Sandbox:Mazia
Historical Perspective
- Small intestinal bacterial overgrowth (SIBO) was first discovered by Barber and Hummel in 1939.
- In 2000, Pimentel et all at Cedars-Sinai Medical Center were first identified that SIBO was present in 78% of patients with irritable bowel syndrome (IBS), and that treatment with antibiotics improved symptoms.
- In May 2015, U.S. Food and Drug Administration (FDA) approved rifaximin to treat SIBO.
Classification
- [Disease name] may be classified according to [classification method] into [number] subtypes/groups:
- [group1]
- [group2]
- [group3]
- Other variants of [disease name] include [disease subtype 1], [disease subtype 2], and [disease subtype 3].
Pathophysiology
- The pathogenesis of small intestinal bacterial overgrowth (SIBO) is characterized by an increased microbial load in the small intestine.
- A healthy individual has less than 103 organisms/mL in the upper small intestine, and the majority of these organisms are gram-positive bacteria.
- Body's homeostatic mechanisms protect against excessive small intestinal colonization by bacteria include :
- Gastric acid and bile eradicate micro-organisms before they leave the stomach
- Migrating motor complex clears the excess unwanted bacteria of upper intestine
- Intestinal mucosa serves as a protective layer for the gut wall.
- Normal intestinal flora (eg, Lactobacillus) maintains a low pH that prevents bacterial overgrowth.
- Physical barrier of the ileocecal valve that prevents retrograde translocation of bacteria from colon to the small intestine.
- Disruption of these protective homeostatic mechanisms can increase the risk of SIBO.
- Bacterial colonization causes an inflammatory response in the intestinal mucosa.
- Damage to the intestinal mucosa leads to malabsorption of bile acids, carbohydrates, proteins and vitamins resulting in symptoms of diarrhea and weightloss.
- On microscopic histopathological analysis, blunting of the intestinal villi, thinning of the mucosa and crypts, and increased intraepithelial lymphocytes are observed as findings of SIBO.
Causes
- [Disease name] may be caused by either [cause1], [cause2], or [cause3].
- [Disease name] is caused by a mutation in the [gene1], [gene2], or [gene3] gene[s].
- There are no established causes for [disease name].
Differentiating [disease name] from other Diseases
- [Disease name] must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as:
- [Differential dx1]
- [Differential dx2]
- [Differential dx3]
Epidemiology and Demographics
- The prevalence of SIBO is unknown.
- In [year], the incidence of [disease name] was estimated to be [number or range] cases per 100,000 individuals in [location].
Age
- Patients of all age groups may develop [disease name].
- [Disease name] is more commonly observed among patients aged [age range] years old.
- Small intestinal bacterial overgrowth is more commonly observed among elderly patients.
Gender
- [Disease name] affects men and women equally.
- [Gender 1] are more commonly affected with [disease name] than [gender 2].
- The [gender 1] to [Gender 2] ratio is approximately [number > 1] to 1.
Race
- There is no racial predilection for [disease name].
- [Disease name] usually affects individuals of the [race 1] race.
- [Race 2] individuals are less likely to develop [disease name].
The prevalence of SIBO in the general population is unknown but estimated to be 0–35% in healthy individuals.9
Anywhere from 30% to 85% of adult
patients with IBS are estimated to have SIBO,9-11 with the most current data reporting 67% as determined by duodenal aspiration and culture.6
Two meta-analyses
have shown 3.5–9.6-fold increased odds of SIBO in patients with IBS.12 In the United States and Europe, one in five school-aged children have been diagnosed with abdominal pain-related functional gastrointestinal disorders, including IBS and functional abdominal pain; SIBO has been shown to occur in 34% of pediatric IBS patients.10 A 2015 study demonstrated that 63% of children aged 4–17 years who were hospitalized for abdominal pain had SIBO.13 Elderly patients may be particularly susceptible to SIBO due to a lack of gastric acid and the use of medications that slow gastrointestinal transit.9
SIBO prevalence may
be as high as 15% in the elderly and is an important cause of unexplained diarrhea in this population.12,14 SIBO also is common in patients with liver cirrhosis (50%), celiac disease (50%)9
and gastroparesis (39%).15
Risk Factors
- Common risk factors in the development of [disease name] are [risk factor 1], [risk factor 2], [risk factor 3], and [risk factor 4].
Natural History, Complications and Prognosis
- The majority of patients with [disease name] remain asymptomatic for [duration/years].
- Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
- If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
- Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
- Prognosis is generally [excellent/good/poor], and the [1/5/10year mortality/survival rate] of patients with [disease name] is approximately [#%].
Diagnosis
Diagnostic Criteria
- The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met:
- [criterion 1]
- [criterion 2]
- [criterion 3]
- [criterion 4]
Symptoms
- [Disease name] is usually asymptomatic.
- Symptoms of [disease name] may include the following:
- [symptom 1]
- [symptom 2]
- [symptom 3]
- [symptom 4]
- [symptom 5]
- [symptom 6]
Physical Examination
- Patients with [disease name] usually appear [general appearance].
- Physical examination may be remarkable for:
- [finding 1]
- [finding 2]
- [finding 3]
- [finding 4]
- [finding 5]
- [finding 6]
Laboratory Findings
- There are no specific laboratory findings associated with [disease name].
- A [positive/negative] [test name] is diagnostic of [disease name].
- An [elevated/reduced] concentration of [serum/blood/urinary/CSF/other] [lab test] is diagnostic of [disease name].
- Other laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].
Imaging Findings
- There are no [imaging study] findings associated with [disease name].
- [Imaging study 1] is the imaging modality of choice for [disease name].
- On [imaging study 1], [disease name] is characterized by [finding 1], [finding 2], and [finding 3].
- [Imaging study 2] may demonstrate [finding 1], [finding 2], and [finding 3].
Other Diagnostic Studies
- [Disease name] may also be diagnosed using [diagnostic study name].
- Findings on [diagnostic study name] include [finding 1], [finding 2], and [finding 3].
Treatment
Medical Therapy
- There is no treatment for [disease name]; the mainstay of therapy is supportive care.
- The mainstay of therapy for [disease name] is [medical therapy 1] and [medical therapy 2].
- [Medical therapy 1] acts by [mechanism of action 1].
- Response to [medical therapy 1] can be monitored with [test/physical finding/imaging] every [frequency/duration].
Surgery
- Surgery is the mainstay of therapy for [disease name].
- [Surgical procedure] in conjunction with [chemotherapy/radiation] is the most common approach to the treatment of [disease name].
- [Surgical procedure] can only be performed for patients with [disease stage] [disease name].
Prevention
- There are no primary preventive measures available for [disease name].
- Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].
- Once diagnosed and successfully treated, patients with [disease name] are followed-up every [duration]. Follow-up testing includes [test 1], [test 2], and [test 3].