Colitis is a very frequent clinical entity,
especially within the hospital setting.
It is becoming increasingly usual that the first diagnostic test run on these patients is an abdominal CT scan,
due to the fact that it is a non-invasive test with great accessibility that,
additionally,
allows ruling out other complications.
It is therefore very important that,
in addition to identifying this pathology,
we get as close as we can to an etiological diagnosis.
When dealing with a CT scan for suspected colitis,
the most relevant to the consideration of an etiologic diagnosis are the clinical context of the patient and the distribution of wall thickening in the colon.
According to the clinical context,
there are several factors that may predispose to different types of colitis.
The most important are: the use of ATB (as clindamycin),
atherosclerotic disease,
thrombotic disorders,
low cardiac output,
immunosuppressive treatments,
radiation...
Concerning the distribution of wall thickening of the colon,
it should be considered various patterns depending on the region and its extension,
leading each of them to one or several etiologies:
1.
Pancolonic: Ulcerative colitis,
Clostridium difficile (pseudomembranous colitis),
GVHD.
2.
Short Segment: Neoplasm,
diverticulitis,
trauma.
3.
Discontinuous: Crohn disease.
4.
Involvement of the terminal ileum: Crohn disease,
infectious colitis (Mycobacterium tuberculosis,
Yersinia enterocolitica or CMV among others),
lymphoma.
5.
Ascending colon: Neutropenic colitis (typhlitis),
amebiasis,
lymphoma.
6.
Transverse colon: Extension of gastric or pancreatic cancer,
pancreatitis.
7.
Splenic flexure: Ischemia.
8.
Sigmoid Diverticulitis,
ischemia,
radiation colitis,
endometriosis.
9.
Rectum: Radiación colitis,
infectious proctitis,
colitis stercoral.
Because of the wide variety of etiologies described,
by their frequency in the clinical setting and presentation,
we will focus our attention on ischemic colitis,
Crohn disease,
ulcerative colitis,
pseudomembranous colitis,
GVHD,
infectious colitis and diverticulitis.