By S. Anderson, M.D.

The medical community long thought that irritable bowel syndrome (IBS) had no structural abnormality but would look at stress and other psychological causes. This is quickly being debunked by new research.  When one suffers from IBS with CFIDS/ME, a recent study has found a there is a post-infectious IBS (PI-IBS) produced by low-levels of inflammation.  This has been shown by lymphocytic infiltration in the mucosa of the gut along with more permeability and an increase in other inflammatory components that include enterochromaffin and mast cells.

     Steroid treatment has not proven to be effective although some preliminary studies of probiotics may prove beneficial (McCarthy et al).  The studies are concentrating on balancing the interleukin-10 and interleukin-12 but are not yet complete.  Studies that delve into serotonin as well as histamine metabolism may also prove relevant. 

     The idea of IBS developing after an infection was first described in 1962 but the actual study of the mechanisms is quite new.  The severity of the disease along with gender seem to put one more at risk for IBS.  Since 2003, the research in this area has exploded!  The largest study to date was one that found 63% had diarrhea as a predominating factor while 24% alternated between diarrhea and constipation and 13% had mostly constipation.  Bloating was part of all groups suffering with PI-IBS.

     Interestingly, only a small percentage of those with PI-IBS had a history of psychiatric features such as anxiety or depression (Curr Opin Gastroenterol, 2006, 22/1).  The above mentioned enterochromaffin cells contain serotonin and Dunlop et al have demonstrated that this is also found in plasma levels.  Interestingly, those with constipated IBS had depressed serotonin release.  Two studies (Gwee et al, Wang et al) found an increased type of interleukin in PI-IBS but not IBS that did not have an infectious origin.  These researchers also linked mast cells to PI-IBS and found the mucosal nerves were affected by the mast cells correlating closely with severity and the frequency of abdominal pain.

     The recent studies of PI-IBS over the last two years that demonstrate increased inflammatory mediators that include serotonin and cytokines could prove helpful to many that suffer from this along with their CFIDS/ME as the work advances.