A very common problem, IBS consists of chronic abdominal pain without any obvious cause. There are almost always other symptoms like diarrhea, constipation, or bloating, which may be more bothersome than the pain. It thought to be due to irregularity in the normal rhythmic movement of the intestines, or to an extra-sensitive intestine. Maybe an intestinal infection sets things off, maybe there’s an alteration in the bowel’s normal bacteria. Stress in life can certainly make IBS worse.
IBS is diagnosed completely by the medical history. The “Rome IV Criteria” define IBS as abdominal pain going on at least once a week for 3 months or more, related to bowel movements. There’s either constipation, diarrhea, or maybe both. One disadvantage with this is that it may include lots of people, many of whom might not perceive themselves as feeling ill (most people don’t like the idea of being labeled with a disease).
The most important part of diagnosis is to rule out other more serious conditions. Patients with bloody stools, weight loss, fevers, pain that keeps getting worse month by month, or pain that awakens a patient. Basic laboratory tests should be normal, such as no anemia, normal white blood cell count, and no tests suggesting inflammation (like the sedimentation rate or C-reactive protein).
It is not necessary to perform more complex tests such as colonoscopy or endoscopy (EGD), unless a patient is over 50 years-old when symptoms begin. Actually, nobody that old should be diagnosed with IBS without referral to a specialist (gastroenterologist).
For IBS with mainly Diarrhea, diagnosis can be based on the Manning Criteria:
- Pain relieved with defecation
- Increased stool frequency at time of pain
- Diarrhea at time of pain
- Mucus in stool
- Sensation of incomplete defecation
- Abdominal bloating seen on physical exam
Accuracy of these for IBS depends on sex, age, & number of criteria. For example:
- 20 y.o. women: 2 out of 6 (50% accuracy) to 6 out of 6 (>90%)
- 60 y.o. man: 2 out of 6 (25%) to 6 out of 6 (70%)
Accuracy for men is always less than for women, and accuracy for everyone decreases after 40 y.o. IBS is a condition of younger people; we’d never diagnose it if it first began over 50 without a decent work-up (including colonoscopy).
Note that “Irritable Bowel Syndrome” (IBS) is much different from “Inflammatory Bowel Disease” (IBD). The latter can cause destruction to the bowel; treatment carries its own risks, and advanced cases may require surgical removal of the bowel. This is never an issue with IBS. See link for definition of “Syndrome“.