Introduction

Medscape interviewed Dr Philip Schoenfeld on the prevalence, diagnosis, and treatment of overlapping functional gastrointestinal (GI) disorders including gastroesophageal reflux disease (GERD), chronic idiopathic constipation (CIC), functional dyspepsia, constipation-predominant irritable bowel syndrome (IBS-C), diarrhea-predominant irritable bowel syndrome (IBS-D), and IBS with both constipation and diarrhea (IBS-M). Table 1 lists the diagnostic criteria for these functional disorders.

Medscape: Dr Schoenfeld, would you please describe the prevalence of individual functional GI disorders and the prevalence of overlapping functional GI disorders?

Dr Schoenfeld: The prevalence of CIC as defined by the Rome criteria^[1] is approximately 10% to 15% in the US population.^[2] Functional dyspepsia is present in 11% to 29% of the population,^[3] and GERD in approximately 17% to as much as 40% of the US population.^[4] The rate varies according to the specific epidemiologic study evaluated and the definition of disease used to confirm these diagnoses. IBS is present in approximately 10% to 18% of the US population; the distribution is approximately 33% for each subtype (IBS-C, IBS-D, and IBS-M).^[2]

Overlap of these GI disorders -- meaning that a patient has both disorders concurrently -- is as follows:

• Among patients with IBS-C, approximately 25% to 50% have concurrent GERD, and approximately 30% to 60% have concurrent functional dyspepsia.^[4]
• Among patients with CIC, approximately 30% to 40% have concurrent GERD, and approximately 40% to 50% have concurrent functional dyspepsia.^[3]

The trends shift when we look primarily at a diagnosis of functional dyspepsia or GERD, which is much more common than IBS-C. Only about 10% to 20% of patients with GERD have concurrent IBS-C,^[4] and about 30% to 40% of patients with GERD have concurrent CIC.^[2] Among patients with functional dyspepsia as their primary diagnosis, the percentages are similar to those for GERD. These findings may suggest that a motility disorder in one area of the GI tract such as the stomach may lead to dysmotility in another part of the GI tract. The pathophysiologic mechanism for this phenomenon is not, however, well understood.

Medscape: Why is it important to identify these concomitant problems?

Dr. Schoenfeld: Many physicians may not be aware of the common overlap of these conditions and may not proactively ask their patients who have symptoms of GERD or IBS-C or CIC about overlapping conditions. This is problematic because the impact of concurrent functional GI disorders may have an additive or synergistic effect that negatively affects quality of life and causes patients to miss work or be less productive at work. Researchers who studied quality of life in patients with functional GI disorders found that compared with controls, patients with only GERD had lower scores on only 1 of 9 HRQoL domains, whereas patients who had overlapping GERD and IBS had lower HRQoL scores on 8 of 9 domains. ^[5] Not recognizing and adequately treating concurrent functional GI disorders such as GERD overlapping with IBS minimizes a provider's ability to improve a patient's quality of life, reduce absenteeism from work, or increase the patient's productivity at work.

Medscape: Can you describe some of the barriers to diagnosing an overlapping functional GI disorder?

Dr. Schoenfeld: As mentioned previously, I think many physicians are not aware of the frequency with which patients have overlapping or concurrent functional GI disorders such as GERD and CIC. Also, physicians have limited time with patients during a visit and often feel that time constraints minimize their ability to proactively discuss other symptoms of functional GI disorders with the patient. They may focus on the patient's primary complaint and not think about searching for other overlapping functional GI disorders.

Medscape: Can you describe for us a practical approach to screening for overlapping disorders?

Dr. Schoenfeld: In my practice we ask patients to complete a health history questionnaire at the beginning of each visit. Included in this questionnaire are specific questions about GERD, functional dyspepsia, CIC, and IBS and its subtypes (IBS-C, IBS-D, and IBS-M). By reviewing the completed questionnaire before I see the patient, I can get a sense of the likelihood that the patient has overlapping GI disorders. Then, when I sit down with the patient I proactively ask them symptom-based questions to determine whether they have concurrent functional disorders. I think that is really the key to identifying overlapping disorders.

Medscape: Do any medications for one problem exacerbate other problems?

Dr. Schoenfeld: There are many over-the-counter medications that are utilized for each of these functional GI disorders. I will start by noting that treatments for GERD, including H₂ receptor antagonists and proton pump inhibitors, rarely affect treatment of IBS or CIC, although approximately 5% to 10% of people treated with proton pump inhibitors develop diarrhea. Antacids, specifically aluminum-based antacids, may induce diarrhea if used in large quantities.

Common over-the-counter therapies for IBS and CIC include fiber-based products such as methylcellulose or ispaghula husk. When used in large quantities, these products may cause bloating, which worsens symptoms of functional dyspepsia as well as GERD.

Osmotic laxatives, which are frequently used to treat IBS-C and CIC, may cause both bloating and cramping in the upper and lower abdomen, leading to a worsening of symptoms of functional dyspepsia or IBS.

Medscape: What are some effective strategies to help patients manage overlapping functional GI disorders?

Dr. Schoenfeld: I think the most important aspect of a management strategy is to ensure that you ask patients with a functional GI disorder about symptoms suggestive of other overlapping functional GI disorders. Again, failing to identify and to proactively treat concurrent GI disorders is problematic because each specific functional GI disorder has an additive or synergistic effect on quality of life and can increase absenteeism from work and have a negative effect on work productivity.

The standard treatment for frequent GERD is to start with a proton pump inhibitor, which is effective at treating symptoms. Proton pump inhibitors inhibit the final common pathway for acid secretion, and have been shown to be extremely effective.

With respect to IBS-C, it is appropriate to start with commonly used over-the-counter therapies such as fiber-based products or osmotic laxatives. Physicians should, however, recognize that these treatments may exacerbate other concurrent functional GI disorders such as functional dyspepsia. Fiber-containing products may induce bloating, and osmotic laxatives lead to increased colonic transit, which may be experienced as discomfort in patients who have functional dyspepsia. If a patient with IBS-C or CIC experiences either ineffectiveness or side effects from these drugs or other functional GI disorders, I recommend that physicians move to FDA-approved treatments such as linaclotide^[6] or lubiprostone^[7] for CIC or IBS-C. These agents do not appear to increase the risk of the symptoms of GERD or functional dyspepsia.

It is important for physicians, especially gastroenterologists, to ask patients about over-the-counter products they have already tried. Since these products are available without prescription, many patients who seek treatment from gastroenterologists have already tried multiple over-the-counter products. If a patient with constipation related to IBS-C or CIC has already tried and failed to obtain relief with osmotic laxatives or fiber-based products, I think it is appropriate for a gastroenterologist to begin an FDA-approved treatment such as linaclotide or lubiprostone for CIC or IBS-C. It is also appropriate for a gastroenterologist to start with a proton pump inhibitor for frequent GERD symptoms.

Table 1. Criteria for Functional Disorders Discussed in this Article

*From Rome Foundation website.^[7]
†FromVakil N, et al. Am J Gastroenterol. 2006;101:1900-1920.^[8]
‡From Longstreth GF, et al. Gastroenterology. 2006;130:1480-1491.^[1]