Irritable Bowel Syndrome (IBS) is identified clinically as a “syndrome” and as such it is defined by a collection of symptoms rather than a definite patho-anatomical disease entity with pathological markers. Various clinical (and patient experience) features of IBS have attracted their own names: irritable colon, spastic colon, nervous colon, colitis, mucous colitis. The cause of IBS has long been considered to be “unknown.” Early theories of IBS implicated psychological problems, psychosomatic or other mental disorders.
Recently however, expanded scientific understanding of the human digestive system has shed light on the complexity of interactions among the gut, the nervous system and the micro-organisms that populate the human gut and can cause disordered function. The outcomes of this disordered function causes the wide variety of patient experienced symptoms: pain, constipation, diarrhea, gas, bloating, etc.
Symptoms of IBS are well recognized and typically show waxing and waning of various combinations of abdominal pain, cramping or bloating typically relieved by passing a bowel movement, excess gas, diarrhea, constipation (sometimes both), and mucus in the stool. Sets of clinical criteria have been formalized to more consistently define IBS. The Manning Criteria developed in 1978 for a diagnosis of IBS include:
- Sensation of incomplete evacuation.
- Pain relieved with defecation.
- More frequent stools at the onset of pain.
- Looser stools at the onset of pain.
- Visible abdominal distention.
- Passage of mucus.
More recently the Rome IV criteria considers IBS of 4 types: 1) IBS with constipation (IBS-C), 2) IBS with diarrhea (IBS-D), 3) mixed IBS, and unclassified IBS.[i],[ii]
Irritable bowel syndrome (IBS) affects an estimated10-15% of the US population. IBS is second only to upper respiratory illness as a cause of absenteeism from work and school. Among those who report IBS symptoms, and 40% or more have not had a formal diagnosis or medical treatment.[iii] People who suffer with IBS experience significant disruption in their lives missing work and leisure activity, modifying daily plans around trips to the bathroom, and putting up with abdominal pain, gas, bloating and the anxiety of never knowing when these symptoms may strike.
Despite the prevalence of IBS and the high social costs of IBS (estimated at ~$21 billion in medical bills and lost productivity), the condition continues to be incompletely understood and treatments are not reliably effective.
Our next post will explore recent developments in the understanding of the human gut in IBS.
[i] Schmulson MJ, Drossman DA. What is new in Rome IV. Neurogastroenterol Motil. 2017
[ii] 1 Lacy BE, et al. Bowel Disorders. Gastroenterology. 2016;150:1393-1407; Rome III Diagnostic Criteria for Functional Gastrointestinal Disorders.
[iii] Sayuk GS, et al. Am J Gastroenterol. January 2017.