“Irritable bowel syndrome (IBS) is one of the most common symptoms complexes seen by the primary care physician, affecting 20 to 30 million Americans.” “The pathogenesis of IBS is multifactorial, with contributions from visceral hypersensitivity (low threshold to painful stimuli arising from the GI tract), neuroendocrine dysfunction, psychosocial factors, stress, enteric infections, altered GI flora, foods sensitivities/allergies, and other factors. New research on treatment of IBS highlights diet and nutrition, psychoneuroendocrinology, commensal bacteria and the immune system.” In addition, disordered cortical pain processing, SIBO and increased intestinal permeability have also been recently implicated.

Stress and emotional distress affect gastrointestinal function and worsen the symptoms of IBS. “Individuals with IBS have higher levels of postprandial serotonin, which corresponds to altered gastric emptying, increased small bowel contractions, faster bowel transit time, and altered pain perception (visceral hypersensitivity). IBS can also develop after an enteric infection known as post-infectious IBS (PI-IBS).

IBS is a diagnosis of exclusion, that is, ruling out other etiologies. Etiologic factors that should be ruled out include: infection (bacterial – esp. C. difficile, viral fungal or parasitic), pancreatic insufficiency, celiac disease, food sensitivities, lactose intolerance, and SIBO, as well as a host of other conditions that can mimic IBS (see table below).

Recent studies have also shown altered gut immune activation, and intestinal and colonic microbiome are associated with IBS.

The differential diagnosis of IBS is broad and ultimately depends on whether the patient has predominant diarrhea or constipation. If a patient has IBS with diarrhea, the differentials includes lactose intolerance, caffeine intake, alcohol intake, gastrointestinal infections (Giardia, Amoeba, HIV), inflammatory bowel disease, medication-induced diarrhea (antibiotic use, proton pump inhibitor, nonsteroidal anti-inflammatory drugs, ACE inhibitor, chemotherapy), celiac disease, malignancies, colorectal cancer, hyperthyroidism, VIPoma, and ischemic colitis.

Conditions That May Mimic IBS

• Gastrogenic dietary factors such as excessive consumption of tea, coffee, carbonated beverages, and simple sugars
• Infectious enteritis such as amebiasis and giardiasis
• Inflammatory bowel disease
• Lactose intolerance
• Laxative abuse
• Intestinal candidiasis
• Disturbed bacterial microflora as a result of antibiotic or antacid use
• Malabsorption disease such as pancreatic insufficiency and celiac disease
• Metabolic disorders such as adrenal insufficiency, diabetes mellitus, and hyperthyroidism
• Mechanical causes of fecal impact
• Diverticular disease
• Neoplasm

References:

Chey WD, Kurlander J, Eswaran S. Irritable bowel syndrome: a clinical review. JAMA. 2015 Mar 03;313(9):949-58.

Simrén M, Barbara G, Flint HJ, Spiegel BM, Spiller RC, Vanner S, Verdu EF, Whorwell PJ, Zoetendal EG., Rome Foundation Committee. Intestinal microbiota in functional bowel disorders: a Rome foundation report. Gut. 2013 Jan;62(1):159-76.

Dupont HL. Review article: evidence for the role of gut microbiota in irritable bowel syndrome and its potential influence on therapeutic targets. Aliment Pharmacol Ther. 2014 May;39(10):1033-42.

Lucak S. Diagnosing irritable bowel syndrome: what's too much, what's enough? MedGenMed. 2004 Mar 12;6(1):17.

In support of IBS and digestive health awareness month, we invite you to review these related Evexia Panels and Specialty Test Kits:

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