Opportunistic Intestinal Infections

 Favors distal small bowel (SB) and colon


image Mucosal hyper- or hypoenhancement; submucosal edema

image Infiltration of mesenteric fat

image Lymphadenopathy is very uncommon


• Mycobacterial
image Mycobacterium avium-intracellulare  (MAI): Thickened SB folds with relatively little submucosal edema

image Tuberculosis (TB): Favors ileocecal distribution

image Mesenteric lymphadenopathy, often with low density (caseation)

image Exudative ascites (may mimic peritoneal carcinomatosis)

• Protozoan (Cryptosporidium, Microsporidia, and  Giardia
image Duodenum and jejunum, sparing distal SB and colon

image Fold thickening without much submucosal edema

image Excess fluid (luminal distention) of proximal small bowel

image No ascites; uncommon lymphadenopathy

• Bacterial (Clostridium difficile colitis, Campylobacter, and others)
image Segmental or, more commonly, pancolitis

image Striking mucosal hyperenhancement and submucosal edema

image Ascites (present in 40% of cases)

image May progress to toxic megacolon or perforation




TOP DIFFERENTIAL DIAGNOSES




• Gastrointestinal lymphoma


CLINICAL ISSUES




• Prevalence of opportunistic GI infections in HIV patients has markedly decreased with potent antiretroviral therapy


DIAGNOSTIC CHECKLIST




• Specific diagnosis can be suggested by CT

• Diagnosis depends on microbiological confirmation by analysis of bowel content or even biopsy

image
(Left) This young woman has cystic fibrosis and lung transplantation, with new onset diarrhea. Axial CECT shows hyperenhancement and submucosal edema image affecting most of the small bowel (SB).


image
(Right) Coronal CECT in the same patient shows the widespread enteritis with engorged mesenteric vessels image. The colon image is spared. Endoscopy and biopsy confirmed cytomegalovirus (CMV) enteritis.

image
(Left) This 35-year-old man with AIDS developed profuse diarrhea and abdominal pain. Axial CECT shows pancolitis with marked submucosal edema image but no hyperenhancement of the mucosa.


image
(Right) Coronal CECT in the same patient shows more evidence of pancolitis image, proven to be due to CMV, which may induce ischemic injury to both the SB and colon in immunocompromised patients.


TERMINOLOGY


Abbreviations




• 


Synonyms




Definitions




• Symptomatic gastrointestinal (GI) infection of immunocompromised host by organisms that usually cause no or minor illness in immunocompetent individuals


IMAGING


General Features




• Best diagnostic clue
image Cytomegalovirus (CMV): Mucosal hyper- or hypoenhancement; submucosal edema
– Distribution: Small bowel (SB), colon >  stomach, esophagus, rectum
image Favors distal small bowel and colon

– Pattern CECT: Mucosal hyper- or hypoenhancement
image Reflects active inflammation vs. ischemic necrosis

image Deep ulcers may be transmural, causing mesenteric infiltration

– Pattern on upper GI series, small bowel series, or barium enema
image Aphthoid erosions in earlier stages

image Deep ulcers, even sinus tracts in later stages

– Barium studies and CT findings may mimic Crohn disease or ulcerative colitis

– Associated findings
image Lymphadenopathy is very uncommon

image Infiltration of mesenteric fat by transmural, deep ulceration

image Mycobacterial
– Mycobacterium avium-intracellulare (MAI): Thickened SB folds with relatively little submucosal edema
image Micronodular fold thickening on SB follow-through

– Tuberculosis (TB)
image Favors ileocecal distribution

image Wall thickening, luminal narrowing, ± obstruction

– Associated findings
image Mesenteric lymphadenopathy, often with low density (caseation)

image Exudative ascites (peritonitis)

image Peritoneal and omental thickening (may mimic peritoneal carcinomatosis)

image Most affected patients do not have overt lung disease

image Protozoan (Cryptosporidium and Giardia)
– Distribution
image Duodenum and jejunum

image Ileum and colon are spared

– Pattern
image Fold thickening without much submucosal edema

image Excess fluid (luminal distention) of proximal small bowel

– Associated findings
image No ascites nor lymphadenopathy

image Bacterial (Clostridium difficile colitis, Campylobacter, and others)
Nov 16, 2016 | Posted by in GASTROINTESTINAL IMAGING | Comments Off on Opportunistic Intestinal Infections

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