Chronic Diarrhea Causes and Consequences

Frequent diarrhea lasting longer than a few weeks is described as chronic diarrhea, whether it occurs every day or every few days. The causes vary and can be easy to address (by changing medication, for example) or serious health problems that need to be evaluated and treated, such as ulcerative colitis and Crohn's disease. Diarrhea itself can, over time, cause new health problems as well.

Diarrhea is most commonly described as frequent, watery stools. If you experience symptoms for several weeks, then you have chronic diarrhea and should be evaluated by a doctor.

Types of Diarrhea

The colon, also known as the large intestine, is responsible for forming solid waste from the unabsorbed remains of the food you eat. Fluid flows into the colon as part of that waste, which allows the stool to pass through the colon more smoothly. Muscles in the colon move the stool along to the rectum for passage out of the body.

When something disrupts the digestive process, causing too much liquid to be eliminated or the solid waste to pass too quickly through the large intestine, diarrhea can result.

Most people have experienced short-term (acute) diarrhea, usually as the result of a gastrointestinal infection. Chronic diarrhea, on the other hand, is less common and is typically caused by medical conditions, allergies, medications, or chronic infections.

Your doctor may describe your diarrhea based on the causative physical mechanisms:

  • Osmotic: Excessive fluid flow into your intestine, often as a result of excess material that cannot be absorbed
  • Secretory: Lack of fluid return from your intestines back into your body
  • Motility Issues: Due to a problem with the movement of your intestines, which can result from nerve damage or muscle dysfunction

You may also have a combination of more than one of the above.

Causes

There are many potential causes of chronic diarrhea, and it's possible that more than one may be at play in your particular case.

Medical Conditions

An underlying medical condition could very well be at the root of your symptoms. As many conditions that can cause diarrhea can be adequately managed with proper treatment, it's important to bring what you are experiencing up to your doctor so you can get a proper diagnosis and treatment plan, if you don't have one already, or revisit a regimen that's already in place if it's insufficient.

A few that may be considered include:

  • Inflammatory Bowel Diseases: Inflammatory bowel diseases (IBD) such as Crohn's disease and ulcerative colitis can cause intermittent, chronic diarrhea. Diarrhea, stomach pain, rectal bleeding, fever, and weight loss may occur for weeks or months on end, often resolving for a period of time before recurring. With these conditions, diarrhea may alternate with constipation or "pencil" (very thin) stools.
  • Food Sensitivities: Several food sensitivities can cause chronic diarrhea, either due to allergic responses or intolerance.
  • Infections: Sometimes gastrointestinal infections either don't resolve, have a tendency to recur, or are followed by other infections, resulting in lingering infections and diarrhea. Some parasites, such as Giardia, are not as easily recognized as other gastrointestinal infections, so they are more likely to be misdiagnosed, linger, and cause chronic diarrhea.
  • Colon Cancer: Early-stage colon cancer rarely causes any symptoms and is a rare cause of chronic diarrhea accompanied by bloody stools and weight loss.

This list, however, is just the beginning, and there are two notable consequences of some of these and other health conditions (as well as circumstances) that can be significant if not the factors that link them to chronic diarrhea.

Malabsorption

Malabsorption is caused by any condition that hampers the processes your body uses to absorb nutrients. Crohn's disease and Giardia are two examples.

Some diseases cause malabsorption of fats, such as chronic pancreatitis, alcoholic liver disease, cystic fibrosis, and tropical sprue, and these tend to cause a distinct kind of diarrhea called steatorrhea.

Lactose intolerance (lactase deficiency) causes diarrhea because the lactose in dairy products isn't broken down in the duodenum, causing poor absorption of sugars and fluids. (Non-absorbable sugars in some candies and food additives can cause malabsorptive diarrhea in the same way lactose can for some.)

Celiac disease can also cause malabsorption. Though celiac often causes stomach pain, diarrhea, fatigue, and weight loss that improves once gluten-containing foods are discontinued, just as with a gluten insensitivity, it is actually an autoimmune condition that's triggered by antibodies that react to gluten. Celiac disease can be life-threatening.

Malabsorption can also be idiopathic (without a known cause) or the result of factors such as excessive antibiotic use, chemotherapy medications, radiation therapy, or gastric bypass.

Motility Issues

Conditions and disorders that affect gastric motility, the rhythmic movement of food and waste through the digestive tract, can cause chronic diarrhea for varying reasons.

Hyperthyroidism often causes diarrhea because excessive thyroid hormones stimulate intestinal movements and impair nutrient absorption.

Diabetes can cause nerve damage and may result in a chronic condition called autonomic neuropathy, which impairs the function of internal organs, possibly resulting in chronic diarrhea. When diabetes produces high blood sugar, it can also cause malabsorption that results in bouts of diarrhea, though this is rarer.

Other motility disorders include irritable bowel syndrome and gastroparesis.

Medications

In addition to malabsorption concerns related to some medications, as mentioned above, some drugs can induce diarrhea either as an allergic reaction or as a normal medication side effect. You can develop chronic medication-induced diarrhea even if you have already been taking a particular medicine, such as Metformin, without problems for years.

Because antibiotics alter the balance of bacteria that line your intestines, some can actually end up causing infectious diarrhea.

Consequences

If you have chronic diarrhea, you can experience serious health problems, even if your diarrhea is caused by a situation that isn't dangerous, such as a food allergy.

  • Nutrition: Chronic diarrhea can cause you to become dehydrated, as your body loses too much fluid. You can also miss out on vitamins, minerals, proteins, and fats when your diarrhea is associated with a lack of absorption of these vital nutrients. And, chronic diarrhea can also result in weight loss if you aren't absorbing enough carbohydrates and calories from the food you eat.
  • Bleeding and Irritation: Chronic diarrhea can cause irritation of the colon or the rectum, potentially resulting in fragile tissue and bleeding.
  • Dehydration: When you lose fluid in the stool, you can become dehydrated. Chronic diarrhea causes mild dehydration, which makes you thirsty. Severe dehydration results in decreased urine volume, dark urine, fatigue, lightheadedness, and low blood pressure. Interestingly, dehydration is more dangerous if you have acute diarrhea, as your body tends to compensate better for dehydration if you have chronic, recurrent diarrhea.

When to See a Doctor

If you have long-term diarrhea, don't put off seeing your doctor. Your doctor may order blood tests or a stool sample to check for blood in the stool or an infection due to bacteria, a virus, or a parasite. You may need a colonoscopy or flexible sigmoidoscopy, which may identify IBD or early signs of colon cancer. Even if it turns out that you have colon cancer, it is usually curable, particularly if detected early.

Signs that you should see your doctor include:

  • Your diarrhea has lasted for more than two weeks (either intermittently or the entire time).
  • You see blood in or on your stool.
  • You have persistent abdominal cramps or severe pain.
  • You're vomiting a lot.
  • You experience alternating constipation and diarrhea.
  • You notice you're losing weight even though you haven't been trying to.

A Word From Verywell

Persistent diarrhea is hard to ignore. Most of the time, the reason behind it is not life-threatening, but the cause and the potential health complications need to be addressed so that you can maintain your energy, nutrition, and a healthy weight.

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