the SARS-CoV2 virus and the role of the intestinal ACE2 receptor, and I came to hypothesize that the rapid worsening of the clinical conditions of these patients was caused by thrombosis with occlusion of the microcirculation in the walls of the bowel. The consequences of the reduction of blood flow to the bowel, depending on its severity, can range from damage to the intestinal barrier with the passage of bacteria and toxins into the circulation, to acute intestinal bleeding from ulceration of the mucosa, and in the most severe cases to the paralysis and marked distension of the colon, possibly associated with the presence of air bubbles inside the intestinal wall.
This situation can complicate an underlying intestinal pathology: for example, in patients with diverticulosis of the bowel, the thrombosis of a diverticulum can lead to hemorrhage and perforation, with the formation of abdominal abscesses or the onset of peritonitis with the need of surgery.
I have collected all these observations and ideas in the two articles below.
- Lotti M, Giulii Capponi M, Dokic D, Bertoli P, Lucianetti A. Unsuspected clinical presentation of coronavirus disease 2019: acute bowel disease. ANZ J Surg, 2020 Aug 8:10.1111/ans.16213 [Epub ahead of print]. doi: 10.1111/ans.16213
- Lotti M, Giulii Capponi M, Magnone S, Campanati L, Lucianetti A. Beware of the acute bowel disease in COVID-19 patients. ANZ J Surg, 2020 Oct 9:10.1111/ans.16384 [Epub ahead of print]. doi: 10.1111/ans.16384
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