IBS (irritable bowel syndrome) is a condition that affects the digestive system causing symptoms such as abdominal pain, bowel habit changes, excess gas, bloating (abdominal distention), abdominal cramping, and food intolerances.
There are three different types of IBS:
- IBS with diarrhea (IBS-D)
- IBS with constipation (IBS-C)
- IBS with mixed bowel habits (IBS-M)
IBS is not the same as Crohn’s disease or colitis, which are separate conditions referred to as inflammatory bowel disease (IBD).
A colonoscopy is both a diagnostic and therapeutic procedure used to examine and treat the rectum, colon, and a portion of the terminal ileum. A colonoscopy is performed with a colonoscope, which is a flexible and steerable instrument used to evaluate the entire colon (large intestine).
A colonoscopy will not detect IBS. IBS is considered a “functional” disorder because it is a problem with the movement (motility) of the digestive tract rather than a result of damage to the tissues of the digestive system. This means there are no changes in the intestinal tissue, so IBS cannot be detected with a colonoscopy, either visually or through a biopsy.
However, a colonoscopy may be ordered to check for colon cancer or inflammatory bowel disease (IBD) because these conditions can cause similar symptoms.
IBS is diagnosed with a patient history and a physical exam. Other tests that may be used to diagnose IBS or rule out other conditions include:
- Blood tests to check for anemia, infection, and digestive diseases
- Stool tests to check for blood in the stool or other signs of infections or diseases
- Hydrogen breath test to check for small intestinal bacterial overgrowth (SIBO) or problems with carbohydrate digestion, such as lactose intolerance
- Upper GI endoscopy with a biopsy to check for celiac disease
What Are Symptoms of IBS?
Symptoms of irritable bowel syndrome (IBS) include:
- Abdominal pain, often related to bowel movements
- Changes in bowel movements
- Bloating
- Feeling as if a bowel movement is incomplete
- Whitish mucus in the stool
Women with IBS may have increased symptoms during their periods.
People who have IBS often experience flare-ups of symptoms, which usually last between two to four days before improving or going away.
What Is the Treatment for IBS?
IBS (irritable bowel syndrome) is treated with changes in diet and lifestyle, medications, probiotics, and therapy.
Dietary changes may include:
Lifestyle changes may include:
Medications used to treat IBS with diarrhea may include:
- Loperamide (Imodium)
- Rifaximin (Xifaxan)
- Eluxadoline (Viberzi)
- Alosetron (Lotronex), only for women to be used with special warnings and precautions
Medications used to treat IBS with constipation may include:
Other medications used to treat abdominal pain associated with IBS may include:
- Antispasmodics
- Antidepressants
- Coated peppermint oil capsules
From 
https://www.niddk.nih.gov/health-information/digestive-diseases/irritable-bowel-syndrome/
https://share.upmc.com/2016/03/irritable-bowel-syndrome-high-fiber-diet/
https://www.nursingtimes.net/clinical-archive/gastroenterology/irritable-bowel-syndrome-19-02-2009/
https://www.healthpartners.com/blog/what-can-a-colonoscopy-detect/