What is the definition of diarrhea?

Definition of Diarrhea

Diarrhea is defined as the passage of three or more loose or liquid stools per day, or more frequently than is normal for an individual person. 1, 2

Clinical Definition and Classification

Diarrhea can be characterized by several key elements:

• Stool consistency: Loose or liquid stools (corresponds to types 5-7 on the Bristol stool chart)
• Frequency: More than three stools in 24 hours
• Volume: Sometimes defined as stool weight greater than 200 g/day, though this is rarely measured clinically 1

Temporal Classification

Diarrhea is classified based on duration:

• Acute diarrhea: Less than 14 days 1, 2
• Persistent diarrhea: 14-29 days (or 2-4 weeks) 1, 2
• Chronic diarrhea: 30 days or longer (more than 4 weeks) 1, 2

Severity Classification

Severity is best assessed by functional impact rather than just stool frequency 2:

• Mild: Some impact on daily activities
• Moderate: Significant impact on daily activities
• Severe: Incapacitating, prevents planned activities

Pathophysiological Classification

Diarrhea can be classified by underlying mechanism 3, 4:

• Secretory diarrhea: Results from impaired electrolyte absorption or active secretion, persists during fasting
• Osmotic diarrhea: Caused by nonabsorbable, osmotically active substances in the intestine, improves with fasting
• Mixed forms: Combination of secretory and osmotic mechanisms

Important Clinical Considerations

When evaluating diarrhea, clinicians should consider:

1. Individual variation: What constitutes diarrhea may vary between individuals, as noted in the ESMO guidelines 1
2. Distinguishing from other conditions: Important to differentiate from fecal incontinence, which patients may misinterpret as diarrhea 1
3. Clinical context: Diarrhea in specific populations (cancer patients, critically ill, post-surgical) may have different etiologies and require specialized management 1, 5

Common Pitfalls to Avoid

• Failure to clarify the patient's definition: Patients may use the term "diarrhea" to describe various symptoms including urgency, incontinence, or frequent formed stools 1
• Overlooking medications and treatments: Many medications, chemotherapies, and radiation therapy can cause diarrhea 1
• Missing alarm features: Blood in stool, fever, severe dehydration, significant weight loss, and nocturnal symptoms require immediate evaluation regardless of duration 2

The definition of diarrhea, while seemingly straightforward, requires careful clinical assessment to ensure proper diagnosis and management of the underlying cause.