Getting the BS out of Irritable Bowel Syndrome with Diarrhea (IBS-D): Let's Make a Diagnosis.

PURPOSE OF REVIEW: Irritable bowel syndrome with diarrhea (IBS-D) is diagnosed when chronic symptoms of abdominal pain accompany loose stools, and alarm features, such as fever, anemia, rectal bleeding, and weight loss are absent. This combination of symptoms makes structural disorders, such as inflammatory bowel disease or cancer, unlikely, but does not exclude other conditions that cause these symptoms. The question is whether making a "positive diagnosis" of IBS-D based on symptoms alone and instituting therapy based on that diagnosis still makes sense. RECENT FINDINGS: Clinical observations suggest that at least two-thirds of cases of IBS-D can be explained by three mechanisms: a) food intolerances (~ 30-40%), b) bile acid diarrhea (~ 20-30%), and c) disturbed microbial flora (~ 15-20%). Other conditions that are less frequent but can cause IBS symptoms or be confused with IBS include: celiac disease, microscopic colitis, mastocytosis/mast cell activation, and drug side-effects. Many cases of IBS-D have a discoverable, underlying cause that can direct therapy more efficiently.

Ileostomy diarrhea: Pathophysiology and management.

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.

Evaluation of chronic diarrhea and irritable bowel syndrome with diarrhea in adults in the era of precision medicine.

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.

Chronic Diarrhea: Diagnosis and Management.

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.

Gastro 2013 APDW/WCOG Shanghai working party report: chronic diarrhea: definition, classification, diagnosis.

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.

Diarrhea and malabsorption in the elderly.

Acute and chronic diarrheal disorders are common problems at all ages. It has been estimated that 5% to 7% of the population has an episode of acute diarrhea each year and that 3% to 5% have chronic diarrhea that lasts more than 4 weeks. It is likely that the prevalence of diarrhea is similar in older individuals. This article reviews the impact of diarrhea in the elderly, many of whom are less fit physiologically to withstand the effect of diarrhea on fluid balance and nutritional balance.

Chronic Diarrhea.

Chronic diarrhea can be due to any of several hundred conditions. When investigation fails to uncover a specific cause that can be treated successfully, nonspecific therapy is implemented. This includes dietary alterations if specific aggravating foods can be identified, enteral or parenteral nutrition if nutritional status is compromised, and use of oral rehydration solutions if diarrhea produces volume depletion. Strategic use of dietary fiber can improve stool consistency and can be of special value when fecal incontinence is present concurrently. Medications of value include opiate antidiarrheal drugs, clonidine, octreotide, and bile acid-binding agents. Less potent opiates such as loperamide and diphenoxylate should be tried first, with more potent agents such as codeine, opium, and morphine used in refractory cases. Clonidine has both proabsorptive and motility effects that facilitate its antidiarrheal effect, but its antihypertensive action limits its utility. Octreotide is of great value in treating diarrhea due to endocrine tumors and dumping syndrome; its efficacy in other conditions or in nonspecific diarrhea is less well established. Bile acid binders such as cholestyramine or colestipol have several specific uses but have limited utility in nonspecific chronic diarrhea.

Safety and effectiveness of large-volume enema solutions.

The effectiveness and side effects of three types of enema solutions were compared in healthy subjects. Using a repeated-measures, double-blind design, the three different enemas (soapsuds, tap water, and polyethylene glycol-electrolyte solution) were given at 1-week intervals to 24 healthy volunteers. Soapsuds and tap water enemas produced significantly greater returns than polyethylene glycol electrolyte solution (PEG-ES) and were also more uncomfortable. Rectal biopsies showed surface epithelium loss after soapsuds and tap water but not after PEG-ES enemas. Before recommending changes in nursing practice, further research is needed to determine the mechanism for the surface epithelium damage and to determine if this damage produces a stronger defecation stimulus and discomfort.

New and emerging treatment options for chronic constipation.

Chronic constipation remains a therapeutic challenge for today's physicians. Traditional approaches include use of fiber, osmotic laxatives, stimulant laxatives, prokinetic agents, biofeedback training, and surgery. These often are tried sequentially and episodically and have little evidence of long-term efficacy. Patients often report inadequate relief of symptoms. There is room for improvement, therefore, in the therapy of chronic constipation. Future advances largely will be based on insights into the enteric nervous system (ENS), the structure and function of which is being revealed in great detail. Manipulating the ENS pharmacologically offers the opportunity to reprogram this key control system to improve bowel function. For example, interneurons in the ENS display 5-HT4 receptors, activation of which enhances the peristaltic reflex. Prokinetic agents that stimulate those receptors, such as tegaserod and prucalopride, have demonstrated efficacy as investigational agents for the treatment of chronic constipation in large studies. Less well studied investigational drugs with presumed activity in the ENS include opiate antagonists and the nerve growth factor neurotrophin-3. Both of these types of agents have been shown to be effective in small groups of patients with constipation. Another approach under development is to stimulate colonic fluid secretion by opening chloride channels in the epithelium pharmacologically. Existing non-pharmacological treatments that can be improved include biofeedback training for pelvic floor dysfunction and surgery. Future developments include investigation of electrical stimulation of the colon and use of stem cells to repopulate degenerated populations of neurons, interstitial cells of Cajal, or smooth muscle cells.

Diagnosis and management of microscopic colitis syndrome.

Microscopic colitis syndrome consists of chronic watery diarrhea, a normal or near-normal gross appearance of the colonic mucosa, and a specific histologic picture described as either lymphocytic colitis or collagenous colitis. The cause of microscopic colitis is unknown, but recent work suggests some immunologic similarities to celiac disease, suggesting that luminal antigens may be important in its pathogenesis. Diarrhea in microscopic colitis seems to be directly related to the extent of inflammation, suggesting that inflammatory mediators are responsible for reduced water absorption by the colon. Microscopic colitis is a frequent diagnosis in patients with chronic diarrhea seen at referral centers. It is often associated with other immune-mediated conditions and frequently is complicated by fecal incontinence. The differential diagnosis is broad, comprising all causes of watery diarrhea. Evaluation is straightforward with the key aspect being review of colon biopsy specimens by an experienced pathologist. Treatment is still being defined: symptomatic management with antidiarrheal agents, 5-aminosalicylate drugs, corticosteroids, especially budesonide, bile acid-binding resins, and bismuth subsalicylate all can be effective. The prognosis is good with no evidence of conversion to classic inflammatory bowel disease or of development of neoplasia over time.