What is the plan of care for a patient with chronic diarrhea?

Plan of Care for Chronic Diarrhea

Begin with a structured algorithmic approach based on clinical presentation, starting with careful history and basic investigations in primary care, followed by risk-stratified secondary evaluation to identify treatable causes while avoiding unnecessary testing in low-risk patients.

Initial Assessment and Definition

Chronic diarrhea is defined as passage of ≥3 loose stools per day for more than 4 weeks, which distinguishes it from acute infectious causes 1. The initial evaluation should focus on identifying alarm features that mandate urgent investigation versus functional symptoms that can be managed more conservatively 1.

Key Historical Elements to Elicit

Alarm features requiring urgent gastroenterology referral include: 1

• Nocturnal diarrhea (suggests organic disease)
• Unintentional weight loss
• Persistent blood in stool
• Fever
• Recent onset (<3 months duration)
• Age >45 years with new symptoms

Critical historical details: 1

• Family history: Specifically ask about inflammatory bowel disease, celiac disease, and colorectal cancer
• Surgical history: Terminal ileum resection, right colectomy, gastric bypass (causes bile acid malabsorption, bacterial overgrowth, or reduced absorptive surface)
• Medication review: Identify diarrheogenic agents including metformin, antibiotics, NSAIDs, proton pump inhibitors
• Dietary factors: Excessive caffeine, lactose, sorbitol, fructose, and FODMAPs
• Alcohol use: Direct toxic effects on intestinal epithelium and pancreatic function
• Systemic diseases: Diabetes (autonomic dysfunction), thyroid disease, systemic sclerosis

Primary Care Management Algorithm

First-Line Investigations (Complete Before Referral)

Blood tests: 1, 2

• Complete blood count (anemia suggests malabsorption or inflammation)
• C-reactive protein
• Comprehensive metabolic panel (electrolytes, renal function)
• Liver function tests
• Iron studies, vitamin B12, folate
• Thyroid function tests
• Anti-tissue transglutaminase IgA with total IgA (celiac disease screening)

Stool studies: 1, 2

• Fecal calprotectin (excludes inflammatory causes; particularly useful in patients <40 years)
• Stool culture if infectious etiology suspected (especially immunocompromised or elderly)
• Fecal immunochemical test (FIT) for occult blood

Primary Care Referral Criteria

Refer to gastroenterology when: 1

• Any alarm features present
• Normal first-line investigations but symptoms severe enough to impair quality of life
• Symptoms not responding to empiric antidiarrheal treatment
• Fecal calprotectin elevated (suggests inflammation)
• Positive FIT test

Important caveat: Many patients adapt their lives to symptoms rather than seeking care. Proactive assessment of quality of life impact is essential to identify those who would benefit from further evaluation 1.

Secondary Care Evaluation Algorithm

Age-Stratified Colonoscopy Approach

Patients ≥45 years: 1, 2

• Full colonoscopy with biopsies is mandatory to exclude colorectal cancer (>90% should undergo lower GI investigation)
• Obtain biopsies from right and left colon (NOT rectum) to diagnose microscopic colitis
• Aim for >90% cecal intubation rate; attempt terminal ileal intubation in >70% if clinically indicated

Patients <40 years without alarm features and normal fecal calprotectin: 1, 2

• Avoid immediate colonoscopy
• Consider positive diagnosis of irritable bowel syndrome using Rome IV criteria after basic screening
• Critical limitation: Rome criteria have only 52-74% specificity and do not reliably exclude inflammatory bowel disease, microscopic colitis, or bile acid diarrhea 1

Evaluation for Common Treatable Causes

Bile acid diarrhea (particularly important in functional-appearing cases): 1

• Make positive diagnosis with SeHCAT testing or serum 7α-hydroxy-4-cholesten-3-one (do not use empiric trial)
• This is frequently missed in patients labeled as IBS-diarrhea

Microscopic colitis: 1

• Requires colonoscopy with biopsies from right and left colon (rectal biopsies insufficient)
• Cannot be diagnosed without histology

Celiac disease: 2

• Should be screened in primary care with anti-tissue transglutaminase IgA and total IgA
• Confirm with duodenal biopsies if serology positive

Lactose maldigestion: 1

• Hydrogen breath testing if available, or therapeutic trial of lactose withdrawal

Small Bowel Evaluation (When Malabsorption Suspected)

Preferred imaging modalities: 1

• MR enterography (first-line for small bowel abnormalities)
• Video capsule endoscopy (alternative based on local availability)
• Do NOT use small bowel barium follow-through (poor sensitivity and specificity)

Enteroscopy: 1

• Reserve only for targeted lesions identified on imaging or capsule endoscopy
• Not a first-line diagnostic tool

Additional Testing for Persistent Undiagnosed Cases

Small bowel bacterial overgrowth: 2

• Glucose or lactulose hydrogen breath testing
• Consider in post-surgical patients, diabetics, or those with systemic sclerosis

Pancreatic insufficiency: 1

• At least one non-invasive pancreatic function test should be accessible
• Consider in patients with history of pancreatic disease, alcohol abuse, or steatorrhea

Symptomatic Management

When Specific Diagnosis Not Established

Loperamide (first-line antidiarrheal): 3

For chronic diarrhea dosing:

• Initial: 4 mg (two 2 mg capsules) followed by 2 mg after each unformed stool
• Titrate to control symptoms, then establish maintenance dose
• Average maintenance: 4-8 mg daily (may give as single or divided doses)
• Maximum: 16 mg daily (eight capsules)
• If no improvement after 10 days at maximum dose, unlikely to respond

Critical safety warnings: 3

• Do NOT exceed recommended dosages (risk of QT prolongation, Torsades de Pointes, cardiac arrest, death)
• Avoid in elderly patients taking QT-prolonging drugs (Class IA/III antiarrhythmics, antipsychotics, certain antibiotics)
• Use caution with CYP3A4 inhibitors (itraconazole), CYP2C8 inhibitors (gemfibrozil), or P-glycoprotein inhibitors (quinidine, ritonavir) as these increase loperamide exposure 2-13 fold
• Monitor hepatic impairment patients for CNS toxicity
• Advise patients to seek emergency care for fainting, irregular heartbeat, or unresponsiveness

Alternative symptomatic agents: 4

• Cholestyramine (particularly for bile acid diarrhea)
• Bulking agents
• Probiotics
• Anticholinergic agents
• Opioids reserved for severe refractory cases

Common Pitfalls to Avoid

1. Premature IBS diagnosis: Rome criteria alone cannot exclude organic disease; always complete basic blood and stool screening first 1

2. Missing microscopic colitis: Requires colonoscopy with biopsies; cannot be diagnosed clinically 1

3. Missing bile acid diarrhea: Common in "functional" presentations; requires objective testing, not empiric treatment 1

4. Inadequate colonoscopy in older patients: >90% of patients ≥45 years should undergo full colonoscopy to avoid missing colorectal cancer 1

5. Loperamide overdosing: Strictly adhere to maximum 16 mg daily; higher doses cause life-threatening cardiac arrhythmias 3

6. Using barium studies for small bowel evaluation: Poor diagnostic yield; use MR enterography or capsule endoscopy instead 1

7. Forgetting celiac serology: Should be completed in primary care before referral 1, 2