Review article: the impact of bariatric surgery on gastrointestinal motility

BACKGROUND

Obesity is a major medical problem worldwide. Different treatment modalities have emerged to treat obese patients, but the best long-term results are achieved with bariatric surgery. Currently, the interventions most commonly performed are laparoscopic adjustable gastric banding (LAGB), Roux-en-Y- gastric bypass (RYGB) and sleeve gastrectomy.

AIM

To review the gastrointestinal motor complications associated with each of these types of bariatric interventions and the clinical implications of such complications.

METHODS

Search of medical database (PubMed) on English-language articles from January 1996 to March 2011. The search terms used were laparoscopic adjustable gastric banding (LAGB), sleeve gastrectomy (LSG), roux-en-Y-gastric bypass (RYGB), using the AND operator with the terms: complications, motility, GERD, reflux, gastric emptying, esophagitis, dysphagia.

RESULTS

Of the three bariatric interventions reviewed, LAGB was the most studied. Most studies reported short follow-up, of ≤ 1 year. Oesophageal motor dysfunction is the most common motility complication following the bariatric interventions that were reviewed and is mainly observed after LAGB. Some data suggest that oesophageal motor function testing predicts development of post-operative symptoms and oesophageal dilation. RYGB offers protection from gastro-oesophageal reflux. Sleeve gastrectomy was the least studied and was associated with an acceleration of gastric emptying.

CONCLUSIONS

The effects of these interventions on GI motility should be considered when selecting patients for bariatric surgery. There is scant information regarding the overall effect of sleeve gastrectomy on gastro-oesophageal reflux patterns and oesophageal motility.

Efficacy of the glucagon-like peptide-1 agonist exenatide in the treatment of short bowel syndrome

BACKGROUND

Short bowel syndrome (SBS) is a serious clinical disorder characterized by diarrhea and nutritional deprivation. Glucagon-like peptide-1 (GLP-1) is a key hormone, produced by L-cells in the ileum, that regulates proximal gut transit. When extensive ileal resection occurs, as in SBS, GLP-1 levels may be deficient. In this study, we test whether the use of GLP-1 agonist exenatide can improve the nutritional state and intestinal symptoms of patients with SBS.

METHODS

Five consecutive patients with SBS based on ≤90 cm of small bowel and clinical evidence of nutritional deprivation were selected. Baseline SBS symptoms, demographic and laboratory data were obtained. Antroduodenal manometry was performed on each subject. Each patient was then started on exenatide and over the following month, the baseline parameters were repeated.

KEY RESULTS

The subjects consisted of four males and one female, aged 46-69 years. At baseline, all had severe diarrhea that ranged from 6 to 15 bowel movements per day, often occurring within minutes of eating. After exenatide, all five patients had immediate improvement in bowel frequency and form; bowel movements were no longer meal-related. Total parenteral nutrition was stopped successfully in three patients. Antroduodenal manometry revealed continuous low amplitude gastric contractions during fasting which completely normalized with exenatide.

CONCLUSIONS & INFERENCES

Exenatide is a novel and safe treatment option for SBS. It produced substantial improvement in the bowel habits, nutritional status and quality of life of SBS patients. Successful treatment with exenatide may significantly reduce the need for parenteral nutrition and small bowel transplant.

Redefining the role of lymphocytes in gastroesophageal reflux disease and eosinophilic esophagitis

Eosinophilic esophagitis (EoE) and reflux esophagitis (RE) overlap clinically and histologically. RE is characterized by epithelial infiltration with small numbers of neutrophils and eosinophils, EoE by a prominent eosinophilic infiltrate. Lymphocytic esophagitis (LE), a new entity characterized by peripapillary lymphocytosis, questions the role lymphocytes play in esophageal inflammation. We test the hypothesis that lymphocyte infiltration in RE differs from EoE. One blinded pathologist read esophageal biopsies from 39 RE and 39 EoE patients. Both groups demonstrated significant numbers of lymphocytes (RE 22.7 +/- 2.2/HPF, EoE 19.8 +/- 1.8/HPF). Eosinophils/HPF in RE and EoE were 2.8 +/- 0.7 and 74.9 +/- 8.2, respectively (P < 0.001). Neutrophils were uncommon in RE (0.26 +/- 0.16/HPF) and EoE (0.09 +/- 0.04; P = 0.07). Eight of the 39 RE specimens had >or=50 lymphocytes in >or=1 HPF. Two were consistent with LE. There was an inverse correlation between numbers of eosinophils and lymphocytes in EoE (R = -0.47; P = 0.002), and no correlation between them in RE (R = 0.18; P = 0.36). The patients with EoE who used antireflux medications had fewer lymphocytes (16.3 +/- 1.3 vs 22.2 +/- 2.3/HPF; P = 0.030) and eosinophils (55.6 +/- 5.2 vs 76.0 +/- 8.7/HPF; P = 0.042) than those who did not. The pathological role of lymphocytes in RE and EoE may be underestimated. Our observation that 5% of the RE specimens meet histopathological criteria for LE potentially blurs the line between these entities. The observation that eosinophil counts are lower in EoE when antireflux meds are used supports the notion that reflux plays a role in the clinical expression of EoE.

Distribution of interstitial cells of Cajal and nitrergic neurons in normal and diabetic human appendix

The objective of this study was to determine the distribution of enteric nerves and interstitial cells of Cajal (ICC) in the normal human appendix and in type 1 diabetes. Appendixes were collected from patients with type 1 diabetes and from non-diabetic controls. Volumes of nerves and ICC were determined using 3-D reconstruction and neuronal nitric oxide synthase (nNOS) expressing neurons were counted. Enteric ganglia were found in the myenteric plexus region and within the longitudinal muscle. ICC were found throughout the muscle layers. In diabetes, c-Kit positive ICC volumes were significantly reduced as were nNOS expressing neurons. In conclusion, we describe the distribution of ICC and enteric nerves in health and in diabetes. The data also suggest that the human appendix, a readily available source of human tissue, may be useful model for the study of motility disorders.

The use of gastric electrical signals for algorithm for automatic eating detection in dogs

Food ingestion increases fundic impedance (FI) and reduces antral slow wave rate (SWR). Our aim was to determine if such changes can be integrated into an algorithm for automatic eating detection (AED). When incorporated in implantable medical devices, AED can time treatment to food intake without need for patient input. Four dogs were implanted with fundic and antral electrodes, connected to an implantable recording device. Changes in FI and SWR induced by fixed meals of different weights were determined, and were used to build an AED algorithm. Its performance was then tested on the same animals given an ad libitum access to food. The effects of gastric balloon distension and nitroglycerin on SWR and FI were also tested. Fixed meals reduced SWR in a weight-dependent manner, R(2) = 0.936, P < 0.05 baseline compared to 50, 100, 200 and 400 g. Meals increased FI above baseline in a weight-dependent manner; R(2) = 0.994, P < 0.05 baseline compared to 200 and 400 g. During ad libitum intake, the AED algorithm detected 86% of all meals > or =15 g. Gastric distension reduced SWR and increased FI. Nitroglycerin reduced SWR. AED, using changes in FI and gastric SWR is feasible. Changes in FI and SWR are induced primarily by the presence of food in the stomach.

Circadian patterns of gastric electrical and mechanical activity in dogs

Gastric motor function assessment, in humans and animals, is typically performed for short recording periods. The aim of this article was to monitor gastric electrical and motor activity in the antrum and fundus simultaneously, for long periods, using a new implantable system. Ten dogs were implanted with fundic and antral electrodes for assessment of impedance and electrical activity. Dogs were studied while in cages, for periods of 22-26 h. From late evening and until feeding on the next day, slow wave (SW) rhythm demonstrated a distinct pattern of intermittent pauses (mean duration = 22.8 +/-4.1 s) that delineated groups of SW's. Phasic increases in fundic tone were seen mostly in association with SW pauses, and were highly correlated with antral contractions, R(2) = 0.652, P < 0.05. The SW rate (events per minute) in the postprandial period, fasting and night time was 4.2 +/- 0.2, 5 +/- 0.2 and 4.7 +/- 0.3, respectively, P < 0.05 postprandial vs other periods. Antral and fundic mechanical activities were highly correlated during fasting, particularly at night. This novel method of prolonged gastric recording provides valuable data on the mechanical and electrical activity of the stomach, not feasible by current methods of recording. During fasting, fundic and antral motor activities are highly correlated and are associated with periodic pauses in electrical activity.

Neural gastrointestinal electrical stimulation enhances colonic motility in a chronic canine model of delayed colonic transit

Neural gastrointestinal electrical stimulation (NGES) induces sequential contractions and enhances emptying in acute canine gastric and colonic models. This study was set to determine (i) the effect of NGES in a chronic canine model of delayed colonic transit and (ii) possible mechanism of action. Four pairs of electrodes were implanted in the distal colon of nine mongrel dogs. Delayed colonic transit was induced by diphenoxylate/atropine and alosetron. Transit was fluoroscopically determined by the rate of evacuation of radiopaque markers, and was tested twice in each dog, in random order, on and off stimulation. Two stimulation sequences, separated by 1 min, were delivered twice a day via exteriorized electrodes. Colonic manometry during stimulation was performed before and after intravenous (i.v.) injection of 1 mg of atropine. Complete evacuation of all markers was significantly shortened by NGES, from 4 days to 2 days, interquartile range 3-4 days vs 2-3 days, respectively, P = 0.016. NGES induced strong sequential contractions that were significantly diminished by atropine: 190.0 +/- 14.0 mmHg vs 48.7 +/- 19.4 mmHg, respectively (P < 0.001). NGES induces strong sequential colonic contractions and significantly accelerates movement of content in a canine model of delayed colonic transit. The effect is atropine sensitive.

Treatment of gastroparesis: a multidisciplinary clinical review

This clinical review on the treatment of patients with gastroparesis is a consensus document developed by the American Motility Society Task Force on Gastroparesis. It is a multidisciplinary effort with input from gastroenterologists and other specialists who are involved in the care of patients with gastroparesis. To provide practical guidelines for treatment, this document covers results of published research studies in the literature and areas developed by consensus agreement where clinical research trials remain lacking in the field of gastroparesis.

Adverse effects of laxatives

Laxatives are among the most commonly used drugs or additives. Most are quite safe when used judiciously, intermittently when possible, and in the absence of contraindications. Bulking agents and nonabsorbable compounds such as lactulose can cause bloating but have very few serious adverse effects except for the allergic reaction to psyllium preparations. Osmotic laxatives containing poorly absorbable ions such as magnesium or phosphate can cause metabolic disturbances, particularly in the presence of renal impairment. However, if taken intermittently, in the absence of conditions such as ileus or bowel obstruction, they have few adverse effects. Polyethylene glycol solutions are emerging as an effective and safe mode of treatment for chronic constipation. Of stimulant laxatives, senna compounds and bisacodyl are the most commonly used. Although there are data to support the neoplastic potential of this class of drugs in in vitro studies, epidemiologic data in humans so far has not established a clear link between these laxatives and colonic neoplasia. The link between stimulant laxatives and structural changes, such as the "cathartic colon" or enteric nerve damage, is not well established either. Danthron compounds should be avoided because of hepatotoxicity.

Loss of interstitial cells of cajal and inhibitory innervation in insulin-dependent diabetes

BACKGROUND & AIMS

Gastrointestinal complications of long-standing diabetes include nausea, vomiting, abdominal pain, diarrhea, and constipation. The pathophysiology underlying these symptoms is poorly understood. Recent evidence suggests an important role for interstitial cells of Cajal in controlling gastrointestinal motility. The aim of this study was to determine changes in interstitial cells of Cajal and enteric innervation in a patient with insulin-dependent diabetes.

METHODS

A full thickness jejunal biopsy was obtained from a 38-year-old insulin-dependent diabetic with evidence for diabetic gastroenteropathy. Immunohistochemistry, confocal microscopy, and 3-dimensional reconstruction techniques were used to quantify changes in the volume of interstitial cells of Cajal and enteric innervation.

RESULTS

Interstitial cells of Cajal were markedly decreased throughout the entire thickness of the jejunum. A decrease in neuronal nitric oxide synthase, vasoactive intestinal peptide, PACAP, and tyrosine hydroxylase immunopositive nerve fibers was observed in circular muscle layer while substance P immunoreactivity was increased.

CONCLUSIONS

The data suggest that long-standing diabetes is associated with a decrease in interstitial cells of Cajal volume and a decrease in inhibitory innervation, associated with an increase in excitatory innervation. The changes in interstitial cells of Cajal volume and enteric nerves may underlie the pathophysiology of gastrointestinal complications associated with diabetes and suggest future therapeutic targets.

A review of diabetic gastropathy

Diabetes mellitus affects various organs, including the gastrointestinal tract. The stomach is commonly affected, and symptoms related to the upper GI tract are frequently reported. Management of diabetic gastropathy involves dietary modifications, pharmacological agents, and occasionally, alternative feeding methods.

Celiac disease is highly prevalent in lymphocytic colitis

A high frequency of celiac disease is reported in patients with collagenous colitis. Limited information is available on the frequency of celiac disease in lymphocytic colitis. The aim of our study was to determine the prevalence of celiac disease in microscopic colitis (collagenous and lymphocytic colitis). Patients were identified from a pathology registry of microscopic colitis from 1987 to 1999. Pathology reports and medical records were reviewed for previous small bowel biopsies and/or celiac serology. We identified 113 patients with microscopic colitis, and 46 patients underwent a small bowel biopsy and/or celiac serology. Of these, 27 patients had lymphocytic colitis (63% female; age, 58.6 +/- 16.2 years) and 19 patients had collagenous colitis (79% female; age, 61.8 +/- 13.6 years). Small bowel biopsy alone was performed in 28 of 46 patients, celiac serology alone was performed in 10, and both small bowel biopsy and celiac serology were performed in 8. Celiac disease was identified in 4 patients by small bowel histology; all had lymphocytic colitis (4 of 27 patients, 15%). This frequency of celiac disease is significantly higher than the highest reported U.S. prevalence of celiac disease (4/1,000 individuals; p < 0.01). There is a high frequency of celiac disease in patients with lymphocytic colitis. Given the importance of the early detection of celiac disease, it should be excluded in all patients with lymphocytic colitis, particularly if diarrhea does not respond to conventional treatment.

Salivary growth factors and cytokines are not deficient in patients with gastroesophageal reflux disease or Barrett's esophagus

Growth factors, such as epidermal growth factor (EGF), are known to protect upper gut mucosa against irritants and to enhance healing of ulcerative lesions in animal models. A number of salivary growth factors are found in human saliva. The aim of this study was to determine if salivary growth factors and cytokines are deficient in patients with esophagitis or with Barrett's metaplasia. Fifteen healthy subjects, eight patients with esophagitis, and 13 patients with Barrett's metaplasia were included. Salivary concentration of EGF, FGF, IL-1, and IL-6 were measured during esophageal saline and hydrochloric acid perfusion and in the postprandial state. There was no statistically significant difference in the concentration of EGF or cytokines among the three study groups in each experimental condition or among the three experimental conditions in each group. FGF basic could not be detected in saliva. In conclusion, these findings do not support the hypothesis that a deficiency in salivary growth factors or cytokines plays a significant role in the development of mild to moderate reflux esophagitis or Barrett's metaplasia.

Small bowel motility: ready for prime time?

The primary function of the small bowel is the absorption of nutrients, and the motor patterns of the healthy bowel are intended to promote that function. The motor patterns of the small bowel are the result of close interaction between the enteric nervous system, extrinsic nerves, regulatory peptides, and the intestinal smooth muscle. The basic electrical rhythm governing intestinal contractions is determined by specialized pacemaker cells called the interstitial cells of Cajal. Diseases affecting any of these components may result in intestinal dysmotility and its associated symptoms. Although transit studies and intestinal manometry are helpful in the diagnosis of dysmotility, our understanding of pathophysiology is hampered by the difficulties involved in obtaining and analyzing intestinal tissue. Treatment of intestinal dysmotility relies on dietary manipulations and nutritional support (enteral or parenteral) because there is no drug therapy that can effectively enhance the propulsive function of the small bowel. Small bowel transplantation remains a life-saving intervention for patients who fail to respond to other therapies.

Diabetic gastropathy: a practical approach to a vexing problem

The clinical presentation of diabetic gastropathy varies, and a diagnosis usually must be confirmed with tests that evaluate the structure and function of the upper gut. Although glucose control, dietary changes, and drug therapy are the current mainstays of treatment, they may not be effective. Gastric pacing, a new technique that stimulates gastric motility, may give physicians another management tool.

Fecal incontinence: a practical approach to evaluation and treatment

Fecal incontinence is a common problem and can have a major impact on the quality of life of those affected. Various disease processes affecting stool consistency, rectal sensitivity, or the anal sphincters can cause fecal incontinence. Obstetric trauma is now known to be a major cause of sphincter dysfunction. The evaluation of the patient with incontinence helps to determine the choice of therapy-medical or surgical. The two most important tests are anorectal manometry, which provides information on sphincter pressures, and rectal sensation, and anal endosonography, which is currently the test of choice for defining the anatomy of the anal sphincters. The choice of therapy depends on the etiology of incontinence, the anatomy of the sphincters, and also on the effect of incontinence on the quality of life of the patient. Control of diarrhea, regardless of the cause, should be attempted first. Biofeedback therapy is effective in the majority of patients and is particularly attractive because it is safe and well tolerated. Surgery is offered when medical therapy is unsuccessful or when the etiology is thought to respond best to surgery, such as in postobstetric trauma. Sphincter repair, for treatment of selective sphincter defects, is the best surgical option. Neoanal sphincters and implanted artificial sphincters are far less attractive because of technical difficulties and low success rate.

Colonic motor function in humans is not affected by gender

Functional abdominal pain, including the irritable bowel syndrome, is more common in females. Our aim was to determine if differences in motility or biomechanical properties of the colon could account for this gender difference. In 18 healthy subjects (nine males), a catheter assembly incorporating a balloon and perfused side holes, connected to a barostat, was positioned in the left colon. The system was used to determine compliance, sensation in response to phasic balloon distension, and changes in motor activity and tone in response to a meal. There was no significant difference in any of these variables between males and females. We conclude that there is no gender difference in colonic motor function or sensation to balloon distension. The increased prevalence of irritable bowel syndrome in females may be related to psychosocial factors rather than differences in colonic motor function.

Intestinal motility in small bowel diverticulosis: a case report and review of the literature

Small bowel diverticulosis is a rare disease that is usually associated with recurrent pseudo-obstruction, bacterial overgrowth, and malabsorption. The more severe complications include hemorrhage and perforation. There is evidence to suggest that this entity is a result of small bowel motor dysfunction. For this reason, it has been associated with disorders in which a myopathic or neuropathic process is involved, such as scleroderma. The majority of patients with jejunal diverticulosis do not require surgery and can be managed medically. We report a case of jejunal diverticulosis in a 63-year-old gentleman who presented with symptoms of pseudo-obstruction. Ambulatory duodenojejunal manometry revealed several abnormalities suggestive of small bowel motor dysfunction. Enteroclysis, however, did not find evidence of mechanical obstruction, and the patient had marked improvement with cisapride and antibiotics.

Saliva and esophageal protection

There has been much interest in recent years in the potential protective role of saliva in the esophagus. Variables such as salivary volume and neutralizing capacity have been studied both during basal conditions and in response to esophageal acid exposure, in healthy subjects and in patients with esophagitis. In addition to its known neutralizing capacity, saliva also contains growth factors. These polypeptides (of which epidermal growth factor has been studied most) have cytoprotective and healing properties in various segments of the gastrointestinal tract. Therefore, a deficiency in one or more of these growth factors might be a contributing factor in the development of gastroesophageal reflux disease (GERD) or its complication, such as Barrett's metaplasia. However, human studies have produced contradictory results regarding salivary growth factor deficiency in such patients. Current methods of investigation make it difficult to assess the importance of saliva in GERD. This may be due in part to the multifactorial nature of the disease and the difficulty in long-term, selective manipulation of salivary function in humans. Given the present data in the literature, it is therefore unknown if saliva plays an important role in esophageal protection.

Constipation: an approach to diagnosis, treatment, referral

When a patient reports constipation, a careful history and physical examination may identify the underlying cause. In many patients, though, no underlying cause is identified. Empiric treatment with exercise, hydration, fiber supplementation, and mild laxatives is often effective. If constipation does not resolve with these measures, then the physician may refer the patient for further testing for slow colonic transit, pelvic floor dysfunction, or anatomical defects, and in difficult and recalcitrant cases for surgical treatment.

Effect of acute hyperglycemia on jejunal compliance and peristaltic reflex in healthy humans

Acute hyperglycemia has been shown to affect gastric motor function and colonic peristaltic reflex, but little is known about its effects on the small bowel. Our aim was to determine the effect of experimentally induced acute hyperglycemia on small bowel compliance and peristaltic reflex. Ten healthy subjects were studied during euglycemia and induced hyperglycemia. Sequential balloon inflation in the jejunum was used to determine pressure-volume relationships. The frequency of jejunal contractions and motility index proximal and distal to a distending balloon were measured for assessment of the peristaltic reflex. The intestinal pressure-volume relationship was not affected by hyperglycemia (In pressure/volume 0.084+/-0.006 vs 0.096+/-0.006, P = 0.19). During hyperglycemia, there was significantly more distal inhibition of frequency of contractions (51.0+/-26.6% vs 26.7+/-22.3%, P < 0.05) and of motility index (18.8+/-10.8% and 10+/-6.4, P < 0.05) in response to balloon inflation. We conclude that in the small bowel of healthy subjects, experimentally induced acute hyperglycemia has no effect on compliance and little effect on enteric nerve function.

Prolonged ambulatory duodeno-jejunal manometry in humans: normal values and gender effect

OBJECTIVE

The aim of this study was to provide a detailed comparison of motor activity in the duodenum and jejunum and between men and women studied by prolonged ambulatory manometry.

METHODS

Thirty healthy volunteers (17 males) underwent prolonged ambulatory recording of duodeno-jejunal motility using a catheter with five built-in strain-gauge transducers (two duodenal and three jejunal). Manometric data was obtained during an extended period of fasting, the postprandial period and during sleep.

RESULTS

There was a wide range of durations of the migrating motor complex (MMC), but at least one phase III was detected during 6 h of fasting, or 6 h of sleep in each subject (0.52+/-0.04 phase III/hour during fasting vs 0.59+/-0.04 during sleep, p=0.1). There was marked variation in the duration and pattern of phase III. Postprandially, frequency of contractions and motility index were maximal in the first 2 h after the meal, in both the duodenum and jejunum. There were no substantive differences between males and females or between the duodenum and jejunum.

CONCLUSION

We conclude that upper small bowel motility is little affected by gender or segment.

Small bowel manometry: short or long recording sessions?

The study of small bowel motility in humans is commonly done by one of two techniques: short-term recording in a stationary patient or long-term recording in an ambulatory patient. To compare the diagnostic yield of short- and long-term manometric studies of small intestinal motility, we reviewed all prolonged records performed in our center over the years. Long-term studies that included less than 6 hr of recording during fasting or less than 5 hr during sleep and short-term studies using the perfused tube technique were excluded, leaving 91/121 tracings suitable for review. We analyzed the first 3 hr of the fasting period and the first 2 hr of the postprandial period on one occasion and the whole tracing on another; the fasting, postprandial and sleep period were analyzed separately. This allowed us to compare short and long recording sessions in the same patient. The two analyses agreed in 81/91 of the cases. In 7/10 patients a study was diagnosed as abnormal in the short recording but was considered normal after review of the long recording, while the opposite occurred in the remaining three. Periods of sleep and fasting contributed similarly to the change in diagnosis. In another 6 patients with equivocal abnormalities during the short period, the long period helped to establish the diagnosis of normality with confidence. Most of the improvement in the long-term study came from extension of the studies during fasting to 6-7 hr from 3 hr. Long-term records of small bowel motility, including study during sleep enhance the diagnostic accuracy of the test. Accuracy can be improved also simply by prolonging the recording during fasting.

Meal-induced secretion of gastrointestinal regulatory peptides is not affected by sleep

The mechanisms responsible for the disruption of the migrating motor complex (MMC) by feeding are not fully understood. Sleep reduces the duration of the postprandial or fed pattern of motility in the intestine. This study was set out to determine if this effect is associated with sleep-induced changes in the secretion of regulatory peptides in response to food.

METHODS

Duodenojejunal motility was studied in 15 healthy ambulant subjects for 2 consecutive days. On one day identical solid meals were consumed in the morning and late in the evening, the latter followed by sleep. On the other day, identical liquid meals were infused into the stomach and the duodenum in the morning and late in the evening, the latter after the onset of sleep. Plasma concentrations of gastrin, neurotensin, peptide YY (PYY), pancreatic polypeptide (PP), motilin and glucose were monitored before and after meals. Sleep significantly shortened the duration of the fed pattern after the solid meal and even more so after the liquid meal. The plasma concentrations of all peptides, except motilin, increased significantly following each meal. Blood glucose levels rose after each meal, the changes being similar with all meals. Food-induced gastrointestinal regulatory peptides secretion and intestinal absorption of glucose are not affected by sleep. The vagal response to a meal, as indicated by PP release, is intact during sleep. The results support the importance of neural mechanisms in the modulation of the postprandial pattern of intestinal motility.

Scintigraphic evaluation of small bowel transit in healthy subjects: inter- and intrasubject variability

OBJECTIVES

This study was performed to evaluate inter- and intrasubject variability of small bowel transit time and the effect of age and sex on transit in the small bowel.

METHODS

Ten young subjects (five females) and nine elderly subjects (four females) were studied. Small bowel transit time was assessed by scintigraphic method using 99mtechnetium-sulfur colloid-labeled eggs. To evaluate intrasubject variability, 10 subjects underwent a second study on a later occasion.

RESULTS

Mean small bowel transit time was 220.9 +/- 49 min with a range of 131 to 322 min, with no significant difference between the young and elderly groups or between sexes. There was a good intraobserver and interobserver reproducibility within the same test (r = 0.92 and r = 0.85, respectively). There was a significant biological variability between the first and the second studies, which was true whether the studies were processed independently (r = 0.43) or whether identical regions of interest were applied (r = 0.50).

CONCLUSION

The normal range of small bowel transit time is wide in normal subjects; and there is a significant intrasubject biological variability for small bowel transit time. These findings should be kept in mind when using scintigraphic techniques for assessment of patients with motility disorders or when using the test repeatedly in the same subject in the evaluation of therapeutic measures. The results do not seem to be affected by age or sex.

Intestinal dysmotility in patients with sphincter of Oddi dysfunction. A reason for failed response to sphincterotomy

Sphincter of Oddi dysfunction (SOD) is associated with abdominal pain and is treated by sphincterotomy. Of 215 patients who underwent biliary sphincterotomy for SOD in our institution, 26 reported no improvement and 25 of those were found to have pancreatic sphincter dysfunction and subsequently underwent pancreatic septotomy. Nine patients remained symptomatic after the second intervention. Six of those nine patients, and seven of the 16 patients who improved after the septotomy, agreed to undergo an ambulatory duodenojejunal (DJ) manometry. DJ manometry was abnormal in four of the six symptomatic patients but only in one of seven patients who became asymptomatic after endoscopic treatment. We conclude that the persistence of symptoms after endoscopic ablation of the biliary and pancreatic sphincters is associated with abnormal intestinal motility, which may explain in part the lack of response to the endoscopic treatment.

Misoprostol is effective treatment for patients with severe chronic constipation

To assess the efficacy of misoprostol in the treatment of patients with severe chronic constipation, nine such patients were enrolled in a double-blind, randomized, crossover study of misoprostol (1200 micrograms/day) or placebo, that lasted three weeks. During this period each patient received the drug for one week and placebo for another with a week washout period in between. A colonic transit study, using radiopaque markers, was performed during each of the treatment weeks, while the number of stools and their total weight was recorded by each patient for the appropriate periods. Colonic transit time was significantly and consistently decreased by misoprostol compared to placebo [66 hr +/- 10.2 vs 109.4 hr +/- 8.1 (P = 0.0005)]. Misoprostol significantly increased the total stool weight per week [976.5 g +/- 288.8 vs 434.6 g +/- 190.5 (P = 0.001)] and also significantly increased the number of stools per week compared to placebo [6.5 +/- 1.3 vs 2.5 +/- 0.11 (P = 0.01)]. The incidence of abdominal pain was similar in both groups. We concluded that misoprostol, during a short trial period, proved effective in increasing the frequency and weight of bowel movements and decreasing colonic transit time in patients with severe chronic constipation. It may be used as a therapeutic measure to treat such patients.

Morphology and pathology of radiation-induced esophagitis. Double-blind study of naproxen vs placebo for prevention of radiation injury

Radiation-induced esophagitis can cause substantial morbidity. Experiments in lab animals have shown that pretreatment with indomethacin protects the esophagus from radiation damage. We conducted a prospective, double-blind, randomized trial of naproxen vs placebo in patients undergoing thoracic radiation therapy for lung cancer. Twenty-eight patients were enrolled, of which 26 completed the study. Sixteen patients were given a short course of radiation (30 Gy/10 fractions/2 weeks), and 10 patients were given a longer course and a larger dose (40-50 Gy/25 fractions/5 weeks). Half of the irradiated patients were treated with naproxen, 375 mg, taken orally twice a day, and half were given an identical placebo. All patients were given ranitidine 300 mg, taken orally once a day. Study drugs were taken throughout the course of radiation. Endoscopy with esophageal biopsies and brushings was performed before and on the last day of treatment. Patients kept a daily diary for symptom scoring. Symptoms such as chest pain, dysphagia, odynophagia, and/or heartburn were reported in 15 patients from both subgroups, resulting in diet restriction to liquids only in eight patients and requiring temporary discontinuation of radiation therapy in one of them. Approximately half the patients in each subgroup developed esophagitis, usually mild and usually limited to the proximal esophagus. Severity of symptoms was not proportional to the severity of esophagitis. Candidiasis was documented in eight patients, but only four had symptoms that were severe in one. We conclude that acute radiation injury to the esophagus is observed in approximately half the patients receiving radiation therapy and can result in substantial morbidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of graded exercise on esophageal motility and gastroesophageal reflux in nontrained subjects

The effects of graded exercise on esophageal motility and gastroesophageal reflux were evaluated in nine nontrained subjects, using a catheter with three strain-gauge transducers connected to a solid-state datalogger and an ambulatory intraesophageal pH monitor. Subjects exercised on a stationary bike at 45%, 60%, 75%, and 90% of peak O2 uptake (VO2 max). Durations of exercise sessions and rest periods varied among subjects. Studies were performed after an overnight fast and subjects received only intravenous infusion of 5% glucose solution during the study. Plasma concentrations of gastrin, motilin, glucagon, pancreatic polypeptide (PP), and vasoactive intestinal peptide (VIP) were determined at rest and before and after each exercise session. The duration, amplitude, and frequency of esophageal contractions declined with increasing exercise intensity, and the differences were significant (P < or = 0.05) for all three variables at 90% VO2 max. The number of gastroesophageal reflux episodes and the duration of esophageal acid exposure were significantly (P < or = 0.05) increased during exercise at 90% VO2 max. Plasma regulatory peptide concentrations showed no significant changes between rest and the various exercise sessions. Thus, exercise has profound effects on esophageal contractions and gastroesophageal reflux, which are intensity dependent. These effects were not mediated by the hormones measured. The results were similar to those observed in highly trained athletes, suggesting that the effects of exercise on esophageal function are similar in trained and nontrained subjects performing at similar percentages of VO2 max, even though the absolute levels of exercise achieved in each group are different.

Effect of misoprostol on postprandial intestinal motility and orocecal transit time in humans

We measured the effect of misoprostol (M), a PGE1 analog, on duodenojejunal postprandial motor activity and orocecal transit in eight healthy volunteers. Intestinal motility was studied by an intraluminal catheter with three strain gauge transducers connected to a solid-state datalogger, and transit time was measured by a hydrogen breath test. Subjects were studied for two consecutive days and fed twice a day with a similar, 600-kcal meal. Misoprostol (M) at 800, 400, or 200 micrograms or placebo were taken orally before every one of the four meals. Transit time was measured after the morning meal on both days, after ingestion of either 800 micrograms of M or placebo. On four occasions, following M, the normal fed pattern was not established and the migrating motor complex (MMC) was not interrupted by the meal. In all other occasions, when the higher doses of M were given, the first 1-2 hr after the meal revealed a hypoactive bowel. This effect was inconsistently seen following 200 micrograms of M. Orocecal transit time was consistently and significantly shorter after M than placebo: 48.3 +/- 9.5 min vs 104.4 +/- 4.8 min, P < 0.0001. Four subjects had diarrhea during the study. We conclude that misoprostol, particularly at higher doses, has a profound effect on intestinal postprandial motility and results in accelerated transit time. The motility changes induced by M may be responsible, in part, for its effect on transit.

Effect of graded exercise on esophageal motility and gastroesophageal reflux in trained athletes

We evaluated the effect of graded exercise on esophageal motility and gastroesophageal reflux. We studied eight trained cyclists using a catheter with three strain-gauge transducers connected to a solid-state datalogger and an ambulatory intraesophageal pH monitor. Each study lasted 4 hr during which subjects exercised on a stationary bike for 1 hr at 60% of peak O2 uptake (O2 max), 45 min at 75% of O2 max, and for 10 min at 90% of O2 max. Subjects rested 1 hr before exercise (control period) and for 30 min between exercise sessions. Studies were performed after an overnight fast and subjects received only intravenous infusion of 5% glucose solution during the study. Plasma concentrations of gastrin, motilin, glucagon, pancreatic polypeptide (PP), and vasoactive intestinal peptide (VIP) were determined at rest and before and after each exercise session. The duration, amplitude, and frequency of esophageal contractions declined with increasing exercise intensity, and the differences were significant (P < or = 0.05) for all three variables at 90% O2 max. The number of gastroesophageal reflux episodes and the duration of esophageal acid exposure were significantly (P < or = 0.05) increased during exercise at 90% O2 max. Plasma hormone concentrations showed no significant changes between rest and the various exercise sessions. Thus, exercise has profound effects on esophageal contractions and gastroesophageal reflux which are intensity dependent. These effects are not mediated by the hormones measured.

Effect of meal composition and sham feeding on duodenojejunal motility in humans

The disruptive effect of meals of different fat content and caloric value and of sham feeding on the interdigestive migrating motor complex (IDMMC) was studied in eight healthy subjects using an ambulatory recording system that allowed continuous monitoring of small bowel motility for three consecutive days. The durations of fed pattern were not significantly different between meals of 800 kcal/50% fat, 400 kcal/50% fat, and 800 kcal/25% fat, but were significantly longer compared to IDMMC cycle length and sham feeding. The latter two were not significantly different. On a separate day, five subjects consumed a meal of 400 kcal/9% fat and a second one of 800 kcal/50% fat. The duration of the fed pattern following the high fat meal was significantly longer than the low fat one. Sham feeding significantly increased plasma concentrations of gastrin and neurotensin (NT), but did not affect those of cholecystokinin (CCK), insulin, and peptide YY (PYY). The various variables of the IDMMC were not different during the two nights of the study, and velocity of migration of phase III during the first day and both nights was similar. We conclude that the duration of the fed pattern depends, in part, on the composition of the meal. Sham feeding, resulting in an increase in both plasma gastrin and NT concentrations, does not disrupt the IDMMC. When using thin probes, IDMMC is stable during prolonged recording.

Effect of exercise on intestinal motility and transit in trained athletes

We measured the effect of exercise, at different intensities, on duodenojejunal motor activity in eight trained, ambulant cyclists, using a catheter with two strain gauge transducers connected to a solid-state data logger. Orocecal transit time was measured by H2 breath test. Subjects were studied for two consecutive days and fed twice a day with a similar, 860-kcal meal. Control recordings on the first day were made at rest and a naloxone infusion was given after the evening meal. On the second day, the athletes exercised after meals for 20 min at 80% of peak O2 uptake (VO2max) and naloxone was infused during the second session. On separate days, five subjects exercised for 3 h at 60% VO2max and for 10 min at 90% VO2max. Plasma concentrations of beta-endorphin were determined before and after exercise. The fed pattern was interrupted by an activity front during 2 of 16 sessions of exercise at 80% VO2max, in the presence of naloxone, and 5 of 8 sessions at 90% VO2max, with and without naloxone. It was not affected by exercise at 60% VO2max. Orocecal transit was not affected by intense exercise. The results show that exercise can affect intestinal postprandial motor activity. The effect is intensity related and may not be mediated by opioids.

Relationship between enteric migrating motor complex and the sleep cycle

To address the question of synchrony between two major biorhythms with a similar periodicity, the cortical rapid eye movement (REM)/non-REM sleep cycle and the enteric migrating motor complex (MMC cycle), we recorded upper small bowel motor activity and sleep activity during nocturnal and diurnal sleep in six healthy subjects. Motility was measured continuously using a fine (2.2 mm OD) and relatively comfortable nasojejunal probe with two pressure-sensitive microtransducers positioned under fluoroscopic control on either side of the ligament of Treitz. Sleep stages were recorded while the subjects slept in a sleep laboratory. Each subject was studied twice; once during normal nocturnal sleep and then after acute reversal of sleep by advancing the time of going to bed by 4 h each night for three nights. The total duration of sleep was similar for diurnal and nocturnal sleep. There was a significantly higher number of REM episodes (P less than 0.001) and REM sleep stage shifts (P less than 0.02) during diurnal (reversed) sleep. During sleep (both diurnal and nocturnal) there was a significant reduction in the MMC cycle length (P less than 0.02, P less than 0.03) and the duration of phase II of the MMC (P less than 0.009, P less than 0.02). The distribution of MMCs among sleep stages and REM sleep was consistent with a random distribution. These data show that periodic activity in the gut is modulated by the presence or absence of sleep, but they also are consistent with the hypothesis that the two cycles are independent and that one is not contingent upon the other.

Spontaneous noncardiac chest pain: value of ambulatory esophageal pH and motility monitoring

We performed esophageal investigations in 20 patients suffering from noncardiac chest pain in order to assess the diagnostic value of short- versus long-term manometric and pH studies. Patients had baseline esophageal manometry with two provocative tests: a Bernstein test and an intravenous injection of edrophonium. On a separate occasion they had a 24-hr ambulatory esophageal pH and motility recording. The Bernstein test provoked chest pain in two patients, while edrophonium injection did not elicit pain in any of the patients. The ambulatory pH study helped to establish the esophagus as the likely source of pain in one patient, and the ambulatory motility one in another. In our experience, ambulatory pH and motility recordings have a low diagnostic yield in the evaluation of patients with noncardiac chest pain.

Prolonged ambulant monitoring of human colonic motility

The study of human colonic motility under physiological conditions has proved to be an elusive goal. We have used a two-stage pernasal technique to position sensors in the human colon for the prolonged monitoring of motility in freely ambulant subjects. Nine healthy volunteers were studied for a total recording time of 263 h, each study lasting between 13 and 48 (mean 29) h. Motor activity in all regions of the large bowel was characterized by scant and irregular contractions with infrequent bursts that did not conform to any pattern. No motor coordination was apparent between different regions of the large bowel. Contractile activity throughout the large bowel was reduced to a minimum during sleep and was enhanced on waking. Meals were an inconsistent stimulus to motor activity. The technique obviates the need for colonic preparation and allows complete freedom of the subjects throughout the study. In demonstrating the practical feasibility of this mode of studying the colon, these preliminary data highlight a requirement for the availability of appropriate equipment but raise questions about the design and use of such equipment and methods of data analysis.

Modulation of the duration of human postprandial motor activity by sleep

We have measured the effect of the presence of food in the gastrointestinal tract on proximal small bowel motility during sleep. Motility was measured in eight healthy ambulant subjects using two strain-gauge microtransducers incorporated in a fine (2.5 mm OD) nasojejunal tube. The subjects ate a 540-cal evening meal (EM) on the first day. On the following day they ate an equicaloric meal (with similar proportion of carbohydrates, proteins, and fats) at lunch time (MM) and then another equicaloric late meal (LM) 15 min before going to bed. All subjects were asleep within 30 min of completing the LM. Postprandial activity was significantly (P less than 0.001) shortened after LM, but there was no difference in the postprandial motor activity after MM and EM. Migrating motor complex (MMC) cycle lengths were similar after MM, EM, and LM. There was no difference in the duration of phase II of the MMC cycle after MM, EM, and LM even though subjects were asleep during the MMC cycles after LM. The MMC propagation velocity after LM and EM was significantly (P less than 0.01, P less than 0.001, respectively) slower than the diurnal MMC propagation velocity after MM. In health, postprandial activity is diminished during sleep, whereas the consumption of a LM restores the phase II activity usually absent during sleep. A LM also abolishes the expected reduction in nocturnal MMC cycle length but maintains the circadian variation in the propagation velocity of the MMC cycle.

Effect of stress on oesophageal motor function in normal subjects and in patients with the irritable bowel syndrome

Stress can modulate the motor function of the stomach, small bowel, and colon in healthy subjects, and of the small bowel and colon in patients with the irritable bowel syndrome (IBS). The effect of stress on oesophageal motility in eight healthy subjects and in eight IBS patients was studied, using two pressure transducers positioned just above the lower oesophageal sphincter and 5 cm proximally. Stressors were: a video arcade game, delayed audio feedback, and hand immersion in cold water. Each stress period was followed by five swallows of water. Frequency and amplitude of oesophageal contractions and the number of simultaneous and multipeaked contractions were manually counted for each stress period and compared to the preceding rest period. Frequency of contractions (per minute) tended to decrease during stress periods, but achieved significance only with the video arcade game in the control group (2.0 (0.6) v 1.2 (0.4); p less than 0.01). No other trend was evident in either control or IBS patients. No abnormalities of oesophageal body function were recorded in IBS patients either in basal conditions, or under stress. Unlike the more complex motor programmes elsewhere in the gut, the preprogrammed nature of oesophageal peristalsis is not modulated by stress.

Effect of pirenzepine on oesophageal, gastric, and enteric motor function in man

The effect of pirenzepine on oesophageal, gastric, and enteric motor function was evaluated in six healthy volunteers. Each subject was studied before and after taking pirenzepine, 100 mg/day, for 3 days. Half and complete gastric emptying times of clear liquid, assessed by epigastric impedance, were significantly delayed by the drug: 6.16 +/- 1.74 min and 13.8 +/- 4.64 min versus 16.65 +/- 3.03 min and 25.1 +/- 8.2 min, respectively (p less than 0.05). Enteric motility was assessed by manometry, and variables studied were the duration of the various phases of the migratory motility complex, the frequency of contractions in phase III, and the amplitude of contractions in phases II, III, and in the postprandial period. Only phase I was affected and was significantly prolonged by the drug: 16.08 +/- 5.94 min versus 31.65 +/- 12.88 min (p less than 0.01). Oesophageal motility was assessed by manometry. Variables studied were amplitude and duration of contractions in the body of the oesophagus, and lower oesophageal sphincter pressure. Results were not significantly changed by the drug. We conclude that pirenzepine, given at a dose used for treatment of peptic ulcer disease, significantly delays the gastric emptying of liquids, has minimal effect on enteric motility, and has no effect on oesophageal motility. The effect on gastric emptying may be therapeutically useful by reducing the acid load on the duodenum in duodenal ulcer disease.

The role of short-term multilumen duodenojejunal manometry in patients with intestinal motor dysfunction

Short-term duodenojejunal manometry, using a multilumen perfused tube, was performed in 12 patients with symptoms of motor dysfunction, 6 patients with irritable bowel syndrome and predominant diarrhea and 6 patients with chronic constipation. Ten healthy individuals served as controls. The durations, in minutes, of the various phases of the migratory motility complex in the three groups were: phase I: 24.4 +/- 22.1, 26.9 +/- 17.3, and 27.2 +/- 18.5; phase II: 86.7 +/- 25.2, 132 +/- 93, and 73.1 +/- 40.8, and those of phase III: 6 +/- 2.5, 6.8 +/- 5, and 6.4 +/- 1.7, respectively. The differences between patients and controls were not statistically significant. Variables of contractions of phase III in the different groups were: frequency (per minute): 10.9 +/- 0.8, 10.7 +/- 0.4, and 11.3 +/- 0.4; Summation of amplitudes per minute: 205.2 +/- 55.7, 288 +/- 57.9, and 337.8 +/- 76.5; Mean amplitude (mm Hg): 19.1 +/- 4.2, 28.6 +/- 5, and 33.5 +/- 7.1, respectively. Results in the patient groups were not significantly different from controls. Short-term duodenojejunal manometry was normal in patients with irritable bowel syndrome and in those with chronic constipation.

Effects of upper dorsal sympathectomy on esophageal motility in humans

To evaluate the role of the sympathetic nervous system in modulating esophageal motility, esophageal manometry was performed on two groups of patients who underwent upper dorsal sympathectomy for relief of palmar hyperhydrosis. In six patients sympathectomy was done by the supraclavicular approach, with removal of T2 and T3 ganglia. Manometry was performed before the operation and three weeks after it. In seven other patients sympathectomy was done by the axillary approach, with removal of T2-T4 ganglia. Manometry in this group was performed 28.4 +/- 22.4 months after the operation. Fifteen individuals with an intact sympathetic system served as controls. Manometric parameters evaluated were esophageal contraction amplitude and duration and lower esophageal sphincter pressure. The difference between the results obtained in the pre- and postoperative periods in the first group was not statistically significant. The differences between the two patient groups and between the patient groups and the control group were not statistically significant either. We conclude that upper dorsal sympathectomy does not affect esophageal motility in man.

Gastric emptying in chronic renal failure patients on hemodialysis

We studied gastric emptying of solid food, using a radionuclide technique, in 18 patients with chronic renal failure patients on hemodialysis: nine with nausea and vomiting or postprandial bloating and nine without. Both groups were compared with a group of normal subjects. Gastric emptying was consistent with a linear elimination in all groups. The regression coefficients of the symptomatic, asymptomatic, and control groups were -0.48 +/- 0.1%, -0.5 +/- 0.14%, and -0.58 +/- 0.15% min, respectively. These were not statistically different. Half-emptying times were 116.4 +/- 7.1 min, 97.8 +/- 13.7 min, and 98.7 +/- 5.6 min, respectively. These also were not statistically different. Values of percentage retention at 2.5 hours for the same groups were 31.6 +/- 5, 24.8 +/- 6.4, and 18.6 +/- 4.4, respectively, again with no statistical difference. Patients with chronic renal failure on hemodialysis, symptomatic or asymptomatic, have no obvious impairment of gastric emptying of solids.

Carcinoma of the large bowel after a single massive dose of radiation in healthy teenagers

Three healthy teenagers were exposed to a single pelvic x-ray irradiation as part of sterilization experiments performed in the Auschwitz concentration camp in 1943. Single and multiple carcinomas of the colon and rectum developed 40 years later in the radiation field. Histologic examination of surgical specimens revealed severe radiation-induced changes in all layers of tumor-adjacent areas. In contrast to previous reports of radiation-induced large bowel cancers, these women had not undergone repeated courses of radiation, had no known co-existing disease that might raise the risk for colonic and rectal malignancies, and had an extremely long and remarkably similar latency period. These cases emphasize the need for long-term surveillance in previously radiated patients. Since thousands of teenagers were subjected to similar sterilization experiments, awareness of this association might help in the early diagnosis of additional cases.

Prognostic factors in colorectal carcinomas arising in adenomas: implications for lesions removed by endoscopic polypectomy

Endoscopic polypectomy has become the preferred technique for the removal of most colorectal adenomas. Whether polypectomy alone or segmental colectomy is the appropriate management of the patient whose adenoma contains carcinoma is a controversial issue. We studied 129 colorectal carcinomas that arose in adenomas and in which invasion was no deeper than the submucosa of the underlying colonic wall. The following factors were evaluated: location; gross appearance (sessile versus pedunculated); histologic type of adenoma (tubular, villous, mixed); grade of carcinoma; level of invasion (0--carcinoma confined to the mucosa, 1--head, 2--neck, 3--stalk, 4--submucosa of underlying colonic wall); vascular invasion; and adequacy of excisional margins. Patients were divided into two groups with respect to outcome: adverse (dead from colorectal carcinoma, alive with colorectal carcinoma or positive nodes on colectomy), and favorable (absence of above). Sixty-three patients were treated by polypectomy alone and 66 by colectomy (21 preceded by polypectomy); there were no operative deaths. Mean follow-up was 81 mo. None of 65 patients with carcinoma confined to the mucosa had an adverse outcome, but 8 of 64 patients with invasive carcinoma did. Level 4 invasion (p less than 0.001) and rectal location (p = 0.025) were the only statistically significant adverse prognostic factors. Seven of 28 level 4 lesions and six of 42 rectal lesions had an adverse outcome; level 4 lesions were overrepresented in the rectum (14 of 42; p = 0.032). We conclude that the level of invasion should be the major factor in determining prognosis for the management of carcinoma arising in an adenoma.

Elevated ANA titers in patients with severely abnormal gastrointestinal motility

We studied a group of six patients with clinical, radiological, and/or manometric features of severely abnormal gastrointestinal motility. Symptoms suggestive of esophageal, small bowel, or colonic involvement were present from 1 1/2 to 40 years. All patients had elevated antinuclear antibody (ANA) titers. None had clinical or radiographic features suggestive of progressive systemic sclerosis or other connective tissue diseases. Two patients had pathologic examinations of intestinal specimens, and these did not show changes suggestive of progressive systemic sclerosis. We conclude that patients with severe gastrointestinal motility disorders can have elevated ANA titers without features of progressive systemic sclerosis or other connective tissue diseases.