Sections

Presentation

History

No specific symptoms are pathognomonic for bacterial overgrowth syndrome (BOS). Nonetheless, various nonspecific GI symptoms are common in affected individuals. Clinicians should have a heightened clinical suspicion for bacterial overgrowth syndrome in patients who present with the following:

Bloating
Flatulence
Abdominal pain
Diarrhea
Dyspepsia
Weight loss

Advanced cases of bacterial overgrowth syndrome may manifest as malabsorption findings, as follows:

Microcytic anemia due to iron deficiency
Macrocytic anemia due to vitamin B-12/folate deficiency
Polyneuropathy due to vitamin B-12 deficiency
Steatorrhea due to lipid malabsorption
Tetany due to hypocalcemia
Night blindness due to vitamin A deficiency
Dermatitis due to selenium deficiency
Bacterial overgrowth syndrome has been linked to rosacea^[6]
Cachexia due to protein-energy malnutrition

Causes

Disorders or structural abnormalities that disrupt the protective mechanisms that guard against increasing bacterial burden can lead to bacterial overgrowth syndrome.

Patients with the following medical conditions are at increased risk for bacterial overgrowth syndrome:

History of upper intestinal tract surgery
Irritable bowel syndrome^[7]
Liver cirrhosis^{[2, 4]}
Celiac disease^{[8, 9]}
Immune deficiency (eg, AIDS, IGA deficiency, severe malnutrition)^{[2, 4]}
Short bowel syndrome^[2]
End stage renal disease^[4]
Gastrojejunal anastomosis
Vagotomy, but not selective parietal cell vagotomy
Antral resection
Pancreatic exocrine insufficiency

Abnormal small intestinal motility due to the following may result in bacterial overgrowth syndrome:

Diabetic autonomic neuropathy
Scleroderma
Pseudo-obstruction
Amyloidosis
Neurological diseases (eg, myotonic dystrophy, Parkinson disease)
Radiation enteritis^{[2, 4]}
Crohn disease^{[2, 4]}
Hypothyroidism

Blind pouches from the following may result in bacterial overgrowth syndrome:

Side-to-side or end-to-side anastomoses
Intra-abdominal reservoirs
Duodenal or jejunal diverticula
Segmental dilatation of the ileum
Blind loop syndrome
Biliopancreatic diversion
Chagasic megacolon

Abnormal bowel communication due to the following may cause bacterial overgrowth syndrome:

Partial obstruction caused by the following may result in bacterial overgrowth syndrome:

Strictures
Adhesions
Abdominal masses
Leiomyosarcoma

Reduced gastric acid secretion from the following may result in bacterial overgrowth syndrome:

Achlorhydria
Vagotomy
Long-term administration of proton pump inhibitors^[10]

Prevalence of BOS rises with age.^{[4, 11]}

Physical Examination

A complete physical examination should be performed with emphasis on abdominal examination and examination for signs of malabsorption of various nutrients. No specific physical examination techniques are required for bacterial overgrowth syndrome.

Complications

Complications of bacterial overgrowth syndrome are possible in patients with prolonged and untreated symptoms, potentially leading to increased morbidity and mortality in higher-risk patients (eg, the very young and elderly).

Malabsorption of iron, vitamin B-12, and folate can lead to anemia

Persistent diarrhea can lead to volume loss and electrolyte disturbances.

Decreased fat absorption can lead to further diarrhea.

Differential Diagnoses

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Author

Chinelo N Animalu, MD, MPH, FIDSA Associate Professor, Division of Infectious Diseases, Department of Internal Medicine, University of Tennessee Health Science Center College of Medicine; Physician, Department of Infectious Disease, University of Tennessee Methodist Physicians (UTMP), Methodist University Hospital

Chinelo N Animalu, MD, MPH, FIDSA is a member of the following medical societies: American College of Physicians, American Medical Association, Infectious Diseases Society of America, Memphis Medical Society, Tennessee Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Joseph F John, Jr, MD, FACP, FIDSA, FSHEA Clinical Professor of Medicine, Molecular Genetics and Microbiology, Medical University of South Carolina College of Medicine; Associate Chief of Staff for Education, Ralph H Johnson Veterans Affairs Medical Center

Joseph F John, Jr, MD, FACP, FIDSA, FSHEA is a member of the following medical societies: Charleston County Medical Association, Infectious Diseases Society of America, South Carolina Infectious Diseases Society

Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center; Master of the American College of Physicians; Fellow, Infectious Diseases Society of America; Fellow of the Royal College of Physicians, London

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Medical Association, Association of Professors of Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, Southern Society for Clinical Investigation

Disclosure: Nothing to disclose.

Additional Contributors

Mark R Wallace, MD, FACP, FIDSA Infectious Disease Physician, Skagit Valley Hospital, Skagit Regional Health

Disclosure: Nothing to disclose.

Saqib Zaheer Syed, MBBS Nephrologist, South Texas Renal Care Group

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors Pedro A Manibusan Jr, DO; Joshua S Hawley, MD; Richard E Frye, MD, PhD; M Akram Tamer, MD; and Burke A Cunha, MD, to the development and writing of this article.

Bacterial Overgrowth Syndrome Clinical Presentation

History

Causes

Physical Examination

Complications

References

Tables

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