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Diagnosing Irritable Bowel Syndrome

Person sitting on the toilet

You have abdominal pain and bloating at least once a week, and it’s been that way for at least three months. Your bowel habits and the consistency of your stool change frequently. One day it’s diarrhea and the next you’re constipated.

You could have irritable bowel syndrome (IBS), the most common gastrointestinal disorder around the globe. In the United States, about 12 percent of people have IBS, according to the National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK). IBS affects women more often than men, though it’s not clear why.

IBS symptoms can come and go. Most people who see their doctor suspecting they might have IBS are between the ages of 20 and 50. About half of all people with IBS have symptoms before they turn 35, according to Johns Hopkins Medicine. However, IBS can start as early as childhood.

In the past, doctors typically ruled out other gastrointestinal disorders before concluding someone had IBS – a diagnosis by exclusion. Today, doctors are more likely to look for patterns in your symptoms and could diagnose IBS even if you’ve had symptoms of the disease for only a short time.

Not everyone’s IBS is the same. Some have constipation. Some have diarrhea. And some have constipation one day and diarrhea another.

If you exhibit the following symptoms, here’s how you and your doctor will determine if it’s IBS or something else.

Abdominal pain and bloating

This is the most common symptom of IBS, no matter what type you have, according to American Family Physician. Most people with IBS describe the pain as cramping. No abdominal pain? It’s probably not IBS. Your pain is also likely to get worse with time. Going to the bathroom may help alleviate your pain, or it may not.

Some people with IBS also feel bloated or complain of a distended stomach, according to Johns Hopkins Medicine. Women may find that their symptoms are worse when they are menstruating.

Diarrhea and constipation

If food goes through your digestive tract rapidly and the result is frequent, watery bowel movements or diarrhea, you could have what's called IBS-D. However, if you wake up at night and experience large, bloody and watery bowel movements it is not likely to be IBS, American Family Physician says.

You could have IBS-C if your digestive system contracts slowly and, as a result, your stools may be hard and you may strain to pass them. This is IBS with constipation.

Or, you could have IBS-M, where you experience both diarrhea and constipation. Sometimes you have diarrhea and the next time constipation, or vice versa. Or, you can have diarrhea and constipation in the same bowel movement.

Episodes of constipation or diarrhea can be frequent, or you might go days or weeks without either, Johns Hopkins Medicine says.

Other symptoms

When going to the bathroom, you may feel as though you’re not able to finish your bowel movements even if you just did, American Family Physician notes. You also may see a whitish mucus in your stool.

Sometimes, people with IBS report symptoms such as headache, sleep disturbances, heart burn, post-traumatic stress disorder and back/pelvic pain. However, these other symptoms are not necessarily related to IBS, according to Johns Hopkins Medicine.

If you experience these symptoms and they’re interfering with your ability to function, you should see your family doctor or a gastroenterologist who specializes in intestinal disorders. You should also see your doctor if your symptoms occur at least once a week for three months or more, but you could see your doctor even if it’s less frequent and you’re concerned.

Your medical history

Your doctor will start with a medical history. According to NIDDK, questions your doctor is likely to ask include:

  • Does your family have a history of digestive diseases and disorders such as celiac disease, colon cancer or inflammatory bowel disease? These disorders can run in families. Your doctor can do tests to see if any of these conditions are the cause of your digestive woes, and rule them out before concluding it’s IBS.
  • Which medicines are you taking, including over-the-counter medications? Some medications can cause changes in bowel habits.
  • Have you had any recent infections?
  • Does stress play a role in when your symptoms seem to flare?
  • What is your diet like? Do certain foods seem to set you off?
  • What other health issues do you have? Some are more common in people with IBS. For example, people with IBS are more prone to fibromyalgia and interstitial cystitis, Johns Hopkins Medicine says.
  • Do you have discomfort during intercourse? About a third of women with IBS report this symptom, according to the GI Society.

Unexplained weight loss, blood in your stool and fever could be signs that something else serious is going on, the GI Society says. Be sure to mention these symptoms to your doctor. Do you get up at night because you have to defecate? This, too, could be a sign of something more serious. Be sure to let your doctor know.

A physical exam

After your medical history, your doctor will do a physical exam.

Your doctor will feel your gut to see if it is tender or bloated. Sometimes, people with IBS experience muscular contractions or spastic colon, the NIDDK says.

Your doctor also will listen to your abdomen with a stethoscope, and may examine your rectum to look for blood in your stool.

Medical tests your doctor might do

There’s no definitive test for IBS. Still, the NIDDK notes that your doctor may order tests including blood and stool samples to look for and rule out other causes for your frequent abdominal pain.

These may include:

  • Blood tests. Your doctor may ask for a blood sample so the lab can run tests to see if you’re anemic (low iron), have an infection or have other digestive diseases.
  • Stool tests. Your doctor can test your stool to see whether it contains blood, bacteria or parasites or a digestive liquid produced in your liver (bile acid), according to the Mayo Clinic. You will be given a sterile container that you use to collect your sample and instructions on how to get it to the lab for testing.
  • Colonoscopy. This is where your doctor looks at your colon with a flexible tube and a camera to look for cancerous growths or inflammatory bowel disease, according to the NIDDK. In most cases, the colonoscopy has replaced the barium enema, which involves coating the colon with barium that can be traced with X-rays.
  • Endoscopy. This procedure involves your doctor looking at your upper GI tract to check for celiac and other gastrointestinal diseases. (Celiac is gluten intolerance.) Your doctor is likely to order this test if you have consistent diarrhea, the Mayo Clinic says.
  • Hydrogen breath test. You breathe into a tube so your doctor can check whether you have bacteria growing in your small intestines, you have problems digesting carbohydrates or you are lactose intolerant, the NIDDK says. Lactose is the sugar found in dairy products.
  • Psychological tests. Your doctor may ask you to fill out questionnaires that can help detect anxiety, depression or other psychological problems that could be causing your gastric upset, the International Foundation for Gastrointestinal Disorders says.

The bottom line

Your symptoms, medical history and test results will help your doctor determine whether you have IBS or some other disorder. Mostly, it’s judgment and experience that will help your doctor reach the right conclusion and offer appropriate treatment. The goal of treatment is to make it so you can live as normally as possible. IBS is a chronic condition, the NIDDK notes. It can be controlled but not cured.

Article references

  1. Diagnosis of IBS, International Foundation for Gastrointestinal Disorders
  2. Diagnosis of Irritable Bowel Syndrome, National Institutes of Diabetes and Digestive and Kidney Diseases
  3. IBS, GI Society, Canadian Society of Intestinal Research
  4. Definition and Facts for IBS, National Institutes of Diabetes and Digestive and Kidney Diseases
  5. Irritable Bowel Syndrome, Diagnosis, Mayo Clinic
  6. Diagnosis of IBS in Adults, American Family Physician,
  7. Irritable Bowel Syndrome, Johns Hopkins Medicine
  8. Symptoms and Causes of IBS, National Institutes of Diabetes and Digestive and Kidney Diseases