Chronic Diarrhea

Chronic Diarrhoea

chronic diarrhoea

1. Definition and Description

Chronic diarrhoea is defined in the British BSG guideline (Arasaradnam et al., Gut 2018) as a persistent change from your normal pattern with looser stools (typically types 5-7 on the Bristol Stool Scale) and/or more than three bowel movements daily for more than 4 weeks. It is the consistency and the change from normal that count, not just the number.

A distinction is often made between:

• Functional diarrhoea: Where no physical disease can be identified (e.g., irritable bowel).
• Organic diarrhoea: Where there is a detectable disease in the intestine or the body (e.g., inflammation or malabsorption).

2. Symptoms

In addition to the frequent and loose stools themselves, accompanying symptoms may vary depending on the cause:

• General symptoms: Bloating, abdominal pain, increased flatulence, nausea.
• Red flag symptoms (Require urgent investigation):
  • Unintentional weight loss.
  • Blood in the stool (visible or black/tarry).
  • Nocturnal diarrhoea (waking up due to the urge to defecate - this is rare in functional disorders).
  • Fever.
  • Sudden change in bowel habits in individuals over 50 years of age.

3. Causes (Etiology)

There are many causes, but in Danish general practice, the most common categories are:

• Irritable Bowel Syndrome (IBS): By far the most common cause. A disorder of bowel function without visible disease. Once organic disease has been ruled out, EndoCap covers IBS-D and functional diarrhoea.
• Inflammatory Bowel Disease (IBD): Crohn's Disease and Ulcerative Colitis.
• Malabsorption (Failure to absorb nutrients):
  • Coeliac disease. Coeliac disease is not an allergy but an autoimmune bowel disease in which the immune system reacts to gluten and damages the lining of the small intestine.
  • Lactose intolerance.
  • Bile acid malabsorption (an often overlooked cause).
• Medication side effects: Metformin (diabetes), antibiotics, proton pump inhibitors (PPIs), NSAIDs, chemotherapy.
• Infections: Less common in chronic diarrhoea in Denmark, but Clostridioides difficile (after antibiotics) and parasites such as Giardia lamblia (after travel) do occur.
• Microscopic colitis: An inflammatory condition primarily affecting older women, where the bowel looks normal during endoscopic examination, but biopsies show inflammation.
• Endocrine diseases: Overactive thyroid (Hyperthyroidism) or diabetes (diabetic enteropathy).
• Cancer: Colon or rectal cancer (Particularly relevant if age > 50 years).

4. Pathophysiology

The mechanism behind diarrhoea is typically divided into four types. Often, a combination is involved:

1. Osmotic diarrhoea: Poorly absorbed substances remain in the bowel and draw water in via osmosis (e.g., in lactose intolerance or use of laxatives). Typically ceases during fasting.
2. Secretory diarrhoea: The intestinal wall actively secretes fluid and electrolytes or fails to absorb them (e.g., due to toxins, bile acid malabsorption, or certain tumours). Does not cease during fasting.
3. Inflammatory/Exudative diarrhoea: Damage to the intestinal mucosa leads to the leakage of mucus, blood, and proteins, as well as reduced absorption (e.g., in Crohn's or Ulcerative Colitis).
4. Motility-related diarrhoea: The intestine moves too quickly, so water does not have time to be absorbed (e.g., in IBS or hyperthyroidism).

5. Investigation in Denmark

The investigation typically begins with the general practitioner and may continue with a specialist in gastrointestinal diseases (gastroenterologist).

Step 1: Medical History (Anamnesis)

• Onset, duration, frequency, consistency, nocturnal stools.
• Travel, medication list, alcohol consumption.
• Heredity (especially IBD, coeliac disease, and bowel cancer).

Step 2: Physical Examination

• Palpation of the abdomen (masses, tenderness).
• Digital rectal examination (checking for tumours in the rectum).

Step 3: Laboratory Tests (Standard Package)

• Blood tests: Haemoglobin (anaemia), CRP (infection marker), TSH (thyroid function), HbA1c (diabetes), electrolytes, and screening for coeliac disease (Transglutaminase antibody).
• Stool samples:
  • F-Calprotectin: An important marker in the Danish work-up. A low value argues against inflammatory bowel disease (IBD) but does not exclude it, and a high value is not a diagnosis in itself, since it is also seen with infection and NSAID use. The cut-off depends on assay and laboratory, and a raised value often leads to endoscopy after clinical assessment. It is not suitable for excluding or monitoring microscopic colitis.
  • Possible culture for pathogenic intestinal bacteria and parasites (especially with a travel history).
  • F-Hb (test for occult blood) is primarily used when cancer is suspected.

Step 4: Specialised Examinations

If basic tests suggest organic disease, or if symptoms persist inexplicably (especially in those >45-50 years old), a referral is made for:

• Colonoscopy: Endoscopic examination of the large intestine with biopsies (even if the mucosa looks normal, to rule out microscopic colitis).
• Gastroscopy: Endoscopic examination of the stomach/duodenum (biopsy for coeliac disease).
• SeHCAT scan: Nuclear medicine test for bile acid malabsorption. Retention of the tracer is measured after 7 days. The British BSG guideline defines a 7-day retention of 10-15% as mild bile acid loss, 5-10% as moderate and 0-5% as severely abnormal, and recommends a trial of bile acid binders at retention below 15% (BSG 2018, Gut 2018;67:1380). This is a British grading, not a Danish standard; the investigating department interprets the result in clinical context.

Which examinations are relevant depends on the duration, the accompanying symptoms, the test results and an overall medical assessment. Where there are alarm features such as blood in the stool, unintended weight loss or anaemia, colonoscopy with biopsies can form part of the work-up, among other things to clarify microscopic colitis.

6. Treatment

Treatment is always directed at the underlying cause.

• For Coeliac Disease: Lifelong gluten-free diet.
• For Lactose Intolerance: Lactose-free/low-lactose diet.
• For IBD (Crohn's/Colitis): Anti-inflammatory medication (corticosteroids, biological drugs).
• For Infections: Possibly antibiotics (if relevant, many resolve on their own).
• For Bile Acid Malabsorption: Medication that binds bile acids (e.g., Cholestyramine).
• If a medicine is suspected: your doctor reviews your medication and decides whether anything should change. Never stop prescribed medicine on your own.

For Functional Diarrhoea / Irritable Bowel Syndrome (IBS-D):

Once serious disease has been ruled out, treatment is symptomatic:

1. Dietary changes: The "Low FODMAP" diet is evidence-based and widely used in Denmark (often in consultation with a dietitian).
2. Fibre: Psyllium husks (Husk/Sylliflor) with or without calcium can bulk up the stool by binding fluid.
3. Anti-diarrhoeal medication: Loperamide (Imodium) can be used as needed, but with caution to avoid causing constipation.

Reference List: Chronic Diarrhoea

1. Definition, Classification, and Diagnosis

1. Definition of Chronic Diarrhoea and Red Flag Symptoms:

   • Source: Schiller, L. R. (2017). Chronic diarrhea. Current Opinion in Gastroenterology, 33(1), 19-24.

   • Supports: The definition of duration (more than 4 weeks) and the list of red flag symptoms (weight loss, nocturnal diarrhoea, blood in the stool) requiring rapid investigation for organic disease.

2. Definition and Criteria for Irritable Bowel Syndrome (IBS-D):

   • Source: Lacy, B. E., Mearin, M. A., & Chang, L. (2016). Bowel Disorders. Gastroenterology, 150(6), 1393-1407.e5.

   • Supports: The classification of IBS as the most frequent functional cause of diarrhoea (IBS-D) and its distinction from organic diarrhoea.

3. Role and Significance of Faecal Calprotectin (F-Calprotectin):

   • Source: Mosli, M. H., Feagan, B. G., & Dulai, P. S. (2015). Fecal calprotectin in the diagnosis and management of inflammatory bowel disease. Expert Review of Gastroenterology & Hepatology, 9(4), 485-493.

   • Supports: The use of F-Calprotectin as an important marker in investigations, particularly to differentiate between inflammatory bowel disease (IBD) and functional disorders.

2. Pathophysiology, Causes, and Treatment

4. The Four Pathophysiological Mechanisms (Osmotic, Secretory, Inflammatory, Motility-related):

   • Source: Fine, K. D., & Schiller, L. R. (1999). AGA technical review on the evaluation and management of chronic diarrhea. Gastroenterology, 116(6), 1464-1486.

   • Supports: The description of the four main mechanisms behind chronic diarrhoea and the underlying causes (e.g., osmotic in lactose intolerance; inflammatory in IBD).

5. Bile Acid Malabsorption (BAM) and Diagnosis (SeHCAT scan):

   • Sources: Vijayvargiya, P., & Camilleri, M. (2019). Bile acid malabsorption: Diagnostic and treatment approaches. Mayo Clinic Proceedings, 94(7), 1324-1331. And: Arasaradnam RP, Brown S, Forbes A, et al. (2018). Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology, 3rd edition. Gut, 67(8), 1380-1399. gut.bmj.com/content/67/8/1380

   • Supports: The inclusion of Bile Acid Malabsorption (BAM) as an important cause, and the use of SeHCAT scan for diagnosis, including the BSG grading of 7-day retention (mild 10-15%, moderate 5-10%, severe 0-5%) and the recommendation of a trial of bile acid binders at retention below 15%. The grading is British; the investigating department interprets the result in clinical context.

6. The Low FODMAP Diet in the Treatment of IBS-D:

   • Source: Altobelli, E., Latella, G., & D'Ovidio, E. (2017). Low-FODMAP Diet Improves Symptoms of Irritable Bowel Syndrome. Nutrients, 9(12), 1269.

   • Supports: The application of the Low FODMAP diet as an evidence-based dietary intervention for functional diarrhoea/IBS-D after ruling out organic disease.

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How the work-up usually proceeds

Investigating long-standing diarrhoea proceeds step by step, and the order is adapted to the individual. The history carries most weight: duration, the appearance of the stool, night-time symptoms, weight, medication, travel and previous surgery. Blood tests and stool tests often follow, among them faecal calprotectin, which can point to inflammation in the bowel. Endoscopy with biopsies is used when suspicion of organic disease remains, not least because microscopic colitis can only be confirmed by microscopy of tissue samples. More targeted investigations, for instance for bile acid malabsorption, come into play when the history points that way. Which steps are relevant is decided by the overall clinical assessment.

What may be relevant?

Long-lasting loose stools can have several causes, and they are usually investigated step by step. What is relevant depends on the duration, the accompanying symptoms, the test results and an overall medical assessment.

Microscopic colitis · Bile acid malabsorption (BAM) · Inflammatory bowel disease (IBD) · Low-FODMAP diet · Colonoscopy