Chronic diarrhea is defined as the passage of loose or watery stools that persist for more than four weeks. It is a common condition, affecting approximately 5% of the adult population at any given time. Chronic diarrhea is important because it can lead to significant dehydration, malnutrition, and a decreased quality of life. It can also be a sign of an underlying medical condition that requires treatment.
Stool production
Stool production begins with food digestion in the stomach, followed by nutrient absorption in the small intestine. The remaining undigested material moves into the colon, where water is reabsorbed, and stool is formed. The quantity and quality of stool are influenced by the digestive tract’s function. Any alteration in absorption, secretion, or motility within the gastrointestinal tract can lead to changes in stool consistency and frequency, potentially resulting in chronic diarrhea.
Types of diarrhea
Chronic diarrhea can be classified into four main types based on the underlying mechanism:
- Osmotic diarrhea: This type occurs when an excessive amount of non-absorbable substances is present in the intestines, leading to water retention. Common causes include lactose intolerance and ingesting certain artificial sweeteners like sorbitol. Osmotic diarrhea typically resolves when the offending substance is removed from the diet.
- Secretory diarrhea: Secretory diarrhea occurs when the intestines secrete more water and electrolytes than they absorb. This can result from infections, certain medications, or conditions like Zollinger-Ellison syndrome. Unlike osmotic diarrhea, secretory diarrhea persists even when fasting.
- Inflammatory/infectious diarrhea: This type is caused by inflammation of the intestinal lining, which can be due to infections, autoimmune diseases like Crohn’s disease, or other inflammatory conditions like ulcerative colitis. Inflammatory diarrhea is often accompanied by blood, mucus, and abdominal pain.
- Motility-related diarrhea: Diarrhea related to motility occurs when the contents of the gastrointestinal tract move too quickly through the intestines, preventing proper absorption of water and nutrients. This can be seen in conditions like irritable bowel syndrome (IBS) or after certain surgeries.
Symptoms and signs of chronic diarrhea in an adult
Chronic diarrhea in adults is typically characterized by the frequent passage of loose, watery stools. Additional symptoms may include abdominal pain or cramping, urgency, bloating, and sometimes, the presence of blood or mucus in the stool. Weight loss, fatigue, and signs of dehydration, such as dry mouth and decreased urine output, may also occur in more severe cases.
What is the most common cause of chronic diarrhea in adults?
Irritable bowel syndrome (IBS) with diarrhea (IBS-D)
Irritable bowel syndrome (IBS) with diarrhea (IBS-D) is one of the most common causes of chronic diarrhea in adults. IBS-D is a functional gastrointestinal disorder characterized by abdominal pain or discomfort associated with altered bowel habits, primarily diarrhea. The exact cause of IBS-D is not fully understood, but it is believed to involve a combination of abnormal gastrointestinal motility, increased visceral sensitivity, and alterations in the gut microbiota. IBS-D is more common in adults under the age of 50 and often affects more women than men. Distinguishing features of IBS-D include the absence of alarm signs such as weight loss, blood in the stool, or anemia. Diagnosis is typically clinical, based on the Rome IV criteria, and treatment focuses on dietary modifications, stress management, and pharmacotherapy such as antispasmodics or low-dose antidepressants.
Other common medical conditions associated with chronic diarrhea in adults
Celiac disease
Celiac disease is an autoimmune disorder triggered by the ingestion of gluten, which damages the small intestine. It typically presents in young adults but can occur at any age. Symptoms include diarrhea, weight loss, and bloating. Diagnosis is confirmed with serological testing and small bowel biopsy. Treatment involves a strict gluten-free diet.
Lactose intolerance
Lactose intolerance is caused by a lactase deficiency, the enzyme responsible for digesting lactose. It is common in adults, particularly those of Asian, African, or Native American descent. Symptoms include diarrhea, abdominal pain, and bloating after consuming dairy products. Diagnosis is based on a lactose tolerance test, and management involves avoiding lactose-containing foods.
Inflammatory bowel disease (IBD)
Inflammatory bowel disease (IBD) includes Crohn’s disease and ulcerative colitis. Typically presents in young adults but can affect older adults as well. Symptoms include chronic diarrhea, abdominal pain, weight loss, and blood in the stool. Diagnosis involves endoscopy and biopsy. Treatment includes anti-inflammatory medications, immunosuppressants, and sometimes surgery.
Chronic pancreatitis
Chronic pancreatitis is characterized by progressive inflammation of the pancreas, leading to the destruction of pancreatic tissue and impaired digestion. It is common in adults with a history of heavy alcohol use or gallstones. Symptoms include steatorrhea (fatty stools), weight loss, and abdominal pain. Imaging and functional tests diagnose chronic pancreatitis. Treatment includes enzyme replacement therapy and dietary modifications.
Small intestinal bacterial overgrowth (SIBO)
Small intestinal bacterial overgrowth (SIBO) results from an excessive growth of bacteria in the small intestine, leading to malabsorption and diarrhea. It is common in older adults and those with previous gastrointestinal surgeries. Symptoms include bloating, flatulence, and chronic diarrhea. A breath test diagnoses SIBO, and treatment involves antibiotics.
Microscopic colitis
Microscopic colitis is an inflammatory colon condition that typically affects older adults. Symptoms include chronic watery diarrhea without blood, often accompanied by abdominal pain. Diagnosis is confirmed through colonoscopy with biopsy. Treatment includes anti-inflammatory medications and dietary changes.
Hyperthyroidism
Hyperthyroidism describes overactivity of the thyroid gland, leading to increased metabolism and diarrhea. It is common in adults, particularly women. Symptoms include weight loss, palpitations, and heat intolerance. Thyroid function tests confirm the diagnosis. Treatment includes antithyroid medications, radioactive iodine, or surgery.
Drug-induced diarrhea
Certain medications, including antibiotics, laxatives, and antacids containing magnesium, can cause chronic diarrhea as a side effect. Symptoms vary depending on the drug but typically resolve with discontinuation of the offending agent.
Diabetic enteropathy
Diabetic enteropathy is a complication of long-standing diabetes. It leads to autonomic neuropathy and gastrointestinal dysmotility, which results in chronic diarrhea. Typically presents in adults with poorly controlled diabetes. Management focuses on optimizing blood glucose control and symptomatic treatment.
Chronic infections
Persistent infections, such as those caused by Giardia, Entamoeba histolytica, or Clostridioides difficile, can cause chronic diarrhea. Common in developing countries and returning travelers. Diagnosis is made through stool testing, and treatment involves appropriate antimicrobial therapy.
Less common but important medical conditions associated with chronic diarrhea in adults
Carcinoid syndrome
Carcinoid syndrome is caused by a neuroendocrine tumor that secretes serotonin and other substances leading to diarrhea, flushing, and wheezing. Typically presents in adults with metastatic disease. Diagnosis is confirmed with imaging and measurement of urinary 5-HIAA levels. Treatment includes somatostatin analogs and surgical resection.
Amyloidosis
Amyloidosis is characterized by the deposition of amyloid proteins in various organs, including the gastrointestinal tract, leading to malabsorption and diarrhea. Typically affects older adults. Diagnosis is made through biopsy and Congo red staining. Treatment is focused on managing the underlying cause and supportive care.
Whipple’s disease
Whipple’s disease is a rare bacterial infection caused by Tropheryma whipplei. It leads to malabsorption and diarrhea and typically affects middle-aged men. Symptoms include weight loss, arthralgia, and chronic diarrhea. A small bowel biopsy and PCR testing confirm the diagnosis. Treatment involves long-term antibiotics.
Zollinger-Ellison syndrome
Zollinger-Ellison syndrome is caused by a gastrin-secreting tumor (gastrinoma), leading to excessive gastric acid production, peptic ulcers, and diarrhea. Typically presents in adults with severe, recurrent peptic ulcers. Diagnosis is confirmed with elevated fasting gastrin levels and imaging. Treatment includes proton pump inhibitors and surgical resection.
Lymphoma
Gastrointestinal lymphomas, particularly those affecting the small intestine, can present with chronic diarrhea. Symptoms may include weight loss, abdominal pain, and fatigue. Diagnosis is made through imaging and biopsy. Treatment includes chemotherapy and sometimes radiation therapy.
Systemic sclerosis (scleroderma)
Systemic sclerosis is a connective tissue disease that can affect the gastrointestinal tract, leading to malabsorption and diarrhea. Typically presents in middle-aged adults. Symptoms include skin thickening, Raynaud’s phenomenon, and gastrointestinal symptoms. Diagnosis is confirmed with serological testing and imaging. Treatment includes immunosuppressants and symptomatic management.
Adrenal insufficiency
Adrenal insufficiency is a condition in which the adrenal glands do not produce enough cortisol, leading to symptoms including chronic diarrhea, fatigue, and weight loss. Cortisol and ACTH levels are used to diagnose this condition, and treatment involves corticosteroid replacement therapy.
Post-surgical syndromes
Chronic diarrhea can occur after certain gastrointestinal surgeries, such as cholecystectomy or small bowel resection, due to altered bile acid metabolism or short bowel syndrome. Management focuses on dietary modifications and medications to reduce diarrhea.
Ischemic colitis
Ischemic colitis occurs when blood flow to part of the colon is reduced, leading to inflammation and diarrhea. Typically affects older adults and those with cardiovascular risk factors. Symptoms include abdominal pain and bloody diarrhea. Diagnosis is made with imaging and colonoscopy. Treatment includes supportive care and addressing the underlying cause.
Radiation enteritis
Radiation enteritis is a complication of abdominal or pelvic radiation therapy, leading to chronic inflammation of the intestines and diarrhea. Typically presents months to years after treatment. Symptoms include abdominal pain, diarrhea, and weight loss. Management includes dietary changes and medications to reduce inflammation.
Clues to aid in the differential diagnosis
The presence of certain symptoms or signs can help narrow down the cause of chronic diarrhea. For example, bloody diarrhea may suggest inflammatory bowel disease or ischemic colitis, while steatorrhea (fatty stools) points toward chronic pancreatitis or celiac disease. Weight loss and systemic symptoms like fever or night sweats raise suspicion for more serious conditions like lymphoma or carcinoid syndrome. A history of recent travel may indicate a chronic infection, and a history of medication use could suggest drug-induced diarrhea.
Advice for patients
Patients experiencing chronic diarrhea should seek medical attention to determine the underlying cause. Treatment will vary depending on the diagnosis but may include dietary modifications, medications to reduce diarrhea, and in some cases, surgery. It is important to stay hydrated and monitor for signs of dehydration, such as dry mouth or decreased urine output. Patients should seek urgent medical care if they experience severe abdominal pain, blood in the stool, or significant weight loss.
Summary
Chronic diarrhea is a common and potentially serious condition in adults, requiring careful evaluation to determine the underlying cause. Irritable bowel syndrome with diarrhea is one of the most common causes, but a wide range of other conditions, including celiac disease, inflammatory bowel disease, and chronic infections, can also be responsible. A thorough history, physical examination, and appropriate diagnostic testing are essential to identify the cause and guide treatment. Early recognition and management are important to prevent complications and improve quality of life.