Testing the competition-colonization trade-off with a 32-year study of a saxicolous lichen community.

Competition-colonization trade-offs are theorized to be a mechanism of coexistence in communities structured by environmental fluctuations. But many studies that have tested for the trade-off have failed to detect it, likely because a spatiotemporally structured environment and many species assemblages are needed to adequately test for a competition-colonization trade-off. Here, we present a unique 32-year study of rock-dwelling lichens in New Mexico, USA, in which photographs were used to quantify lichen life history traits and interactions through time. These data allowed us to determine whether there were any trade-offs between traits associated with colonization and competition, as well as the relationship between diversity and disturbance in the community. We did not find evidence for a trade-off between competitive ability and colonization rate or any related life history traits. Interestingly, we did find a peak in all measures of species diversity at intermediate levels of disturbance, consistent with the intermediate disturbance hypothesis pattern. We suggest that the coexistence of the dominant species in this system is regulated by differences in persistence and growth rate mediating overgrowth competition rather than a competition-colonization trade-off.

American Neurogastroenterology and Motility Society consensus statement on intraluminal measurement of gastrointestinal and colonic motility in clinical practice.

Tests of gastric, small intestinal and colonic motor function provide relevant physiological information and are useful for diagnosing and guiding the management of dysmotilities. Intraluminal pressure measurements may include concurrent measurements of transit or intraluminal pH. A consensus statement was developed and based on reports in the literature, experience of the authors, and discussions conducted under the auspices of the American Neurogastroenterology and Motility Society in 2008. The article reviews the indications, methods, performance characteristics, and clinical utility of intraluminal measurements of pressure activity and tone in the stomach, small bowel and colon in humans. Gastric and small bowel motor function can be measured by intraluminal manometry, which may identify patterns suggestive of myopathy, neuropathy, or obstruction. Manometry may be most helpful when it is normal. Combined wireless pressure and pH capsules provide information on the amplitude of contractions as they traverse the stomach and small intestine. In the colon, manometry assesses colonic phasic pressure activity while a barostat assesses tone, compliance, and phasic pressure activity. The utility of colonic pressure measurements by a single sensor in wireless pressure/pH capsules is not established. In children with intractable constipation, colonic phasic pressure measurements can identify patterns suggestive of neuropathy and predict success of antegrade enemas via cecostomy. In adults, these assessments may be used to document severe motor dysfunction (colonic inertia) prior to colectomy. Thus, intraluminal pressure measurements may contribute to the management of patients with disorders of gastrointestinal and colonic motility.

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.

Paraneoplastic gastrointestinal motor dysfunction: clinical and laboratory characteristics.

OBJECTIVES: The aim of this study was to describe the clinical, manometric, and serological characteristics of 12 patients with paraneoplastic GI motor dysfunction and to assess the contributory role of diagnostic tests. METHODS: Twelve patients diagnosed with malignant tumors and GI motor dysfunction were identified at the Mayo Clinic from 1985 to 1996. RESULTS: Cancers identified were: nine small cell lung carcinoma (SCLC), one anaplastic lung adenocarcinoma, one retroperitoneal lymphoma, and one ovarian papillary serous adenocarcinoma. GI symptoms preceded the tumor diagnosis in all cases of SCLC (mean, -8.7 months, range, -1 to -24 months, n = 9). The diagnosis of a malignant tumor preceded the onset of GI symptoms in the three patients with other neoplasms (6, 12, and 24 months). Five of the nine patients found to have SCLC had no evidence of tumor on initial chest x-ray. One or more paraneoplastic autoantibodies were found in 10 of the 11 patients tested by autoimmune serology. Type 1 antineuronal nuclear antibody (ANNA-1 or anti-Hu) was detected in eight of the nine patients with SCLC (one patient was not tested). The patient with ovarian carcinoma had type 1 Purkinje cell cytoplasmic antibody (PCA-1 or anti-Yo). N-type calcium channel antibodies were found in one patient with SCLC, one with a retroperitoneal B cell lymphoma, and one with ovarian carcinoma. Gastric emptying was delayed in 89% (eight of nine tested) and 80% (four of five tested) had esophageal dysmotility. Autonomic reflex tests were abnormal in the seven patients tested. CONCLUSIONS: The diagnosis of paraneoplastic GI motor dysfunction requires a high index of clinical suspicion. A panel of serological tests for paraneoplastic autoantibodies, scintigraphic gastric emptying, and esophageal manometry are useful as first-line screening tests. Seropositivity for ANNA-1, PCA-1, or N-type calcium channel-binding antibodies should prompt further evaluation for an underlying malignancy even when routine imaging studies are negative.

Tegaserod accelerates orocecal transit in patients with constipation-predominant irritable bowel syndrome.

BACKGROUND & AIMS: This study evaluated the effects of a partial 5-hydroxytryptamine (5-HT)(4) agonist, tegaserod, on gastric small bowel and colonic transit in constipation-predominant irritable bowel syndrome (IBS). METHODS: After a 1 week run-in period, 24 patients with constipation-predominant IBS were randomized to 1 week of tegaserod, 2 mg twice daily, or placebo treatment. Scintigraphic gastric emptying, small bowel transit, and colonic transit were determined before administration of study drug and after 1 week on the medication. Colonic transit was also measured using radiopaque markers and a single radiograph on day 5. RESULTS: Gastric emptying was unaltered by tegaserod. Proximal colonic filling at 6 hours, a measure of orocecal transit, was accelerated by tegaserod (70.4% +/- 1.3% [mean +/- SEM] vs. placebo, 46.4 +/- 1.9; P = 0.015). Proximal colonic emptying half-time and geometric center at 48 hours were also accelerated by tegaserod compared with baseline, but not compared with placebo. Mean colonic transit time was similar in both groups at baseline and after drug administration (tegaserod, 59.5 +/- 2.1 hours; placebo, 62.1 +/- 2.1 hours). CONCLUSIONS: Tegaserod accelerates orocecal transit, tends to accelerate colonic transit, and deserves further study in patients with constipation-predominant IBS.

Intestinal angioedema mimicking Crohn's disease.

Angioedema usually presents as episodic attacks of swelling of the face, airway and extremities, but it may also involve visceral tissues. A 58-year-old woman with repeated episodes of abdominal pain, nausea and vomiting had two laparotomies and was treated for Crohn's disease for two years before a diagnosis of acquired intestinal angioedema was made. This case provides important insights into the presentation of intestinal angioedema.

Near-total completion gastrectomy for severe postvagotomy gastric stasis: analysis of early and long-term results in 62 patients.

The aim of this study was to evaluate results of completion gastrectomy for severe postgastrectomy gastric stasis. A total of 51 women and 11 men underwent completion gastrectomy for gastric stasis between 1985 and 1996; follow-up was complete in 98% at 5.4 +/- 5 years. All patients had modified Visick scores preoperatively of grade III (37%) or IV (63%). Presentation included combinations of nausea, vomiting, postprandial pain, chronic abdominal pain, and chronic narcotic use. All had undergone prior vagotomy and had a median of four previous gastric operations. Hospital mortality was zero. Complications occurred in 25 patients (40%) and included the following: narcotic withdrawal syndrome (18%), ileus (10%), wound infection (5%), intestinal obstruction (2%), and anastomotic leak (5%). All or most symptoms were relieved in 43% (Visick grade I or II), but 57% of the patients remained in Visick grade III or IV. Nausea, vomiting, and postprandial pain were reduced from 93% to 50%, 79% to 30%, and 58% to 30%, respectively (P<0.05), but chronic pain, diarrhea, and dumping syndrome were not significantly affected. Univariate analysis revealed no preoperative characteristic to be predictive of good outcome. Logistic regression analysis suggested that the combination of nausea, need for total parenteral nutrition, and retained food in the stomach predicted a poor outcome (P<0.05). Completion gastrectomy is successful in 43% of patients. The combination of nausea, need for total parenteral nutrition, and retained food at endoscopy are negative prognostic factors.

Videoendoscopic diagnosis of esophageal motility disorders.

BACKGROUND: Esophageal motility disorders are usually diagnosed by manometry. We evaluated videoendoscopy as a diagnostic test. METHODS: In this study, 20 patients with achalasia, 13 with scleroderma, and 33 control subjects had a standard endoscopic examination followed by protocol videotaping of swallows to observe contractions in the esophagus and in the lower esophageal sphincter. Tapes were later reviewed by 2 blinded observers who recorded their motility findings and diagnoses. RESULTS: In the mid esophagus at 25 cm, lumen-occluding peristaltic contractions were identified in 26 of 33 control subjects versus 1 of 20 achalasia (p < 0.001) and 3 of 13 scleroderma patients (p < 0.005). As viewed in the lower esophagus, the lower esophageal sphincter opened normally in 31 of 33 control subjects versus 1 of 20 achalasia (p < 0.001). In scleroderma, the sphincter never closed in 12 of 13 patients (p < 0. 001 versus control subjects). A diagnostic sequence of sphincter opening followed by contraction in the esophageal body and subsequent sphincter closing was seen in 33 of 33 control subjects, 2 of 20 achalasia, and 1 of 13 scleroderma patients (both, p < 0. 001). The observers made the correct diagnosis in 96% of cases. CONCLUSIONS: Achalasia and esophageal scleroderma can be identified by endoscopic observation of motility. This procedure may represent an adjunctive diagnostic test to manometry.

Evaluation and treatment of constipation and fecal impaction in adults.

Constipation is a common complaint that physicians encounter. Understanding the patient's definition of constipation and focusing the history and physical examination provide clues to the underlying cause. Initially, an empiric treatment trial is recommended. For patients with warning symptoms or those in whom treatment fails, a limited diagnostic work-up is suggested. Tests of physiologic function are reserved for patients whose condition is refractory to therapy. Fecal impaction can be considered extreme constipation. The pathophysiologic features of fecal impaction are discussed, and recommendations are provided for treatment and prevention.

Effects of an irritable bowel syndrome educational class on health-promoting behaviors and symptoms.

OBJECTIVE: The degree to which patient education in the areas of diet, exercise, and stress management can improve symptoms of irritable bowel syndrome (IBS) through healthier lifestyle behaviors is unknown. The aim of this study was to determine the effects of outpatient education on the short and long term outcomes, and the association between health-promoting behaviors and symptoms. METHODS: Pender's Health Promotion Model provided the theoretical framework. The study had a prospective longitudinal design. A consecutive sample of 52 adult outpatients with IBS attended a structured class that taught health-promoting modifications of lifestyle. Participants completed the Health-Promoting Lifestyle Profile (HPLP) and selected items from a Bowel Disease Questionnaire (BDQ) before the class and 1 month and 6 months later. Spearman rank correlations were used to assess the association between HPLP and symptom scores. Wilcoxon rank sum tests compared changes in scores versus their baseline values. RESULTS: Response rates at 1 and 6 months were 75% and 83%, respectively. Results revealed significant 1- and 6 month-improvements in pain and Manning symptoms (p < 0.01) and in some HPLP scores (exercise at 1 month, p < 0.05; stress management at 6 months, p < 0.01). Significant associations were found between some, but not all, HPLP and symptom scores over time. CONCLUSION: A structured IBS educational class for patients with IBS improved symptoms and some health-promoting behaviors. However, relationships among specific behaviors and specific symptoms did not consistently correspond with this improvement.

Motility and tone of the left colon in constipation: a role in clinical practice?

OBJECTIVES: Colonic motor mechanisms deranged in constipation are not understood completely. Our aim was to measure left colonic motility and tone, during fasting and postprandially in patients with chronic constipation. METHODS: During 1 h fasting and 2 h postprandially, we measured pressures (multilumen manometry) and tone (barostat) in the left colon of 15 healthy controls and 40 patients with chronic constipation associated with slow (n = 15) or normal colonic transit (n = 12) or outlet obstruction (n = 13). RESULTS: Fasting tone was similar in all groups, and all demonstrated a significant increase in motor activity to food. There was lower postprandial tone (p < 0.05) in the slow transit and outlet obstruction groups. There were no differences in the timing of the tonic response or the number or amplitude of high-pressure propagated contractions. The slow transit group had lower postprandial phasic responses in the rectosigmoid (p < 0.05) and descending (p < 0.1) colon; the outlet obstruction group had lesser descending (p < 0.05) and rectosigmoid (p < 0.1) colon phasic motility. CONCLUSIONS: Colonic intraluminal measurements alone do not discriminate subgroups of chronic constipation more accurately than transit and pelvic floor tests, and currently have a limited role in clinical practice. However, manometry and tone measurements may be helpful in confirming a diagnosis of slow transit constipation (colonic inertia) in patients considered candidates for surgical treatment.

Antral axial forces postprandially and after erythromycin in organic and functional dysmotilities.

Our aims were to measure antral axial forces in patients with suspected upper gut dysmotilities and to compare the number of antral contractions detected by an axial force catheter and by manometric sensors in the distal antrum and pylorus. Fifteen patients (2 men, 13 women; mean age 42 years) underwent studies for 3 hr fasting, 2 hr postprandially, and up to 60 min after intravenous erythromycin (3mg/kg). Seven patients had gastroparesis or chronic intestinal pseudoobstruction, five functional disease, and three subacute obstruction. Postprandially, the number of peaks detected by the two methods was not significantly different; however, after erythromycin, the axial catheter detected more contractions (P = 0.02). Erythromycin significantly increased the number of postprandial axial forces (from 1.2 +/- 0.3/min to 2.5 +/- 0.3/min, P < or = 0.01) in the whole group and in the organic dysmotility group (P = 0.01). Erythromycin significantly increases the number of axial forces in functional and organic upper gut dysmotilities, but the axial force catheter is not advantageous over manometry for postprandial measurements of antral motility.

Axial forces during gastric emptying in health and models of disease.

The propulsive forces involved in gastric emptying of solid and liquid chyme are incompletely characterized, and the contribution of the proximal region of the stomach to overall propulsion has not been quantifiable. We have used an axial force catheter to characterize longitudinally directed forces during gastric emptying in man. The topography of these forces has been described relative to circumferential contractions, and the contribution of axial forces in experimental models of dumping and gastric stasis were quantified by assessing the effects of intravenous erythromycin and intraduodenal lipid, respectively. There is an excellent correlation between axial forces and gastric emptying of solids in health and in models of gastric dysmotility, suggesting that the axial force catheter semiquantitatively measures propulsive forces during emptying of the human stomach.

Gastric axial forces in experimentally delayed and accelerated gastric emptying.

The aim of this study was to assess the relationship between altered axial forces and gastric emptying of solids by experimentally inhibiting or stimulating gastric axial forces by intraduodenal lipid or intravenous erythromycin, respectively. In 15 healthy volunteers, we simultaneously measured gastric emptying of solids by scintigraphy, gastroduodenal motility by manometry, and forces along the longitudinal axis of the distal stomach by an axial force transducer. When 25% of the radiolabel had emptied from the stomach, subjects (n = 5 in each group) received normal saline (controls), intraduodenal lipid, or intravenous erythromycin. The test period consisted of the infusion period (10 min) and the subsequent 30 min. Lipid significantly reduced and erythromycin increased axial forces compared with control (lipid: median 0.6 N [0-1.4 interquartile range (IQR)]; erythromycin: median 18.2 N (16.5-20.5 IQR); control: median 4.7 N (3.9-5.2 IQR); P < 0.01). Similarly, antral phasic pressure activities were different relative to control. Gastric axial forces correlated significantly with gastric emptying (Spearman rank correlation = 0.86; P < 0.01). These data are consistent with the hypothesis that axial forces affect gastric emptying of solids and suggest that measurement of axial forces provides an assessment of overall gastric propulsion during the emptying of solids.

Measurement of axial forces during emptying from the human stomach.

Our aim was to measure axial forces in the stomach and to evaluate their relation to circumferential contractions of the gastric walls and the emptying of gastric content. We used a combination of simultaneous radioscintigraphy, gastroduodenal manometry, and an axial force transducer with an inflatable 2-ml balloon fluoroscopically placed in the antrum. In vitro studies demonstrated that the axial force transducer records only antegrade forces along the longitudinal axis of this probe in an intensity-dependent manner. In vivo studies were performed in five healthy subjects for at least 3 h after ingestion of radiolabeled meals. When administered separately, the emptying of liquids or solids from the stomach is associated with generation of antral axial forces and coincident phasic pressure activity; however, almost 20% (average) of gastric axial forces during emptying of liquids or solids are unassociated with proximal or distal antral pressure activity ("isolated" forces). High amplitude antral axial forces and pressures occur during both lag and postlag emptying phases. During emptying of liquids, there is a trend for axial forces to be coincident more often with proximal than with distal antral pressure activity and vice versa for the emptying of solids (P = 0.015). These data suggest that when placed in the antrum, the transducer can semiquantitatively record axial forces during gastric emptying. By combining these observations with the data from in vitro studies, it appears that axial forces predominantly result from traction on the balloon by the longitudinal vector resulting from circumferential gastric contractions. The combination of radioscintigraphy and measurement of antral axial forces is a promising method to evaluate mechanical forces involved in the emptying of the human stomach.

Balance studies and polymeric glucose solution to optimize therapy after massive intestinal resection.

The aim of this study was to determine whether fluid homeostasis could be maintained by using a hypo-osmolar (200 to 221 mosmol/kg), relatively low-sodium (50 to 52 mmol/liter) solution that contained a glucose polymer in a 54-year-old patient with high ileostomy output attributed to short-gut syndrome and resultant prerenal azotemia. Sequential balance studies were performed to assess stool and urinary output, stool fat, and urinary electrolytes initially during intravenous rehydration and subsequently during administration of the necessary fluids and nutrients exclusively by oral supplementation. The additional effects of high-fat and low-fat diet, loperamide hydrochloride, and octreotide acetate were evaluated. When the patient sipped a hypo-osmolar oral rehydration solution while she was awake during the day and received a high dose of loperamide and a 40-g fat, disaccharide-free diet, salt and water homeostasis was maintained. The addition of octreotide did not substantially enhance fluid balance; rather, it increased fecal fat and fluid losses from the small bowel. Thus, hypo-osmolar polymeric glucose solutions maintain fluid homeostasis in patients with the short-gut syndrome. In such patients, simple balance studies are useful for assessing the absorptive capacity of the residual intestine, for developing an optimal individualized treatment, and for eliminating the need for costly, long-term home parenteral nutrition.

The irritable bowel syndrome: mechanisms and a practical approach to management.

OBJECTIVE: To develop a practical strategy that facilitates the management of patients with the irritable bowel syndrome (IBS). STUDY SELECTION AND DATA EXTRACTION: Review of the pertinent literature published in major English-language journals for the last 25 years, describing the pathophysiology and treatment of subgroups of patients with IBS. RESULTS: A stepwise approach for practical management of patients with suspected IBS is identified. The first step includes a combination of positive diagnosis of symptoms with limited investigations to exclude underlying structural or biochemical disorders. In the second step, therapeutic trials focus on alleviating the predominant symptoms. For patients with intractable symptoms, the third step combines novel tests to assess altered function and therapeutic trials to correct the dysfunction identified in the individual patient. CONCLUSIONS: A practical approach has been developed for management of IBS. It is based on advances in our understanding of the mechanisms resulting in IBS and on targeting therapy to correct the dysfunctions in these patients.