Estimates range from 100,000 to 300,000 individuals exposed to nerve agents.While low-level exposure to nerve agents has been suggested as the cause of GWI, the 2008 report by the U.S. Department of Veterans Affairs (VA) Research Advisory Committee on Gulf War illnesses (RAC) stated that "evidence is inconsistent or limited in important ways." The VAs 2014 RAC report concluded that, "exposure to the nerve gas agents sarin/cyclosarin has been linked in two more studies to changes in structural magnetic resonance imaging findings that are associated with cognitive decrements, further supporting the conclusion from evidence reviewed in the 2008 report that exposure to these agents is etiologically important to the central nervous system dysfunction that occurs in some subsets of Gulf War veterans. "A 2022 study by Dr. Robert W. Haley of the University of Texas Southwestern Medical Center, et al., of 1,016 U.S. Gulf War veterans found evidence of a causal link between GWI and exposure to low levels of sarin, which was released into the air by coalition bombing of Iraqi chemical weapons facilities. Significantly, the study found an increased incidence of GWI not only among veterans who recounted hearing nerve agent alarms, but also among veterans with the RR or QR (as opposed to the QQ) forms of the PON1 gene, which produces an enzyme that deactivates organophosphates (including sarin) through hydrolysis. By contrast, GWI was inversely associated with higher levels of the type Q isozyme, which is more efficient at breaking down sarin than its type R counterpart.
abdominal computed tomography, abdominal X-rays) and an examination with a camera inserted into the rectum (sigmoidoscopy, colonoscopy).An important investigation in the assessment of colitis is biopsy. A very small piece of tissue (usually about 2mm) is removed from the bowel mucosa during endoscopy and examined under the microscope by a histopathologist. It can provide important information regarding the cause of the disease and the extent of bowel damage. Types
There are many types of colitis. They are usually classified by the cause. Types of colitis include:

Autoimmune
Inflammatory bowel disease (IBD) – a group of chronic colitides. Ulcerative colitis (UC) – a chronic colitis that affects the large intestine. Crohns disease (CD) – another type of IBD that often leads to colitis. Unknown
Microscopic colitis – a colitis diagnosed by microscopic examination of colonic tissue; macroscopically ("to the eye") it appears normal. Lymphocytic colitis
Collagenous colitis

Treatment-caused
Diversion colitis
Chemical colitis
Chemotherapy-induced colitis
Radiation colitis
Checkpoint inhibitor induced colitis

Vascular disease
Ischemic colitis

Infectious
Infectious colitisA subtype of infectious colitis is Clostridioides difficile colitis, which is informally abbreviated as "C-diff colitis". It classically forms pseudomembranes and is often referred to as pseudomembranous colitis, which is its (nonspecific) histomorphologic description. Enterohemorrhagic colitis may be caused by Shiga toxin in Shigella dysenteriae or Shigatoxigenic group of Escherichia coli (STEC), which includes serotype O157:H7 and other enterohemorrhagic E. coli.Parasitic infections, like those caused by Entamoeba histolytica, can also cause colitis. Unclassifiable colitides
Indeterminate colitis is the classification for colitis that has features of both Crohns disease and ulcerative colitis.