Disorders of Small Intestinal Motility

Bidirectional Relationship between Gastric Emptying and Plasma Glucose Control in Normoglycemic Individuals and Diabetic Patients

Gastric emptying and glycemic control pathways are closely interrelated processes. Gastric chyme is transferred into the duodenum with velocities depending on its solid or liquid state, as well as on its caloric and nutritional composition. Once nutrients enter the intestine, the secretion of incretins (hormonal products of intestinal cells) is stimulated. Among incretins, glucagon-like peptide-1 (GLP-1) has multiple glycemic-regulatory effects that include delayed gastric emptying, thus triggering a feedback loop lowering postprandial serum glucose levels. Glycemic values also influence gastric emptying; hyperglycemia slows it down, and hypoglycemia accelerates it, both limiting glycemic fluctuations. Disordered gastric emptying in diabetes mellitus is understood today as a complex pathophysiological condition, with both irreversible and reversible components and high intra- and interindividual variability of time span and clinical features. While limited delays may be useful for reducing postprandial hyperglycemias, severely hindered gastric emptying may be associated with higher glycemic variability and worsened long-term glycemic control. Therapeutic approaches for both gastric emptying and glycemic control include dietary modifications of meal structure or content and drugs acting as GLP-1 receptor agonists. In the foreseeable future, we will probably witness a wider range of dietary interventions and more incretin-based medications used for restoring both gastric emptying and glycemic levels to nearly physiological levels.

Chronic intestinal pseudo-obstruction caused by an intestinal inflammatory myopathy: case report and review of the literature

Chronic intestinal pseudo-obstruction (CIP) is an uncommon disorder that may be of primary or secondary origin. We report a case of a 37-year-old woman with CIP due to inflammatory disorder of unknown origin involving the skin (eosinophilic fasciitis), the lungs (decreased diffusion capacity) and the gastrointestinal tract. History, clinical examination, plain abdominal film, barium X-ray and colonoscopy established a diagnosis of recurrent pseudo-obstruction. A full-thickness biopsy was performed during explorative laparotomy, and histological examination revealed findings compatible with an inflammatory myopathy due to a dense lymphoid infiltrate and extensive loss of the muscularis propria layers. Immunosuppressive therapy with cyclosporin was initiated, with significant clinical improvement. This case illustrates another form of CIP, characterized by an inflammatory myopathy, which is histologically distinct from other known visceral myopathies and neuropathies.

Development of a new method for small bowel transit study

BACKGROUND AND PURPOSE

Currently, most studies combine the small bowel transit examination with gastric emptying time examination. There are significant drawbacks to this method. The radiotracer does not enter the small intestine in a bolus and the starting time for transit in the duodenum is difficult to define. This makes the result unreliable. In this study, we used a commercial enteric capsule containing radioactive charcoal to solve these problems.

MATERIALS AND METHODS

Activated charcoal powder was mixed with Tc-99m pertechnetate and loaded to the enteric capsule which can resist gastric acid and dissolve only in the small intestine. In-vitro stability experiment was performed by immersing these capsules in a colorless phosphate buffer of variable pH which mimicked the condition in stomach and small intestine. In addition, ten healthy Chinese volunteers were included for in-vivo experiment. Anterior and posterior views of abdomen were obtained at regular 30-minute intervals until the eighth hour after administration of the radioactive enteric capsule. Small bowel transit time was calculated.

RESULTS

The enteric capsule remained intact for at least 480 minutes in the solution mimicking gastric content (pH = 3.0) and disrupted at a mean duration of 227.2 minutes at a pH of 6.8 and at a mean duration of 212.4 minutes at a pH of 7.4 in the solution mimicking pancreaticobiliary secretions. In nine of ten volunteers, the small bowel transit time was between 30 to 270 minutes with a mean transit time of 140 min. In one volunteer, we failed to detect the exact time of small bowel transit because the capsule remained in the stomach throughout the study for up to 8 hours.

CONCLUSIONS

We consider activated charcoal labeled with Tc-99m pertechnetate using an enteric capsule as the carrier to be a potential radioactive marker for small bowel transit study.

Neuropathophysiology of irritable bowel syndrome

Widespread symptoms associated with the irritable bowel syndrome (IBS) are abnormal defecation and abdominal pain, both of which can be exacerbated by psychogenic stress. Disordered defecation may present as diarrhea or constipation. A subgroup of IBS patients alternate from one to the other over time. Urgency to stool often accompanies the diarrheal-state, and patients with the constipation-predominant form of IBS report straining and the feeling of incomplete evacuation. Basic scientific research aims for improved understanding of the physiology and pathophysiology of the digestive systems from which the arrays of IBS symptoms emerge. The key systems for the defecation-related symptoms are the intestinal secretory glands, the musculature, and the nervous system that controls and integrates their activity. Abdominal pain and discomfort arising from these systems adds the dimension of sensory neurophysiology. This review details current concepts of the underlying pathophysiology in terms of the physiology of intestinal secretion, motility, nervous control, sensing function, immuno-neural communication, and the brain-gut axis.

Recurrence of acute colonic pseudo-obstruction in selective adrenergic dysautonomia associated with infectious toxoplasmosis

BACKGROUND

Acute colonic pseudo-obstruction is a life-threatening condition associated with several pathologic conditions, whose pathophysiology is still uncertain.

CASE

Autonomic function in a young patient operated on for acute colonic pseudo-obstruction was carefully evaluated; none of the common clinical conditions described in the literature was found to have caused the syndrome. Selective adrenergic failure was suggested by the presence of severe orthostatic hypotension, low basal plasma catecholamine level, and absence of the expected increase on standing and by the findings of provocation tests, cardiovascular tests, and acetylcholine sweat spot test. Biopsy specimens from the colon and small-bowel wall did not show any morphologic or immunohistochemical alteration either in muscle layers or in the autonomic plexus, testifying to the possible occurrence of extrinsic denervation in the presence of an intact plexus. Infectious toxoplasmosis was proved through indirect and direct hemagglutination assays, enzyme-linked immunosorbent assay IgG, IgM, and IgA, immunosorbent agglutination IgM assay, and the protozoa were demonstrated in a biopsy specimen from the rectus abdominis muscle.

CONCLUSIONS

Selective adrenergic denervation of the gut resulted in recurrent episodes of colonic pseudo-obstruction, probably by direct toxicity or a cross-reaction between the immune process and a toxoplasmic antigen, stressing the importance of sympathetic inhibitory modulation on colon motor activity.

Ambulatory 24-hour jejunal motility in diarrhea-predominant irritable bowel syndrome

BACKGROUND

Whether small-bowel motility is abnormal in the irritable bowel syndrome (IBS) is a controversy at present. The aim of our study was to compare ambulatory long-term jejunal motility in 35 IBS patients with predominant diarrhea to normal values obtained in 50 healthy controls.

METHODS

Twenty-four-hour motility was recorded in the proximal jejunum with a portable datalogger and tube-mounted miniature pressure sensors. Fasting motility in the waking (W) and sleeping (S) state and the motor response to a standardized evening meal of 600 kcal underwent visual and computer-aided analysis.

RESULTS

Fasting motility in patients showed migrating motor complex (MMC) cycles of normal length and composition. Uninterrupted runs of discrete clustered contractions during phase II (W) occurred in 57% of patients and 52% of controls but had a significantly longer duration in patients (33 +/- 5 versus 19 +/- 7 min; p < 0.005). During phase II (W) IBS patients had an increase in aborally propagated contractions (41 +/- 2% versus 35 +/- 2%; p < 0.01) and higher contraction amplitudes (26.3 +/- 0.8 versus 23.0 +/- 0.5 mm Hg; p < 0.01). Similar differences were obtained during postprandial motility (47 +/- 3% versus 39 +/- 3%; p < 0.01, and 25.9 +/- 0.9 versus 23.8 +/- 0.05 mm Hg; p < 0.02). In three patients (8.6%) disturbed aboral migration of phase III and irregular burst activity, manometric features of chronic idiopathic intestinal pseudo-obstruction, were identified. Whereas 57% of patients had an entirely normal 24-h manometry, 43% had at least one finding not present in any healthy control.

CONCLUSION

Small-intestinal motility is frequently but not universally abnormal in diarrhea-predominant IBS. The abnormal manometric findings are heterogeneous and range from subtle quantitative changes to severe qualitative abnormalities resembling chronic idiopathic intestinal pseudo-obstruction in a small subset of patients.

Whole-gut transit scintigraphy in the evaluation of small-bowel and colon transit disorders

Scintigraphic methods for performing gastric emptying and colon transit studies are now well standardized. Although not as well established, several methods have been proposed for measuring small-bowel transit. The measurement of orocecal transit time appears to be a practical scintigraphic measurement of small-bowel transit. When combined into a single test of gastric emptying, small-bowel, and colon transit, whole-gut transit scintigraphy is an important, noninvasive tool for documenting dysmotility of any segment of the gastrointestinal tract. Despite attempts to simplify the study, whole-gut transit scintigraphy still requires a significant commitment of time and equipment. As with other gastrointestinal studies, each laboratory must determine which protocol best fits its clinical needs, equipment, and staffing. Attention must be paid to adhere to established protocols, or normal values will need to be determined for each laboratory. Despite these difficulties, whole-gut transit scintigraphy now represents an important clinical tool for the evaluation of patients with a wide range of abdominal complaints.

Effect of octreotide and erythromycin on idiopathic and scleroderma-associated intestinal pseudoobstruction

Treatment of chronic intestinal pseudoobstruction with prokinetic agents has been disappointing. Our study was designed to determine if octreotide and erythromycin would provide sustained relief from nausea, abdominal pain, and bloating in pseudoobstruction. Using gastrointestinal manometry, quantitative parameters of the activity front of the migrating motor complex at baseline and after prokinetic therapy with erythromycin and octreotide were determined in 14 patients with intestinal pseudoobstruction who had nausea, abdominal pain, and bloating. Patients were treated with erythromycin and octreotide for 20-33 weeks. Octreotide increased the frequency, duration, and motility index of activity fronts (AFs) from 1.2 +/- 0.3 AFs/4 hr, 2.7 +/- 0.7 min, and 85 +/- 23 min mm Hg to 4.1 +/- 0.8 AFs/4 hr, 5.5 +/- 0.7 min, and 152 +/- 24 min mm Hg, respectively (P < 0.05). Antral activity was decreased from 63 +/- 14 to 23 +/- 8% by octreotide (P < 0.05). Erythromycin induced antral activity; however, small intestinal motor activity was suppressed. While on erythromycin and octreotide, five patients had long-term improvement of nausea and abdominal pain. All responders had at least 5 AFs/4 hr induced by octreotide. We conclude that octreotide and erythromycin relieve abdominal pain and nausea in pseudoobstruction. Patients who have at least 5 AFs/4 hr after octreotide administration are most likely to clinically respond.

Chronic diarrhea in diabetes mellitus: mechanisms and an approach to diagnosis and treatment

In this study, our aim was to develop a practical strategy to facilitate the management of patients with diabetes mellitus and chronic diarrhea in a tertiary referral practice. We reviewed the pertinent English-language literature of the past 30 years that described the pathophysiologic mechanisms and treatment of patients with diabetic diarrhea and retrospectively reviewed the medical records of all patients with diabetic diarrhea examined at the Mayo Clinic during 1990. Three typical case studies are described to illustrate the diverse mechanisms that lead to chronic diarrhea in patients with diabetes. No report in the literature has systematically evaluated all the putative mechanisms of chronic diarrhea in any group of patients with diabetes. In our tertiary referral practice, diabetic diarrhea was frequently due to celiac sprue, bacterial overgrowth in the small bowel, or fecal incontinence in conjunction with anorectal dysfunction; however, in almost 50% of the patients, these causes were excluded, and abnormal intestinal motility or secretion was postulated to be one of the likely causes of the diarrhea. These data suggest a practical algorithm based on three sequential assessments: first, tests of blood and stool specimens and flexible sigmoidoscopy to detect evidence of malabsorption or disease in the distal colon; second, small bowel aspirate and biopsy if the results of initial blood or stool tests are abnormal or anorectal function tests if those test results are normal; and, finally, measurement of gastrointestinal transit or therapeutic trials with opioids, clonidine hydrochloride, and, rarely, cholestyramine resin or octreotide acetate (or both methods). The mechanisms whereby abnormal neural function due to diabetes results in altered digestive, secretory, absorptive, or motor function necessitate further elucidation. The management of chronic diarrhea in patients in a tertiary referral practice, however, can be based on a practical algorithm to determine the cause and to adopt specific treatment to correct it.

Small intestinal motility and transit in disease

Disorders of small intestinal motility and transit are becoming increasingly recognized partly as a result of a greater awareness of their existence and partly because suitable diagnostic methods are more widely available. Usually, the neuropathic and myopathic forms can be separated, and gut disease secondary to a generalized neuromuscular disorder can be identified by the clinician. The availability of better non-invasive methods for the diagnosis of disorders of motility and transit would greatly facilitate their management. Treatment must include the restoration and maintenance of nutrition, attempts to improve intestinal motor function and resection of any segments of localized disease. Regrettably, all such measures are ineffective in the severest cases. In the future, a greater understanding of the enteric neural control of the smooth muscle and an ability to manipulate it with novel, specific drugs or peptidergic receptor agonists and antagonists, or electrical pacing, may lead to more effective therapies.

Towards a less costly but accurate test of gastric emptying and small bowel transit

Our aim is to develop a less costly but accurate test of stomach emptying and small bowel transit by utilizing selected scintigraphic observations 1-6 hr after ingestion of a radiolabeled solid meal. These selected data were compared with more detailed analyses that require multiple scans and labor-intensive technical support. A logistic discriminant analysis was used to estimate the sensitivity and specificity of selected summaries of scintigraphic transit measurements. We studied 14 patients with motility disorders (eight neuropathic and six myopathic, confirmed by standard gastrointestinal manometry) and 37 healthy subjects. The patient group had abnormal gastric emptying (GE) and small bowel transit time (SBTT). The proportion of radiolabel retained in the stomach from 2 to 4 hr (GE 2 hr, GE 3 hr, GE 4 hr), as well as the proportion filling the colon at 4 and 6 hr (CF 4 hr, CF 6 hr) were individually able to differentiate health from disease (P less than 0.05 for each). From the logistic discriminant model, an estimated sensitivity of 93% resulted in similar specificities for detailed and selected transit parameters for gastric emptying (range: 62-70%). Similarly, combining selected observations, such as GE 4 hr with CF 6 hr, had a specificity of 76%, which was similar to the specificity of combinations of more detailed analyses. Based on the present studies and future confirmation in a larger number of patients, including those with less severe motility disorders, the 2-, 4-, and 6-hr scans with quantitation of proportions of counts in stomach and colon should provide a useful, relatively inexpensive strategy to identify and monitor motility disorders in clinical and epidemiologic studies.

Gastrointestinal motor dysfunction in acquired selective cholinergic dysautonomia associated with infectious mononucleosis

This report documents the disturbance in gastrointestinal motor function in a patient with selective cholinergic dysautonomia that occurred following acute infectious mononucleosis. Apart from the gut, other organs affected included the pupils, sweat glands, lacrimal and salivary glands, and urinary bladder. Autonomic function tests showed the preservation of sympathetic adrenergic functions in contrast to the generalized involvement of postganglionic parasympathetic and sympathetic cholinergic nerves, including denervation hypersensitivity of the pupil and urinary bladder to exogenous cholinergic agonists. Cardiac and abdominal vagal responses were abnormal. Colon myenteric plexus ganglion cells were normal by morphological and immunohistochemical studies, suggesting that the selective cholinergic dysautonomia was the most likely pathophysiologic process responsible for the observed motility disorder. This study documents the occurrence of selective cholinergic dysautonomia following a viral illness, the importance of the extrinsic neural control on the motor function of the gastrointestinal tract, and the usefulness of combined motility and autonomic function testing in the evaluation of patients with symptoms suggestive of gut dysmotility.

Ileocolonic transfer of solid chyme in small intestinal neuropathies and myopathies

The aims of this study were to assess gastric emptying, small bowel transit and colonic filling in patients with motility disorders, with particular attention to the patterns of colonic filling. Gastrointestinal transit was assessed using a previously validated radiolabeled mixed meal. Fourteen patients with clinical and manometric features of chronic intestinal pseudoobstruction & classified as intestinal neuropathy and 6 as intestinal myopathy, were studied. The results were compared with those from 10 healthy controls studied similarly. Gastric emptying and small bowel transit of solids were significantly slower in both groups of patients than in healthy controls (P less than 0.05). In health, the ileocolonic transit of solid chyme was characterized by intermittent bolus transfers. The mean size of boluses transferred to the colon (expressed as a percentage of ingested radiolabel) was significantly less (P less than 0.05) in patients with intestinal myopathy (10% +/- 4% (SEM)] than in healthy controls (25% +/- 4%) or in patients with intestinal neuropathy (25% +/- 4%). The intervals between bolus transfer of solids (plateaus in the colonic filling curve) were longer (P less than 0.05) in myopathies (212 +/- 89 minutes) than in health (45 +/- 7 minutes) or neuropathies (53 +/- 11 minutes). Thus, gastric emptying and small bowel transit were delayed in small bowel neuropathies and myopathies. Bolus filling of the colon was less frequent and less effective in patients with myopathic intestinal pseudoobstruction, whereas bolus transfer was preserved in patients with neuropathic intestinal pseudoobstruction.