Because there are usually no physical signs to definitively diagnose irritable bowel syndrome, diagnosis is often a process of elimination. To help in this process, researchers have developed diagnostic criteria, known as Rome criteria, for IBS and other functional gastrointestinal disorders. These are conditions in which the bowel appears normal, but doesn't function normally. According to these criteria, you must have certain signs and symptoms before a doctor diagnoses irritable bowel syndrom.
The most important symptom is abdominal pain and discomfort lasting at least 12 weeks, though the weeks don't have to occur consecutively
You also must have at least two of the following:
- A change in the frequency or consistency of your stool — for example, you may change from having one normal, formed stool every day to three or more loose stools daily, or you may have only one hard stool every few days
- Straining, urgency or a feeling that you can't empty your bowels completely
- Mucus in your stool
- Bloating or abdominal distension
Your doctor will likely assess how you fit these criteria, as well as whether you have any other signs or symptoms that might suggest another, more-serious condition. Some red flag signs and symptoms that might prompt your doctor to do additional testing include:
- New onset after age 50
- Weight loss
- Rectal bleeding
- Nausea or recurrent vomiting
- Abdominal pain, especially if it's not completely relieved by a bowel movement
- Diarrhea that is persistent or awakens you from sleep
If you have these red flag signs or symptoms, you'll need additional testing to further assess your condition. If you fit the IBS criteria and don't have any red flag signs or symptoms, your doctor may suggest a course of treatment without doing additional testing.