Irritable Bowel Syndrome (IBS): Symptoms, Diagnosis, and Treatment Options

Irritable bowel syndrome (IBS) is a common disorder of how the gut and brain work together. It causes belly pain along with diarrhea, constipation, or both. IBS does not damage the intestines or cause cancer, and most people can control their symptoms with the right combination of diet, lifestyle, and medicine.

Symptoms

• Belly pain or cramping, often better or worse after a bowel movement
• Bloating and gas
• Diarrhea, constipation, or alternating between the two
• Mucus in the stool
• Feeling that you haven't fully emptied your bowels

IBS is grouped by the main stool pattern: IBS-D (diarrhea), IBS-C (constipation), and IBS-M (mixed).

These are not typical of IBS and should be checked: rectal bleeding, weight loss, anemia, fever, symptoms that wake you at night, trouble swallowing, persistent vomiting, new symptoms after age 45, or a family history of colon cancer, celiac disease, or inflammatory bowel disease.

Causes

The exact cause is unknown. Several factors play a role:

• Gut-brain signaling: the nerves of the gut are more sensitive, so normal gas or movement can feel painful.
• Changes in gut movement: contractions that are too fast (diarrhea) or too slow (constipation).
• A past gut infection: IBS can start after food poisoning or a stomach bug (post-infectious IBS).
• Changes in gut bacteria, including small intestinal bacterial overgrowth (SIBO), which can cause IBS-like symptoms.
• Food triggers and stress, which do not cause IBS but can make symptoms worse.

Diagnosis

IBS is diagnosed from your symptoms (the Rome IV criteria): belly pain at least one day a week over the last 3 months, linked to bowel movements or to a change in how often you go or how your stool looks. Tests help rule out other conditions:

• Blood count and a celiac disease blood test
• For diarrhea: a stool test for inflammation (fecal calprotectin) and infections such as Giardia
• A breath test for SIBO or for lactose or fructose intolerance when appropriate
• Colonoscopy for warning signs or routine screening at 45

Treatment options

Diet

• Low-FODMAP diet: FODMAPs are carbohydrates that ferment in the gut, found in foods such as onions, garlic, wheat, beans, some fruits, and dairy. You limit them for 2 to 6 weeks, then add them back one group at a time to find your personal triggers. A dietitian makes this much easier.
• Soluble fiber such as psyllium (Metamucil) helps both constipation and pain. Insoluble fiber like bran can worsen bloating.
• Eat regular meals and limit caffeine, alcohol, fatty foods, carbonated drinks, and sugar-free sweeteners (sorbitol, mannitol) if they bother you.

Lifestyle

• Regular exercise, good sleep, and stress management.
• Gut-directed therapy: cognitive behavioral therapy (CBT) and gut-directed hypnotherapy, in person or through apps, help many people with IBS.

Medicines for pain and bloating

• Peppermint oil capsules (enteric-coated)
• Antispasmodics such as dicyclomine and hyoscyamine, for cramping
• Low-dose gut-brain neuromodulators, such as amitriptyline or nortriptyline. At low doses they calm gut nerve pain; they are not being used for depression.

Medicines for IBS with diarrhea (IBS-D)

• Rifaximin (Xifaxan): a gut antibiotic taken for 2 weeks; can be repeated if symptoms return
• Eluxadoline (Viberzi): not for people without a gallbladder or with a history of pancreatitis
• Alosetron: for women with severe IBS-D
• Loperamide (Imodium) for diarrhea, and bile acid binders such as cholestyramine when bile acid diarrhea is suspected

Medicines for IBS with constipation (IBS-C)

• Linaclotide (Linzess) and plecanatide (Trulance)
• Lubiprostone (Amitiza)
• Tenapanor (Ibsrela)
• Polyethylene glycol (Miralax) for constipation (it helps stool frequency but not pain)

See constipation and chronic diarrhea for more.

Living with IBS

IBS is a long-term condition, but symptoms often come and go and can be well controlled. Keeping a food and symptom diary helps you and your doctor find patterns. If your symptoms change or warning signs appear, let us know.

Make an appointment

Our gastroenterologists in Temple City care for patients from Arcadia, San Gabriel, Pasadena, Monrovia, Monterey Park, and across the San Gabriel Valley. We accept most PPO plans (see accepted insurances), and our doctors speak English, Vietnamese, and Mandarin. Schedule an appointment or call 626-898-4560.

This article is for general education and is not a substitute for medical advice. Talk with your doctor about your own health.