What is IBS? Rome III criteria - the recurrence of abdominal pain/discomfort at least 3 days out of the month in the past 3 months associated with two or more of the following:

2) onset associated with change in frequency of stool

Updates to the Rome III criteria? The Rome III criteria are commonly used but there are now Rome IV criteria that contain minor tweaks.

Rome IV says pain has to be related to defecation

Rome IV also says the pain lasts for at least one day per week in the last 3 months.

What is the sensitivity and specificity for certain exam findings?

Looser stools at onset of pain, more frequent stools at onset of pain, patient reported visible abdominal distension - 39-58%/70%

IBD - consider CRP because if < 0.5, it is associated with less than 1% probability of having IBD (based on analysis of 4 studies with 800 adults). Also consider fecal calprotectin - again, if <40 less than 1% chance of IBD (based on 8 studies looking at over 1000 adults)

Celiac disease - consider serologic testing because a systematic review of observational studies showed an odds ratio of 4.3 for celiac disease for patients meeting criteria for IBS.

However, if they don’t have these symptoms and they fit the Rome III/IV criteria, you can stop there.

While the differential can be broad, you want to look out for red flag symptoms like nighttime awakenings from pain, age greater than 60 at onset, family history of bowel or ovarian cancer, family history of IBD, unintended weight loss, rectal bleeding/melena.

What causes IBS? We aren’t sure but there are many proposed mechanisms including small intestine bacterial overgrowth, imbalance in microflora, allergies and neurologic/muscular hypersensitivity. More research is pointing to a biological basis of disease.

Talley NJ et. al. The irritable bowel syndrome and psychiatric disorders in the community: is there a link? Am J Gastroenterol. 2001 Apr;96(4):1072-9. PMID: 11316149 .

There are also a number of associated conditions like fibromyalgia, migraines and depression when you look at population studies, However, one study found that psychiatric disorders in young people was not associated with IBS.

There appears to be a relation between antibiotic use with number needed to harm of 4-6 for functional bowel symptoms over the following four months after antibiotic use.

Thabane M et. al. Systematic review and meta-analysis: The incidence and prognosis of post-infectious irritable bowel syndrome. Aliment Pharmacol Ther. 2007 Aug 15;26(4):535-44. Review. PMID: 17661757 .

Ford AC et. al. Effect of antidepressants and psychological therapies, including hypnotherapy, in irritable bowel syndrome: systematic review and meta-analysis. Am J Gastroenterol. 2014 Sep;109(9):1350-65. PMID: 24935275 .

TCA: Same review of 11 RCTs including 750 patients comparing placebo to TCA’s found NNT of 4 to 8 with less side effects than SSRIs.

SSRIs: Systematic review in 2014 of 7 RCTs showed NNT 3 to 7 for symptom reduction with 32% reduction in symptoms compared to placebo.

Antidepressants: both SSRIs and TCA’s have the highest quality evidence for treatments in IBS.

Kaptchuk TJ et. al. Placebos without deception: a randomized controlled trial in irritable bowel syndrome. PLoS One. 2010 Dec 22;5(12):e15591. PMID: 21203519 .

Placebo: open-label RCT (patients knew they were taking a placebo pill) among 80 adults showed improvement in global symptom score.

Medications: evidence in this area is also weak

Bijkerk CJ et. al. Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebo controlled trial. BMJ. 2009 Aug 27;339:b3154. PMID: 19713235 .

RCT in 2009 comparing psyllium to bran or placebo showed NNT waned from 2 to 6 over 3 months.

Moayyedi P et. al. The effect of fiber supplementation on irritable bowel syndrome: a systematic review and meta-analysis. Am J Gastroenterol. 2014 Sep;109(9):1367-74. PMID: 25070054 .

Soluble fiber (psyllium) may improve symptoms (weak recommendation by the American College of Gastroenterology, based on 14 trials of 900 patients with NNT of 7 to improve symptoms). This effect seems to wane over time.

Insoluble fiber like vegetables might help constipation but worsens other IBS symptoms.

One RCT examined antibody-guided elimination of foods based on IgG levels compared to a sham diet. They found reduction of symptoms of only 38 on a 500-point scale.

Ondansetron: A 2014 RCT including 120 patients showed NNT of 2 for global symptoms with ondansetron 8mg three times daily. Not FDA approved for this use.

Ford AC et. al. Efficacy of 5-HT3 antagonists and 5-HT4 agonists in irritable bowel syndrome: systematic review and meta-analysis. Am J Gastroenterol. 2009 Jul;104(7):1831-43; PMID: 19471254 .

Alosetron (Lotronex): FDA approved for IBS with diarrhea only in women. Like ondansetron, its a 5-HT receptor blocker. Systematic review of 8 trials including 5000 patients found NNT of 8 for global improvement in IBS symptoms and abdominal pain. Side effect is ischemic colitis. Prescribers have to register with Risk Evaluation and Mitigation Strategy (REMS), following a specific protocol.

Menees SB et. al. The efficacy and safety of rifaximin for the irritable bowel syndrome: a systematic review and meta-analysis. Am J Gastroenterol. 2012 Jan;107(1):28-35; PMID: 22045120 .

Rifaximin: Best evidence comes from 2012 systematic review of five RCTs including 1800 patients that showed NNT of 10-11. Follow-up was only 3 to 12 weeks with no difference in adverse effects. It is taken as 550 mg tablet three times a day. It costs about $1300 for the two week treatment. You can repeat two more times.

Eluxadoline (Viberzi): FDA approved 2015, mixed opioid activity in the gut. The two industry-sponsored RCTs showed questionable efficacy. It is taken twice a day and costs about $1000 per month. It can’t be taken by those with a history of severe constipation, pancreatitis, biliary duct obstruction, liver impairment, or those who drink three or more alcoholic beverages daily.

Loperamide is NOT recommended. Though it seems to help with diarrhea it does not improve overall symptoms.

Shah E et. al.. Evaluation of harm in the pharmacotherapy of irritable bowel syndrome. Am J Med. 2012 Apr;125(4):381-93. PMID: 22444104 .

The major side effects to worry about are anticholinergic effects but recent review in 2012 showed no difference in adverse effects as compared to placebo.

Ruepert L et. al. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database Syst Rev. 2011 Aug 10;(8) PMID: 21833945 .

Enteric coated peppermint oil capsules 187mg to 325mg three times a day are also among the most effective.

Most effective was dicyclomine (Bentyl) at 20mg four times a day.

Antispasmodics: Cochrane review in 2011 looking at 29 trials comparing antispasmodics to placebo found NNT of 4 to 11 and higher rates of improvement in global assessment.

Avoid lactulose.

Polyethylene glycol - no evidence it improves symptoms.

NuLytley (GoLytley with electrolytes) has been shown to improve the number of weekly bowel movements. A bottle runs about $10-20.

Linaclotide (Linzess): FDA approved for IBS constipation and chronic idiopathic constipation. A 2013 review of 7 RCTs comparing it to placebo showed significant improvement in overall symptoms with NNT of 7. It costs $300 per month for once daily 290mcg.