IBS – Work Up

IBS - Work Up

Historically irritable bowel syndrome (IBS) has been thought of as a diagnosis of exclusion, meaning that people are diagnosed with the condition only when the other causes of the symptoms are ruled out by a battery of tests.  In contrast to some other GI diseases that may have an organic cause, research studies have found that diagnostic tests such as blood tests, stool tests, lactulose breath tests, and abdominal or colonic imaging do not reliably predict IBS.  Because IBS has not been found to have an organic cause, or a diagnostic biomarker, a negative test result does not rule out IBS, and a positive test result does not rule in IBS.  Research has shown that symptoms are the best predictor of IBS, and therefore physicians base the diagnosis of IBS on signs and symptoms rather than tests, which may be unreliable.

Some physicians may use alarm symptoms to begin the process of evaluating a person for IBS or other causes.  It has been found that on average, 1.65 alarm symptoms are reported by people with IBS, with night symptoms (40%) and age over 50 (32%) being the most common:
* Age greater than or equal to 50
* Unintentional weight loss
* Family history of GI malignancy
* Severe, unrelenting large-volume diarrhea
* Fever, chills, recent travel to endemic region
* Symptoms that awaken the patient at night
* Regurgitating blood
* Physical examination findings (arthritis, skin lesions, swollen lymph nodes, abdominal mass)

Although diagnostic tests are unreliable predictors for IBS, the tests may be used to rule out other causes of the abdominal pain and stool changes.  Patients 50 years or older shoud have a colonoscopy to screen for colon cancer.  Abdominal x-rays or ultrasounds can be used to diagnose an abdominal swelling or mass.  Tests for ova and parasites in the stool can be used to rule out parasites as the cause of diarrhea or changes in stool.  A careful history and physical exam, blood tests, and blood cultures can rule out systemic bacterial infections that may be associated with abdominal pain, diarrhea, and fever.  However for the most part, IBS is diagnosed after any other possible disorder has been ruled out.


Lehrer J. Irritable Bowel Syndrome. eMedicine [web page]. Aug 8 2007; www.emedicine.com/med/TOPIC1190.HTM. Accessed June 24, 2008.

Videlock EJ, Chang L. Irritable bowel syndrome: current approach to symptoms, evaluation, and treatment. Gastroenterol Clin North Am. Sep 2007;36(3):665-685, x.