Contributions of pain sensitivity and colonic motility to IBS symptom severity and predominant bowel habits.

OBJECTIVES: Irritable bowel syndrome (IBS) patients show pain hypersensitivity and hypercontractility in response to colonic or rectal distention. Aims were to determine whether predominant bowel habits and IBS symptom severity are related to pain sensitivity, colon motility, or smooth muscle tone. METHODS: One hundred twenty-nine patients classified as IBS with diarrhea (IBS-D, N = 44), IBS with constipation (IBS-C, N = 29), mixed IBS (IBS-M, N = 45), and unspecified IBS (IBS-U, N = 11) based on stool consistency, and 30 healthy controls (HC) were studied. A manometric catheter containing a 600-mL capacity plastic bag was positioned in the descending colon. Pain threshold was assessed using a barostat. Motility was assessed for 10 min with the bag minimally inflated (individual operating pressure [IOP]), 10 min at 20 mmHg above the IOP, and for 15-min recovery following bag inflation. Motility was also recorded for 30 min following an 810-kcal meal. RESULTS: Compared with HC, IBS patients had lower pain thresholds (medians 30 vs 40 mmHg, P < 0.01), but IBS subtypes were not different. IBS symptom severity was correlated with pain thresholds (rho =-0.36, P < 0.001). During distention, the motility index (MI) was significantly higher in IBS compared with HC (909 +/- 73 vs 563 +/- 78, P < 0.01). Average barostat bag volume at baseline was higher (muscle tone lower) in HC compared with IBS-D and IBS-M but not compared with IBS-C. The baseline MI and bag volume differed between IBS-D and IBS-C and correlated with symptoms of abdominal distention and dissatisfaction with bowel movements. Pain thresholds and MI during distention were uncorrelated. CONCLUSIONS: Pain sensitivity and colon motility are independent factors contributing to IBS symptoms. Treatment may need to address both, and to be specific to predominant bowel habit.

Increased colonic pain sensitivity in irritable bowel syndrome is the result of an increased tendency to report pain rather than increased neurosensory sensitivity.

OBJECTIVE: The aim was to determine whether lower visceral pain thresholds in irritable bowel syndrome (IBS) primarily reflect physiological or psychological factors. METHODS: Firstly, 121 IBS patients and 28 controls underwent balloon distensions in the descending colon using the ascending methods of limits (AML) to assess pain and urge thresholds. Secondly, sensory decision theory analysis was used to separate physiological from psychological components of perception: neurosensory sensitivity (p(A)) was measured by the ability to discriminate between 30 mm Hg vs 34 mm Hg distensions; psychological influences were measured by the report criterion-that is, the overall tendency to report pain, indexed by the median intensity rating for all distensions, independent of intensity. Psychological symptoms were assessed using the Brief Symptom Inventory (BSI). RESULTS: IBS patients had lower AML pain thresholds (median: 28 mm Hg vs 40 mm Hg; p<0.001), but similar neurosensory sensitivity (median p(A): 0.5 vs 0.5; p = 0.69; 42.6% vs 42.9% were able to discriminate between the stimuli better than chance) and a greater tendency to report pain (median report criterion: 4.0 ("mild" pain) vs 5.2 ("weak" pain); p = 0.003). AML pain thresholds were not correlated with neurosensory sensitivity (r = -0.13; p = 0.14), but were strongly correlated with report criterion (r = 0.67; p<0.0001). Report criterion was inversely correlated with BSI somatisation (r = -0.26; p = 0.001) and BSI global score (r = -0.18; p = 0.035). Similar results were seen for the non-painful sensation of urgency. CONCLUSION: Increased colonic sensitivity in IBS is strongly influenced by a psychological tendency to report pain and urge rather than increased neurosensory sensitivity.

Treatment of Functional GI Disorders With Psychotropic Medicines: A Review of Evidence With a Practical Approach.

Functional gastrointestinal disorders (FGIDs) are complex in their physiology and clinical presentation. With no known biologic marker, investigators and clinicians use the Rome criteria to make a positive diagnosis. Psychosocial factors, although not part of these criteria, do contribute to illness presentation, severity, healthcare-seeking behavior and response to treatment. In this regard, psychoactive drugs are valuable in the management of FGIDs, particularly for patients with severe symptoms. The appropriate selection of antidepressants based on predominant symptom, side-effect profile, and psychological condition is an integral part of a successful management program.