OVERVIEW

What is chronic diarrhea?

Diarrhea refers to increased frequency of bowel movements (>3 times/day), increased stool volume (>200 grams/day), loose stool consistency, and increased water content (>85%).

Chronic diarrhea is defined as diarrhea lasting more than two months or recurrent diarrhea with intervals of 2-4 weeks.

Chronic diarrhea is a common clinical symptom rather than a disease. Its causes are complex, and the condition persists for a long time. Depending on the underlying cause, clinical symptoms vary, and treatment principles differ.

How common is chronic diarrhea?

In China, chronic diarrhea is most prevalent among infants aged 6 months to 2 years, with about 50% of cases occurring in those under 1 year old. Additionally, elderly individuals, immunocompromised patients, and travelers are also high-risk groups for diarrhea.

SYMPTOMS

What are the common manifestations of chronic diarrhea?

• Increased frequency of bowel movements: more than 3 times per day;

• Increased stool volume: more than 200 grams per day;

• Watery stools with increased moisture: water content exceeding 85%;

• Persisting for more than two months, or recurring with intervals of 2–4 weeks;

• Most patients experience abdominal pain, which may ease after defecation, along with symptoms like rectal heaviness and weight loss.

CAUSES

What Causes Chronic Diarrhea?

The causes of chronic diarrhea include the following:

• Intestinal Infectious Diseases: Primarily caused by intestinal infections, pathogens responsible for infectious diarrhea include bacteria, viruses, parasites, and fungi.

• Non-Specific Intestinal Inflammation: Such as inflammatory bowel disease, diverticulitis, ischemic bowel disease, and radiation enteritis.

• Digestive and Absorption Disorders:

  • Small Intestinal Malabsorption: Damage to the small intestinal mucosa, lactose intolerance, short bowel syndrome, proximal small intestine-colon anastomosis or fistula, Whipple's disease, α2 heavy chain disease, systemic sclerosis, and primary small intestinal malabsorption.

  • Gastrogenic Diarrhea: Hypo- or hypersecretion of gastric acid, partial gastrectomy, gastrojejunostomy, or gastrocolic fistula formation, with frequent reflux of intestinal contents or bile into the stomach.

  • Biliary Diarrhea: Obstruction of bile excretion or reduced conjugated bile salts, leading to malabsorption of intestinal fats and steatorrhea.

  • Pancreatic Diarrhea: Chronic pancreatitis, cystic fibrosis of the pancreas, etc.

• Tumors: Such as small intestinal lymphoma, colon cancer, rectal cancer, gastrinoma, and endocrine tumors (e.g., medullary thyroid carcinoma, carcinoid syndrome, pancreatic non-β-cell tumors, VIPoma).

• Gastrointestinal Functional Disorder-Related Diarrhea: Such as irritable bowel syndrome, functional diarrhea, and hyperthyroidism.

• Drug-Induced Diarrhea: Medications such as magnesium sulfate, neostigmine, acetylcholine, and reserpine can cause diarrhea.

• Dysbiosis: In recent years, researchers have recognized that dysbiosis is also a cause of chronic diarrhea.

• Others: Additionally, food or chemical poisoning and allergic reactions in the intestines can also lead to chronic diarrhea.

Why Does Chronic Diarrhea Often Occur in Hyperthyroidism Patients?

In hyperthyroidism patients, accelerated intestinal motility and poor digestion and absorption result in increased bowel movement frequency or even diarrhea, often with undigested food in the stool.

Chronic diarrhea caused by hyperthyroidism is usually accompanied by other symptoms, such as increased appetite, irritability, weight loss, and heat intolerance. Diagnosis can be confirmed by measuring thyroid hormone levels in the blood.

Can Chronic Diarrhea Be Caused by AIDS?

Persistent chronic diarrhea may be related to AIDS, but it is not necessarily the cause. Further tests, such as HIV antibody testing, are needed for confirmation.

What Are the Characteristics of Chronic Diarrhea Caused by Intestinal Infections?

Most microbial intestinal infections are acute and resolve on their own. However, certain bacterial or parasitic infections can cause persistent intestinal inflammation, leading to chronic diarrhea.

Common bacteria causing chronic diarrhea include *Clostridioides difficile* and *Aeromonas*. Parasitic infections include dysentery, *Cryptosporidium*, *Giardia*, and *Entamoeba*. Travel history to endemic areas and antibiotic use are important diagnostic clues.

Is Chronic Diarrhea Contagious?

It can be contagious.

Chronic diarrhea caused by viral, bacterial, or microbial infections may be contagious. The most common transmission route is fecal-oral, so handwashing before meals and after using the toilet is essential.

DIAGNOSIS

What tests are needed for chronic diarrhea?

• Blood tests:

  • Tests include complete blood count, erythrocyte sedimentation rate, liver and kidney function, electrolytes, plasma folate, and vitamin B12 levels.

  • Detection of specific antibodies such as anti-gliadin IgG and IgA, anti-endomysial IgA, and anti-tissue transglutaminase IgA can diagnose celiac disease.

  • Measurement of plasma hormones and mediators is used to diagnose secretory diarrhea, such as serotonin, substance P, histamine, prostaglandins (carcinoid); plasma vasoactive intestinal peptide (VIPoma); gastrinoma (Zollinger-Ellison syndrome); calcitonin (medullary thyroid carcinoma); thyroxine (hyperthyroidism).

• Stool tests:

  • Common tests include fecal occult blood test; microscopic examination for red and white blood cells, macrophages, fat, intestinal epithelial cells, tumor cells, parasites, and ova.

  • Smear test for the ratio of intestinal cocci to bacilli; stool culture to identify pathogens; immunological tests for specific antigens or antibodies of pathogenic microorganisms in stool.

• Small intestine absorption function tests:

  • Fecal fat content measurement: Elevated fecal fat indicates fat malabsorption, seen in small intestinal mucosal diseases, bacterial overgrowth, or bile and pancreatic exocrine insufficiency.

  • D-xylose absorption test: A positive result suggests malabsorption due to jejunal disease or small intestinal bacterial overgrowth.

  • Pancreatic exocrine function test (BT-PABA test) helps diagnose malabsorption caused by pancreatic diseases.

  • Vitamin B12 absorption test (Schilling test) assesses terminal ileum absorption function. Reduced urinary vitamin B12 excretion is seen in terminal ileum malabsorption, post-resection, pernicious anemia, bacterial overgrowth, or pancreatic exocrine insufficiency.

  • Hydrogen breath test: Commonly used to detect lactose malabsorption, but also for sucrose malabsorption or glucose/galactose transport defects.

  • Bile salt absorption test (75SeHCAT test) evaluates bile salt malabsorption due to ileal disease.

• Imaging tests:

  • X-ray examinations, including abdominal plain films, barium meal, and barium enema, help observe gastrointestinal mucosal morphology, tumors, and motility.

  • Abdominal ultrasound and CT scans assess liver, biliary, and pancreatic diseases. Recent spiral CT virtual endoscopy improves detection and accuracy of intestinal lesions.

• Endoscopy:

  • Colonoscopy can diagnose inflammatory bowel disease, colon cancer, chronic bacillary dysentery, and amoebic dysentery. Intestinal swab smears, cultures, or mucosal biopsies may be performed.

  • Small bowel endoscopy examines duodenal, jejunal, and ileal lesions. Small bowel mucosal biopsies or jejunal fluid cultures aid in diagnosing conditions not detected by X-ray barium studies.

  • Capsule endoscopy is suitable for patients intolerant to conventional gastroscopy or colonoscopy, or for diagnosing chronic diarrhea of unknown cause.

  • Endoscopic retrograde cholangiopancreatography (ERCP) helps diagnose biliary and pancreatic diseases.

• Small bowel mucosal biopsy: Helps diagnose collagenous sprue, tropical sprue, parasitic infections, Crohn’s disease, and small bowel lymphoma.

• Genetic testing: Used for specific diarrhea-related genetic diagnoses, such as cystic fibrosis (CFTR gene mutation). Celiac disease (gluten-sensitive enteropathy) is an autoimmune disorder, with over 99% of patients positive for HLA-DQ2 or HLA-DQ8.

What diseases can chronic diarrhea be confused with?

Chronic diarrhea should be distinguished from fecal incontinence, which involves involuntary defecation and is usually caused by neuromuscular or pelvic floor disorders affecting the anorectal region.

TREATMENT

Which department should patients with chronic diarrhea visit?

Patients with chronic diarrhea usually have a prolonged course of illness. If the cause of diarrhea cannot be identified for a long time, it is recommended to visit the gastroenterology department of a large tertiary hospital. In case of emergencies such as dehydration or severe abdominal pain, immediate medical attention should be sought in the emergency department.

How is chronic diarrhea treated?

Etiological treatment is the fundamental principle for managing chronic diarrhea. Targeted measures should be taken to address the underlying disease and correct diarrhea:

• For diarrhea caused by bacterial infections, sensitive antibiotics should be selected;

• For lactose intolerance and celiac disease, lactose or gluten components in food should be eliminated, respectively;

• For osmotic diarrhea, hypertonic foods and medications should be discontinued;

• For secretory diarrhea, while treating the cause, attention should be paid to correcting water and electrolyte imbalances;

• For colonic diarrhea caused by impaired bile salt reabsorption, cholestyramine can be used to adsorb bile acids and stop diarrhea;

• For steatorrhea caused by bile acid deficiency, medium-chain fats can replace long-chain fats in the diet.

Symptomatic treatment:

• Correct water, electrolyte disturbances, and acid-base imbalances caused by diarrhea;

• Provide nutritional support for severely malnourished patients;

• Severe non-infectious diarrhea can be treated with antidiarrheal medications.

Treatment of intestinal dysbiosis:

• Use antibiotics rationally. Clinicians should be particularly cautious with antibiotic use in chronic diarrhea patients, especially those with severe infections. Strict indications should be followed, and blind, long-term use of broad-spectrum antibiotics should be avoided to prevent worsening dysbiosis. If intestinal dysbiosis is confirmed, the original antibiotics should be discontinued, and appropriate antibiotics should be selected based on microbial analysis and drug sensitivity tests.

• Use microbial regulators to exclude chronic diarrhea caused by bacterial dysentery, intestinal parasites, allergic diseases (e.g., food allergies, Henoch-Schönlein purpura), endocrine disorders, gastrointestinal hormone-secreting tumors, intestinal tuberculosis, inflammatory bowel disease, or pancreatic diarrhea.

• Promote intestinal mucosal repair. The severity and repair speed of mucosal damage are closely related to the course of diarrhea. Glutamine is an amino acid specifically required by rapidly growing intestinal mucosal cells and is involved in mucosal immunity and protein synthesis.

Psychological therapy: For patients with functional diarrhea or diarrhea-predominant irritable bowel syndrome, in addition to correcting gastrointestinal smooth muscle motility disorders and regulating visceral hypersensitivity, individualized psychological interventions should be incorporated.

What role do probiotics play in treating chronic diarrhea?

Probiotic preparations contain live beneficial bacteria similar to those naturally found in the human gastrointestinal tract. Probiotics can help eliminate pathogenic bacteria entering the body, thereby alleviating diarrhea. Some yogurts also contain live probiotics. Commonly used probiotic medications on the market include Medilac and Bifico.

Can chronic diarrhea be completely cured?

Not necessarily.

First, the underlying cause of chronic diarrhea must be identified. If the disease causing chronic diarrhea is curable, then chronic diarrhea can be completely cured. However, if the underlying disease cannot be fully treated, chronic diarrhea will require medication to control its progression.

DIET & LIFESTYLE

What should patients with chronic diarrhea pay attention to in their daily life and diet?

• Patients with diarrhea should pay attention to replenishing water, electrolytes, and energy.

• During diarrhea, minimize the burden on the digestive tract. Follow a clear liquid diet to maintain hydration and electrolyte balance without straining the stomach. Eat 5–6 small meals a day or sip liquids every few minutes as tolerated. Clear liquids include:

  • Water, including carbonated water (ensure it is sugar-free and caffeine-free).

  • Pulp-free juices and lemonade.

  • Strained tomato or vegetable juice.

  • Clear broth (avoid cream-based soups).

• Gradually reintroduce solid foods. By the next day, you may try small portions of semi-solid or bland foods. If symptoms worsen, revert to clear liquids and retry later. Opt for mild, low-fat, and low-fiber options.

• Stick to low-fiber foods initially, as high-fiber foods may cause bloating and worsen diarrhea. Avoid fresh fruits and vegetables (except bananas) until recovery. Whole grains and bran are also high in fiber. However, long-term fiber intake helps regulate bowel movements. If diarrhea is frequent, consider increasing fiber gradually.

• Identify the cause of chronic diarrhea early and tailor treatment accordingly. For example, patients with steatorrhea due to bile salt deficiency may benefit from medium-chain triglycerides, while those with celiac disease should avoid gluten-containing foods.

• Take medications as prescribed by a doctor and avoid self-adjusting dosages.

PREVENTION

How to Prevent Chronic Diarrhea?

Currently, there is no feasible method to prevent all causes of chronic diarrhea. The most effective approach to prevent diarrhea from becoming a persistent issue is to promptly identify the underlying cause and receive timely treatment.

For infectious diarrhea, maintaining dietary hygiene can help prevent it. Especially when someone around you has acute or chronic diarrhea of unknown cause, it is important to get timely check-ups and ensure cleanliness during meal preparation and consumption. If the cause of acute infectious diarrhea is identified, it should be treated thoroughly to prevent it from developing into a chronic infection.