OVERVIEW

What is diarrhea?

Normal bowel movement frequency ranges from 3 times per day to 3 times per week. Diarrhea is defined as having loose or watery stools with more than 3 bowel movements per day and a daily stool weight exceeding 200g.

What are the differences between acute, persistent, and chronic diarrhea?

Diarrhea is typically classified by duration:

• Acute diarrhea: Lasts no longer than 2 weeks and often resolves on its own.
• Persistent diarrhea: Continues for more than 2 weeks but less than 4 weeks.
• Chronic diarrhea: Lasts longer than 4 weeks and is usually a symptom of an underlying systemic condition.

What is acute diarrhea?

Acute diarrhea usually has a sudden onset and short duration, typically lasting 1–3 days but potentially up to 14 days. In severe cases, individuals may lose control of bowel movements, though most cases resolve without treatment.

SYMPTOMS

What are the symptoms of acute diarrhea?

Acute diarrhea may be accompanied by symptoms such as nausea, vomiting, abdominal pain, fever, occult blood in stool, or even bloody stool. These accompanying symptoms can help guide the diagnosis of acute diarrhea. For example:

• Severe abdominal pain may indicate diarrhea related to gastrointestinal motility;
• The presence of fever suggests a higher likelihood of bacterial infection;
• Occult blood or bloody stool often indicates gastrointestinal bleeding.

Can acute diarrhea cause dehydration?

Dehydration is the most common and primary complication of diarrhea, especially in children. Diarrhea leads to the loss of large amounts of bodily fluids, primarily water and electrolytes. If severe diarrhea is not promptly compensated by adequate fluid intake or intravenous rehydration, dehydration may occur.

Dehydration can develop very quickly in children, particularly in infants, so parents should take it seriously.

What are the symptoms of dehydration in acute diarrhea?

Early signs of dehydration include reduced urine output, dry mouth, and decreased tears. If dehydration worsens, symptoms may progress to no tears, dry eyes, dry skin, and even lethargy.

CAUSES

What are the common causes of acute diarrhea?

The usual cause of acute diarrhea is unclean food consumption, where food is contaminated by viruses, bacteria, fungi, or parasites.

Bacteria and viruses often come from contaminated or spoiled food or water, while parasites are usually related to travel to epidemic areas.

In addition to the above causes, allergies, poisoning, or other diseases may also lead to acute diarrhea.

Is acute diarrhea contagious?

Not always, but it should be treated as potentially contagious. Whether acute diarrhea is contagious depends on its cause:

• When sanitation conditions or hygiene habits are poor, diarrhea caused by Salmonella, Vibrio cholerae, or dysentery bacilli contaminating food or water is highly contagious.

• Diarrhea in children is often caused by viruses like rotavirus or norovirus, which tends to spread among groups.

• Diarrhea caused by parasitic infections can also spread through the fecal-oral route (pathogens in feces contaminating water, food, toys, or hands, leading to oral infection).

• Diarrhea due to allergies, poisoning, or certain weak or non-virulent microorganisms is not contagious, but this is usually impossible to predict in advance.

Therefore, regardless of the cause, preventing contamination by the patient's stool, minimizing contact, practicing effective disinfection, and frequent handwashing are effective ways to prevent transmission.

How does acute diarrhea occur?

During diarrhea, stools are often loose or even watery, mainly due to increased water content in the feces.

In normal digestion and absorption, the gastrointestinal tract secretes large amounts of digestive fluids to keep food in a liquid state, which is later absorbed in the lower intestines to form solid stools.

When gastrointestinal secretions increase excessively, the lower intestines fail to absorb enough water, or food mixed with digestive fluids passes through the intestines too quickly, stools become loose or even watery.

DIAGNOSIS

What conditions need to be differentiated from acute diarrhea?

Although the following four conditions often accompany diarrhea, they still need to be distinguished from diarrhea when they occur alone:

• Fecal incontinence: Fecal incontinence refers to the inability to control bowel movements before reaching the toilet, often resulting in involuntary defecation into clothing. Patients with this condition usually suffer from other underlying diseases.

• Rectal urgency: This involves a sudden and intense urge to defecate, requiring immediate bowel movement. If a toilet is unavailable, fecal incontinence may occur.

• Incomplete defecation: After passing stool, the patient soon feels the need to defecate again, but little or no stool is passed the second time. This should not be mistaken for increased frequency due to diarrhea.

• Pseudodiarrhea: Pseudodiarrhea is often caused by gastrointestinal motility disorders or anorectal diseases. It typically manifests as increased stool frequency without loose or watery consistency—meaning the stool's appearance remains unchanged, only the frequency increases.

Effectively distinguishing these conditions before a hospital visit can save time. If unsure, patients should describe their symptoms in detail to the doctor rather than simply stating they have diarrhea or fecal incontinence.

What issues should be noted with acute diarrhea?

Doctors will first ask about the diarrhea, such as how it started, the appearance of the stool (e.g., watery, bloody, mucus-containing, egg-drop-like, or foul-smelling), and whether symptoms like tenesmus or borborygmi are present.

They will also inquire about recent food intake, travel history, current medications, whether others around have similar symptoms, and any additional symptoms beyond diarrhea.

Finally, the doctor will perform a physical examination to assess positive signs and the degree of dehydration.

What tests are needed for acute diarrhea patients?

Most cases of acute diarrhea resolve on their own without further testing. However, if the condition is severe, doctors may conduct stool routine tests, complete blood count (CBC), blood biochemistry tests, stool microbial cultures, or even parasite examinations if necessary.

What is the significance of tests for acute diarrhea?

• Stool routine test: Checks for occult blood, red blood cells, white blood cells, mucus, etc. If the patient has traveled to parasite-endemic areas, a parasite examination may also be performed.

• Complete blood count (CBC): Evaluates white blood cells, differential counts, hemoglobin, and other indicators to determine infection status and severity.

• Blood biochemistry test: Measures electrolytes like potassium and sodium to accurately assess dehydration and electrolyte imbalance.

TREATMENT

Which department should I visit for acute diarrhea?

Adults with diarrhea should see a gastroenterologist. If the diarrhea is severe or accompanied by dehydration or other emergencies, they should be sent to the emergency department immediately.
Children with diarrhea should visit the pediatric outpatient clinic. Some hospitals have specialized intestinal clinics.

When should a patient with acute diarrhea seek immediate medical attention?

If the following symptoms occur, it indicates severe diarrhea, and immediate medical attention is required:

• Diarrhea lasting more than 2 days;
• Signs of dehydration: severe thirst, dry mouth, dry skin, reduced or no urination, extreme fatigue, dizziness, and dark yellow urine;
• Severe abdominal or rectal pain;
• Bloody or black stools;
• Fever with a temperature exceeding 39°C.

When should children or infants with acute diarrhea seek medical attention?

For children, diarrhea can easily lead to dehydration, so it is recommended to seek medical attention immediately if symptoms do not improve within 24 hours. Infants often cannot express discomfort clearly, so the following symptoms should prompt immediate medical attention:

• Fever exceeding 39°C;
• Black or bloody stools;
• Dry lips or crying without tears;
• Lethargy or irritability;
• Severe sunken abdomen, eyes, or cheeks;
• Pinched skin does not return to normal quickly.

How is acute diarrhea generally treated?

Upon arrival at the hospital, medical history and physical examination will be conducted. If bacterial or parasitic infection is confirmed, targeted treatment such as antibiotics or antiparasitic drugs will be administered. For non-infectious cases, antidiarrheal medications may be given to relieve symptoms.

Symptomatic treatment may also be provided for complications like nausea, vomiting, fever, or dehydration.

Should diarrhea be stopped immediately?

Most cases of acute diarrhea resolve on their own without treatment. Diarrhea is a protective mechanism that helps expel pathogens and toxins from the intestines. Stopping diarrhea prematurely may trap harmful substances in the body.

Therefore, it is not advisable to stop diarrhea blindly. Persistent diarrhea should be evaluated by a doctor to identify the underlying cause.

Can smectite be used for acute diarrhea?

Smectite can adsorb pathogens and toxins while maintaining intestinal absorption and secretion functions. It enhances the intestinal barrier and differs from simple antidiarrheal drugs. It can generally be used in most cases.

How should dehydration from acute diarrhea be managed?

For dehydration, drink plenty of water or low-fat broth to replenish lost fluids. Since water lacks electrolytes like potassium and sodium, oral rehydration salts (ORS) or low-fat broths are recommended to prevent electrolyte imbalance.

Severe dehydration requires intravenous fluids.

How should oral rehydration salts (ORS) be used for dehydration?

ORS is highly effective for mild to moderate dehydration caused by acute diarrhea and for maintenance after intravenous rehydration.

The latest WHO-recommended formula includes: sodium chloride 2.6g, potassium chloride 1.5g, sodium citrate 2.9g, and anhydrous glucose 13.5g.

Improper preparation can worsen symptoms, so homemade ORS or adding sugar/salt to commercial ORS is not recommended.

What is the role of probiotics in acute diarrhea?

Probiotics contain beneficial live bacteria similar to those in the gut. They help eliminate harmful bacteria and reduce diarrhea. Probiotics should be taken at least 2 hours apart from antibiotics to avoid killing the beneficial bacteria.

What medications can be used at home to relieve acute diarrhea?

Mild diarrhea usually resolves on its own within days and does not require medical treatment. ORS can be kept at home to prevent dehydration.

Probiotics may also be helpful. However, these medications may not be safe for children, so professional medical advice should be sought.

When should antibiotics be used for acute diarrhea?

Most acute diarrhea cases resolve without antibiotics. Even in bacterial infections, antibiotics are often unnecessary. However, antibiotics may be used in the following cases:

• Diarrhea with high fever and chills;
• Severe or prolonged diarrhea;
• Patients with weakened immunity (e.g., heart failure, lung disease, HIV/AIDS);
• Stool tests confirming parasites or severe bacterial infections (e.g., Clostridioides difficile or Shigella);
• Traveler's diarrhea.

Antibiotics should only be used under medical supervision to avoid misuse and worsening of symptoms.

DIET & LIFESTYLE

What should patients with acute diarrhea pay attention to in daily life?

• Drink plenty of fluids, replenish liquids, or take oral rehydration salts to prevent water-electrolyte imbalances;

• Consume semi-liquid or low-fiber foods, such as steamed egg custard or soft noodles, and eat small portions frequently;

• Avoid foods that may worsen diarrhea, such as high-fiber, high-fat, or heavily seasoned foods (e.g., rich meats, commercially fried chicken cutlets), and refrain from consuming caffeine-containing products.

Should infants with acute diarrhea stop breastfeeding?

Unless severe vomiting prevents continued feeding, breastfeeding should be maintained for infants with diarrhea. In fact, breastfeeding not only provides strong protection against intestinal inflammation but also supplies adequate nutrition for recovery and effectively prevents dehydration.

What dietary precautions should acute diarrhea patients take?

During diarrhea, digestive function is somewhat impaired. To allow the gastrointestinal tract to rest, the diet should be light and easy to digest. Plain congee or clear noodle soup is ideal, as it ensures energy supply while minimizing digestive burden. Pickled vegetables can be added to maintain salt intake.

Until diarrhea improves, avoid spicy or greasy foods to reduce gastrointestinal irritation.

If preparing separate meals for the patient is not feasible, a normal diet is acceptable, but spicy or overly cold foods should be avoided to lessen stomach irritation.

Beyond food choices, hygiene is crucial. Always wash hands before eating, and thoroughly clean fruits or other uncooked foods.

PREVENTION

How to Prevent Acute Diarrhea?

Most cases of acute diarrhea can be prevented by following these measures:

• Wash hands frequently and master proper handwashing techniques, especially after using the toilet or before eating.

• Develop good hygiene habits: thoroughly wash raw vegetables or fruits before consumption, never use the same cutting board or knife for raw and cooked foods, and refrigerate raw meat promptly after purchase to minimize room-temperature storage.

• Avoid contact with contaminated water sources or undercooked food when traveling.