How Diarrhea-Predominant IBS (IBS-D) Is Treated

Diarrhea-predominant IBS (IBS-D) is a subtype of irritable bowel syndrome that causes frequent bouts of diarrhea with abdominal pain and bloating. IBS-D is considered a disorder of gut-brain interaction (previously called a functional gastrointestinal disorder), in which there is no visible disease to account for the symptoms.

The diagnosis of IBS-D is based on the exclusion of all other possible causes. The condition can often be managed with changes in your diet, while certain over-the-counter (OTC) and prescription drugs can also help ease pain and diarrhea.

This article explains the causes and symptoms of IBS-D, including how this disorder is diagnosed and treated.

How Are IBS-D Symptoms Different?

The primary symptoms of all three subtypes of IBS are abdominal pain or discomfort. With diarrhea-predominant IBS, there will also be:

• Frequent bowel movements
• Loose or watery stools
• A feeling of urgency (like you need to run to the bathroom)
• Gas and bloating
• Abdominal cramping
• Tenesmus (a sensation that your bowel is never empty)
• Mucus in the stool
  

According to the diagnostic criteria for IBS, symptoms must occur at least once a week for at least three months.

Some people with IBS-D will suddenly stop having diarrhea and meet the diagnostic criteria for constipation-predominant IBS (IBS-C). If you switch back and forth between diarrhea and constipation, you are said to have mixed-type IBS (IBS-M).

What Causes IBS-D?

All forms of IBS are thought to be caused by the dysfunction of the gut-brain axis. This is the biochemical signaling between the central nervous system (involving the brain and spinal cord) and the gastrointestinal system.

These communications, in turn, direct all of the other systems that regulate digestion, including the endocrine system (which directs the production of digestive enzymes) and the autonomic nervous system (which regulates involuntary functions like the muscular contractions of the intestines).

When the gut-brain axis is working as it should, your bowel movement and stool consistency will be normal. If the communications go awry, gut motility and digestive enzyme production can suddenly increase, leading to diarrhea, cramping, and other symptoms of IBS-D.

While the cause of this dysfunction is unknown, there are several explanations as to why these systems will suddenly speed up. They include:

• Food intolerance or allergies
• Gut dysbiosis (an imbalance in organisms in the intestine)
• Small intestinal bacterial overgrowth (SIBO)
• Idiopathic bile acid malabsorption (a condition in which the digestive enzyme bile builds up rather than being absorbed by the intestines)
  

How Is ISB-D Diagnosed?

You may meet the diagnostic criteria for IBS-D if you have the characteristic symptoms and they happen at least once weekly for no less than three months. However, to confirm the diagnosis, your healthcare provider will need to exclude all other possible causes.

This is an important step because it may reveal an otherwise treatable condition—or ones that are serious and need immediate, aggressive treatment.

Examples include:

• Celiac disease
  
• Colon cancer
• Crohn’s disease
• Dyssynergic defecation
• Giardiasis
• Non-celiac gluten sensitivity
• Thyroid disease
• Ulcerative colitis

As part of the differential diagnosis, various tests and procedures may be ordered, including blood tests, stool cultures, abdominal ultrasound, hydrogen breath test, endoscopy, and biopsies.

How Is IBS-D Best Treated? 

If you have been diagnosed with IBS-D, your treatment plan may involve dietary changes and OTC or prescription drugs. The selection of treatment is based on the severity and frequency of your symptoms.

Diet

The American College of Gastroenterology recommends that all people with IBS try a low-FODMAP diet to see if it helps ease symptoms.

FODMAP stands for “fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.” These are short-chain carbohydrates (sugars) that the small intestine can’t fully absorb and end up fermenting the gut, causing gas and pain.

People with IBS-D may benefit from other dietary changes, such as:

• Eating smaller meals
• Avoiding high-fat meals
• Avoiding fried foods
• Keeping a food diary to identify and avoid food triggers

IBS-D symptoms may also be reduced with mind/body therapies or cognitive-behavioral therapy (CBT) to help ease stress that contributes to IBS symptoms.

Medications

There are certain prescription drugs approved for the treatment of IBS as well as OTC or prescription medications used off-label to relieve symptoms.

OTC drug options include:

• Peppermint oil
• Probiotics
• Anti-diarrheal drugs, like Imodium (loperamide)
• Soluble fiber supplements

Prescription drug options include:

• Antidepressants like Elavil (amitriptyline) and Tofranil (imipramine) to slow motility and ease pain
  
• Antispasmodics like Levsin (hyoscyamine) to reduce gut cramping and pain
• Xifaxan (rifaximin), a targeted antibiotic
• Prevalite (cholestyramine), a bile acid
• Viberzi (eluxadoline), a targeted opioid medication
  

Summary

Diarrhea-predominant IBS (IBS-D) is a form of irritable bowel syndrome that causes frequent loose stools along with abdominal pain, cramping, gas, bloating, and mucus. It can be diagnosed if these symptoms occur at least once weekly for three months and all other causes have been excluded. The treatment may involve a FODMAP diet and targeted drugs like Viberzi and Xifaxan.