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==Overview==
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{{SK}}SIBO; small bowel bacterial overgrowth.{{SI}}
'''Small bowel bacterial overgrowth syndrome''' ('''SBBOS'''), or '''small intestinal bacterial overgrowth''' ('''SIBO'''), also termed '''bacterial overgrowth'''; is a disorder of excessive bacterial growth in the [[small intestine]]. Unlike the [[colon (anatomy)|colon]] (or large bowel), which is rich with [[bacteria]], the small bowel usually has less than 10<sup>4</sup> organisms per millilitre.<!--
==Overview==
    --><ref name=Quigley>{{cite journal | author = Quigley E, Quera R | title = Small intestinal bacterial overgrowth: roles of antibiotics, prebiotics, and probiotics. | journal = Gastroenterology | volume = 130 | issue = 2 Suppl 1 | pages = S78-90 | year = 2006 | id = PMID 16473077}}</ref>  <!--
Small intestinal bacterial overgrowth (SIBO) was first discovered by Barber and Hummel in 1939. There is no established system for the [[classification]] of small intestinal bacterial overgrowth (SIBO).The [[pathogenesis]] of small intestinal bacterial overgrowth (SIBO) is characterized by an increased [[Microbial|microbial load]] in the [[Small intestine|small intestine.]] Disruption of protective [[homeostatic]] [[Mechanisms of action|mechanisms]] can increase the risk of SIBO. [[Bacterial|Bacterial colonization]] causes an [[inflammatory]] response in the [[intestinal mucosa]]. Damage to the [[intestinal mucosa]] leads to [[malabsorption]] of [[Bile acid|bile acids]], [[carbohydrates]], [[proteins]] and [[vitamins]] resulting in [[symptoms]] of [[diarrhea]] and [[weight loss]]. On [[gross pathology]], [[Mucosal|mucosal edema]], loss of normal vascular pattern, [[Erythema|patchy erythema]], friability and [[ulceration]] of the [[Small intestinal|small intestinal wall]] is associated with small intestinal bacterial overgrowth (SIBO). On [[microscopic]] [[histopathological]] [[analysis]] [[small intestine]] and [[colon]] are [[normal]] in most [[patients]] with SIBO. Findings include blunting of the [[intestinal villi]], thinning of the [[Mucosal|mucosa]] and [[Crypt (anatomy)|crypts]], increased [[Intraepithelial lymphocyte|intraepithelial lymphocytes]]. Small intestinal bacterial overgrowth (SIBO) must be differentiated from other diseases that cause [[chronic]] [[diarrhea]]. Small intestinal bacterial overgrowth is more commonly observed among [[elderly]] [[patients]]. Small intestinal bacterial overgrowth (SIBO) affects [[men]] and [[women]] equally.There is no [[racial]] predilection for small intestinal bacterial overgrowth (SIBO). Early [[clinical]] features include [[bloating]], [[flatulence]], [[abdominal pain]]. If left untreated, [[patients]] with small intestinal bacterial overgrowth (SIBO) may progress to develop [[diarrhea]], [[dyspepsia]] and [[weight loss]]. [[Prognosis]] is generally good and associated with frequent [[Relapse|relapses]] and [[symptom]]-free periods. The [[diagnosis]] of small intestinal bacterial overgrowth (SIBO) is made when at least one of the following [[diagnostic criteria]] are met: a [[positive]] [[carbohydrate]] [[breath]] [[test]] or [[bacterial]] [[concentration]] of >103 units/mL in a [[Jejunum|jejunal]] [[aspirate]] [[Culture medium|culture]]. [[Physical examination]] may be remarkable for [[distended abdomen]] with positive succussion splash as a result of distended [[bowel]] loops and [[peripheral edema]] due to [[malabsorption]]. Small intestinal bacterial obstruction(SIBO) may also be [[Diagnosis|diagnosed]] using [[breath]] [[Test|tests]]. The mainstay of [[therapy]] for small intestinal bacterial overgrowth (SIBO) is [[antibiotic therapy]]. Surgical approach can only be performed for [[patients]] with [[strictures]], [[fistulae]], and [[Diverticular|diverticula]] or any other structural abnormality resulting in [[obstruction]] and resultant bacterial overgrowth. Effective measures for the [[prevention]] of small bowel bacterial overgrowth syndrome include avoiding [[medications]] like [[narcotics]] and [[benzodiazepines]] that decrease [[Intestinal|intestinal motility]] and avoid [[achlorhydria]] in high-risk [[patients]]. Consider [[Antibiotic|antibiotic prophylaxis]] for [[patients]] with four or more episodes of recurrent [[small bowel]] bacterial overgrowth syndrome within one year.
-->Patients with bacterial overgrowth typically develop symptoms including [[nausea]], [[bloating]], [[vomiting]] and [[diarrhea]], which is caused by a number of mechanisms. The [[diagnosis]] of bacterial overgrowth is made by a number of techniques, with the [[gold standard (test)|gold standard]] diagnosis being an [[Needle aspiration biopsy|aspirate]] from the [[jejunum]] that grows in excess of 10<sup>5</sup> [[bacteria]] per millilitre. [[Risk factor]]s for the development of bacterial overgrowth include the use of medications including [[proton pump inhibitors]], [[anatomy|anatomical]] disturbances in the bowel, including [[fistula]]e, [[diverticula]] and blind loops created after surgery, and resection of the [[ileo-cecal valve]]. Small bowel bacterial overgrowth syndrome is treated with [[antibiotic]]s, which may be given in a cyclic fashion to prevent tolerance to the antibiotics.


==Clinical presentation==
==Historical Perspective==
[[Image:Cobalmin.png|left|thumb|Deficiency of [[vitamin B12]] can occur in bacterial overgrowth]]
*Small intestinal bacterial overgrowth (SIBO) was first discovered by  Barber and Hummel in 1939.
Bacterial overgrowth can cause a variety of [[symptom]]s, many of which are also found in other conditions, making the [[diagnosis]] challenging at times.<!--
*In 2000, Pimentel et all at Cedars-Sinai Medical Center first identified that SIBO was present in 78% of patients with [[Irritable bowel syndrome|irritable bowel syndrome (IBS)]], and that [[Treatment IND|treatment]] with [[antibiotics]] improved [[symptoms]]<ref name="pmid11151884">{{cite journal| author=Pimentel M, Chow EJ, Lin HC| title=Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome. | journal=Am J Gastroenterol | year= 2000 | volume= 95 | issue= 12 | pages= 3503-6 | pmid=11151884 | doi=10.1111/j.1572-0241.2000.03368.x | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11151884  }} </ref>.
--><ref name=Quigley/><ref name=Teo>{{cite journal | author = Teo M, Chung S, Chitti L, Tran C, Kritas S, Butler R, Cummins A | title = Small bowel bacterial overgrowth is a common cause of chronic diarrhea. | journal = J Gastroenterol Hepatol | volume = 19 | issue = 8 | pages = 904-9 | year = 2004 | id = PMID 15242494}}</ref>  <!--
*In May 2015,  U.S. [[Food and Drug Administration|Food and Drug Administration (FDA)]] approved [[rifaximin]] to treat SIBO.
-->Many of the symptoms are due to [[malabsorption]] of nutrients due to the effects of bacteria which either metabolize nutrients or cause inflammation of the small bowel impairing absorption. The symptoms of bacterial overgrowth include [[nausea]], [[bloating]], [[flatus]], and [[chronic]] [[diarrhea]]. Some patients may develop abdominal discomfort and lose weight. Children with bacterial overgrowth may develop [[malnutrition]] have difficulty attaining [[failure to thrive|proper growth]].  [[Steatorrhea]] is a sticky type of diarrhea, where [[lipid]]s are malabsorbed and spill into the stool.<!--
  --><ref name=Kirsch>{{cite journal | author = Kirsch M | title = Bacterial overgrowth. | journal = Am J Gastroenterol | volume = 85 | issue = 3 | pages = 231-7 | year = 1990 | id = PMID 2178395}}</ref><!--
-->


Patients with bacterial overgrowth that is longstanding can develop complications of their illness as a result of malabsorption of nutrients.  [[Anemia]] may occur from a variety of mechanisms, as many of the nutrients involved in production of [[red blood cell]]s are absorbed in the affected small bowel.  [[Iron]] is absorbed in the more proximal parts of the small bowel, the [[duodenum]] and [[jejunum]], and patients with malabsorption of iron can develop a [[microcytic anemia]], with small red blood cells.  [[Vitamin B12]] is absorbed in the last part of the small bowel, the [[ileum]], and patients who malabsorb vitamin B12 can develop a [[megaloblastic anemia]] with large red blood cells.<ref name=Kirsch/>
==Classification==
*There is no established system for the [[classification]] of small intestinal bacterial overgrowth (SIBO).


==Pathophysiology==
==Pathophysiology==
[[Image:E coli at 10000x, original.jpg|left|thumb|''E. coli'', shown in this electron micrograph, is commonly isolated in patients with bacterial overgrowth]]
*The [[pathogenesis]] of small intestinal bacterial overgrowth (SIBO) is characterized by an increased [[microbial]] load in the [[small intestine]].<ref name="pmid3890541">{{cite journal |vauthors=Mathias JR, Clench MH |title=Review: pathophysiology of diarrhea caused by bacterial overgrowth of the small intestine |journal=Am. J. Med. Sci. |volume=289 |issue=6 |pages=243–8 |year=1985 |pmid=3890541 |doi= |url=}}</ref><ref name="pmid15156063">{{cite journal |vauthors=Hao WL, Lee YK |title=Microflora of the gastrointestinal tract: a review |journal=Methods Mol. Biol. |volume=268 |issue= |pages=491–502 |year=2004 |pmid=15156063 |doi=10.1385/1-59259-766-1:491 |url=}}</ref><ref name="pmid20572300">{{cite journal |vauthors=Bures J, Cyrany J, Kohoutova D, Förstl M, Rejchrt S, Kvetina J, Vorisek V, Kopacova M |title=Small intestinal bacterial overgrowth syndrome |journal=World J. Gastroenterol. |volume=16 |issue=24 |pages=2978–90 |year=2010 |pmid=20572300 |pmc=2890937 |doi= |url=}}</ref>
 
*A [[healthy]] individual has less than 103 organisms/mL in the upper [[small intestine]] and the majority of these [[organisms]] are [[gram-positive bacteria]].
Certain species of bacteria are more commonly found in aspirates of the [[jejunum]] taken from patients with bacterial overgrowth. The most common isolates are ''[[Escherichia coli]]'', ''[[Streptococcus]]'', ''[[Lactobacillus]]'', ''[[Bacteroides]]'', and ''[[Enterococcus]]'' species.<!--
*[[Human body|Human body's]] [[Homeostatic|homeostatic mechanisms]] that protect against excessive [[small intestinal]] colonization by [[Bacterial|bacteria]] include :
  --><ref name=Bouhnik>{{cite journal | author = Bouhnik Y, Alain S, Attar A, Flourié B, Raskine L, Sanson-Le Pors M, Rambaud J | title = Bacterial populations contaminating the upper gut in patients with small intestinal bacterial overgrowth syndrome. | journal = Am J Gastroenterol | volume = 94 | issue = 5 | pages = 1327-31 | year = 1999 | id = PMID 10235214}}</ref> <!--
**[[Gastric acid]] and [[bile]] eradicate [[micro-organisms]] before they leave the [[stomach]].
-->
**[[Migrating motor complex]] clears the excess  bacteria of upper intestine.
 
**[[Intestinal]] [[mucosa]] serves as a [[Protecting group|protective layer]] for the [[Gut tract|gut wall]].
Soon after birth, the [[gastrointestinal tract]] is colonized with bacteria, which, on the basis of models with animals raised in a germ-free environment, have beneficial effects on function of the gastrointestinal tract. There are 500-1000 different species of bacteria that reside in the bowel.<!--
**Normal [[intestinal flora]] (eg, [[Lactobacillus]]) maintains a low [[pH]] that prevents bacterial overgrowth.
  --><ref name=Germ>{{cite journal | author = Hao W, Lee Y | title = Microflora of the gastrointestinal tract: a review. | journal = Methods Mol Biol | volume = 268 | issue = | pages = 491-502 | year = | id = PMID 15156063}}</ref> <!--
**Physical barrier of the [[ileocecal]] [[valve]] that prevents retrograde translocation of [[bacteria]] from [[colon]] to the [[small intestine]].
-->However, if the flora of the small bowel is altered, inflammation or altered digestion can occur, leading to symptoms.  Many patients with chronic diarrhea have bacterial overgrowth as a cause or a contributor to their symptoms.<ref name=Teo/>  While the consensus definition of chronic diarrhea varies, in general it is considered to be an alteration in stool consistency or increased frequency, that occurs for over three weeks.  Various mechanisms are involved in the development of diarrhea in bacterial overgrowth.  First, the excessive bacterial concentrations can cause direct inflammation of the small bowel cells, leading to an ''inflammatory'' diarrhea.  The malabsorption of [[lipid]]s, [[protein]]s and [[carbohydrate]]s may cause poorly digestible products to enter into the [[colon (anatomy)|colon]].  This can cause diarrhea by the [[osmosis|osmotic drive]] of these molecules, but can also stimulate the secretory mechanisms of colonic cells, leading to a ''secretory diarrhea''.<ref name=Kirsch/>
*Disruption of these protective [[Homeostatic|homeostatic mechanisms]] can increase the risk of SIBO.
 
*[[Bacterial|Bacterial colonization]] causes an [[inflammatory]] response in the [[intestinal mucosa]].
==Risk factors and causes==
*Damage to the [[intestinal mucosa]] leads to [[malabsorption]] of [[Bile acid|bile acids]], [[carbohydrates]], [[proteins]], and [[vitamins]] resulting in [[symptoms]] of [[diarrhea]] and [[weight loss]].
[[Image:Ileocecal valve.jpg|thumb|left|The [[ileo-cecal valve]] prevents reflux of bacteria from the colon into the small bowel.  Resection of the valve can lead to bacterial overgrowth]]
*On [[gross pathology]], [[mucosal]] [[edema]], loss of normal [[vascular]] pattern, patchy [[erythema]], friability and [[ulceration]] of the [[Small intestinal|small intestinal wall]] is associated with small intestinal bacterial overgrowth (SIBO).
*On [[microscopic]] [[histopathological]] [[analysis]] [[small intestine]] and [[colon]] is normal in most [[patients]] with SIBO. However, in some patients, findings may include:
**Blunting of the [[intestinal]] [[villi]]
**Thinning of the [[mucosa]] and [[Crypt (anatomy)|crypts]]
**Increased [[Intraepithelial lymphocyte|intraepithelial lymphocytes]]
==Causes==
*Small intestinal bacterial overgrowth (SIBO) may be caused by disruption of the [[Protective group|protective]] [[homeostatic]] [[Mechanisms of action|mechanisms]] that control [[enteric]] [[Bacterial|bacteria]] [[population]].<ref name="pmid27123301">{{cite journal |vauthors=Deng L, Liu Y, Zhang D, Li Y, Xu L |title=Prevalence and treatment of small intestinal bacterial overgrowth in postoperative patients with colorectal cancer |journal=Mol Clin Oncol |volume=4 |issue=5 |pages=883–887 |year=2016 |pmid=27123301 |pmc=4840787 |doi=10.3892/mco.2016.807 |url=}}</ref><ref name="pmid20572300">{{cite journal |vauthors=Bures J, Cyrany J, Kohoutova D, Förstl M, Rejchrt S, Kvetina J, Vorisek V, Kopacova M |title=Small intestinal bacterial overgrowth syndrome |journal=World J. Gastroenterol. |volume=16 |issue=24 |pages=2978–90 |year=2010 |pmid=20572300 |pmc=2890937 |doi= |url=}}</ref><ref name="pmid6412829">{{cite journal |vauthors=McEvoy A, Dutton J, James OF |title=Bacterial contamination of the small intestine is an important cause of occult malabsorption in the elderly |journal=Br Med J (Clin Res Ed) |volume=287 |issue=6395 |pages=789–93 |year=1983 |pmid=6412829 |pmc=1549133 |doi= |url=}}</ref>
*Causes of small intestinal bacterial overgrowth (SIBO) include:
**'''Irregular [[small intestinal]] [[motility]]:'''
***[[Diabetic]] [[autonomic]] [[neuropathy]]
***[[Scleroderma]]
***[[Pseudo-obstruction-intestinal|Pseudo-obstruction]]
***[[Amyloidosis]]
***[[Neurological]] [[diseases]] (eg, [[myotonic]] [[dystrophy]], [[Parkinson]] [[disease]])
***[[Radiation]] [[enteritis]]
***[[Crohn disease]]
***[[Hypothyroidism]]
**'''Blind pouches in the gastrointestinal tract:'''
***Side-to-side or end-to-side [[anastomoses]]
***[[Duodenal]] or [[Jejunum|jejunal]] [[Diverticular|diverticula]]
***Segmental dilatation of the [[ileum]]
***[[Blind loop syndrome]]
***Biliopancreatic diversion
***[[Megacolon|Chagasic megacolon]]
**'''[[Fistula]]:'''
***[[Fistulae|Gastrocolic fistulae]]
***[[Fistulae|Jejunal-colic fistulae]]
**'''Partial [[Obstruction]]:'''
***[[Strictures]]
***[[Adhesions]]
***[[Abdominal]] [[Mass|masses]]
***[[Leiomyosarcoma]]
**'''Decreased [[gastric acid]] [[Secretions|secretion]]:'''
***[[Achlorhydria]]
***[[Vagotomy]]
***Long-term [[proton pump inhibitor]] [[therapy]]


Certain patients are more predisposed to the development of bacterial overgrowth because of certain risk factors. These factors can be grouped into three categories: (1) disordered [[motility]] or movement of the small bowel or anatomical changes that lead to [[stasis]], (2) disorders in the [[immune system]] and (3) conditions that cause more bacteria from the [[colon (anatomy)|colon]] to enter the [[small bowel]].<ref name=Quigley/>
==Differentiating Small Intestinal Bacterial Overgrowth from other Diseases==
*Small intestinal bacterial overgrowth (SIBO) must be differentiated from other diseases that cause chronic diarrhea. For differential diagnosis of chronic diarrhoea, click '''[[Chronic diarrhea differential diagnosis|here]].'''
==Epidemiology and Demographics==
Epidemiology and demographics of small intestinal bacterial overgrowth is as follows: <ref name="pmid437407">{{cite journal |vauthors=King CE, Toskes PP |title=Small intestine bacterial overgrowth |journal=Gastroenterology |volume=76 |issue=5 Pt 1 |pages=1035–55 |year=1979 |pmid=437407 |doi= |url=}}</ref>
===Age===
*Small intestinal bacterial overgrowth is more commonly observed among [[elderly]] [[patients]].
===Gender===
*Small intestinal bacterial overgrowth (SIBO) affects [[men]] and [[women]] equally.
===Race===
*There is no [[racial]] predilection for small intestinal bacterial overgrowth (SIBO).


Problems with motility may either be diffuse, or localized to particular areas.  Diseases like [[scleroderma]]<!--
==Risk Factors==
    --><ref name=Scleroreview>{{cite journal | author = Rose S, Young M, Reynolds J | title = Gastrointestinal manifestations of scleroderma. | journal = Gastroenterol Clin North Am | volume = 27 | issue = 3 | pages = 563-94 | year = 1998 | id = PMID 9891698}}</ref> <!--
*Common [[risk factors]] in the development of small intestinal bacterial overgrowth (SIBO) are :<ref name="pmid6412829">{{cite journal |vauthors=McEvoy A, Dutton J, James OF |title=Bacterial contamination of the small intestine is an important cause of occult malabsorption in the elderly |journal=Br Med J (Clin Res Ed) |volume=287 |issue=6395 |pages=789–93 |year=1983 |pmid=6412829 |pmc=1549133 |doi= |url=}}</ref><ref name="pmid20572300">{{cite journal |vauthors=Bures J, Cyrany J, Kohoutova D, Förstl M, Rejchrt S, Kvetina J, Vorisek V, Kopacova M |title=Small intestinal bacterial overgrowth syndrome |journal=World J. Gastroenterol. |volume=16 |issue=24 |pages=2978–90 |year=2010 |pmid=20572300 |pmc=2890937 |doi= |url=}}</ref>
-->and possibly [[celiac disease]]<!--
**[[Intestinal tract]] [[surgery]]
    --><ref name=Tursi>{{cite journal | author = Tursi A, Brandimarte G, Giorgetti G | title = High prevalence of small intestinal bacterial overgrowth in celiac patients with persistence of gastrointestinal symptoms after gluten withdrawal. | journal = Am J Gastroenterol | volume = 98 | issue = 4 | pages = 839-43 | year = 2003 | id = PMID 12738465}}</ref> <!--
**[[Irritable bowel syndrome]]<ref name="pmid31750966">{{cite journal| author=Ghoshal UC, Nehra A, Mathur A, Rai S| title=A meta-analysis on small intestinal bacterial overgrowth in patients with different subtypes of irritable bowel syndrome. | journal=J Gastroenterol Hepatol | year= 2020 | volume= 35 | issue= 6 | pages= 922-931 | pmid=31750966 | doi=10.1111/jgh.14938 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=31750966  }} </ref>
-->cause diffuse slowing of the bowel, leading to increased bacterial concentrations.  More commonly, the small bowel may have anatomical problems, such as out-pouchings known as [[diverticula]] that can cause bacteria to accumulate.<!--
**[[Liver cirrhosis]]
  --><ref name=Kongara>{{cite journal | author = Kongara K, Soffer E | title = Intestinal motility in small bowel diverticulosis: a case report and review of the literature. | journal = J Clin Gastroenterol | volume = 30 | issue = 1 | pages = 84-6 | year = 2000 | id = PMID 10636218}} </ref><!--
**[[Celiac disease]]
-->  After surgery involving the [[stomach]] and [[duodenum]] (most commonly with [[Billroth II]] antrectomy), a ''blind loop'' may be formed, leading to stasis of flow of intestinal contents.  This can cause overgrowth, and is termed ''blind loop syndrome''.<!--
**[[Immune]] [[deficiency]] (eg, [[AIDS]], [[IgA deficiency]], [[Malnutrition|severe malnutrition]])
  --><ref name=Kim>{{cite journal | author = Isaacs P, Kim Y | title = Blind loop syndrome and small bowel bacterial contamination. | journal = Clin Gastroenterol | volume = 12 | issue = 2 | pages = 395-414 | year = 1983 | id = PMID 6347463}}</ref><!--
**[[Short bowel syndrome]]
-->
**[[End-stage renal disease]]
**Gastrojejunal [[anastomosis]]
**Antral [[resection]]
**[[Pancreatic]] [[exocrine]] insufficiency


Disorders of the immune system can cause bacterial overgrowth.  Chronic [[pancreatitis]], or inflammation of the [[pancreas]] can cause bacterial overgrowth through mechanisms linked to this.<!--
== Natural History, Complications and Prognosis==
  --><ref>{{cite journal | author = Trespi E, Ferrieri A | title = Intestinal bacterial overgrowth during chronic pancreatitis. | journal = Curr Med Res Opin | volume = 15 | issue = 1 | pages = 47-52 | year = 1999 | id = PMID 10216811}}</ref>  <!--
*Early [[clinical]] [[Features (pattern recognition)|features]] include [[bloating]], [[flatulence]], [[abdominal pain]].<ref name="pmid437407">{{cite journal |vauthors=King CE, Toskes PP |title=Small intestine bacterial overgrowth |journal=Gastroenterology |volume=76 |issue=5 Pt 1 |pages=1035–55 |year=1979 |pmid=437407 |doi= |url=}}</ref><ref name="pmid15156063">{{cite journal |vauthors=Hao WL, Lee YK |title=Microflora of the gastrointestinal tract: a review |journal=Methods Mol. Biol. |volume=268 |issue= |pages=491–502 |year=2004 |pmid=15156063 |doi=10.1385/1-59259-766-1:491 |url=}}</ref>
-->The use of [[immunosuppressant]] medications to treat other conditions can cause this, as evidenced from animal models.<!--
*If left untreated, [[patients]] with small intestinal bacterial overgrowth (SIBO) may progress to develop [[diarrhea]], [[dyspepsia]] and [[weight loss]].
  --><ref name=Marshall>{{cite journal | author = Marshall J, Christou N, Meakins J | title = Small-bowel bacterial overgrowth and systemic immunosuppression in experimental peritonitis. | journal = Surgery | volume = 104 | issue = 2 | pages = 404-11 | year = 1988 | id = PMID 3041643}}</ref> <!--
*Common [[complications]] of small intestinal bacterial overgrowth (SIBO) include:<ref name="pmid7805370">{{cite journal |vauthors=Saltzman JR, Russell RM |title=Nutritional consequences of intestinal bacterial overgrowth |journal=Compr Ther |volume=20 |issue=9 |pages=523–30 |year=1994 |pmid=7805370 |doi= |url=}}</ref>
-->  Other causes include inherited immunodeficiency conditions, such as [[combined variable immunodeficiency]], IgA deficiency, and [[hypogammaglobulinemia]].<!--
**[[Iron]] [[deficiency]] resulting in [[microcytic]] [[anemia]]
  --><ref name=Pediatrics>{{cite journal | author = Pignata C, Budillon G, Monaco G, Nani E, Cuomo R, Parrilli G, Ciccimarra F | title = Jejunal bacterial overgrowth and intestinal permeability in children with immunodeficiency syndromes. | journal = Gut | volume = 31 | issue = 8 | pages = 879-82 | year = 1990 | id = PMID 2387510}}</ref><!--
**[[Vitamin B-12]] or [[folate deficiency]] resulting in [[macrocytic anemia]]
-->
**[[Vitamin B-12|Vitamin B-12 deficiency]] associated [[polyneuropathy]]
**[[Steatorrhea]]
**[[Hypocalcemia]]
**[[Vitamin A deficiency]] resulting in [[night blindness]]
**[[Selenium deficiency]] causing [[dermatitis]]
**[[Rosacea]]
**[[Cachexia]] as a result of [[Protein energy malnutrition|protein-energy malnutrition]]
*[[Prognosis]] is generally good and associated with frequent [[Relapse|relapses]] and [[symptom]]-free [[periods]].


Finally, abnormal connections between the [[bacteria]]-rich colon and the small bowel can increase the bacterial load in the small bowel.  Patients with [[Crohn's disease]] or other diseases of the [[ileum]] may require surgery that removes the [[ileo-cecal valve]] connecting the small and large bowel; this leads to an increased reflux of bacteria into the small bowel.<!--
== Diagnosis ==
  --><ref name-Kholoussy>{{cite journal | author = Kholoussy A, Yang Y, Bonacquisti K, Witkowski T, Takenaka K, Matsumoto T | title = The competence and bacteriologic effect of the telescoped intestinal valve after small bowel resection. | journal = Am Surg | volume = 52 | issue = 10 | pages = 555-9 | year = 1986 | id = PMID 3767143}}</ref>  <!--
===Diagnostic Criteria===
-->  After [[bariatric surgery]] for obesity, connections between the stomach and the [[ileum]] can be formed, which may increase bacterial load in the small bowel.<!--
  --><ref name=AJS>{{cite journal | author = Abell T, Minocha A | title = Gastrointestinal complications of bariatric surgery: diagnosis and therapy. | journal = Am J Med Sci | volume = 331 | issue = 4 | pages = 214-8 | year = 2006 | id = PMID 16617237}}</ref>  <!--
-->[[Proton pump inhibitor]] medications that decrease acid in the [[stomach]] cause bacterial overgrowth by a similar mechanism, as they prevent the anti-bacterial effects of acid in the stomach.  The clinical significance of this in causing symptoms is unclear.<!--
  --><ref name=PPI>{{cite journal | author = Laine L, Ahnen D, McClain C, Solcia E, Walsh J | title = Review article: potential gastrointestinal effects of long-term acid suppression with proton pump inhibitors. | journal = Aliment Pharmacol Ther | volume = 14 | issue = 6 | pages = 651-68 | year = 2000 | id = PMID 10848649}}</ref><ref name=PPI2>{{cite journal | author = Williams C, McColl K | title = Review article: proton pump inhibitors and bacterial overgrowth. | journal = Aliment Pharmacol Ther | volume = 23 | issue = 1 | pages = 3-10 | year = 2006 | id = PMID 16393275}}</ref>


==Diagnosis==
[[Clinical practice guideline]]s by the American College of Gastroenterology guide diagnosis<ref name="pmid32023228">{{cite journal| author=Pimentel M, Saad RJ, Long MD, Rao SSC| title=ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. | journal=Am J Gastroenterol | year= 2020 | volume= 115 | issue= 2 | pages= 165-178 | pmid=32023228 | doi=10.14309/ajg.0000000000000501 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32023228  }} </ref>.
[[Image:Agar plate with colonies.jpg|left|thumb|Aspiration of from the [[jejunum]] is the gold standard for diagnosis.  A bacterial load of greater than 10<sup>5</sup> bacteria per milillitre is diagnostic for bacterial overgrowth]]
*The [[diagnosis]] of small intestinal bacterial overgrowth (SIBO) is made when at least one of the following [[diagnostic]] [[criteria]] are met:
**A [[positive]] [[carbohydrate]] [[breath]] [[test]] with an increase in hydrogen concentrations of 20 ppm from baseline within 90 - 120 minutes.
**[[Bacterial]] [[Concentrations|concentration]] of >= 10<sup>3</sup> colony-forming units per milliliter (CFU/mL) in a duodenal/jejunal aspirate


The diagnosis of bacterial overgrowth can be made by physicians in various ways.  [[Malabsorption]] can be detected by a test called the ''D-xylose'' test.  [[Xylose]] is a sugar that does not require enzymes to be digested.  The D-xylose test involves having a patient to drink a certain quantity of D-xylose, and measuring levels in the [[urine]] and [[blood]]; if there is no evidence of D-xylose in the [[urine]] and [[blood]], it suggests that the small bowel is not absorbing properly (as opposed to problems with enzymes required for digestion).<!--
=== Symptoms ===
  --><ref name=Dxylose>{{cite journal | author = Craig R, Atkinson A | title = D-xylose testing: a review. | journal = Gastroenterology | volume = 95 | issue = 1 | pages = 223-31 | year = 1988 | id = PMID 3286361}}</ref><!--
*[[Symptoms]] of small intestinal bacterial overdose (SIBO) may include the following:<ref name="pmid7805370">{{cite journal |vauthors=Saltzman JR, Russell RM |title=Nutritional consequences of intestinal bacterial overgrowth |journal=Compr Ther |volume=20 |issue=9 |pages=523–30 |year=1994 |pmid=7805370 |doi= |url=}}</ref>
-->
:*[[Bloating]]
:*[[Flatulence]]
:*[[Abdominal discomfort]]
:*[[Chronic]] [[watery diarrhea]]
:*[[Weight loss]]


The gold standard for detection of bacterial overgrowth is the aspiration of more than 10<sup>5</sup> bacteria per millilitre from the small bowel.  The normal small bowel has less than 10<sup>4</sup> bacteria per millilitre.<!--
=== Physical Examination ===
  --><ref name=Corazza>{{cite journal | author = Corazza G, Menozzi M, Strocchi A, Rasciti L, Vaira D, Lecchini R, Avanzini P, Chezzi C, Gasbarrini G | title = The diagnosis of small bowel bacterial overgrowth. Reliability of jejunal culture and inadequacy of breath hydrogen testing. | journal = Gastroenterology | volume = 98 | issue = 2 | pages = 302-9 | year = 1990 | id = PMID 2295385}}</ref><!--
*[[Patients]] with small intestinal bacterial overgrowth (SIBO) usually appear normal.<ref name="pmid15156063">{{cite journal |vauthors=Hao WL, Lee YK |title=Microflora of the gastrointestinal tract: a review |journal=Methods Mol. Biol. |volume=268 |issue= |pages=491–502 |year=2004 |pmid=15156063 |doi=10.1385/1-59259-766-1:491 |url=}}</ref>
-->
*[[Physical examination]] may be remarkable for:
:*[[Distended abdomen]] with [[positive]] succussion splash as a result of distended [[bowel]] loops
:*[[Peripheral edema]] due to [[malabsorption]]


[[Image:Coeliac path.jpg|thumb|left|Biopsies of the small bowel in bacterial overgrowth can mimic [[celiac disease]], with partial [[villi|villous]] atrophy.]]
=== Laboratory Findings ===
Breath tests have been developed to test for bacterial overgrowth, based on bacterial metabolism of [[carbohydrates]] to [[hydrogen]], or based on the detection of by-products of digestion of carbohydrates that are not usually metabolized.  The hydrogen breath test involves giving patients a load of carbohydrate (usually in the form of [[rice]]) and measuring expired hydrogen concentrations after a certain time. It compares well to jejunal aspirates in making the diagnosis of bacterial overgrowth.<!--
*A  [[positive]] [[carbohydrate]] [[breath]] [[test]] has a sensitivity of 55% and specificity of 82% of small intestinal bacterial overgrowth (SIBO).<ref name="pmid31743632">{{cite journal| author=Losurdo G, Leandro G, Ierardi E, Perri F, Barone M, Principi M | display-authors=etal| title=Breath Tests for the Non-invasive Diagnosis of Small Intestinal Bacterial Overgrowth: A Systematic Review With Meta-analysis. | journal=J Neurogastroenterol Motil | year= 2020 | volume= 26 | issue= 1 | pages= 16-28 | pmid=31743632 | doi=10.5056/jnm19113 | pmc=6955189 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=31743632  }} </ref>
  --><ref name=Kerlin>{{cite journal | author = Kerlin P, Wong L | title = Breath hydrogen testing in bacterial overgrowth of the small intestine. |  
*An elevated concentration of [[bacterial]] [[Colony Forming Units (CFU)|colony forming units]] >103/mL in [[Jejunum|jejunal]] [[aspirate]] culture is [[diagnostic]] of small intestinal bacterial overgrowth (SIBO).
journal = Gastroenterology | volume = 95 | issue = 4 | pages = 982-8 | year = 1988 | id = PMID 3410238}}</ref> <!--
*Other [[laboratory]] findings consistent with the [[diagnosis]] of small intestinal bacterial overgrowth (SIBO) include:
--><sup>13</sup>C and <sup>14</sup>C based tests have also been developed based on the bacterial metabolism of D-xylose.  Increased bacterial concentrations are also involved in the deconjugation of bile acids.  The glycocholic acid breath test involves the administration of the bile acid <sup>14</sup>C glychocholic acid, and the detection of <sup>14</sup>CO<sub>2</sub>, which would be elevated in bacterial overgrowth.<!--
**[[Macrocytic anemia]]
  --><ref name=Geri>{{cite journal | author = Donald I, Kitchingmam G, Donald F, Kupfer R | title = The diagnosis of small bowel bacterial overgrowth in elderly patients. | journal = J Am Geriatr Soc | volume = 40 | issue = 7 | pages = 692-6 | year = 1992 | id = PMID 1607585}}</ref>  <!--
**[[B12 deficiency]]
-->
**Presence of [[fecal fat]] on [[stool examination]].  
**Low levels of [[thiamine]] and [[niacin]]
**Elevated serum [[folate]] and [[vitamin K]] levels


Some patients with symptoms of [[bacterial overgrowth]] will undergo [[gastroscopy]], or visualization of the stomach and duodenum with an endoscopic [[camera]].  Biopsies of the small bowel in [[bacterial overgrowth]] can mimic those of [[celiac disease]], making the diagnosis more challenging.  Findings include blunting of [[villi]], hyperplasia of crypts and an increased number of [[lymphocyte]]s in the [[lamina propria]].<!--
===Imaging Findings===
--><ref name=Toskes>{{cite journal | author = Toskes P, Giannella R, Jervis H, Rout W, Takeuchi A | title = Small intestinal mucosal injury in the experimental blind loop syndrome. Light- and electron-microscopic and histochemical studies. | journal = Gastroenterology | volume = 68 | issue = 5 Pt 1 | pages = 1193-203 | year = 1975 | id = PMID 1126607}}</ref><!--
*The [[CT-scans|CT]] [[abdomen]] or [[MRI]] may demonstrate associated [[strictures]], [[Malrotation of gut|malrotation]], [[fistulae]].<ref name="pmid15156063">{{cite journal |vauthors=Hao WL, Lee YK |title=Microflora of the gastrointestinal tract: a review |journal=Methods Mol. Biol. |volume=268 |issue= |pages=491–502 |year=2004 |pmid=15156063 |doi=10.1385/1-59259-766-1:491 |url=}}</ref>
-->
*Small intestinal bacterial overgrowth can result in [[small bowel obstruction]] that presents as [[small bowel]] feces sign on abdominal CT.
*Small bowel feces sign is the presence of particulate feculent material mingled with gas bubbles in the lumen of the small intestine, it is believed to be the result of delayed intestinal transit.
[[File:Ischaemic-bowel-5.jpg||center|400px|thumb|Small bowel faeces sign<small>Case courtesy of Dr Ian Bickle, <a href="https://radiopaedia.org/">Radiopaedia.org</a>. From the case <a href="https://radiopaedia.org/cases/29769">rID: 29769</a></small>]]


However, some physicians suggest that if the suspicion of bacterial overgrowth is high enough, the best diagnostic test is a trial of treatment. If the symptoms improve, an empiric diagnosis of bacterial overgrowth can be made.<!--
===Other Diagnostic Studies===
    --><ref name=Singh>{{cite journal | author = Singh VV, Toskes PP | title = Small Bowel Bacterial Overgrowth: Presentation, Diagnosis, and Treatment. | journal = Curr Treat Options Gastroenterol | volume = 7 | issue = 1 | pages = 19-28 | year = 2004 | id = PMID 14723835}}</ref>
====Breath Tests====
*Small intestinal bacterial obstruction (SIBO) may also be [[Diagnose|diagnosed]] using [[breath]] [[Test|tests]].<ref name="pmid10773721">{{cite journal |vauthors=Stotzer PO, Kilander AF |title=Comparison of the 1-gram (14)C-D-xylose breath test and the 50-gram hydrogen glucose breath test for diagnosis of small intestinal bacterial overgrowth |journal=Digestion |volume=61 |issue=3 |pages=165–71 |year=2000 |pmid=10773721 |doi=10.1159/000007753 |url=}}</ref><ref name="pmid24095975">{{cite journal |vauthors=Saad RJ, Chey WD |title=Breath testing for small intestinal bacterial overgrowth: maximizing test accuracy |journal=Clin. Gastroenterol. Hepatol. |volume=12 |issue=12 |pages=1964–72; quiz e119–20 |year=2014 |pmid=24095975 |doi=10.1016/j.cgh.2013.09.055 |url=}}</ref><ref name="pmid437407">{{cite journal |vauthors=King CE, Toskes PP |title=Small intestine bacterial overgrowth |journal=Gastroenterology |volume=76 |issue=5 Pt 1 |pages=1035–55 |year=1979 |pmid=437407 |doi= |url=}}</ref>
*[[Breath]] [[Test|tests]] have the advantage of being easy to perform, noninvasive, and inexpensive. [[Breath]] [[Test|tests]] are based on the principle that [[carbohydrates]] are [[metabolized]] by [[bacteria]] in the [[gut]] to produce [[hydrogen]] or [[methane]] that is [[Absorbed dose|absorbed]] and [[excreted]] in [[breath]].
*The findings on [[carbohydrate]] [[breath]] [[test]] [[diagnostic]] of small intestinal bacterial obstruction (SIBO) include:
**An increase in [[hydrogen]] by ≥20 ppm above [[Baseline (medicine)|baseline]] within 90 minutes.
**A [[methane]] level ≥10 ppm regardless of the time during the [[breath]] [[test]].
'''Preparation for breath testing'''


==Treatment==
''Indications for the patient''
Bacterial overgrowth is usually treated with a course of antibiotics. A variety of antibiotics, including [[neomycin]], [[rifaximin]], [[amoxicillin-clavulanate]], [[fluoroquinolone]] antibiotics and [[tetracycline]] have been used; however, the best evidence is for the use of [[norfloxacin]] and [[amoxicillin-clavulanate]].<!--
* Fasting period prior to test should be 8-12 h
    --><ref name=RCT>{{cite journal | author = Attar A, Flourié B, Rambaud J, Franchisseur C, Ruszniewski P, Bouhnik Y | title = Antibiotic efficacy in small intestinal bacterial overgrowth-related chronic diarrhea: a crossover, randomized trial. | journal = Gastroenterology | volume = 117 | issue = 4 | pages = 794-7 | year = 1999 | id = PMID 10500060}}</ref>
* Antibiotics should be avoided 4 weeks prior to test
* Prokinetic agents (e.g. cisapride, domperidone, erythromycin) and laxatives should be stopped 1 week prior to test–''if tolerated by the patient''
* Complex carbohydrates (e.g. bread, pasta, rice, legumes, etc.) should be avoided 24 hours prior to test
* Physical activity should be avoided during the test
* Smoking should be avoided on the day of the test
* It is not necessary to stop proton pump inhibitors for the test
''Indications for the physician''
* Lactulose dose: 10 g followed by one cup of water
* Glucose dose: 75 g mixed with or followed by one cup of water
* Lactose: 25 g mixed with one cup of water
* Fructose: 25 g mixed with or followed by one cup of water


A course of one week of antibiotics is usually sufficient to treat the condition. However, if the condition recurs, antibiotics can be given in a cyclical fashion in order to prevent tolerance. For example, antibiotics may be given for a week, followed by three weeks off antibiotics, followed by another week of treatment. Alternatively, the choice of antibiotic used can be cycled.<ref name=Singh/>
== Treatment ==
Treatment options available for small intestinal bacterial overgrowth syndrome are as follows: <ref name="pmid19243285">{{cite journal |vauthors=Pimentel M |title=Review of rifaximin as treatment for SIBO and IBS |journal=Expert Opin Investig Drugs |volume=18 |issue=3 |pages=349–58 |year=2009 |pmid=19243285 |doi=10.1517/13543780902780175 |url=}}</ref><ref name="pmid437407">{{cite journal |vauthors=King CE, Toskes PP |title=Small intestine bacterial overgrowth |journal=Gastroenterology |volume=76 |issue=5 Pt 1 |pages=1035–55 |year=1979 |pmid=437407 |doi= |url=}}</ref>
===Medical Therapy===
*The mainstay of [[therapy]] for small intestinal bacterial overgrowth (SIBO) is [[antibiotic therapy]].<ref name="pmid28078798">Gatta L, Scarpignato C. Systematic review with meta-analysis: rifaximin is effective and safe for the treatment of small intestine bacterial overgrowth. Aliment Pharmacol Ther. 2017 Mar;45(5):604-616. doi: 10.1111/apt.13928. Epub 2017 Jan 12. PMID: [http://pubmed.gov/28078798 28078798]; PMCID: PMC5299503.</ref>
*[[Antibiotics]] acts by eliminating the [[bacterial]] [[Overgrowth syndrome|overgrowth]].
* [[Rifaximin]] is the [[antibiotic]] of choice for the [[Treatments|treatment]] of small intestinal bacterial overgrowth (SIBO).
** Rifaximin may only work in patients who have [[irritable bowel syndrome]]<ref name="pmid25319626">{{cite journal| author=Boltin D, Perets TT, Shporn E, Aizic S, Levy S, Niv Y | display-authors=etal| title=Rifaximin for small intestinal bacterial overgrowth in patients without irritable bowel syndrome. | journal=Ann Clin Microbiol Antimicrob | year= 2014 | volume= 13 | issue=  | pages= 49 | pmid=25319626 | doi=10.1186/s12941-014-0049-x | pmc=4201689 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=25319626  }} </ref>
**Preferred regimen: [[Rifaximin]] 550 mg PO q8h for 14 days.
*Response to [[antibiotics]] can be assessed by the [[symptomatic]] improvement. In case of recurrent [[symptoms]], the [[antibiotic]] [[dose]] is repeated.


The condition that predisposed the patient to bacterial overgrowth should also be treated.  For example, if the bacterial overgrowth is caused by [[chronic pancreatitis]], the patient should be treated with coated pancreatic [[enzyme]] supplements.
=== Surgery ===
*[[Surgery|Surgical approach]] can only be performed for [[patients]] with [[strictures]], [[fistulae]], and [[Diverticular|diverticula]] or any other structural abnormality resulting in [[obstruction]] and resultant bacterial overgrowth.<ref name="pmid15156063">{{cite journal |vauthors=Hao WL, Lee YK |title=Microflora of the gastrointestinal tract: a review |journal=Methods Mol. Biol. |volume=268 |issue= |pages=491–502 |year=2004 |pmid=15156063 |doi=10.1385/1-59259-766-1:491 |url=}}</ref>


[[Probiotic]]s are bacterial preparations that alter the bacterial flora in the bowel to cause a beneficial effect.  Their role in bacterial overgrowth is somewhat uncertain.<ref name=Quigley/>
=== Prevention ===
*Effective measures for the [[prevention]] of small bowel bacterial overgrowth syndrome include:<ref name="pmid437407">{{cite journal |vauthors=King CE, Toskes PP |title=Small intestine bacterial overgrowth |journal=Gastroenterology |volume=76 |issue=5 Pt 1 |pages=1035–55 |year=1979 |pmid=437407 |doi= |url=}}</ref>
**Avoiding [[medications]] like [[narcotics]] and [[benzodiazepines]] that decrease [[intestinal]] [[motility]].
**Avoid [[achlorhydria]] in high-risk [[patients]].
**Consider [[antibiotic]] [[prophylaxis]] for [[patients]] with four or more episodes of recurrent small bowel bacterial overgrowth syndrome within one year.


==References==
==References==
<div class="references-small"><references/></div>
<div class="references-small"><references /></div>


==External links==
==External links==
* [http://www.medicinenet.com/irritable_bowel_syndrome/page6.htm IBS and small intestinal bacterial overgrowth (SIBO)]
* [http://www.medicinenet.com/irritable_bowel_syndrome/page6.htm IBS and small intestinal bacterial overgrowth (SIBO)]


[[Category:Bacteria]]
[[Category:Bacteria]]

Latest revision as of 02:14, 9 August 2021


Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Mazia Fatima, MBBS [2]

Small intestinal bacterial overgrowth syndrome
ICD-10 K63
ICD-9 579.9
DiseasesDB 29209
MedlinePlus 000222
eMedicine med/198 

Synonyms and keywords:SIBO; small bowel bacterial overgrowth.

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Overview

Small intestinal bacterial overgrowth (SIBO) was first discovered by Barber and Hummel in 1939. There is no established system for the classification of small intestinal bacterial overgrowth (SIBO).The pathogenesis of small intestinal bacterial overgrowth (SIBO) is characterized by an increased microbial load in the small intestine. Disruption of 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 weight loss. On gross pathology, mucosal edema, loss of normal vascular pattern, patchy erythema, friability and ulceration of the small intestinal wall is associated with small intestinal bacterial overgrowth (SIBO). On microscopic histopathological analysis small intestine and colon are normal in most patients with SIBO. Findings include blunting of the intestinal villi, thinning of the mucosa and crypts, increased intraepithelial lymphocytes. Small intestinal bacterial overgrowth (SIBO) must be differentiated from other diseases that cause chronic diarrhea. Small intestinal bacterial overgrowth is more commonly observed among elderly patients. Small intestinal bacterial overgrowth (SIBO) affects men and women equally.There is no racial predilection for small intestinal bacterial overgrowth (SIBO). Early clinical features include bloating, flatulence, abdominal pain. If left untreated, patients with small intestinal bacterial overgrowth (SIBO) may progress to develop diarrhea, dyspepsia and weight loss. Prognosis is generally good and associated with frequent relapses and symptom-free periods. The diagnosis of small intestinal bacterial overgrowth (SIBO) is made when at least one of the following diagnostic criteria are met: a positive carbohydrate breath test or bacterial concentration of >103 units/mL in a jejunal aspirate culture. Physical examination may be remarkable for distended abdomen with positive succussion splash as a result of distended bowel loops and peripheral edema due to malabsorption. Small intestinal bacterial obstruction(SIBO) may also be diagnosed using breath tests. The mainstay of therapy for small intestinal bacterial overgrowth (SIBO) is antibiotic therapy. Surgical approach can only be performed for patients with strictures, fistulae, and diverticula or any other structural abnormality resulting in obstruction and resultant bacterial overgrowth. Effective measures for the prevention of small bowel bacterial overgrowth syndrome include avoiding medications like narcotics and benzodiazepines that decrease intestinal motility and avoid achlorhydria in high-risk patients. Consider antibiotic prophylaxis for patients with four or more episodes of recurrent small bowel bacterial overgrowth syndrome within one year.

Historical Perspective

Classification

  • There is no established system for the classification of small intestinal bacterial overgrowth (SIBO).

Pathophysiology

Causes

Differentiating Small Intestinal Bacterial Overgrowth from other Diseases

  • Small intestinal bacterial overgrowth (SIBO) must be differentiated from other diseases that cause chronic diarrhea. For differential diagnosis of chronic diarrhoea, click here.

Epidemiology and Demographics

Epidemiology and demographics of small intestinal bacterial overgrowth is as follows: [7]

Age

  • Small intestinal bacterial overgrowth is more commonly observed among elderly patients.

Gender

  • Small intestinal bacterial overgrowth (SIBO) affects men and women equally.

Race

  • There is no racial predilection for small intestinal bacterial overgrowth (SIBO).

Risk Factors

Natural History, Complications and Prognosis

Diagnosis

Diagnostic Criteria

Clinical practice guidelines by the American College of Gastroenterology guide diagnosis[10].

Symptoms

  • Symptoms of small intestinal bacterial overdose (SIBO) may include the following:[9]

Physical Examination

Laboratory Findings

Imaging Findings

  • The CT abdomen or MRI may demonstrate associated strictures, malrotation, fistulae.[3]
  • Small intestinal bacterial overgrowth can result in small bowel obstruction that presents as small bowel feces sign on abdominal CT.
  • Small bowel feces sign is the presence of particulate feculent material mingled with gas bubbles in the lumen of the small intestine, it is believed to be the result of delayed intestinal transit.
Small bowel faeces signCase courtesy of Dr Ian Bickle, <a href="https://radiopaedia.org/">Radiopaedia.org</a>. From the case <a href="https://radiopaedia.org/cases/29769">rID: 29769</a>

Other Diagnostic Studies

Breath Tests

Preparation for breath testing

Indications for the patient

  • Fasting period prior to test should be 8-12 h
  • Antibiotics should be avoided 4 weeks prior to test
  • Prokinetic agents (e.g. cisapride, domperidone, erythromycin) and laxatives should be stopped 1 week prior to test–if tolerated by the patient
  • Complex carbohydrates (e.g. bread, pasta, rice, legumes, etc.) should be avoided 24 hours prior to test
  • Physical activity should be avoided during the test
  • Smoking should be avoided on the day of the test
  • It is not necessary to stop proton pump inhibitors for the test

Indications for the physician

  • Lactulose dose: 10 g followed by one cup of water
  • Glucose dose: 75 g mixed with or followed by one cup of water
  • Lactose: 25 g mixed with one cup of water
  • Fructose: 25 g mixed with or followed by one cup of water

Treatment

Treatment options available for small intestinal bacterial overgrowth syndrome are as follows: [14][7]

Medical Therapy

Surgery

Prevention

References

  1. ↑ Pimentel M, Chow EJ, Lin HC (2000). "Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome". Am J Gastroenterol. 95 (12): 3503–6. doi:10.1111/j.1572-0241.2000.03368.x. PMID 11151884.
  2. ↑ Mathias JR, Clench MH (1985). "Review: pathophysiology of diarrhea caused by bacterial overgrowth of the small intestine". Am. J. Med. Sci. 289 (6): 243–8. PMID 3890541.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Hao WL, Lee YK (2004). "Microflora of the gastrointestinal tract: a review". Methods Mol. Biol. 268: 491–502. doi:10.1385/1-59259-766-1:491. PMID 15156063.
  4. ↑ 4.0 4.1 4.2 Bures J, Cyrany J, Kohoutova D, Förstl M, Rejchrt S, Kvetina J, Vorisek V, Kopacova M (2010). "Small intestinal bacterial overgrowth syndrome". World J. Gastroenterol. 16 (24): 2978–90. PMC 2890937. PMID 20572300.
  5. ↑ Deng L, Liu Y, Zhang D, Li Y, Xu L (2016). "Prevalence and treatment of small intestinal bacterial overgrowth in postoperative patients with colorectal cancer". Mol Clin Oncol. 4 (5): 883–887. doi:10.3892/mco.2016.807. PMC 4840787. PMID 27123301.
  6. ↑ 6.0 6.1 McEvoy A, Dutton J, James OF (1983). "Bacterial contamination of the small intestine is an important cause of occult malabsorption in the elderly". Br Med J (Clin Res Ed). 287 (6395): 789–93. PMC 1549133. PMID 6412829.
  7. ↑ 7.0 7.1 7.2 7.3 7.4 King CE, Toskes PP (1979). "Small intestine bacterial overgrowth". Gastroenterology. 76 (5 Pt 1): 1035–55. PMID 437407.
  8. ↑ Ghoshal UC, Nehra A, Mathur A, Rai S (2020). "A meta-analysis on small intestinal bacterial overgrowth in patients with different subtypes of irritable bowel syndrome". J Gastroenterol Hepatol. 35 (6): 922–931. doi:10.1111/jgh.14938. PMID 31750966.
  9. ↑ 9.0 9.1 Saltzman JR, Russell RM (1994). "Nutritional consequences of intestinal bacterial overgrowth". Compr Ther. 20 (9): 523–30. PMID 7805370.
  10. ↑ Pimentel M, Saad RJ, Long MD, Rao SSC (2020). "ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth". Am J Gastroenterol. 115 (2): 165–178. doi:10.14309/ajg.0000000000000501. PMID 32023228 Check |pmid= value (help).
  11. ↑ Losurdo G, Leandro G, Ierardi E, Perri F, Barone M, Principi M; et al. (2020). "Breath Tests for the Non-invasive Diagnosis of Small Intestinal Bacterial Overgrowth: A Systematic Review With Meta-analysis". J Neurogastroenterol Motil. 26 (1): 16–28. doi:10.5056/jnm19113. PMC 6955189 Check |pmc= value (help). PMID 31743632.
  12. ↑ Stotzer PO, Kilander AF (2000). "Comparison of the 1-gram (14)C-D-xylose breath test and the 50-gram hydrogen glucose breath test for diagnosis of small intestinal bacterial overgrowth". Digestion. 61 (3): 165–71. doi:10.1159/000007753. PMID 10773721.
  13. ↑ Saad RJ, Chey WD (2014). "Breath testing for small intestinal bacterial overgrowth: maximizing test accuracy". Clin. Gastroenterol. Hepatol. 12 (12): 1964–72, quiz e119–20. doi:10.1016/j.cgh.2013.09.055. PMID 24095975.
  14. ↑ Pimentel M (2009). "Review of rifaximin as treatment for SIBO and IBS". Expert Opin Investig Drugs. 18 (3): 349–58. doi:10.1517/13543780902780175. PMID 19243285.
  15. ↑ Gatta L, Scarpignato C. Systematic review with meta-analysis: rifaximin is effective and safe for the treatment of small intestine bacterial overgrowth. Aliment Pharmacol Ther. 2017 Mar;45(5):604-616. doi: 10.1111/apt.13928. Epub 2017 Jan 12. PMID: 28078798; PMCID: PMC5299503.
  16. ↑ Boltin D, Perets TT, Shporn E, Aizic S, Levy S, Niv Y; et al. (2014). "Rifaximin for small intestinal bacterial overgrowth in patients without irritable bowel syndrome". Ann Clin Microbiol Antimicrob. 13: 49. doi:10.1186/s12941-014-0049-x. PMC 4201689. PMID 25319626.

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