Common gastrointestinal symptoms: irritable bowel syndrome.

The diagnosis of irritable bowel syndrome (IBS) should be considered when patients have had abdominal pain/discomfort, bloating, and change in bowel habits for 6 months. Patients may experience variation between periods of constipation and diarrhea. When evaluating patients with IBS, physicians should be alert for red flag symptoms, such as rectal bleeding, anemia, nighttime pain, and weight loss. Physicians also should consider other medical conditions that manifest similarly to IBS. Clinicians who are confident in diagnosing IBS based on symptoms typically do not obtain many tests unless the patient has red flag symptoms. Various etiologic mechanisms have been proposed for IBS, including abnormal bowel motility, inflammation, altered mucosal permeability, genetic predisposition, and visceral hypersensitivity. Lack of certainty about the etiology makes it difficult to develop effective management approaches; thus, management is directed toward symptom relief. Dietary changes, such as avoiding fermentable carbohydrates, may benefit some patients, especially those with bloating. Constipation-dominant IBS can be managed with antispasmodics, lubiprostone, or linaclotide, whereas diarrhea-dominant IBS can be managed with loperamide or alosetron, though the latter drug can cause ischemic colitis. For long-term therapy, tricyclic antidepressants or selective serotonin reuptake inhibitors have good efficacy. Peppermint oil and probiotics also may provide benefit.