CT Abdomen - Lung Windows
Human Immunodeficiency Virus (HIV) patient presented with cachexia, constipation, bloating and abdominal swelling.
CD4+ lymphocyte count was 12 cells/mm3 and plasma viral load was <40 copies/ml while receiving highly active anti-retroviral therapy (HAART) suggesting failure to reconstitute. He was diagnosed with Mycobacterium Avium Complex (MAC) infection five years ago.
Presentation abdominal XR to evaluate cause for abdominal distension demonstrated dilated loops of large bowel with evidence of florid intramural gas i.e. pneumatosis intestinalis (Fig 1).
When compared with an earlier abdominal film three months ago, similar but less severe pneumatosis was demonstrated.
Subsequent CT of the abdomen and pelvis demonstrated gross ascites and thickened, collapsed small bowel loops. Findings which are characteristic for MAC infection (Fig. 2). In addition, there is gross pneumatosis of the large bowel wall throughout its entire length. These were more conspicious on lung windows (Fig. 3).
Pneumatosis intestinalis is a rare finding in patients who are HIV-seropositive. Literature search with the keywords ‘HIV’, ‘AIDS’, ‘pneumatosis’ returned only 20 relevant items with the first case of pneumatosis intestinalis reported in an AIDS patient in 1990. 
It is defined as the presence of gas within the serosal or mucosal layer bowel wall. 
Many authors have theorised that pneumatosis in immunocompromised patients are secondary to bowel infarction or perforation due to infection.  But others have also suggested that gas-forming bacteria gain access to the submucosa via breaks and form gas within the bowel wall. 
Co-infection with MAC or Cryptosporidium is not uncommon in HIV patients. As in the case of our patient, along with the end-stage intramural pneumatosis, he also displayed radiological findings for MAC infection. He was diagnosed with antibiotic resistant MAC infection 5 years prior to this presentation and had remained on treatment.
No case reports on a patient with MAC and HIV infection who is known to have pneumatosis intestinalis have been published to date on literature review.
Many cases of HIV associated pneumatosis reported were incidental findings and clinical correlation is important. As in this patient, there was no requirement for surgical intervention. The patient was able to eat and drink normally and managed conservatively. Pneumatosis can be difficult to identify on different CT windows and appropriate alteration of CT windowing should be done to improve the sensitivity of detecting this abnormality, especially when it is subtle.
In an acutely unwell patient, for example with intestinal infarction, pneumatosis of this degree would present with greater clinical deterioration and abnormal laboratory findings. However, by comparing it with a three month old radiograph, it appeared that the pneumatosis in this patient was longstanding, similar to existing literature on this topic. And so, no surgical intervention was required.
It remains important to note that an acute surgical abdomen needs to be thoroughly investigated, even in a patient with a history of chronic pneumatosis.
 A Patel (1990) Pneumatosis intestinalis in AIDS: an unreported complication. British Journal of Clinical Practice (PMID: 2102237)
 P Sooby (2015) An unusual triad of pneumatosis intestinalis, portal venous gas and pneumoperitoneum in an asymptomatic patient. Journal of Surgical Case Reports (PMID: 25858266)
 B J Wood (1995) Pneumatosis intestinalis in adults with AIDS: clinical significance and imaging findings. American Journal of Roentgenology (PMID: 7484571)
 V Sivarajah (2013) Atypical distribution of pneumatosis intestinalis in a patient with AIDS. BMJ Case Reports (PMID: 23536641)
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