Irritable bowel syndrome overview
| https://https://www.youtube.com/watch?v=9f5wxYW0Z3k%7C350}} |
|
Irritable bowel syndrome Microchapters |
|
Differentiating Irritable bowel syndrome from other Diseases |
|---|
|
Diagnosis |
|
Treatment |
|
Case Studies |
|
Irritable bowel syndrome overview On the Web |
|
American Roentgen Ray Society Images of Irritable bowel syndrome overview |
|
Risk calculators and risk factors for Irritable bowel syndrome overview |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
Irritable bowel syndrome is a functional bowel disorder characterized by abdominal pain and changes in bowel habits which are not associated with any abnormalities seen on routine clinical testing. The disease is fairly common and makes up 20–50% of visits to gastroenterologists. Lower abdominal pain, and bloating associated with alteration of bowel habits and abdominal discomfort relieved with defecation are the most frequent symptoms. The abdominal pain type is usually described in a patient as either diarrhea-predominant (IBS-D), constipation-predominant (IBS-C) or IBS with alternating stool pattern (IBS-A). In some individuals, IBS may have an acute onset and develop after an infectious illness characterised by two or more of the following: fever, vomiting, acute diarrhea or positive stool culture. This post-infective syndrome has consequently been termed "post-infectious IBS" (IBS-PI) and is acute onset Rome II criteria positive. This condition is more homogeneous, being mostly IBS-D and is drawing much clinical investigation.
Chronic functional abdominal pain (CFAP) is quite similar to, but less common than IBS. CFAP can be diagnosed if there is no change in bowel habits.
Because of the name, IBS can be confused with inflammatory bowel disease (IBD).
Historical Perspective
Irritable Bowel syndrome(IBS) was first mentioned in the Rocky Mountain Medical Journal in 1950. IBS was described as a psychosomatic disorder, not explained by any biochemical or structural abnormalities. Apley and Nash conducted a famous study on 1000 children in Bristol, United Kingdom and were the first to describe Recurrent Abdominal Pain (RAP) as the predominant feature of IBS. In 1978, the first diagnostic criteria i.e. the Manning criteria was described. It did not specify any required duration for the symptoms of IBS. The subsequent criteria saw a reduction in the required duration of symptoms to facilitate early diagnosis and treatment. In Rome in 1995, an international group of gastroenterologists defined the diagnostic criteria for IBS and this was published in 1999 under the title of the Rome II criteria. This criteria underwent modification and was described as the Rome III criteria. Since June 2016, the criteria being followed is the Rome IV criteria.
Classification
Irritable bowel syndrome (IBS) may be classified according to Rome IV criteria into four sub types/groups: IBS with predominant constipation , IBS with predominant diarrhea, IBS with mixed bowel habits,and IBS unclassified. In addition, IBS occurring subsequent to GI infections is known as Post infectious-IBS or PI-IBS. The rationale behind these different sub types is to maintain consistency of patient selection. This increases understanding of pathophysiological mechanisms, aids in effective diagnosis, treatment and patient recruitment for clinical trials.
Pathophysiology
IBS is caused by the complex interaction of various factors such as intrinsic gastrointestinal factors, CNS dysregulation and psychosocial factors, genetic and environmental factors. Intrinsic gastrointestinal factors include motor abnormalities, visceral hypersensitivity, immune activation and mucosal inflammation, altered gut microbiota and abnormal serotonin pathways. Visceral hypersensitivity is a decreased threshold for the perception of visceral stimuli that affects spinal excitability brain stem and cortical modulation, activation of specific gastrointestinal mediators and recruitment of peripheral silent nociceptors. Immune activation and mucosal inflammation involves an interaction of lymphocytes, mast cells and proinflammatory cytokines. Environmental factors encompass dietary changes and infections. Psychosocial factors such as stress, anxiety and depression directly shape adult connectivity in the executive control network consisting of structures such as the insula, anterior cingulate cortex and the thalamus. Semipermanent/permanent changes in complex neural circuits lead to central pain amplification and contribute to abdominal pain in IBS patients. The dorsolateral prefrontal cortex activity (responsible for vigilance and alertness of the human brain) and the mid-cingulate cortex (engaged in attention pathways and responses) is reduced in IBS patients, which may lead to alterations in the subjective sensations of pain. Genetic factors also play a role in IBS. It has high twin concordance and familial aggregation. It is associated with Single nucleotide polymorphisms (SNPs) in genes involved in immune activation, neuropeptide hormone function, oxidative stress, nociception, permeability of the GI tract, host-microbiota interaction, inflammation, and TNF activity.
Causes
There is no definite cause that has been established for irritable bowel syndrome (IBS). However, an interplay of several factors contribute to the development of IBS such as emotional disturbances, stress, adverse early life events, history of inflammatory bowel disease, and acute gastrointestinal infections. Less common causes of IBS include genetics and hormonal changes.
Differentiating IBS from Other Diseases
Irritable bowel syndrome must be differentiated from other diseases that cause diarrhea, constipation, and abdominal pain, such as Celiac disease, Inflammatory bowel disease(Crohn's disease and Ulcerative colitis) Thyroid disease (Hyper or Hypothyroidism), strictures due to ischemia, diverticulitis or ischemia, among others.
The differential diagnosis for Irritable bowel syndrome can be listed based on predominant symptoms, such as constipation predominant, diarrhea predominant and pain predominant diseases.
Epidemiology and Demographics
IBS is an extremely common disorder in the population. The incidence of IBS is approximately 200 per 100,000 individuals worldwide. The prevalence of IBS is approximately 11,200 per 100,000 individuals worldwide. The prevalence of IBS varies with geographical and demographic distribution. Females are more commonly affected by IBS than males. The female to male ratio is approximately 1.5-3. The prevalence of IBS in USA and Europe is 10,000-20,000 per 100,000 individuals. In USA and Australia, 1 in every 10 people fulfill the Rome criteria for IBS. In Asia, Africa and South America, IBS is becoming increasingly prevalent as a disease of urbanization and industrialization. This is due to increased access to health care, higher stress levels and differing dietary choices.
Risk Factors
Common risk factors in the development of IBS include stress, anxiety, depression, history of IBD and acute gastrointestinal infections.
Screening
There is insufficient evidence to recommend routine screening for Irritable Bowel Syndrome.
Natural History, Complications, and Prognosis
The symptoms of IBS usually develop in the second decade of life, and start with symptoms such as abdominal pain, diarrhea and constipation. IBS may develop after exposure to early life adverse events, sexual abuse, anxiety, depression and stressors. Psychological conditions may also develop as complications of the disease. If left untreated, patients with IBS may progress to develop malnutrition (resulting from food intolerance), impacted bowel, and poor quality of life. Common complications of IBS include dehydration, hemorrhoids and fatigue. Prognosis is good, as IBS does not lead to life threatening complications or shorten lifespan of an individual. IBS patients tend to have long symptom free intervals interspersed with periods of severe symptoms. Although Irritable bowel syndrome may be a life-long condition, symptoms can often be improved or relieved through treatment.