What is the management approach for a patient with chronic diarrhoea, considering their medical history, dietary habits, and lifestyle?

Management of Chronic Diarrhoea

Begin with a structured diagnostic approach prioritizing alarm features, followed by systematic investigation to identify treatable causes, and implement targeted therapy based on the underlying etiology rather than empiric symptomatic treatment alone. 1, 2

Initial Assessment and Risk Stratification

Define the Problem

• Chronic diarrhoea is passage of ≥3 loose stools per day for more than 4 weeks, distinguishing it from acute infectious causes 2
• Patients may describe loose consistency, increased frequency, urgency, or incontinence—clarify what they mean by "diarrhoea" 3

Identify Alarm Features Requiring Urgent Referral

• Nocturnal diarrhoea, unintentional weight loss >10kg, persistent blood in stool, fever, age >45 years with new-onset symptoms, or duration <3 months mandate urgent gastroenterology evaluation 1, 2, 4
• These features suggest organic disease rather than functional disorders and require expedited investigation 1

Critical Historical Elements

• Previous surgery: Terminal ileal resection causes bile acid diarrhoea (responds to bile acid sequestrants); extensive small bowel resection causes malabsorption 1
• Medications: Up to 4% of chronic diarrhoea is drug-induced—review magnesium supplements, ACE inhibitors, NSAIDs, gliptins, PPIs, antacids, antibiotics, and antiarrhythmics 1, 2
• Systemic disease: Hyperthyroidism, diabetes mellitus, adrenal disease, systemic sclerosis all cause diarrhoea through various mechanisms 1
• Alcohol abuse: Causes direct epithelial toxicity, rapid transit, and pancreatic dysfunction 1
• Dietary triggers: Excessive caffeine, lactose (in lactase deficiency), sorbitol, fructose, and FODMAPs 1, 2
• Family history: Particularly inflammatory bowel disease, coeliac disease, or colorectal cancer 1

Primary Care Investigations (First-Line)

Mandatory Blood Tests

• Complete blood count, C-reactive protein, comprehensive metabolic panel (including albumin, calcium), liver function tests, iron studies (ferritin), vitamin B12, folate, thyroid function tests 1, 2, 4
• Anti-tissue transglutaminase IgA with total IgA (mandatory coeliac disease screening—selective IgA deficiency causes false negatives) 1, 2, 4
• Abnormal ESR, anaemia, or low albumin have high specificity for organic disease 1

Stool Studies

• Fecal calprotectin to distinguish inflammatory from non-inflammatory causes 2, 4
• Stool culture if infectious aetiology suspected or recent travel 1, 2
• Clostridium difficile toxin if recent antibiotic use 1, 2
• Fecal immunochemical test (FIT) for occult blood to guide urgency of colonoscopy 2, 4

Referral Criteria from Primary Care

• Normal first-line investigations with symptoms severe enough to impair quality of life and not responding to treatment 1
• Presence of any alarm features 1

Secondary Care Evaluation

Age-Stratified Endoscopic Approach

• Patients ≥45 years: Full colonoscopy with biopsies is mandatory due to frequency and clinical significance of colorectal neoplasia 2, 4
• Patients <40 years without alarm features and normal fecal calprotectin: Consider positive diagnosis of IBS using Rome IV criteria after basic screening, avoiding immediate colonoscopy 2
• Elevated calprotectin (>900) or any alarm features at any age: Full colonoscopy with biopsies 2, 4

Critical Biopsy Protocol

• Obtain biopsies from both right and left colon even if mucosa appears completely normal—microscopic colitis has entirely normal-appearing mucosa on endoscopy but shows characteristic histologic changes 2, 4
• Do not biopsy rectum alone—microscopic colitis requires colonic biopsies 2, 4

Common Pitfall to Avoid

• CT imaging is inadequate for detecting microscopic colitis, early inflammatory bowel disease, or subtle mucosal abnormalities—these require endoscopy with histology 2
• Normal CT does not exclude significant colonic pathology 2

Evaluation for Specific Treatable Causes

Bile Acid Diarrhoea

• Diagnose with SeHCAT testing or serum 7α-hydroxy-4-cholesten-3-one—do not use empiric trial 2
• Typically occurs after meals, responds to fasting 1
• Treatment: Bile acid sequestrants (colesevelam better tolerated than cholestyramine) 1

Microscopic Colitis

• Cannot be diagnosed without colonoscopy and histology—requires biopsies from right and left colon 2, 4
• Treatment: Budesonide 4

Coeliac Disease

• If anti-tissue transglutaminase IgA positive or equivocal: Upper endoscopy with distal duodenal biopsies 2
• Treatment: Strict lifelong gluten-free diet 4

Pancreatic Insufficiency

• Fecal elastase is the preferred non-invasive test (requires moderate impairment for adequate sensitivity) 2
• Treatment: Pancreatic enzyme replacement therapy 4

Small Intestinal Bacterial Overgrowth

• Consider in patients with previous gastric surgery, jejunoileal bypass, or extensive small bowel resection 1
• Treatment: Broad-spectrum antimicrobial therapy, often requiring prolonged and cyclical courses 1

Symptomatic Management

First-Line Antidiarrheal Therapy

• Loperamide: Initial dose 4 mg, followed by 2 mg after each unformed stool (maximum 16 mg daily); average maintenance dose 4-8 mg daily 1, 2
• Can be used for symptomatic relief while investigating underlying cause 1

Alternative Symptomatic Agents

• Probiotics (Lactobacillus, Bifidobacterium) can be used as alternative symptomatic agent 1, 2
• Need further safety analysis in immunocompromised patients 1

Anticholinergic/Antispasmodic Agents

• Can alleviate bowel cramping 1

Octreotide

• Reserved for patients not responsive to loperamide with severe toxicity (100 μg three times daily) 1

Dietary Management

Specific Dietary Modifications

• Reduce fatty foods, lactose-free diet if lactose intolerance suspected, avoid caffeine and alcohol 1, 2
• Identify and reduce high FODMAP foods (fermentable oligo-, di-, mono-saccharides and polyols) 1
• Lactose restriction trial if substantial intake (>280 ml milk/day), particularly in non-European descent patients 1
• Avoid excessive fructose, sorbitol, and food additives 1

Dietary Counseling Approach

• Keep a 2-week diary of symptoms, stresses, and dietary intake to identify aggravating factors 1
• Referral to expert dietitian after completion of 7-day dietary diary 1
• Dietary modification not recommended for prophylactic purposes but useful when patient is developing diarrhoea 1

Functional Diarrhoea and IBS-D

Positive Diagnosis Criteria

• Rome IV criteria: Pain that peaks before defecation, is relieved by defecation, and is associated with changes in stool form or frequency 3
• Rome IV criteria have only 52-74% specificity—cannot reliably exclude microscopic colitis, IBD, or bile acid diarrhoea 2
• Diagnosis requires completion of basic blood and stool screening first 2

Management Approach

• Explanation and reassurance using simple analogies (cramps, spasms, brain-gut interactions) 1
• Address patient fears—high proportion believe they have cancer 1
• Lifestyle modifications: Regular exercise, adequate time for defecation, stress management 1

Pharmacological Options for IBS-D

• Rifaximin 550 mg three times daily for 14 days (FDA-approved for IBS-D; can retreat up to two times for symptom recurrence) 5
• Loperamide for symptomatic relief 1, 2

Critical Pitfalls to Avoid

• Premature IBS diagnosis without completing basic blood and stool screening 2
• Missing microscopic colitis by not performing colonoscopy with biopsies 2, 4
• Missing bile acid diarrhoea by not performing objective testing 2
• Inadequate colonoscopy in older patients leading to missed colorectal cancer 2, 4
• Forgetting coeliac serology 2, 4
• Relying on CT alone when elevated calprotectin or alarm features present 2
• Assuming functional diarrhoea when Rome IV criteria alone are used without investigation 2

Special Populations

Cancer Patients

• Rehydration (oral or parenteral) is essential—large volume diarrhoea causes rapid dehydration with risk of prerenal impairment or shock 1
• Monitor for electrolyte imbalance (mainly hypokalaemia) 1
• Skin barriers for incontinent patients to prevent pressure ulcer formation 1
• Review medications (laxatives, antibiotics, antacids, PPIs, NSAIDs) and adjust as needed 1

Advanced Care Patients

• Consider overflow diarrhoea from incomplete obstruction or impacted stools (treat with enema) 1
• Exocrine pancreatic insufficiency (treat with enzyme therapy) 1
• Late effects of radiotherapy (see chronic RT-induced diarrhoea management) 1