Dear Doctors: My internist has recommended a colonoscopy. I dread having it because I’m concerned about the liquid laxative prep it requires. I suffer from IBS, which is often painful. Is it possible the prep will provoke a severe IBS occurrence?
Dear Reader: Unfortunately, there is no clearcut answer.
Irritable bowel syndrome, or IBS, is a disorder that causes pain, discomfort and dysfunction in the large intestine. In addition to cramping, bloating, gas and abdominal pain, people with IBS experience ongoing episodes of diarrhea or constipation, often both. A chronic condition, it has no cure.
Though the cause of the syndrome isn’t clear, recent research has linked it to changes that take place in the gut microbiome. The vast majority of the microbiota that comprise the gut microbiome reside in the colon — the large intestine, which is the portion of the gastrointestinal tract examined during a colonoscopy.
To perform an effective colonoscopy, the large intestine, which is where the body’s solid waste collects, must be free of all debris. That’s the only way for abnormalities to be visible. This necessitates the colonoscopy prep, which entails a brief change of diet followed by the use of a laxative drink to completely void the bowel.
While cleansing the bowel provides the clear field of vision needed to identify potential cancers, it also affects the intestinal flora. Studies show this process alters the population of microbes in the gut and that it takes weeks for the microbiome to recover.
How this affects people with IBS, whose gut microbiome might already be out of balance, isn’t clear. People’s experiences vary. Some say they are unaffected by the prep. Some experience a mild flareup. Others say their IBS symptoms go away altogether for weeks after the bowel is cleansed.
Colonoscopy prep has been much improved in recent years. The gallon of liquid once required is now often just two small bottles. There is evidence that splitting the dose, with half consumed the night before the procedure and half the morning of, is easier on the gut. Each colonoscopy center has its own protocols, so check.
Your reluctance to undergo a colonoscopy due to the potential effects of the prep is understandable. But the benefits of screening for colon cancer outweigh the risk of an IBS flareup.
A colonoscopy can identify precancerous polyps, which can be removed before they turn into cancer. Colorectal cancers found early are highly treatable. And, with normal results, you won’t need another colonoscopy for 10 years.
Dr. Eve Glazier and Dr. Elizabeth Ko are internists at UCLA Health.
