How IBS Is Diagnosed

Diagnosing irritable bowel syndrome (IBS) is as much about confirming what you don't have as ensuring that your symptoms are in line with what is characteristic of the condition itself. IBS causes regular bouts of diarrhea, constipation and abdominal pain—symptoms that are consistent with many other gastrointestinal issues. Many of the tests that your doctor orders, including blood work and imaging, will help rule out these concerns. By doing so, your IBS diagnosis is more conclusive.

There is no way for you to definitively determine if you IBS yourself, which is why it is highly recommended that you make an appointment with your primary care physician if you are experiencing recurrent symptoms.

It's helpful to start keeping a simple symptom diary, so you have a log of exactly what you've been experiencing and for how long.

Keep track of what you eat and how your body responds. Additionally, record when you have pain, diarrhea, and/or constipation. You should also log any other symptoms you experience like bloating, flatulence (gas), and acid reflux. Even symptoms like fatigue, headaches, heart palpitations, and bladder urgency should be recorded, especially if you consistently experience them along with the more obvious IBS symptoms.

This won't help you make a diagnosis, but it might help your doctor do so. You can use our Doctor Discussion Guide below to help you talk about your symptoms with a professional.

In many cases, doctors choose to diagnose IBS with a minimum of diagnostic procedures including:

• Routine blood work (Your doctor may also test your blood to see if you have celiac disease.)
• Fecal occult bleeding test (a test for blood in the stool)

The results will be considered with the information from your symptom diary and your medical history in mind.

Rome IV Criteria

Because IBS is considered a functional disorder, in that there is no visible disease process, physicians often use the Rome IV Criteria to diagnose IBS.

According to these criteria, IBS is diagnosed if symptoms have been present at least one day per week during a month’s time.

Symptoms also must consist of recurrent abdominal pain or discomfort with two or more of the following being true:

• Pain is relieved by a bowel movement
• Onset of pain is related to a change in frequency of stool
• Onset of pain is related to a change in the appearance of stool

While the Rome III Criteria is a helpful resource, many primary care doctors prefer that a more thorough investigation be done and may refer you to a gastroenterologist.

Gastroenterologists use their knowledge of the workings of the entire digestive system and their experience in the various disorders of the gastrointestinal system to come up with a comprehensive diagnosis and treatment plan.

Should your symptoms or family medical history warrant it, your doctor might recommend additional testing to be sure that you do not have another condition that mimics IBS, such as inflammatory bowel disease (IBD) and colon polyps.

If this happens, he or she may recommend one of these other common gastrointestinal procedures:

• Colonoscopy: A scope of your entire large intestine
• Sigmoidoscopy: Examination of the rectum and the lowest part of the colon, called the sigmoid colon
• Upper endoscopy: A scope of your upper digestive tract, including your esophagus, stomach, and duodenum
• Lower GI series (barium enema): X-ray of the large intestine with barium used for contrast
• Upper GI series: X-rays of the upper digestive system with barium used for contrast
• Lactose intolerance testing
• Stool test (to rule out intestinal parasites)

There are a number of common digestive health problems that share some of the same symptoms of IBS. For instance, celiac disease (an autoimmune response to eating gluten) and food intolerances (gastrointestinal responses to certain foods) often have symptoms that are similar to IBS.

Meanwhile, IBD, Crohn's disease, ulcerative colitis, and colon cancer also have similar symptoms. The difference is that people with these diseases many times experience rectal bleeding in addition to abdominal pain, gas, bloating, diarrhea and constipation; those with IBS usually do not have rectal bleeding unless it is from hemorrhoids.

Even if you are experiencing no rectal bleeding or other red-flag symptoms, most doctors prefer to rule out these conditions before making a diagnosis of IBS.