Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that is estimated to affect between 25 and 45 million people in the United States, and about 5–10% of the population worldwide. IBS symptoms include abdominal pain or discomfort, bloating and changes in stool frequency and/or appearance.

IBS-D is a type of IBS that includes diarrhea (i.e., stools that are loose or more frequent than usual).

Who gets IBS-D?

IBS-D can affect anyone, but it’s more common among two particular groups: young women and older people.

What causes IBS-D?

The cause of IBS-D is unknown but it is likely due to many factors.

In some patients, rapid contractions of the intestine may cause pain and faster stool movement. This gives the intestine less time to absorb water from digested food, which can lead to loose or watery stools.

Some patients develop IBS-D after an infection in the intestine or gut. This post-infectious IBS can last for up to several months or even years.

Sensitivity or allergies to certain foods may also lead to IBS-D in some people. For example, a lot of patients develop IBS-D symptoms after they eat foods that contain gluten or lactose. Unfortunately, routine allergy testing isn’t a reliable way to determine if specific foods cause a person’s IBS-D.

Some IBS-D patients simply have a more sensitive gut than others, so they feel more intense pain or discomfort when they have gas or intestinal contractions.

Recent research also suggests that changes in the types or number of normal bacteria that are living in a person’s gut may contribute to IBS-D.

While stress or anxiety do not cause IBS-D, they can make a person’s IBS symptoms worse.

What are the symptoms of IBS-D?

Common IBS-D symptoms include frequent abdominal pain or discomfort, abdominal bloating and diarrhea. People with IBS-D often report that they’ve experienced these symptoms for months (or even years). They describe the pain as abdominal cramps that come and go, often improving after a bowel movement.

People with IBS-D say that while awake, they have frequent bowel movements that are usually loose and sometimes contain mucus. Diarrhea that wakes a person up on a regular basis is not normally associated with IBS-D, so a patient should mention this to their doctor if it’s something they’re experiencing. Triggers for pain and diarrhea vary for each patient with IBS-D.

How do gastroenterologists diagnose IBS-D?

Gastroenterologists diagnose IBS-D by reviewing the patient’s medical history and conducting a thorough physical examination. These specialists consider an array of symptoms and factors when they diagnose, including the presence of abdominal pain or discomfort and/or any changes in bowel movements. While clinical symptoms alone are sufficient to make a diagnosis of IBS-D, your gastroenterologist may order additional testing (e.g., blood work, imaging studies or endoscopy) to rule out other conditions that may present similarly to IBS-D.

How do gastroenterologists treat IBS-D?

IBS-D isn’t life-threatening but can affect a person’s quality of life. Since there is no known cure for this disease, gastroenterologists strive to reduce patients’ symptoms to the greatest extent possible. Some of the treatments that they use are designed to reduce a patient’s abdominal pain, discomfort or bloating, while others focus on improving one’s bowel function. These treatments can include lifestyle modifications, dietary changes, psychosocial therapy and medication.

Dietary Therapy

Some people who have mild IBS-D can control their symptoms by changing their lifestyle and diet. There is no reliable test to determine which foods trigger IBS-D symptoms, but gastroenterologists recommend that people who have IBS-D avoid food that contains lactose or gluten. Other steps that people can take to reduce the effects of IBS-D include consuming a diet that is low in both FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) and fructose, which is a type of sugar that is found in many types of fruit. Avoiding foods that increase gas production — such as onions, celery, carrots, beans, prunes, wheat, alcohol or caffeine — can also help.

Gastroenterologists often encourage IBS-D patients to consult with a dietitian.

Medical Therapy

Along with a change in diet, gastroenterologists often help patients who have IBS-D with medicine. This includes:

• Medications to reduce abdominal discomfort: Prescription antispasmodics like dicyclomine and hyoscyamine relax the muscle in the intestine, which may reduce pain, bloating and the urgent need to go to the bathroom. Over-the-counter medicine that contains peppermint oil may offer similar benefits.
  
  
• Medications to improve bowel function: For people whose primary IBS-D symptom is diarrhea, the first treatment option that gastroenterologists normally recommend is fiber supplements. Fiber makes one’s stool less loose or watery. Anti-diarrheal medications like loperamide may also help on this front.
  
  Once it is produced by the liver, most bile is reabsorbed by the body as it moves down the small intestine. But if enough bile does not get reabsorbed before it reaches the large intestine (i.e., colon), it can cause diarrhea. Consequently, gastroenterologists sometimes prescribe medicine that binds this extra bile to reduce a patient’s diarrhea.
  
  When these medications don’t prove effective, gastroenterologists can use other medical options to care for an IBS-D patient — including antibiotics and medications that are specifically designed to reduce pain in the intestine.
• Probiotics: Gut bacteria play an important role in one’s normal bowel health and function. Probiotics are foods or pills that contain live bacteria that may promote gut health. In some cases, a gastroenterologist will recommend that a patient who has IBS-D take probiotics because it may reduce their abdominal discomfort, bloating and gas. However, it is important to note that medical experts are still evaluating probiotics from several key perspectives, including the overall effectiveness, which types offer the greatest benefits and the optimal amounts that people should take.
  
  
• Antibiotics: Antibiotics are another way to provide relief for IBS-D symptoms, but there are some potential risks associated with prolonged use, including losing effectiveness over time and the potential for developing serious infections. The risks can be reduced when a non-absorbable antibiotic like rifaximin is used.
  
  
• Antidepressants: Certain antidepressants have been shown to improve abdominal pain and gut function by decreasing the sensitivity of the nerves in the GI tract. Of note, some patients with IBS-D may experience anxiety and/or depression as a result of their gut symptoms or worsening of these conditions can lead to more IBD-D flares. In such situations, antidepressants may provide an additional tool for managing these conditions.

When should someone see a gastroenterologist for IBS-D?

People who have chronic symptoms of IBS-D should schedule an appointment with a gastroenterologist (or ask for a referral from their primary care physician). These highly and specially trained physicians can provide patients who have IBS-D with a proper diagnosis and treatment plan — including over-the-counter and prescription medicine — that will enable patients to reduce and manage their symptoms, improve bowel function and be more comfortable.

Patients should always let their gastroenterologist know about any personal or family history of gastrointestinal diseases like cancer, inflammatory bowel disease, celiac disease or any abdominal discomfort or symptoms that they have that are associated with weight loss, bleeding or iron deficiency (low levels of iron based on blood tests) — especially after they turn 50.