Feeding and colonic distension provoke altered autonomic responses in irritable bowel syndrome.

OBJECTIVE: Alterations in autonomic balance, detectable by heart rate variability (HRV) analysis, have been shown to occur after a meal in patients with irritable bowel syndrome (IBS). There are few data on changes in sympathovagal responses in IBS to other forms of enteric stimulation such as colonic distension. The aim of this study was to determine the effects of colonic balloon distension on HRV in the fasting and the postprandial state in healthy subjects and in IBS patients. MATERIAL AND METHODS: Eight IBS patients and 8 age- and gender-matched healthy subjects underwent unsedated descending colonic distension before and after a 1000 kcal liquid meal. Low- (LF) and high-frequency (HF) HRV band values obtained from 2-min ECG segments recorded before and during distension were compared between groups, and between fasting and postprandial states. A visual analogue scale was used to determine sensation during colonic distension. RESULTS: HF values decreased significantly with feeding in IBS patients (p=0.01), but not in healthy subjects. The low-to-high frequency (LF/HF) ratio was significantly higher postprandially in IBS patients (p=0.02) and, additionally, was decreased (p<0.01) with colonic distension in the fed state, independently of colonic sensitivity or distending volume. Moreover, changes in the LF/HF ratio with distension in the fed versus the fasting state were negatively correlated in IBS patients but positively correlated in healthy subjects (both p<0.05). CONCLUSIONS: IBS patients demonstrated altered autonomic responses to feeding and colonic distension. Further studies should determine whether these alterations could explain the postprandial exacerbation of symptoms in IBS.

Gastrointestinal symptoms in spinal cord injury: relationships with level of injury and psychologic factors.

INTRODUCTION: Previous surveys of gastrointestinal symptoms after spinal cord injury have not used validated questionnaires and have not focused on the full spectrum of such symptoms and their relationship to factors, such as level of spinal cord injury and psychologic dysfunction. This study was designed to detail the spectrum and prevalence of gastrointestinal symptoms in spinal cord injury and to determine clinical and psychologic factors associated with such symptoms. METHODS: Established spinal cord injury patients (>12 months) randomly selected from a spinal cord injury database completed the following three questionnaires: 1) Rome II Integrative Questionnaire, 2) Hospital Anxiety and Depression Scale, and 3) Burwood Bowel Dysfunction after spinal cord injury. RESULTS: A total of 110 patients participated. The prevalence of abdominal bloating and constipation were 22 and 46 percent, respectively. Bloating was associated with cervical (odds ratio = 9.5) and lumbar (odds ratio = 12.1) level but not with thoracic level of injury. Constipation was associated with a higher level of injury (cervical odds ratio = 5.6 vs. lumbar) but not with psychologic factors. In contrast, abdominal pain (33 percent) and fecal incontinence (41 percent) were associated with higher levels of anxiety (odds ratio = 6.8, and odds ratio = 2.4) but not with the level of injury. CONCLUSIONS: There is a high prevalence and wide spectrum of gastrointestinal symptoms in spinal cord injury. Abdominal bloating and constipation are primarily related to specific spinal cord levels of injury, whereas abdominal pain and fecal incontinence are primarily associated with higher levels of anxiety. Based on our findings, further physiologic and psychologic research studies in spinal cord injury patients should lead to more rational management strategies for the common gastrointestinal symptoms in spinal cord injury.

Attenuation of the colorectal tonic reflex in female patients with irritable bowel syndrome.

Alterations in normal intestinointestinal reflexes may be important contributors to the pathophysiology of irritable bowel syndrome (IBS). Our aims were to compare the rectal tonic responses to colonic distension in female IBS patients with predominant constipation (IBS-C) and with predominant diarrhea (IBS-D) to those in healthy females, both fasting and postprandially. Using a dual barostat assembly, 2-min colonic phasic distensions were performed during fasting and postprandially. Rectal tone was recorded before, during, and after the phasic distension. Colonic compliance and colonic sensitivity in response to the distension were also evaluated fasting and postprandially. Eight IBS-C patients, 8 IBS-D patients, and 8 age- and sex-matched healthy subjects (group N) participated. The fasting increments in rectal tone in response to colonic distension in both IBS-C (rectal balloon volume change -4.6 +/- 6.1 ml) and IBS-D (-7.9 +/- 4.9 ml) were significantly reduced compared with group N (-34 +/- 9.7 ml, P = 0.01). Similar findings were observed postprandially (P = 0.02). When adjusted for the colonic compliance of individual subjects, the degree of attenuation in the rectal tonic response in IBS compared with group N was maintained (fasting P = 0.007; postprandial P = 0.03). When adjusted for colonic sensitivity there was a trend for the attenuation in the rectal tonic response in IBS patients compared with group N to be maintained (fasting P = 0.07, postprandial P = 0.08). IBS patients display a definite attenuation of the normal increase in rectal tone in response to colonic distension (colorectal reflex), fasting and postprandially. Alterations in colonic compliance and sensitivity in IBS are not likely to contribute to such attenuation.

Modulatory influences on antegrade and retrograde tonic reflexes in the colon and rectum.

Tonic reflexes in the colon and rectum are likely to be important in health and in disorders of gastrointestinal function. The aim of this study was to evaluate the fasting and postprandial "colorectal" and "rectocolic" reflexes in response to 2-min isobaric distensions of the colon and rectum, accounting for enteric sensation, compliance, and distending balloon volume. In 14 healthy fasting subjects, a dual barostat assembly was positioned (descending colon and rectum). A 2-min phasic distension was performed in the colon and rectum in random order while the opposing balloon volume was recorded. Sensation (phasic distension) and compliance (ramp distension) were also determined. The experiment was repeated postprandially. Colonic distension resulted in significant rectal tonic contraction in the fasting (rectal volume change: -35.4 +/- 8.4 ml, P < 0.01) and postprandial (-22.2 +/- 8.4 ml, P < 0.01) states. After adjustment for colonic sensitivity, for compliance, and for distending balloon volume, the rectal volume change remained significant; the extent of the tonic response, however, correlated significantly with increasing pain score (P < 0.01). In contrast, rectal distension did not produce a significant tonic response in the colon (fasting: -6.5 +/- 7.3 ml; postprandial: 2.7 +/- 7.3 ml), either unadjusted or adjusted for rectal sensitivity, compliance, and distending balloon volume. In conclusion, the colorectal reflex, but not the rectocolic reflex, can be readily demonstrated both before and after a meal in response to a 2-min isobaric distension in the colon and rectum, respectively. Although the presence of the colorectal reflex does not depend on colonic sensitivity or the volume of the distending colonic balloon, these factors modulate the reflex, especially in the fasting state.