How to Determine the Cause of Diarrhea Based on Stool Characteristics
Nov 19, 2025
Source: Cainiu Health
Dr. Huang Yuhong
Introduction
Diarrhea causes can be primarily assessed by evaluating stool characteristics, including color, consistency (softness or hardness), odor intensity, shape and form, and the presence of accompanying substances, combined with a comprehensive analysis of symptoms. If diarrhea persists for more than 3 days, is accompanied by high fever or bloody stools, prompt medical consultation is recommended to determine the underlying cause. Yellow or yellowish-brown soft stool is considered normal.
Diagnosing the cause of diarrhea based on stool characteristics primarily involves evaluating indicators such as stool color, consistency (softness or hardness), odor intensity, shape and form, and the presence of accompanying substances, combined with clinical symptoms for comprehensive analysis. If diarrhea persists for more than three days, is accompanied by high fever or bloody stools, prompt medical evaluation is recommended to determine the underlying cause.
1. Observe stool color: Yellow or light brown soft stool is normal. Black, tarry stool may indicate upper gastrointestinal bleeding; grayish-white stool could be related to biliary obstruction; red stool may suggest lower gastrointestinal bleeding or dietary influences.
2. Assess consistency: Watery stool is commonly caused by viral infection or indigestion; paste-like stool may indicate intestinal dysbiosis; mucus-containing stool often occurs in bacterial infections or inflammatory bowel disease; pus and blood in stool typically suggest bacterial infections such as bacillary dysentery.
3. Evaluate odor: Normal stool has a mild odor. A sour smell is often associated with indigestion and carbohydrate fermentation; a foul odor may indicate protein malabsorption or overgrowth of putrefactive bacteria in the gut; absence of strong odor may occur in early stages of viral infection.
4. Examine shape and form: Well-formed soft stool is normal. Watery stool is typical of acute gastroenteritis; stool resembling egg-drop soup is common in infants with rotavirus infection; narrowed stool or stool with grooves warrants concern for possible space-occupying lesions in the intestine.
5. Check for accompanying substances: Presence of undigested food particles usually indicates indigestion; mucus, pus, or blood suggests intestinal inflammation or infection; bubbles in stool may result from poor carbohydrate digestion/absorption or excessive gas production in the intestines.
During episodes of diarrhea, it's important to drink warm water or lightly salted water to prevent dehydration. Diet should include light, easily digestible foods such as millet porridge or noodle soup. Spicy, greasy, raw, or cold foods should be avoided. Adequate rest is essential, and minimizing intestinal irritation can support recovery.
