If you’ve ever wondered exactly what the “requirements” are to be diagnosed with IBS, here they are:

• Three months of continuous or recurrent abdominal pain or discomfort that is relieved with having a bowel movement or associated with a change in the frequency or consistency of stool.

Also two or more of the following on at least 25% of occasions or days:

• Altered stool frequency or form;
• Passage of mucus; or
• A bloated feeling.

IBS can be categorized as diarrhea predominant, constipation predominant, or alternating diarrhea or constipation.

The Rome I criteria were revised in 1999 to the Rome II criteria by a special consensus committee which is now also internationally recognized but has not yet been validated in the scientific community. You may be thinking, that’s a little bit too detailed, but if you’re a physician, especially a pain physician who follows the research in FMS, you come to know very quickly that the “devil is in the details.” That’s because in one study FMS patients were found to fulfill Rome II criteria more than Rome I criteria – 81% vs 65%. So, almost 20% of the FMS patients who had IBS by one criterion would not have had it by the other criterion, even though nothing would have changed in their symptoms. The prevalence of approximately 65% would have been in keeping with values reported in other studies done in the past. Part of the reason may be due to the requirement in Rome I of symptoms being present for at least three consecutive months in the previous year which may miss patients because of the waxing and waning nature of some cases of IBS.

The first association between FMS and gastrointestinal symptoms was proposed by one of the premier researchers in FMS, Dr. Yunus, in 1981 but it was not until 1991 that specific studies were first published. Dr. Yunus actually initially came up with the some of the important criteria by which FMS could be diagnosed in the early 1980’s and it was his criteria that the American College of Rheumatology heavily relied upon when they published their 1990 guidelines under the direction of Dr. Frederick Wolfe. 

The first studies reported altered bowel function in 73% of FMS patients with 63% reporting alternating diarrhea and constipation and 64% with additional complaints of dyspepsia. Dyspepsia is a fancy medical term that simply means, indigestion or an upset stomach (medically, it sounds more important than, “upset stomach.”)  Another study found IBS in 70% of FMS patients and then looked at IBS patients and examined them for FMS and found that diagnosis in 65% of those folks. Other studies have found a prevalence of IBS in FMS ranging from 32% to 73%. The strong association between IBS and FMS has led to the suggestion of screening IBS patients for FMS if they have not been diagnosed with FMS.

The severity of IBS is strongly affected by psychosocial factors, both in patients with FMS and those without and, as you would expect, influence the clinical outcome. Both also similarly manifest flares brought on by stress, sleep disturbances, and fatigue. Two studies in patients with FMS have specifically mentioned the association of IBS symptoms with stressful life events, which doesn’t come as much of a surprise, but it did need to be proven in a scientific study. Of co-morbid psychological symptoms, depression ranks high, being found in 40% of FMS patients with IBS.  Does depression contribute to IBS or does IBS contribute to depression – you can be the judge of that.

In examining the reverse perspective, although one study has suggested the severity of IBS does not appear to be dependent on the presence of FMS most find those people with both IBS and FMS have the highest Functional Bowel Disease Severity Index (FBDSI) scores and the lowest health related quality of life.  The FBDSI is the equivalent of the Fibromyalgia Impact Questionnaire for IBS patients and measures how much IBS interferes with their lives – a higher score is not good.

Likewise, there are differences between FMS patients with and without IBS. One study found significantly more tender points in FMS + IBS patients than FMS alone, a second showed a strong association of IBS in those FMS patients manifesting more significant symptoms such as diffuse pain sensations, sleep disturbances, and fatigue.  A confounding factor is medication use. Tricyclic antidepressants and opioids have constipation as a common side effect.  Since constipation-predominant IBS is a category of IBS it’s hard to tell what is due to the IBS and what’s due to the medications. Use of tricyclic medications usually corresponds to a higher incidence of laxative usage; 19% in one study so you would tend to think that the medications are playing a significant role.

Independent of FMS, up to 79% of IBS patients have gastroesophageal reflux disease (GERD) and there is a debate in the medical field as to whether IBS and GERD are one disease or an overlap of two disorders.  The prevalence of GERD can be as high as 79% in patients with IBS, with higher values present in older age groups. Unfortunately, the older age groups are those where FMS is now showing up more frequently, or in medical terms, having a greater prevalence. You can read more about prevalence in the short report on epidemiology. Patients will present with classic symptoms of dyspepsia, i.e., indigestion, dysphagia (translation – difficulty swallowing), heartburn, belching, acid regurgitation, and possibly wheezing, chronic cough, hoarseness, or chest pain.  Approximately half of patients with FMS will have complaints of dyspepsia and the impact on their quality of life can be substantial.  Consequently, if you have FMS and IBS you should also be screened for GERD as well. This is another reason you need a physician who has experience with FMS – most physicians don’t know this.

Two reports appeared in the gastroenterology literature of an association between IBS and abnormal findings on something called the lactulose hydrogen breath test (LHBT) which is thought to provide evidence of small intestine bacterial overgrowth (SIBO). SIBO is a condition in which the normal bacterial flora of the large intestine became “overgrown” and extended backward into the small intestine. The researchers felt that antibiotic treatment effectively decreased IBS symptoms by reducing SIBO. However, not only did those studies garner considerable attention in the lay press, the internet, and among FMS patients they also generated several critical “letters to the editor” to the medical journal in which the research appeared.
Other physicians and researchers pointed out methodological errors in the original studies. A major error was the low sensitivity of LHBT in detecting SIBO ( about 16%). You can read more about sensitivity in the short report on epidemiology and FMS. Basically, the sensitivity of a test measures how well that test can do what it is supposed to do, in this case detect SIBO. You want a test with high sensitivity; someone certainly does not want a test with low sensitivity incorrectly indicating they have cancer and need to start chemotherapy when that is not the case. Unfortunately, the researchers are still fighting that battle. One 2009 study cited a prevalence of 54% SIBO in IBS using LHBT while a 2011 report claims LHBT measurements fail to support any diagnosis of SIBO what-so-ever.

Remember - I said the devil was in the details. The relevance to FMS with these studies regards an association between FMS, IBS, and SIBO. In one study, subjects were recruited based on a diagnosis of FMS using the 1990 ACR criteria and not on the presence of abdominal complaints. All of the FMS patients supposedly had an abnormal LHBT compared to 85% of the patients with IBS and 20% of normal, healthy people, which was thought to be suggestive of people with FMS automatically having SIBO. (The fact that all of the FMS patients tested positive sounded a little funny.)

The hypothesis put forth, based on animal studies in the laboratory, was that movement of chemicals that bacteria are producing, called gram negative endotoxins, could be producing a type of whole-body increased pain sensation, or hyperalgesia. Since the bacteria have overgrown into the large and small intestine, they are producing exceptionally large quantities of these endotoxins. In other words, SIBO could be one of the reasons patients with FMS experience so much pain. If so, then if you kill off the bacteria with antibiotics it should follow that a substantial portion of the pain should subside.  
In a double blind study (meaning neither the FMS patients nor their treating physicians knew who was getting the antibiotic and who was getting the sugar pill) FMS patients who tested positive for SIBO received 500 mg of liquid neomycin (the antibiotic) twice a day for 10 days of which 60.7% were determined to have achieved a killing-off of their overgrown bacteria.  At the conclusion of the treatment, compared to those who did not have eradication of their bacteria, there was a statistically significant improvement in the Fibromyalgia Impact Questionnaire, pain as measured on the visual impact questionnaire, and improvement on a measure called the modified health assessment questionnaire, but not on trigger point scores, although the latter were improved from the measurements taken when people first entered the study. This sounded encouraging, but at this point, the study needs to be replicated in larger numbers of FMS patients, which it has not been to date, and the patients actually had to be proven to have had SIBO by something else other than the LHBT.

IBS is also important for another reason. It supports something called a “hypervigilance” model of pain perception. Basically, this model says that as a result of having IBS, patients with FMS are simply made more aware of painful sensations, wherever they arise. This is not something that happens consciously but rather is a function of how their nervous system changes as a result of being bombarded by a constant input of pain signals from the nerves in their body, and the gastrointestinal system has quite a large number of nerves.

Actually, the number of nerves in the gastrointestinal system, called the enteric nervous system, is just about on par with the number of nerves in the spinal cord – about 500 million – sounds unbelievable, but it’s true. Incidentally, the enteric nervous system is called, the “second brain.” (So, now if you’re wondering, the human brain has about 100 billion neurons. If it takes you 20 minutes to read this short report then during that time 125 neurons in your brain will have died a natural death as the brain loses about 9,000 neurons per day as a result of natural aging.)

Technically, the pain from the gut is called “visceral hypersensitivity” and has been demonstrated through experiments with FMS patients that apply stimulation through probes inserted into the rectum. I know this doesn’t sound pleasant to begin with, and it wouldn’t be pleasant to anyone, but it is even more unpleasant to patients with FMS. This hypersensitivity has become a recurrent theme in another pain syndrome more common to patients with FMS –interstitial cystitis, which you can read about in a forthcoming short report. As you will soon find out, the pain in FMS is linked together in very unique ways. And, we haven’t even begun to talk about how it all meshes together in the central nervous system. The devil is indeed in the details.