What Is Irritable Bowel Syndrome With Constipation (IBS-C)?

Constipation-predominant irritable bowel syndrome (IBS-C) is a condition characterized by chronic constipation with associated abdominal pain.

It's a subtype of irritable bowel syndrome (IBS). About one-third of people with IBS have the IBS-C type.

IBS-C is a functional gastrointestinal disorder. These are gastrointestinal (GI) disorders that produce symptoms but have no identifiable cause despite standard diagnostic tests. These disorders can cause significant distress.

Diet changes, fiber supplements, medication, and behavior changes may reduce the symptoms of IBS with constipation. Some people also try the low-FODMAP diet to know which foods to avoid for symptom relief.

IBS-C Symptoms

The main symptoms of IBS-C are frequent constipation accompanied by abdominal pain when having a bowel movement.

Criteria

It's normal to have one or two bowel movements per day, or not to have one every day. Characteristics of constipation include:

• Having fewer than three bowel movements in a week
• Lumpy or hard stools
• The need to strain during a bowel movement

The Rome IV criteria define IBS based on specific signs and symptoms. According to these criteria, IBS-C is specifically defined as a condition in which:

• Constipation associated with pain occurs at least three days per month
• Symptoms have persisted over the past three months
• At least 25% of stools are hard and less than 25% of stools described as soft

Associated Symptoms

In addition to the Rome IV criteria for IBS-C, you may experience other symptoms if you have constipation-predominant IBS.

Common symptoms of IBS-C include:

• Abdominal pain
• Gas and bloating
• A feeling of incomplete evacuation
• Mucus on the stool
• A sensation of blockage in the anus or rectum
• Need to use fingers to remove stool (digital evacuation)

Loose stools rarely occur with IBS-C, unless using a laxative.

IBS-C vs. Chronic Idiopathic Constipation (CIC)

IBS-C and chronic idiopathic constipation (also known as functional constipation) share many of the same symptoms.

According to the Rome IV criteria, the biggest difference is:

• IBS-C causes abdominal pain and discomfort alongside constipation.
• Idiopathic constipation is typically painless.

Gastroenterologists question if the two conditions are manifestations of the same disorder along a single disease spectrum, rather than two separate disorders.

However, the two conditions respond to different treatments. This suggests they may be two different conditions. At this point, the answer isn't clear.

Causes of IBS-C

There is no known cause of IBS-C. The symptoms occur because the digestive system does not function as it should, but there is no identifiable cause for this.

Dyssynergic defecation, which is dysfunction of the pelvic floor muscles, is often present in people with IBS-C.

How Is IBS-C Diagnosed?

IBS-C is traditionally a diagnosis of exclusion. This means that it's only diagnosed after ruling out other disorders that may cause your symptoms. However, diagnostic guidelines released in 2021 by the American College of Gastroenterology (ACG) aim to make it a "positive" diagnosis instead.

The ACG says its recommended diagnostic method will make the process faster and get you on proper treatments sooner. It's not clear how the guidelines, explained below, will change your healthcare provider's IBS diagnostic process. Either method can diagnose you accurately.

Diagnosis of Exclusion

If your healthcare provider suspects IBS-C, they'll likely:

• Ask about your symptoms
• Do a medical exam
• Order blood work
• Conduct a stool sample analysis.

Other tests may be recommended depending on your symptoms and medical history. These include imaging tests and interventional tests such as colonoscopy.

If your symptoms match the diagnostic criteria for IBS-C, and there is no evidence of any red-flag symptoms or other illness, you can be diagnosed with IBS-C.

Positive Diagnosis

Rather than doing extensive testing, the ACG's recommended diagnostic method includes focusing on your medical history and physical exam in addition to key symptoms, including:

• Abdominal pain
• Altered bowel habits
• Minimum of six months of symptom duration
• The absence of alarm features of other possible conditions
• Possible anorectal physiology testing if a pelvic floor disorder is suspected or if constipation doesn't respond to standard treatments

No further testing is recommended for IBS-C.

IBS-C Treatment

The ACG treatment protocol for IBS-C includes diet modifications, supplements, prescription medications, and lifestyle and behavioral changes.

Diet and Supplements

• Diet changes: A short-term trial of a low-FODMAP diet can help you identify foods that contribute to your symptoms so that you know which foods to avoid.
• Fiber: Slowly increasing the amount of fiber, especially soluble fiber, in your diet (or through supplements) may promote more frequent bowel movements.
• Peppermint oil: Enteric-coated capsules of peppermint oil may help your intestinal muscles relax, lower pain and inflammation, and eliminate harmful bacteria.

Prescription Medications

• Amitiza (lubiprostone): Increases fluid secretion in the intestines
• Linzess (linaclotide) or Trulance (plecanatide): Increase bowel movements
• Zelnorm (tegaserod): Speeds digestion and reduces hypersensitivity in the digestive organs (recommended only for women under 65 with no cardiovascular risk factors and no response to other medications)
• Tricyclic antidepressants: Prescription medications that may affect the nerves of the GI system through changing activity of the neurotransmitters norepinephrine and dopamine

Behavior Changes

• Cognitive behavioral therapy or gut-directed hypnotherapy: May help establish healthier habits and overcome emotional components of IBS
• Biofeedback: Recommended for those with dyssynergic defecation

Not Recommended

The ACG says some common IBS-C treatments don't have enough evidence of effectiveness to be recommended. These include:

• Antispasmodic drugs
• Probiotic supplements
• Polyethylene glycol (an ingredient in some over-the-counter laxatives)
• Fecal transplant