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IBS Center

Irritable Bowel Syndrome Diagnosis

If you suspect you are experiencing irritable bowel syndrome, it is important to seek medical advice immediately to make sure that symptoms aren’t caused by any other illnesses. After an initial evaluation, your doctor may refer you to a specialist in digestive disorders (a gastroenterologist) for more extensive testing.

To help in the diagnostic process, doctors developed diagnostic criteria for IBS and other functional gastrointestinal disorders. According to these criteria, you must exhibit certain signs and symptoms before a doctor diagnoses irritable bowel syndrome. The most important symptoms are abdominal pain and discomfort lasting at least 12 weeks (not consecutive). You also need to experience at least two of the following symptoms of IBS in order to be diagnosed:

  • abdominal distension
  • bloating
  • a change in the frequency or consistency of the stool
  • a feeling that you can't empty your bowels completely
  • straining during bowel movements
  • mucus in your stool
  • urgency before a bowel movement

Medical history
Your doctor may start by asking you questions about symptoms you are experiencing. If symptoms exhibit a pattern over time, the pattern may make it clear to your doctor that IBS is the cause. If symptoms have just started, something else may be the cause. Be ready to answer the following questions so that you can reserve time to go over any points you want to spend more time on. You may be asked:

  • What are your symptoms?
  • When did you first notice these symptoms?
  • Do you have any family history of bowel disorders or colon cancer?
  • Do signs and symptoms include fever?
  • Do signs and symptoms include vomiting?
  • Do symptoms come and go, or stay about the same?
  • Does anything seem to trigger symptoms (foods, stress, menstrual period)?
  • Have you lost weight without trying?
  • Have you noticed any blood in your stools?
  • Have you recently experienced significant stress, emotional difficulty or loss?
  • Have you ever been diagnosed with a food allergy or with lactose intolerance?
  • Have you been diagnosed with any other medical conditions?
  • To what extent do symptoms affect quality of life, including personal relationships and ability to function at school or work?
  • What is your typical daily diet?
  • What medications are you taking, including prescription and over-the-counter medications, vitamins, herbs and supplements?

Medical exams
Doctors do not typically depend upon physical signs to definitively diagnose irritable bowel syndrome. This is why diagnosis is often a process of elimination. If the symptoms that you are experiencing match IBS criteria and are not accompanied by signs or symptoms of other GI disorders, your doctor may suggest a course of treatment without doing additional testing. But if you don't respond to that treatment, you'll likely require more tests.

Your doctor may also need to perform some additional tests, such as a blood test or colonoscopy, to make sure that symptoms aren't caused by something other than IBS. Several tests, including stool studies to check for infection or malabsorption problems may be recommended. Among the tests that you may undergo to rule out other causes for your symptoms are the following:

Blood tests - Celiac disease may cause signs and symptoms similar to irritable bowel syndrome symptoms. Blood tests may help rule out that disorder.

Colonoscopy -In some cases, your doctor may perform this diagnostic test, during which a small, flexible tube is used to examine the entire length of the colon.

Gastroscopy – This procedure is used to rule out possible stomach ulcers and/or tumor(s).

Computerized tomography (CT) scan - CT scans produce cross-sectional X-ray images of the abdomen and pelvis to help doctors rule out other possible causes of symptoms.

Contrast radiothermal scan (RTG) – This image of the intestine is used to rule our possible diverticulitis/diverticulum or tumor(s).

Flexible sigmoidoscopy - This test examines the lower part of the colon using a flexible, lighted tube.

Lactose intolerance tests - Lactase is an enzyme needed to digest the sugar found in dairy products. If you don't produce this enzyme, symptoms may be similar to those caused by irritable bowel syndrome, Your doctor may order a breath test or ask you to exclude milk and milk products from your diet for several weeks in order to test for lactose intolerance.

Additional testing
Some symptoms that might prompt your doctor to perform additional testing include:

  • abdominal pain (not relieved by a bowel movement)
  • diarrhea (persistent or that wakes you from sleep)
  • fever
  • nausea or recurrent vomiting
  • new onset after age 50
  • rectal bleeding
  • weight loss

After a doctor diagnoses you with IBS, you can choose from a variety of treatment options. Talk with your doctor about potential side effects and what to do if you experience them. To continue reading about IBS treatment, click here.

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