Functional Gastrointestinal Disorders
GENERAL PRINCIPLES
• Functional GI disorders are characterized by the presence of abdominal symptoms in the absence of a demonstrable organic disease process. Symptoms can arise from any part of the luminal gut.
• Irritable bowel syndrome (IBS), primarily characterized by abdominal pain linked to altered bowel habits of at least 3 months in duration, is the best-recognized functional bowel disease.74
DIAGNOSIS
• Clinical evaluation should be directed toward excluding organic processes in the involved area of the gut while initiating therapeutic trials when functional symptoms are suspected.74
• Serologic tests for celiac sprue are recommended in IBS patients. The prevalence of celiac sprue in diarrhea-predominant IBS patients is estimated at 3.6% compared with 0.7% of the general population.74
• Patients gt;50 years old with new-onset bowel symptoms, patients with alarm symptoms (GI bleeding, anemia, weight loss, early satiety), and patients with symptoms not responding to empiric treatment need further workup with endoscopy. Routine cross-sectional imaging is not recommended with typical functional symptoms without alarm features.
TREATMENT
Nonpharmacologic Measures
Patient education, reassurance, and help with diet and lifestyle modification are keys to an effective physician-patient relationship. The psychosocial contribution to symptom exacerbation should be determined, and its management may be sufficient for many patients.
• Diets low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) appear to reduce functional GI symptoms in patients with IBS.75 Food items that reliably trigger symptoms can also be avoided, for example, dairy products.
• Peppermint oil can improve symptoms in some patients with functional bowel disease.
It can be administered either in capsule form or 6-8 drops in a glass of water taken daily.76• Adjunctive measures useful in functional bowel disease include cognitive and behavioral therapy, hypnotherapy, mindfulness, acupuncture, and physical exercise.
Medications
• Symptomatic management
î Antiemetic agents are useful in functional nausea and vomiting syndromes, in addition to neuromodulators.
î When pain and bloating are the predominant symptoms, antispasmodic or anticholinergic medications (hyoscyamine, 0.125-0.25 mg PO/sublingual up to qid; dicyclomine, 10-20 mg PO qid) may provide short-term relief.
î Stool frequency, but not abdominal pain, improves with increased dietary fiber (25 g/d) supplemented with PRN laxatives in constipation-predominant IBS.
î Loperamide (2-4 mg, up to qid/PRN) can reduce stool frequency, urgency, and fecal incontinence.
î Short-term nonabsorbable antibiotic therapy (particularly rifaximin) may improve bloating and diarrhea in IBS; long-term treatment has not been adequately studied.77 Probiotics (e.g., bifidobacteria) are sometimes beneficial.
î Lubiprostone (8 #956;g bid), a selective chloride channel activator, linaclotide (290 #956;g daily), and plecanatide (3 mg daily), guanylate cyclase C agonists, improve constipation-predominant IBS symptoms. Polyethylene glycol 3350 and electrolytes are suitable for use in constipation- predominant IBS.74
° Eluxadoline (Viberzi, 75-100 mg bid), a #956;- and #954;-opioid receptor agonist, is approved for the management of diarrhea-predominant IBS.78 Acute pancreatitis is a potentially serious side effect occurring in 0.4%; history of past pancreatitis, cholecystectomy, alcohol abuse, and hepatic
impairment are contraindications.
î Alosetron (Lotronex, 1 mg daily to bid), a 5-HT3 antagonist, is useful in women with diarrhea- predominant IBS.79 However, its use is restricted to refractory diarrhea because of the rare potential for ischemic colitis.
• Neuromodulators
î Low-dose TCAs (e.g., amitriptyline, nortriptyline, imipramine, doxepin: 25-100 mg at bedtime) have neuromodulatory and analgesic properties that are independent of their psychotropic effects. These can be beneficial, especially in pain-predominant functional GI disorders.74
î Selective serotonin reuptake inhibitors (SSRIs) (e.g., fluoxetine, 20 mg; paroxetine, 20 mg; sertraline, 50 mg; duloxetine, 20-60 mg) may also have efficacy, sometimes with better side effect profiles compared with TCAs.
î Cyclic vomiting syndrome (CVS) is an increasingly recognized condition with stereotypic episodes of vigorous vomiting and asymptomatic intervals between episodes.80 Treatment with low-dose TCAs or antiepileptic medications (zonisamide, levetiracetam) has prophylactic benefits. Sumatriptan (25-50 mg PO, 5-10 mg transnasally, or 6 mg SC) or other triptans may abort an episode, especially if administered during a prodrome or early in the episode. Established episodes may require IV hydration, scheduled IV antiemetics (ondansetron, prochlorperazine), benzodiazepines (lorazepam), and pain control with IV narcotics. Before the diagnosis of CVS is made, structural causes and cannabinoid hyperemesis syndrome need to be ruled out.80