An in vitro electrophysiological study of the colon from patients with idiopathic chronic constipation

Heart rate variability in the irritable bowel syndrome: a review of the literature

BACKGROUND

Patients with irritable bowel syndrome (IBS) often present with disturbances of bowel habits (diarrhea, constipation) and abdominal pain/discomfort that are modulated by the autonomic nerve system (ANS). In this narrative review, we analyzed studies that measured ANS functioning in IBS by means of heart rate variability (HRV).

METHODS

The PUBMED was searched with the keywords 'irritable bowel syndrome' AND ('heart rate variability' OR 'autonomic function'). We included only papers that used 'traditional' HRV indices and diagnosed IBS based on Manning or Rome criteria. Studies were sub-grouped according to methodological features of HRV analysis (24-h monitoring, short-term laboratory records, records during sleep).

KEY RESULTS

Most studies reported no difference in HRV when the IBS population was compared to healthy controls. Dividing the IBS sample into subgroups--according to their predominant bowel symptoms, the severity of clinical course, the presence of depressive symptoms, or a history of abuse in the past--revealed changes in autonomic functioning.

CONCLUSIONS & INFERENCES

Patients with IBS appear to experience symptoms that may be the result of changes in ANS functioning. HRV measures in clinical routine may allow assessing these changes, but further studies performed in a standardized fashion should improve the validity of HRV measures for clinical research first.

Gastrointestinal neuromuscular pathology in chronic constipation

Some patients with chronic constipation may undergo colectomy yielding tissue appropriate to diagnosis of underlying neuromuscular pathology. The analysis of such tissue has, over the past 40 years, fueled research that has explored the presence of neuropathy, myopathy and more recently changes in interstitial cells of Cajal (ICC). In this chapter, the data from these studies have been critically reviewed in the context of the significant methodological and interpretative issues that beset the field of gastrointestinal neuromuscular pathology. On this basis, reductions in ICC appear to a consistent finding but one whose role as a primary cause of slow-transit constipation requires further evaluation. Findings indicative of significant neuropathy or myopathy are variable and in many studies subject to considerable methodological bias. Methods with practical diagnostic utility in the individual patient have rarely been employed and require further validation in respect of normative data.

Idiopathic chronic constipation: tachykinins as cotransmitters in colonic contraction

BACKGROUND

Tachykinins (TKs) have been shown to be involved in the excitatory enteric motor pathway. This study aimed to examine the direct and nerve-mediated effect of specific NK1, NK2 and NK3 receptor agonists and antagonists in colonic preparations from control subjects and patients with idiopathic chronic constipation (ICC).

MATERIALS AND METHODS

Cumulative concentrations of Sar9Met(O2)11 substance P (selective NK1 receptor agonist), [Ala5,beta-Ala8]-neurokinin A (4-10) (selective NK2 receptor agonist) and [MePhe7]-neurokinin B (selective NK3 receptor agonist) were tested on colonic circular muscle strips to evaluate the direct drug effects. In addition, in the presence of atropine, the role of TKs in the off-contraction that follows the typical inhibitory response evoked by low frequencies of electrical field stimulation (0.5--10 Hz, 20 V, 1 ms pulse trains lasting 1 min) was investigated.

RESULTS

In control preparations, the rank order of potency was: NK2 receptor-selective agonist > NK3 receptor-selective agonist > NK1 receptor-selective agonist. The off-contraction was found to be reduced by about 30--40% in colonic circular muscle from ICC patients with respect to controls. Incubation with the NK1 receptor agonist did not modify the off-contraction measurements in either control or ICC preparations. Conversely, both NK2 and NK3 receptor agonists significantly (P < 0.01) increased the off-contraction in ICC preparations only. This increased response was fully antagonized by MEN-10627, a NK2 and NK3 receptor antagonist depending on the dose.

CONCLUSIONS

We may conclude that ICC is hyporesponsive to TKs and that the contractile reflex to distension is greatly reduced in ICC disease, but can be restored by incubation with NK2 and NK3 receptor agonists.

Smooth muscle inclusion bodies in slow transit constipation

Slow transit constipation (STC) is a disorder of intestinal motility of unknown aetiology. Myopathies, including those characterized by the finding of inclusion bodies, have been described in enteric disorders. Amphophilic inclusion bodies have been reported in the muscularis externa of the colon of STC patients. This study formally tested the hypothesis that these represent a primary muscle disorder, specific to STC. In a systematic, blinded, dual observer qualitative and quantitative analysis, colonic and ileal tissue from patients with STC (n=36) were compared with selected control populations: total colonic aganglionosis (n=10), Chagas' disease (n=6), isolated rectal evacuation disorders (n=6), and a control population of a range of ages (n=80). All sections were stained with haematoxylin and eosin and periodic acid Schiff. Further immunostains were used in an attempt to determine inclusion body composition. Round or ovoid (4-22 microm diameter) amphophilic inclusions increased in number in normal subjects with age. Inclusions were more frequent in idiopathic STC than in age-matched controls or rectal evacuation disorders [ileum (33% vs. 9%), ascending (50% vs. 19%, p<0.05), and sigmoid colon (43% vs. 20%)] and were very frequent in the sigmoid (71%) of patients with STC arising after pelvic surgery. The number of inclusions per unit area was significantly higher in patients with STC (p<0.001). Inclusions were found in all Chagas' patients, but not with aganglionosis. It was not possible to determine inclusion body composition, despite the use of a wide range of conventional and immunostains. This study demonstrates that inclusion body myopathy is identifiable in patients with STC and that it may arise secondary to denervation.

Effect of colectomy on gastric emptying in idiopathic slow-transit constipation

INTRODUCTION

Gastric emptying is delayed in patients with idiopathic slow-transit constipation (ISTC). Gastric emptying was measured before and after colectomy and ileorectal anastomosis in patients with ISTC to determine whether the abnormality persists after operation.

METHODS

Twelve patients undergoing colectomy for severe ISTC had solid-phase gastric emptying measured after an overnight fast. All 12 had an uncomplicated subtotal colectomy and ileorectal anastomosis; 11 had an excellent functional outcome. In ten of these patients gastric emptying was repeated within 3 months of operation. Seven patients (including the remaining two) had the study performed at 1 year.

RESULTS

All 12 patients had severely delayed gastric emptying before operation. Gastric emptying remained delayed in the ten patients who underwent an early postoperative gastric emptying study. Six of seven patients assessed at 1 year had improved gastric emptying, of whom four had returned to normal. Functional outcome did not relate to gastric emptying.

CONCLUSION

Patients with ISTC have delayed gastric emptying. In some patients this returns to normal after colectomy, but is persistent in others. This may have implications for our understanding of ISTC.

Slow transit constipation: a model of human gut dysmotility. Review of possible aetiologies

Slow transit constipation is a severe condition of gut dysmotility that predominantly affects young women and may result in surgical intervention. Current medical treatments for STC are often ineffective, and the outcome of surgery is unpredictable. STC was first described almost a century ago. Since this time, progress in improving therapy for this condition has been complicated by a lack of understanding of the aetiology, and great variation in the methods and criteria used for the study of patients with this debilitating disorder. It is difficult to find unequivocal data, and harder still to give a definitive picture of the cause or causes of STC. Here we consider the evidence for various aetiologies of STC, in the light of the physiological and pathological findings.

Cholinergic stimulation and nonadrenergic, noncholinergic relaxation of human colonic circular muscle in idiopathic chronic constipation

The aim of our study was to further investigate the pathophysiological mechanism underlying idiopathic chronic constipation (ICC), a disorder of colonic motility. A possible alteration of excitatory and inhibitory neurotransmission and also the role of inhibitory neurotransmitters such as nitric oxide (NO), 5'-adenosine triphosphate (ATP), and vasoactive intestinal peptide (VIP) has been evaluated on preparations of distal colon from patients with or without ICC. The isometric tension was recorded from isolated circular muscle strips of both experimental groups during pharmacological and electrical field stimulation (EFS). The contractile response obtained by acetylcholine (ACh 20 microM), EFS (20 Hz, 20 V, 1 msec, pulse trains lasting 1 min) and substance P (SP 1 microM) was significantly lower in ICC than in control preparations. The effect of inhibitory nonadrenergic, noncholinergic innervation was evaluated using EFS at low frequencies (0.5-8 Hz), after cholinergic and sympathetic blockade with atropine (3 microM) and guanethidine (3 microM). The maximum relaxation value expressed as percentage of inhibition of SP-induced contraction was significantly higher in ICC than in control preparations (87+/-2.4 and 67+/-6.3, respectively; P<0.05). Experiments with substances that antagonize or reduce the effect of putative inhibitory mediators (VIP 6-28, apamin and N(G)-nitro-L-arginine) suggest that an alteration in NO and ATP release is present in ICC preparations. In particular at a higher inhibitory frequency NO-mediated relaxation is enhanced in ICC vs control, supporting the hypothesis that excessive NO production may be involved in pathophysiological mechanism of constipation.

Anorectal and pelvic floor function. Relevance of continence, incontinence, and constipation

Anorectal tests need to be tailored to the presentation of the individual patient. Clearly the tests are most useful when they identify anatomic or physiologic abnormalities for which there are successful treatments. For the incontinent patient, anal manometry is the most useful test. Sphincter injuries should be repaired, whereas neurogenic incontinence is best treated initially with biofeedback. Three tests are more useful for the constipated patient: colonic transit time, degree of pelvic floor descent on straining, and balloon expulsion. Colonic inertia responds to total colectomy and pelvic floor dysfunction to biofeedback. Meanwhile, patients with irritable bowel syndrome require rereferral back to their physicians.