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Constipation is a symptom that affects around 11-20% of the adult population yearly. Most physicians consider infrequency of defecation as a hallmark of constipation. However, most patients view excessive straining as the biggest component of constipation and only a minority of patients with constipation have infrequent bowel movements. Constipation might be due to many different medical conditions or occur as a side-effect of drug therapy. When these medical conditions or drug therapies are not present, a diagnosis of functional constipation, chronic idiopathic constipation, or irritable bowel syndrome with constipation is often made. In all patients with constipation, rectal outlet dysfunction should be excluded by physical examination because this condition occurs in approximately 25% of patients diagnosed with idiopathic constipation and can be improved with different therapeutic approaches than administration of laxatives. Because of the availability of over-the-counter laxatives, most patients consider themselves able to self-manage constipation, and patients have often tried many different treatments before seeking professional help. The physician must carefully assess these previous efforts of self-treatment, optimise them, and strategically use the increasing list of prescription medications for management.

BACKGROUND: Chronic diarrhea in patients with neuroendocrine tumors (NET) may be caused by bioactive products of NET, bile acid malabsorption (BAM), ileal resection (IR) or steatorrhea. AIM: To quantitate BA and fat malabsorption in NET with diarrhea. METHODS: As part of evaluation in medical oncology clinical practice, 67 patients [42F, 25M; median age 64.0y (17.0 IQR)] with well-differentiated NET and diarrhea underwent clinically indicated measurements of 48h fecal BA [(FBA), fecal weight (normal 2,337μmol/48h) or >10% primary FBA or combination >4% primary FBA plus >1,000μmol total FBA/48h. We also measured fecal elastase (for pancreatic insufficiency) in 13 patients. RESULTS: BAM was present in 48/52 (92%) patients with NET. There were significant correlations between total FBA and 48h fecal weight (Rs=0.645, P10% in 69%. In 22 patients with no IR, 13/15 tested (87%) had BAM. Among 6 patients with pancreatic NET and no IR, 80% had BAM. Fecal fat was >15g/day in 18/42 (43%). In 4/17 (24%) with IR 25cm fecal fat was 44.0(40.5) and 38.0(38.0)g/day, respectively. CONCLUSION: A majority of patients with NET and diarrhea had BAM, even with

To evaluate recently published information about the frequency of maldigestion and malabsorption in older individuals, likely diagnoses causing these problems, and the diagnostic scheme when these diagnoses are being considered. Although the prevalence of malnourishment and frank malnutrition may be increasing among older adults admitted to the hospital, this appears to be due to reduced food intake rather than maldigestion or malabsorption. The mechanisms of food digestion and absorption seem to be resilient, even in old age, but concurrent illness may produce malabsorption in older individuals. Illnesses that may be more common among the elderly include small intestinal bacterial overgrowth, exocrine pancreatic insufficiency, enteropathies, vascular disease, diabetes, and certain infections, such as Whipple’s disease. In addition, older adults may have had previous surgeries or exposure to medicines which may induce malabsorption. The presentation of maldigestion and malabsorption in the elderly may be different than in younger individuals, and this may contribute to delayed recognition, diagnosis, and treatment. Diagnostic testing for maldigestion and malabsorption generally is similar to that used in younger patients. Maldigestion and malabsorption occur in older individuals and require a high level of suspicion, especially when weight loss, sarcopenia, or nutrient deficiencies are present.

Ileostomy is a common component of surgical treatments for various gastrointestinal conditions. Loss of the fluid absorptive capacity of the colon results in increased fluid and electrolyte losses, which causes a state of relative fluid depletion. These losses can be offset in part by increased oral intake, but the remaining small intestine also compensates by increasing the efficiency of fluid and electrolyte absorption, a process termed adaptation, which occurs within weeks to months of ileostomy creation. Some patients fail to adapt adequately and have high ileostomy outputs from the time of surgery. Others with a previously well-adapted ileostomy may encounter periods of sustained high output when some additional process causes diarrhea. Many patients experience periods of high output after ileostomy creation and often require hospital readmission for this reason. Any patient with an ileostomy is at great risk of dehydration and electrolyte depletion should output rise dramatically. Prompt attention should be given to rehydration and identification of the underlying cause so that directed therapies may be implemented. This review discusses the alteration of normal intestinal fluid balance from colectomy with ileostomy, proposed mechanisms for adaptation, the differential diagnosis of ileostomy diarrhea, the evaluation of ileostomy diarrhea, and current treatment options.

Chronic diarrhea is a common problem in all age groups but is a particularly challenging diagnostic problem in the elderly, since many different conditions need to be considered. The purpose of this review is to discuss the evaluation of chronic diarrhea in older individuals. It highlights those conditions that seem to occur with increased frequency in the elderly, discusses the diagnostic tests that are of greatest value in sorting out these problems, and presents an approach to evaluation that is both practical and affordable. There appears to be little value in distinguishing irritable bowel syndrome with diarrhea (IBS-D) from functional diarrhea in most patients, including older individuals. Both conditions need a thoughtful analysis of potential causes that may lead to more focused treatment. Older individuals may be more at risk of having certain structural disorders, and these need to be considered when constructing a differential diagnosis. In addition, elderly patients may have atypical presentations of specific disorders that require an increased index of suspicion. Diagnostic tests generally seem to perform well in older patients but have not been validated in this cohort of patients. Although the pretest probabilities of certain diseases are different in the elderly, the conventional algorithm for assessment of chronic diarrhea should lead to a diagnosis in most cases. Better studies are needed to adequately quantitate the likelihood of different diagnoses and the operating characteristics of diagnostic tests in older patients with chronic diarrhea. Lacking that information, physicians can still do a good job of making a diagnosis in these patients by adopting a stepwise approach.

Chronic diarrhea is a common clinical problem, affecting roughly 5% of the population in any given year. Evaluation and management of these patients can be difficult due to the extensive differential diagnosis of this symptom. Many patients with chronic diarrhea have structural problems, such as inflammatory bowel disease or celiac disease, that can be readily identified. Others do not, and often are given a diagnosis of irritable bowel syndrome with diarrhea (IBS-D). When based on generally accepted clinical criteria, a diagnosis of IBS-D identifies a group of patients who are unlikely to have disorders producing anatomical changes in the gut. It is less clear that a diagnosis of IBS-D identifies a specific pathophysiology or leads to better management of symptoms. Disorders such as small intestinal bacterial overgrowth, bile acid malabsorption, food intolerance, and motility disorders may account for symptoms in patients with IBS-D. More effective tests are being developed to identify the clinical problems underlying IBS-D and may lead to more specific diagnoses that may improve the results of therapy. Application of the principles of precision medicine (identifying a specific mechanism for disease and applying treatments that work on that mechanism) should lead to more expeditious diagnosis and treatment for patients with chronic diarrhea including IBS-D, but currently is limited by the availability of sufficiently sensitive and specific tests for underlying mechanisms that can predict response to treatment.

OBJECTIVES: Irritable bowel syndrome (IBS) and chronic idiopathic constipation (CIC) are functional bowel disorders. Evidence suggests that disturbance in the gastrointestinal microbiota may be implicated in both conditions. We performed a systematic review and meta-analysis to examine the efficacy of prebiotics, probiotics, and synbiotics in IBS and CIC. METHODS: MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched (up to December 2013). Randomized controlled trials (RCTs) recruiting adults with IBS or CIC, which compared prebiotics, probiotics, or synbiotics with placebo or no therapy, were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% confidence interval (CI). Continuous data were pooled using a standardized or weighted mean difference with a 95% CI. RESULTS: The search strategy identified 3,216 citations. Forty-three RCTs were eligible for inclusion. The RR of IBS symptoms persisting with probiotics vs. placebo was 0.79 (95% CI 0.70-0.89). Probiotics had beneficial effects on global IBS, abdominal pain, bloating, and flatulence scores. Data for prebiotics and synbiotics in IBS were sparse. Probiotics appeared to have beneficial effects in CIC (mean increase in number of stools per week=1.49; 95% CI=1.02-1.96), but there were only two RCTs. Synbiotics also appeared beneficial (RR of failure to respond to therapy=0.78; 95% CI 0.67-0.92). Again, trials for prebiotics were few in number, and no definite conclusions could be drawn. CONCLUSIONS: Probiotics are effective treatments for IBS, although which individual species and strains are the most beneficial remains unclear. Further evidence is required before the role of prebiotics or synbiotics in IBS is known. The efficacy of all three therapies in CIC is also uncertain.

Acute diarrhea often runs a self-limited course and little by way of treatment is needed except for oral rehydration therapy. Chronic diarrhea poses a longer-term problem. If not treatable with specific therapy aimed at the underlying pathophysiology, chronic diarrhea often needs long-term symptomatic therapy. This paper aims to examine the options for symptomatic, nonspecific treatment of diarrhea. The most frequently used therapies are opiate antidiarrheal drugs. These drugs are effective for a wide variety of diarrheal conditions and generally can be used safely if monitored closely. They work by slowing motility and allowing more time for absorption. They vary in potency and in addictive liability. In recent years, a variety of other drugs have been developed, which provide more targeted therapy that can mitigate diarrhea in specific situations. These drugs work on other regulatory pathways in the gut or on mucosal absorptive mechanisms. There is evidence for efficacy for both traditional and newer agents used for the symptomatic management of diarrhea. Opiates are used most often for this indication. Other agents may benefit individuals, but further research is needed to establish indications and best practices.

Fiber has been used for many years to treat irritable bowel syndrome (IBS). This approach had fallen out of favor until a recent resurgence, which was based on new randomized controlled trial (RCT) data that suggested it might be effective. We have previously conducted a systematic review of fiber in IBS, but new RCT data for fiber therapy necessitate a new analysis; thus, we have conducted a systematic review of this intervention.MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched up to December 2013. Trials recruiting adults with IBS, which compared fiber supplements with placebo, control therapy, or "usual management", were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy as well as number needed to treat (NNT) with a 95% confidence interval (CI).We identified 14 RCTs involving 906 patients that had evaluated fiber in IBS. There was a significant benefit of fiber in IBS (RR=0.86; 95% CI 0.80-0.94 with an NNT=10; 95% CI=6-33). There was no significant heterogeneity between results (I(2)=0%, Cochran Q=13.85 (d.f.=14), P=0.46). The benefit was only seen in RCTs on soluble fiber (RR=0.83; 95% CI 0.73-0.94 with an NNT=7; 95% CI 4-25) with no effect seen with bran (RR=0.90; 95% CI 0.79-1.03).Soluble fiber is effective in treating IBS. Bran did not appear to be of benefit, although we did not uncover any evidence of harm from this intervention, as others have speculated from uncontrolled data.

Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder. Evidence relating to the treatment of this condition with antidepressants and psychological therapies continues to accumulate.We performed an updated systematic review and meta-analysis of randomized controlled trials (RCTs). MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched (up to December 2013). Trials recruiting adults with IBS, which compared antidepressants with placebo, or psychological therapies with control therapy or "usual management," were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% confidence interval (CI).The search strategy identified 3,788 citations. Forty-eight RCTs were eligible for inclusion: thirty-one compared psychological therapies with control therapy or "usual management," sixteen compared antidepressants with placebo, and one compared both psychological therapy and antidepressants with placebo. Ten of the trials of psychological therapies, and four of the RCTs of antidepressants, had been published since our previous meta-analysis. The RR of IBS symptom not improving with antidepressants vs. placebo was 0.67 (95% CI=0.58-0.77), with similar treatment effects for both tricyclic antidepressants and selective serotonin reuptake inhibitors. The RR of symptoms not improving with psychological therapies was 0.68 (95% CI=0.61-0.76). Cognitive behavioral therapy, hypnotherapy, multicomponent psychological therapy, and dynamic psychotherapy were all beneficial.Antidepressants and some psychological therapies are effective treatments for IBS. Despite the considerable number of studies published in the intervening 5 years since we last examined this issue, the overall summary estimates of treatment effect have remained remarkably stable.

Diarrhea is best defined as passage of loose stools often with more frequent bowel movements. For clinical purposes, the Bristol Stool Form Scale works well to distinguish stool form and to identify loose stools. Laboratory testing of stool consistency has lagged behind. Acute diarrhea is likely to be due to infection and to be self-limited. As diarrhea becomes chronic, it is less likely to be due to infection; duration of 1 month seems to work well as a cut-off for chronic diarrhea, but detailed scientific knowledge is missing about the utility of this definition. In addition to duration of diarrhea, classifications by presenting scenario, by pathophysiology, and by stool characteristics (e.g. watery, fatty, or inflammatory) may help the canny clinician refine the differential diagnosis of chronic diarrhea. In this regard, a careful history remains the essential part of the evaluation of a patient with diarrhea. Imaging the intestine with endoscopy and radiographic techniques is useful, and biopsy of the small intestine and colon for histological assessment provides key diagnostic information. Endomicroscopy and molecular pathology are only now being explored for the diagnosis of chronic diarrhea. Interest in the microbiome of the gut is increasing; aside from a handful of well-described infections because of pathogens, little is known about alterations in the microbiome in chronic diarrhea. Serological tests have well-defined roles in the diagnosis of celiac disease but have less clearly defined application in autoimmune enteropathies and inflammatory bowel disease. Measurement of peptide hormones is of value in the diagnosis and management of endocrine tumors causing diarrhea, but these are so rare that these tests are of little value in screening because there will be many more false-positives than true-positive results. Chemical analysis of stools is of use in classifying chronic diarrhea and may limit the differential diagnosis that must be considered, but interpretation of the results is still evolving. Breath tests for assessment of carbohydrate malabsorption, small bowel bacterial overgrowth, and intestinal transit are fraught with technical limitations that decrease sensitivity and specificity. Likewise, tests of bile acid malabsorption have had limited utility beyond empirical trials of bile acid sequestrants.

Definitions for 'chronic diarrhoea' are arbitrary and are not evidence-based. The duration of illness that would differentiate acute from chronic diarrhoea is often taken as four weeks and serves best to exclude most infectious causes of diarrhoea which run their courses within that time interval. Patients tend to identify loose stool consistency rather than increased frequency of bowel movements when they say that they have diarrhoea. Some patients complaining of diarrhoea have frequent passage of formed stools and some have fecal incontinence. It is incumbent on the treating physician to inquire exactly what is meant by diarrhoea by a given patient. The pathophysiology of diarrhoea is complex, but generally comes down to explaining why there is excess water in stools. This can result from impaired absorption, excess secretion or retention of intraluminal fluid due to osmotic forces generated by poorly absorbed substances. The evaluation of diarrhoea is challenging. An algorithmic approach is feasible.

Chronic diarrhea is a common problem affecting up to 5% of the population at a given time. Patients vary in their definition of diarrhea, citing loose stool consistency, increased frequency, urgency of bowel movements, or incontinence as key symptoms. Physicians have used increased frequency of defecation or increased stool weight as major criteria and distinguish acute diarrhea, often due to self-limited, acute infections, from chronic diarrhea, which has a broader differential diagnosis, by duration of symptoms; 4 weeks is a frequently used cutoff. Symptom clusters and settings can be used to assess the likelihood of particular causes of diarrhea. Irritable bowel syndrome can be distinguished from some other causes of chronic diarrhea by the presence of pain that peaks before defecation, is relieved by defecation, and is associated with changes in stool form or frequency (Rome criteria). Patients with chronic diarrhea usually need some evaluation, but history and physical examination may be sufficient to direct therapy in some. For example, diet, medications, and surgery or radiation therapy can be important causes of chronic diarrhea that can be suspected on the basis of history alone. Testing is indicated when alarm features are present, when there is no obvious cause evident, or the differential diagnosis needs further delineation. Testing of blood and stool, endoscopy, imaging studies, histology, and physiological testing all have roles to play but are not all needed in every patient. Categorizing patients after limited testing may allow more directed testing and more rapid diagnosis. Empiric antidiarrheal therapy can be used to mitigate symptoms in most patients for whom a specific treatment is not available.

In patients with chronic nausea and/or vomiting, gastroparesis is frequently diagnosed, often on the basis of abnormal gastric emptying scintigraphy (GES). When typical treatments fail, patients may be referred to a referral center. This retrospective study evaluated the diagnoses made in patients referred for chronic nausea and vomiting and appraised the GES utilized to assess these patients. Records of outpatients referred for chronic nausea and vomiting over a 3-year period were analyzed for previous evaluation and treatment, subsequent investigation, and response to treatment. Of 248 patients referred for chronic nausea and vomiting, 156 (63%) were referred with a suspected diagnosis of gastroparesis. Of 102 GES available for review, 95 were done with nonstandardized methods. Repeat standardized testing was normal in 27 of 36 patients (75%). Only 28 patients (11%) had confirmed gastroparesis. The most common specific diagnosis in the entire group was chronic vestibular dysfunction (CVD, 64 patients, 26%) made by abnormal modified Fukuda stepping test, nystagmus, or abnormal Romberg test. CVD patients did not typically report a history of an inner-ear disorder or vertigo. Eighty-nine percent of CVD patients were given trials of antivertiginous medications; of the 39 followed for a median of 5 months, improvement occurred in two thirds. Diagnosis of gastroparesis should not be based on a nonstandardized GES. In our referred patients, gastroparesis was infrequent, while CVD was much more likely. Treatment for CVD may mitigate the nausea and vomiting.

Irritable bowel syndrome (IBS) is common in western Europe and North America, and many aspects of its epidemiology, risk factors, and natural history have been described in these regions. Recent data suggest, however, that IBS is also common in the rest of the world and there has been some evidence to suggest some differences in demographics and presenting features between IBS in the west and as it is experienced elsewhere. The World Gastroenterology Organization, therefore, established a Task Force comprising experts on the topic from all parts of the world to examine IBS from a global perspective. IBS does, indeed, seem to be common worldwide though with some significant variations in prevalence rates between regions and countries and there may well be some potentially interesting variations in presenting symptoms and sex distribution. The global map of IBS is far from complete; community-based prevalence data is not available from many areas. Furthermore, while some general trends are evident in terms of IBS impact and demographics, international comparisons are hampered by differences in diagnostic criteria, study location and methodology; several important unanswered questions have been identified that should form the basis for future collaborative research and have the potential to shed light on this challenging disorder. © 2012 by Lippincott Williams & Wilkins.

Several high-profile drug withdrawals for safety issues have brought into focus the FDA's process for approving drugs and monitoring adverse experiences with those agents after marketing has begun. Gastroenterologists and their patients have been affected adversely by removal from the marketplace of two licensed agents for irritable bowel syndrome (IBS): alosetron and tegaserod. The criteria used by the FDA for assessment of the risks and benefits of drugs used for functional bowel problems seem to be different than those used for the treatment of other conditions and have resulted in drastic limitation of access to these drugs rather than just warnings about risks as they are discovered. Decisions that affect the availability of drugs for patients with functional bowel disease should be discussed with clinicians who take care of those patients before going into effect. The absence of this sort of consultation leaves physicians with serious limitations on their abilities to take care of patients.

Small bowel bacterial overgrowth historically has been associated with malabsorption syndrome attributed to deconjugation of bile acids in the upper small intestine. Recent reports raise the possibility that bacterial overgrowth may be a cause of watery diarrhea or irritable bowel syndrome. Quantitative culture of jejunal contents has been the gold standard for diagnosis, but a variety of indirect tests have been developed (and mostly discarded) over the years in an attempt to facilitate the diagnosis of small bowel bacterial overgrowth. These include breath tests and biochemical tests based on bacterial metabolism of various substrates. Problems with these indirect tests include rapid transit, which may cause substrate to reach the luxuriant bacterial flora in the colon, producing false positives and vagaries of the tests themselves, which may produce falsely negative results. The perfect test for small bowel bacterial overgrowth is yet to be devised.

Diet often is blamed for digestive symptoms, particularly diarrhea, and patients with diarrhea and malabsorption usually request guidance about what to eat. Food-induced symptoms are very common. Although many recommendations have been made for dietary management in diarrheal diseases, there is little supportive evidence for efficacy for any of them. Knowledge of gastrointestinal physiology and the physiologic effects of foods can be used to design a dietary program for individual patients. Coordination of diet with drug therapy is an important part of a comprehensive treatment plan for these patients.

Fecal incontinence is a symptom of many disorders that can affect the nerves and muscles controlling defecation; it is not just due to exceptionally voluminous diarrhea. Underlying problems should be identified and treated, because that may improve incontinence. If treatment of the underlying problem does not correct incontinence, several approaches can be employed successfully. General approaches include stimulation of defecation at intervals to empty the rectum under supervised conditions; treatment of diarrhea, if present; addressing coexisting psychologic problems, such as depression; use of continence aids, such as adult diapers; and perineal skin care to prevent skin breakdown. Drug therapy includes use of constipating drugs, such as loperamide or diphenoxylate, that can impede the gastrocolic reflex, thereby limiting rectal filling and the likelihood of incontinence. Biofeedback training is useful in patients with some ability to sense rectal distention and to contract the external anal sphincter; instrumental learning using manometric or electromyographic biofeedback can be used to reinforce the rectoanal contractile response to rectal distention. Improvement in continence has been noted in up to 70% of suitable candidates with a single biofeedback training session. Patients with external anal sphincter disruption due to childbirth injury or other trauma may benefit from direct external anal sphincter repair (sphincteroplasty). In others, tightening up the anal canal by encirclement with nonabsorbable mesh (Thiersch procedure), perianal injection of fat, collagen, or synthetic gel, or radiofrequency electrical energy (Stretta procedure) may provide some palliation. Creation of a new sphincter mechanism by muscle transposition and encirclement of the anal canal is another approach that has been improved by use of electrical stimulators to keep the neosphincter contracted. Artificial anal sphincters patterned after artificial urinary sphincters have met with some success, but local infection remains problematic. When all else fails, fecal diversion (ileostomy, colostomy) can be effective in rehabilitating patients.

Irritable bowel syndrome (IBS) and chronic idiopathic constipation ((CIC) also referred to as functional constipation) are two of the most common functional gastrointestinal disorders worldwide. IBS is a global problem, with anywhere from 5 to 15 % of the general population experiencing symptoms that would satisfy a defi nition of IBS ( 1,2 ). In a systematic review on the global prevalence of IBS, Lovell and Ford ( 1 ) documented a pooled prevalence of 11 % with all regions of the world suff ering from this disorder at similar rates. Given its prevalence, the frequency of symptoms, and their associated debility for many patients and the fact that IBS typically occurs in younger adulthood, an important period for furthering education, embarking on careers, and / or raising families, the socioeconomic impact of IBS is considerable. Th ese indirect medical costs are frequently compounded by the direct medical costs related to additional medical tests and the use of various medical and nonmedical remedies that may have limited impact. CIC is equally common; in another systematic review, Suares and Ford ( 3 ) reported a pooled prevalence of 14 % , and also noted that constipation was more common in females, in older subjects, and those of lower socioeconomic status ( 3 ). Chronic constipation has also been linked to impaired quality of life ( 4 ), most notably among the elderly ( 5 ). Neither IBS nor CIC are associated with abnormal radiologic or endoscopic abnormalities, nor are they associated with a reliable biomarker; diagnosis currently rests entirely, therefore, on clinical grounds. Although a number of clinical defi nitions of both IBS and CIC have been proposed, the criteria developed through the Rome process, currently in its third iteration, have been those most widely employed in clinical trials and, therefore, most relevant to any review of the literature on the management of these disorders. According to Rome III, IBS is defi ned on the basis of the presence of

Diarrhea, defined as loose stools, occurs when the intestine does not complete absorption of electrolytes and water from luminal contents. This can happen when a nonabsorbable, osmotically active substance is ingested ("osmotic diarrhea") or when electrolyte absorption is impaired ("secretory diarrhea"). Most cases of acute and chronic diarrhea are due to the latter mechanism. Secretory diarrhea can result from bacterial toxins, reduced absorptive surface area caused by disease or resection, luminal secretagogues (such as bile acids or laxatives), circulating secretagogues (such as various hormones, drugs, and poisons), and medical problems that compromise regulation of intestinal function. Evaluation of patients with secretory diarrhea must be tailored to find the likely causes of this problem. Specific and nonspecific treatment can be valuable.

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice and Practice Economics Committee. The paper was approved by the committee on September 27, 1998.

In people with constipation, it is not known if decreased frequency of defecation is associated with abnormalities in the weight or in the consistency of stools or if the weight or the consistency of stools correlates with the severity of various discomforts associated with bowel movements. In neither normal nor constipated subjects has the consistency of stools been carefully correlated with their relative contents of water and solids. Our aim was to gain insight into these questions. Twenty subjects with idiopathic chronic constipation and 20 age- and sex-matched control subjects were recruited by advertisement. Stools were collected for one week. After each bowel movement, the subject's perception of various discomforts associated with the bowel movement were recorded. The stools were then analyzed. The results and conclusions were as follows: (1) Stool weight per bowel movement was similar in the two groups but stool weight per week was markedly reduced in constipated subjects. (2) Reduced stool weight per week in constipated subjects was due to a nearly proportional reduction in stool water and stool solids output. (3) Using data from both groups, there was a curvilinear correlation between percent insoluble stool solids and stool hardness, as measured by a texture analyzer; hardness increased only slightly as percent insoluble solids increased between 7 and 20%, but hardness increased dramatically when percent insoluble solids exceeded 25%. (4) Only 6% of stools from constipated subjects (2 of 34) had abnormally high values for percent stool solids and physical hardness. (5) In subjects with constipation, the severity of various discomforts associated with bowel movements (such as straining) correlated poorly with the weight or the hardness of stool that was produced by the bowel movement.

BACKGROUND & AIMS: Net sodium absorption from oral rehydration solution is increased by both glucose-sodium cotransport and solvent drag. The aim of this study was to measure the relative importance of glucose- sodium cotransport and solvent drag in the stimulation of net sodium absorption by oral rehydration solution. METHODS: Total intestinal perfusion was used in normal subjects with and without intrajejunal cholera toxin using three test solutions containing 100 mmol/L sodium and either 100 mmol/L mannitol (control), 100 mmol/L glucose, or no additional solute (hypotonic solution). The increase in sodium absorption greater than control with hypotonic solution represented sodium absorption stimulated by solvent drag; the further increase in sodium absorption induced by glucose, greater than that noted with the hypotonic solution, represented sodium absorption stimulated by cotransport. RESULTS: Without cholera toxin, solvent drag and cotransport promoted sodium absorption at rates of 62 and 33 mmol/h, respectively. With cholera toxin, solvent drag and cotransport promoted sodium absorption at rates of 44 and 71 mmol/h, respectively. CONCLUSIONS: Net sodium absorption caused by cotransport increased more than twofold after exposure of the intestine to cholera toxin (P < 0.003). This could be mediated by increased cotransport, a change in the stoichiometry of cotransport, or an increase in chloride permeability. (Gastroenterology 1997 May;112(5):1529-35)

Polyethylene glycol (PEG) has been used as apoorly absorbable marker in intestinal perfusionstudies, but there is controversy about theabsorbability of PEG, particularly when glucose-sodiumcotransport is occurring. Total intestinal perfusionstudies were done in five normal humans using threesolutions containing 1 g/liter PEG 3350 and designed toproduce low rates of water absorption, high rates of water absorption, or high rates ofglucose-sodium cotransport. Water absorption rates werecalculated by traditional nonabsorbable marker equationsand by a novel balance technique in which absorption was taken as the difference between the volumes ofsolution infused and recovered during steady-stateconditions. Effluent PEG recovery was 99 ± 4%,109 ± 2%, and 104 ± 6% of the amountinfused with each solution. Water absorption rates measured by use of PEGconcentrations were similar to those calculated by thebalance technique (r = 0.99). The complete recovery ofPEG confirms the poor absorbability of PEG 3350, and the excellent agreement between techniquesvalidates PEG as a poorly absorbed marker, even whenglucose-sodium cotransport is occurring.

Diarrhea is best defined as passage of loose stools often with more frequent bowel movements. For clinical purposes, the Bristol Stool Form Scale works well to distinguish stool form and to identify loose stools. Laboratory testing of stool consistency has lagged behind. Acute diarrhea is likely to be due to infection and to be self-limited. As diarrhea becomes chronic, it is less likely to be due to infection; duration of 1 month seems to work well as a cut-off for chronic diarrhea, but detailed scientific knowledge is missing about the utility of this definition. In addition to duration of diarrhea, classifications by presenting scenario, by pathophysiology, and by stool characteristics (e.g. watery, fatty, or inflammatory) may help the canny clinician refine the differential diagnosis of chronic diarrhea. In this regard, a careful history remains the essential part of the evaluation of a patient with diarrhea. Imaging the intestine with endoscopy and radiographic techniques is useful, and biopsy of the small intestine and colon for histological assessment provides key diagnostic information. Endomicroscopy and molecular pathology are only now being explored for the diagnosis of chronic diarrhea. Interest in the microbiome of the gut is increasing; aside from a handful of well-described infections because of pathogens, little is known about alterations in the microbiome in chronic diarrhea. Serological tests have well-defined roles in the diagnosis of celiac disease but have less clearly defined application in autoimmune enteropathies and inflammatory bowel disease. Measurement of peptide hormones is of value in the diagnosis and management of endocrine tumors causing diarrhea, but these are so rare that these tests are of little value in screening because there will be many more false-positives than true-positive results. Chemical analysis of stools is of use in classifying chronic diarrhea and may limit the differential diagnosis that must be considered, but interpretation of the results is still evolving. Breath tests for assessment of carbohydrate malabsorption, small bowel bacterial overgrowth, and intestinal transit are fraught with technical limitations that decrease sensitivity and specificity. Likewise, tests of bile acid malabsorption have had limited utility beyond empirical trials of bile acid sequestrants.

Background/Aims: Loose stools are a common and troublesome feature in diarrhea. The purpose of this study was to investigate factors that determine different degrees of stool looseness in diarrhea. Methods: Fecal consistency was measured visually. Stools were analyzed for content of water and solids. Water-holding capacity of insoluble solids was measured in vitro. Results: Formed stools from normal subjects had a near constant ratio of water to solids despite a sevenfold variation in daily stool weight. In diarrhea, loose consistency was correlated directly with percent fecal water. For any level of percent water, steatorrhea stools were looser than nonsteatorrhea stools. Ingestion of psyllium reduced stool looseness without changing the percent water. Both the effect of fat and psyllium could be explained by consideration of the ratio of fecal water to water-holding capacity of insoluble solids. Conclusions: (1) The normal intestine delivers stools that differ widely in quantity but maintains percent fecal water within a narrow range. (2) Stool looseness in diarrhea is determined by the ratio of fecal water to water-holding capacity of insoluble solids. (3) In patients with diarrhea with normal stool weight, loose stools are due to low output of insoluble solids without the concomitant reduction in water output that occurs in normal subjects when insoluble solids are low.

To evaluate the utility of screening for multiple gastrointestinal peptides in the evaluation of patients with chronic diarrhea, we studied 193 patients referred for evaluation of chronic diarrhea and eight patients with known peptide-secreting tumors as a reference group. Fasting plasma samples were assayed for motilin, neurotensin, pancreatic polypeptide, somatostatin, substance P, vasoactive intestinal polypeptide, gastrin-releasing peptide, and calcitonin during a protocol evaluation for causes of chronic diarrhea. Although none of the referred patients were found to have tumors, abnormal levels of one or more peptides were found in 86 of 193 patients (45%). Abnormal plasma peptide levels were sometimes as high in these patients as in patients with known peptide-secreting tumors and would have led to mistaken diagnoses of tumors much more often than they would have led to correct diagnoses. The positive predictive value of elevation of any assayed peptide was2% at realistic prevalence rates for peptide-secreting tumors; the negative predictive value of a series of normal results was99%, but much of this was due to the rarity of these tumors. Patients with chronic diarrhea should not be screened routinely with a panel of plasma peptide assays in an effort to detect tumors; instead, peptide levels should be ordered selectively. Elevated fasting concentrations of the plasma peptides measured in this study are most likely epiphenomena due to diarrhea and should not be the sole basis for invasive diagnostic or surgical management of these patients.

Microscopic colitis and collagenous colitis are similar conditions that are differentiated by the presence or absence of subepithelial collagen table thickening. To better understand the relationship between these two disorders and the role of collagen table thickening in the pathogenesis of diarrhea, colonic mucosal biopsy specimens from 24 patients with microscopic or collagenous colitis and 9 control subjects were analyzed using a computer-assisted morphometric method to evaluate the average thickness of the subepithelial collagen table. The collagen table thickness in colitis patients taken together formed a multimodal rather than a unimodal distribution. There was no tendency for collagen table thickening to increase with age or with duration of symptoms. In general, the types and distribution of inflammatory cells were similar in patients with normal and thickened collagen tables. Stool weight correlated with lamina propria cellularity but not with collagen table thickening. The multimodal distribution of collagen table thickening and the lack of correlation with age, duration of symptoms, or inflammation suggest that microscopic colitis and collagenous colitis are discrete conditions, although the inflammatory changes in the two conditions are similar. Moreover, because stool weight correlates with lamina propria cellularity but not with collagen table thickening, diarrhea probably is caused by the inflammatory changes and not by collagen table thickening per se.