Summary Chronic diarrhea is common and presents as the first manifestation of several diagnoses or as a long-term disorder in which the frequency, urgency, and incontinence of bowel movements have a significant impact on quality of life. It is necessary to take a good medical history, with different causes to consider: the onset and duration of symptoms, previous treatments, coexisting conditions, travel and drug use may all be relevant. Tests include blood and stool tests. Exclusion of inflammatory bowel disease and colorectal neoplasia is important and may require colonoscopy. Celiac disease, microscopic colitis, and bile acid diarrhea are common conditions that should not be overlooked, as specific therapy is available for each of them. Functional bowel disorders with diarrhea are common and overlap with other, more treatable conditions. Dietary assessment and advice are helpful. Knowledge of high FODMAP foods, with identification of individual sensitivities, is often beneficial. |
Key points
|
Chronic diarrhea is a common reason for consultation in general practice and secondary care. Studies have estimated a prevalence of up to 5% in a Western population. It can be defined as the passage of soft or watery stools (type 5-7 on the Bristol stool chart) more frequently, persisting for more than 4 weeks .
Despite its high prevalence, making the correct diagnosis can be challenging.
First, the optimal strategy for evaluating these patients varies. In 2018, the British Society of Gastroenterology (BSG) published updated guidance. However, the guidance on how, when and for how long to investigate is not the same for all patients.
Second, there is a significant overlap in symptoms between organic and functional diarrhea , where a diagnosis is formed based on symptoms and a negative physical examination, according to the 2016 revised Rome IV criteria. This overlap can lead to inappropriate investigations, or conversely to delayed diagnosis, where patients are labeled as having functional diarrhea or diarrhea-predominant irritable bowel syndrome (IBS-D) without investigations.
Third, there are a wide range of possible causes of chronic diarrhea that must be considered (Table 1). It may be useful to try to distinguish malabsorption diarrhea from inflammatory and secretory causes to help focus investigations. Particularly in malabsorption, there may be steatorrhea or complaints of bulky, foul-smelling stools.
The BSG guidelines provide more detailed guidance on the investigation and management of certain conditions. Below we provide some tips to help direct investigations to make the correct diagnosis.
Causes of chronic diarrhea (Table 1)
| Common | Infrequent | Strange |
|
|
|
Adapted from BSG 2018. 2 IBS = irritable bowel syndrome; VIPoma = vasoactive intestinal tumor peptide.
History is key
Every specialist says this; However, it really rings true in the chronic diarrhea approach. There are important discriminators that can be extracted from the history that will direct investigations for suspected diagnoses.
Assess red flag symptoms
The presence of red flag symptoms should prompt urgent further investigation. These symptoms include:
- Unexplained rectal bleeding
- Unexplained weight loss
- Unexplained change in bowel habit for more than 6 weeks in patients over 60 years of age.
Time of appearance
A patient who presents with a history of diarrhea for the past 2 to 3 months is more likely to have organic pathology than a patient with diarrhea for 3 years. Recent gastrointestinal infections, travel, treatments (including cancer therapy), and starting new medications are all relevant.
Surgical history
A detailed surgical history for any history of colonic resection (particularly of the right colon and terminal ileum) or cholecystectomy leads to diarrhea due to fat and carbohydrate malabsorption and bile acid diarrhea. Small intestinal bacterial overgrowth can also develop under these circumstances.
Family history
Asking specifically about colorectal cancer, inflammatory bowel disease (IBD), and celiac disease in the family can help focus research on conditions where there may be a genetic predisposition.
Common things are common
Table 1 breaks down the various causes of chronic diarrhea by the frequency with which they are diagnosed.
Too often there is a delay in diagnosis of common and highly treatable conditions (such as celiac disease), and patients are labeled as having IBS-D for many years. In a 2014 population-based study of 825 people with celiac disease, 32% reported a delay in diagnosis of more than 10 years .
Similarly, a patient-organized survey of 91 people diagnosed with bile acid diarrhea (BAD), showed that 44% had experienced symptoms for more than 5 years.
To avoid missing serious or common causes of chronic diarrhea, screening investigations should include blood tests to look for evidence of malabsorption: complete blood count, kidney profile, liver function tests, albumin, B12, folic acid, ferritin, and vitamin D .
The C-reactive protein test has a high sensitivity to organic diseases.
Thyroid function tests (to exclude hyperthyroidism) and serologic testing for celiac disease (including total immunoglobulin A levels) are part of a basic investigational screen.
Fecal calprotectin is necessary and can help distinguish between IBD and IBS. Values of <50 μg/g make IBD unlikely, but elevated calprotectin may be found in colorectal cancer, infectious gastroenteritis, and with the use of nonsteroidal anti-inflammatory drugs.
Fecal immunochemical testing for hemoglobin and fecal elastase, which is a sensitive and specific test for pancreatic exocrine insufficiency , may also be considered.
Do not forget
There may be a fine line between over- and under-investigation of patients with chronic diarrhea. When warning symptoms are present, the guidance for investigation is more explicit with a clear priority to exclude IBD, colonic neoplasia, and causes of malabsorption. However, it can be difficult to know which patients to investigate further in secondary care to find a possible cause of chronic diarrhea or simply give a diagnosis of IBS-D.
When symptoms are significant enough to affect a patient’s quality of life, or when simple pharmacological and lifestyle measures have not helped, further research is needed.
Celiac Disease
The prevalence of celiac disease in the adult population in the UK is approximately 1%. This figure may be 10% in high-risk groups with chronic diarrhea. In light of this, celiac disease serology with tissue transglutaminase antibodies should be checked as part of screening investigations in patients with chronic diarrhea.
Bile acid diarrhea (BAD)
Bile acids are necessary for the emulsification and absorption of fats. They are absorbed in the ileum, undergoing enterohepatic circulation to be secreted again by the liver. Bile acid diarrhea can result from bile acid malabsorption, usually from ileal resection or disease, or be due to overproduction of bile acids when there is impaired negative feedback regulation by FGF19.
Consequently, there is an excess of bile acids present in the colon, resulting in secretory diarrhea.
About 30% of IBS-D patients have DAB. The Selenium Homocholic Acid Taurine Test (SeHCAT), which measures 7-day retention of 75Se-labeled bile acid, is recognized as the best investigation for DAB and is widely available in the UK.
Excessive bile acid loss is classified as severe, moderate, or mild when seven-day retention is <5%, 5-10%, and 10-15%, respectively, and predicts the response of these patients to treatment with acid sequestrants. bile such as colesevelam or cholestyramine.
Microscopic colitis
This form of IBD is less recognized and often undiagnosed. On colonoscopy , the intestine is macroscopically normal, but biopsies of the left and right colon make the histological diagnosis. Excess lymphocytes in the intraepithelial and lamina propria layers, with a thickened subepithelial collagen band, give rise to the subtypes of lymphocytic and collagenous colitis, respectively.
In a meta-analysis of studies of patients diagnosed with IBS-D, the prevalence of microscopic colitis was 9.8%. Microscopic colitis has been linked to the use of commonly used medications (such as nonsteroidal anti-inflammatory drugs, proton pump inhibitors, and selective serotonin reuptake inhibitors); Stopping these medications may relieve symptoms. For those who do not respond, controlled-release budesonide is an effective treatment.
Drug-induced diarrhea, a common cause
Drug-induced diarrhea should be considered early in the investigation of chronic diarrhea and is an important part of the initial history.
More than 700 medications implicate diarrhea as an adverse reaction, and in an aging population with complex comorbidities, we are likely to encounter drug-induced diarrhea with increasing frequency.
Multiple overlapping mechanisms can lead to drug-induced diarrhea and these include osmotically active substances attracting water to the intestine, inhibition of electrolyte and nutrient absorption or increasing electrolyte secretion into the intestinal lumen, prokinetic effects in the lumen or causing epithelial inflammation. .
Medications commonly implicated include antibiotics (particularly macrolides such as erythromycin), nonsteroidal anti-inflammatory drugs, magnesium-containing products, hypoglycemic agents (especially metformin and dipeptidyl peptidase-4 inhibitors), antineoplastic agents, and cardiovascular medications (furosemide and angiotensin-converting inhibitors). enzymes). Whenever possible, withdrawal of offending medications is suggested; however, this will need to be done on a risk/benefit basis.
Dietary advice in chronic diarrhea
A patient’s diet can play a role in both causing and exacerbating the symptoms of chronic diarrhea. There is no one-size-fits-all approach, and this can lead to confusing and contradictory patient advice.
A "healthy diet," rich in fruits and vegetables, and containing protein, carbohydrates, and fat, may cause your symptoms to worsen.
Particular forms of carbohydrates that can trigger digestive symptoms are fermentable oligosaccharides, di-, monosaccharides, and polyols (FODMAPs). These are poorly digested and absorbed, so they reach the colon where they are fermented by bacteria. This can cause diarrhea, bloating, and abdominal pain. Meta-analyses have shown an improvement in patients’ symptoms and quality of life by reducing FODMAP intake.
Some foods high in FODMAPS (fermentable oligosaccharides, di, monosaccharides and polyols)
|
Lactose malabsorption is an example of FODMAP sensitivity. This occurs as a result of lactase nonpersistence, the usual global phenotype of the adult human, due to downregulation of the enzyme after weaning in infancy.
Evolution has developed lactase persistence in certain populations, for example in northwestern Europe, but it remains a common cause of diarrhea. A trial of exclusion of dairy from the diet may show improvement in symptoms. A hydrogen breath test can give a definitive diagnosis if in doubt.
Another source of FODMAPs are polyols (sorbitol and xylitol), artificial sweeteners commonly found in chewing gum and soft drinks.
