K59.1
Functional diarrhea
Functional diarrhea is a chronic gastrointestinal disorder characterized by the recurrent passage of loose or watery stools without the presence of predominant abdominal pain or bloating, which distinguishes it from Irritable Bowel Syndrome with Diarrhea (IBS-D). According to the Rome IV criteria, the condition is defined by loose or watery stools (Bristol Stool Form Scale 6 or 7) occurring in at least 25% of bowel movements for at least three months, with symptom onset at least six months prior to diagnosis. It is a diagnosis of exclusion, requiring the absence of inflammatory, infectious, or structural abnormalities. Pathophysiology may involve rapid colonic transit, bile acid malabsorption, or dietary sensitivities.
Clinical Symptoms
- Frequent passage of loose or watery stools
- Sudden urge to have a bowel movement (urgency)
- Increased frequency of bowel movements
- Absence of significant abdominal pain or discomfort
Common Causes
- Altered intestinal motility
- Accelerated colonic transit time
- Bile acid malabsorption
- Gut microbiome dysbiosis
- Dietary sensitivities or malabsorption of carbohydrates (e.g., lactose, fructose, sorbitol)
Documentation & Coding Tips
Clearly document the absence of abdominal pain to differentiate functional diarrhea from Irritable Bowel Syndrome with Diarrhea (IBS-D).
Example: Patient reports watery stools daily but denies any associated abdominal cramping or pain.
Note the duration of symptoms and the stool consistency using the Bristol Stool Scale.
Example: Patient reports Bristol Type 6-7 stools for the past 9 months.
Ensure organic causes such as Celiac disease, Inflammatory Bowel Disease (IBD), and chronic infections have been considered or ruled out.
Example: Negative serology for Celiac disease and normal fecal calprotectin support a functional diagnosis.