APPROACH TO THE PATIENT WITH GAS AND BLOATING



APPROACH TO THE PATIENT WITH GAS AND BLOATING

Physiology

• Patients frequently attribute various abdominal symptoms to excessive bowel gas.

• The major sources of bowel gas are:

o Air swallowing.

o Diffusion from the blood.

o Bacterial production.

o Reaction of bicarbonate.

• Gas is removed from the lumen via:

o Eructation.

o Passage per rectum.

o Bacterial consumption.

o Diffusion into the blood.

• The net of these processes for each individual determines the quantity of gas present in the gut at any moment.

Volume and Composition of Bowel Gas

• The normal gut usually contains less than 200 mL of gas.

• Daily gas expulsion averages 600 to 700 mL.

• On average, healthy men pass flatus 14 times per day, although as many as 25 daily expulsions are considered normal.

• Larger volumes are passed after meals, but flatus production persists during sleep at a slower rate.

• Numerous foods alleged to enhance excretion of rectal gas (baked beans, and lactose).

• N2, O2, CO2, H2, and methane account for more than 99% of gas passed per rectum.

• Gases produced by colonic bacteria (CO2, H2, and methane) represent 74% of flatus.

Sources of Bowel Gas

Air Swallowing

• Air swallowing is the major source of stomach gas and comprise:

o 17.7 mL of gas is swallowed with each 10-mL bolus of liquid.

o Air swallowed with food and saliva.

o Repetitive subconscious air swallowing.

Intraluminal Gas Production

• Three gases CO2, H2, and CH4 are produced in appreciable quantity and a variety of gases are produced in trace concentrations.

Odoriferous Gases

• The unpleasant odor of feces results from sulfur-containing compounds such as methanethiol and dimethyldisulfide.

Diffusion of Gas between the Lumen and the Blood

• Gases passively diffuse between the lumen and the mucosal blood, and the direction of movement is determined by the partial pressure gradient.

Clinical Gas Problems

Eructation or belching

• This is the retrograde expulsion of esophageal or gastric gas from the mouth.

• Exacerbated by foods that reduce lower esophageal sphincter tone.

• Manometric studies of eructation ( ↓LES tone followed by upper esophageal sphincter relaxation.

• In contrast, people who repeatedly eructate can usually be shown to aspirate air into the hypopharynx before each belch.

• Chronic eructation is a functional disorder, and an evaluation with radiographic and laboratory studies should be reserved for patients who have additional complaints suggestive of thoracic or abdominal abnormality.

Abdominal Distention and Bloating

• Flatulence is the involuntary release of gas from the anus.

• Manometric studies performed during flatulence demonstrate propagated colon contractions and increased rectal pressure coupled with early anal sphincter relaxation.

• Bloating is the perception of retained excess gas within the gut lumen.

• Abdominal discomfort and bloating, thought to be caused by too much gas, are among the most frequently encountered gastrointestinal complaints.

• Most subjects who complain of bloating have normal quantities of bowel gas on radiographic examination.

• The distended subject has greatly increased quantities of gastric, small bowel, and colonic gas, presumably secondary to air swallowing.

• IBS subjects with apparently normal volumes of bowel gas sense that their gut is distended:

o Bowel of patients with IBS is sensitive to balloon distention.

• The frequent claim that various foods turn to gas may represent the ability of foods:

o To stimulate abnormal motility that is perceived as bloating.

o To increase gas retention in the gut, causing sensations of bloating.

Unusually Voluminous

• Excessive passage of gas per anus may be a source of social embarrassment.

• Healthy subjects pass gas up to 20 times per day.

• Excessive flatulence usually results from excessive intraluminal gas production.

• Because flatus H2 and CO2 are largely derived from fermentation of malabsorbed carbohydrate, flatulence may be indicative of an abnormality of carbohydrate absorption (either a generalized or isolated abnormality).

Odoriferous Rectal Gas

• The passage of malodorous flatus is a not uncommon complaint.

• Bacterial production of sulfur-containing gases appears to be the major cause of this malodor.

• Orally administered products that have been tested for their ability to reduce fecal sulfur gases include activated charcoal (eight 260 mg tablets daily) and bismuth subsalicylate (eight 262 mg tablets daily), which almost totally eliminated hydrogen sulfide (via binding of sulfide by bismuth).

Pneumatosis Cystoides Intestinalis

• Characterized by the presence of gas-filled cysts in the wall of the small bowel or colon.

• May be asymptomatic or associated with diarrhea, bloating, or abdominal pain.

• Associated with very high net H2 production in the intestine.

• Treatment

o Administration of high concentrations of O2 via inhalation.

o Antibiotics that inhibit H2 production.

o Elimination of nonabsorbable carbohydrates that provide a substrate for H2.

Colonic Explosions

• Two gases formed in the colon, H2 and CH4, are combustible and potentially explosive.

• Triggered by electrocautery performed through the proctosigmoidoscope.

Other symptoms experienced by patients with complaints of excess gas include

o Abdominal pain.

o Halitosis.

o Anorexia.

o Early satiety.

o Nausea.

o Loud borborygmi.

o Constipation.

CLINICAL SYNDROMES

PATHOGENESIS

• Gas and bloating are reported in a number of disorders.

• These gaseous symptoms may result from

o Excess gas production.

o Abnormal gas transit.

o Abnormal perception of normal amounts of gas within the gut.

Carbohydrate Maldigestion

• Maldigestion and malabsorption of carbohydrates ( intestinal gas production.

• Substances that cause gaseous symptoms ( simple and complex CHO & dietary fiber.

• Unabsorbed carbohydrates are propelled to the colon( bacterial catabolism ( liberates hydrogen gas and short-chain fatty acids.

o Flatulence is the initial symptom.

o Borborygmi and bloating develop with greater degrees of malabsorption.

o Abdominal pain and diarrhea develop with the highest levels.

• Carbohydrate maldigestion and malabsorption may result from:

o Loss of enterocyte enzymes in normal intestinal mucosa (Lactose intolerance).

o Inability to transport a poorly absorbed sugar in a healthy individual.

o Organic disorder of the intestinal mucosa, such as celiac disease.

Small Intestinal Bacterial Overgrowth

• The stomach and small intestine are relatively sterile compared to the colon.

• Small bowel bacterial overgrowth is defined by the presence of more than 10/5 colony-forming units per milliliter in intestinal fluid samples.

• The main organisms cultured are Streptococcus, Escherichia coli, Lactobacillus, and Bacteroides.

• Causes:

o Adhesions, Crohn's disease, radiation enteritis, ulcer disease, after vagotomy, small intestinal diverticula and malignancy.

o Patients with functional gut disorders, including intestinal pseudo-obstruction, exhibit overgrowth because of an impairment of gut clearance mechanisms.

o Disorders that increase bacterial delivery to the upper gut, such as cologastric fistulae and coprophagia.

• Manifestations: gas, bloating, diarrhea, abdominal discomfort, and nausea, nutrient malabsorption, weight loss, metabolic bone disease and an increased risk for spontaneous bacterial peritonitis in cirrhotic patients.

Dysmotility Syndromes

• Conditions that alter gut motor function may produce prominent gas and bloating.

o Gastroparesis resulting from gastric retention of solids, liquids, and gases.

▪ Diabetes mellitus.

▪ Scleroderma.

▪ Amyloidosis.

▪ Familial conditions.

▪ Paraneoplastic syndromes.

▪ Endocrine disease.

o Fat intolerance and rapid gastric emptying.

o Fundoplication for GERD reduces the ability to belch or vomit.

o Chronic intestinal pseudo-obstruction due to delayed gas transit and small intestinal bacterial overgrowth.

o Chronic constipation.

Functional Bowel Disorders

• Functional bloating is a recurrent sensation of abdominal distention that may or may not be associated with measurable distention, but is not part of another functional bowel or gastroduodenal disorder.

• Diagnostic Criteria for Functional Bloating

Must include both of the following:

1. Recurrent feeling of bloating or visible distention at least 3 days/month in 3 months

2. Insufficient criteria for a diagnosis of functional dyspepsia, IBS, or other functional GI disorder

• Gas and bloating are prevalent complaints of patients with functional bowel disorders, such as irritable bowel syndrome (IBS) and functional dyspepsia.

• Among different IBS subtypes, patients with constipation-predominant IBS experience greater bloating than those with diarrhea.

Pathophysiology

Proposed hypotheses

• Increased distention of IBS results from weak abdominal muscles, recent weight gain, a low position of the diaphragm, or exaggerated lumbar lordosis.

• Abnormal fermentation.

• Helicobacter pylori infection.

• Abnormal gastrointestinal motor and sensory functions.

o Abnormal gas transit.

o Abnormality of visceral afferent function.

o Abnormal gas retention.

Miscellaneous Causes

• Aerophagia

o Negative intrathoracic pressure pulls air into the esophagus across an open upper esophageal sphincter.

o Worsened by gum chewing, smoking, or oral irritation.

o Causes:

o After laryngectomy.

o Peptic ulcer disease, GERD.

o Biliary colic.

• Intestinal obstruction may produce bloating.

• Endocrinopathies such as hypothyroidism may result in bloating.

• Medications (anticholinergics, opiates, calcium channel antagonists, antidepressants) produce gas through effects on gut motility.

EVALUATION OF THE PATIENT

History

• History of anxiety or other psychiatric disease ( aerophagia or functional bowel disorder.

• Family history can determine the risk for carbohydrate maldigestion syndromes, such as lactase deficiency.

• Dietary history may correlate symptoms with specific foods.

• Gum chewing, smoking, and chewing tobacco, predispose to aerophagia.

• History of conditions that predispose to small intestinal bacterial overgrowth.

• Medications that delay gut transit should be questioned.

• Relief of symptoms with defecation or flatus + absence of symptoms that awaken the patient from deep sleep ( IBS.

• Vomiting, fever, weight loss, nocturnal diarrhea, rectal bleeding, or steatorrhea ( organic disease.

Physical Examination

• Usually normal in patients with excess gas.

• Findings suggestive of organic disease include:

o Sclerodactyly ( scleroderma.

o Dermatitis herpetiformis ( celiac disease.

o Peripheral or autonomic neuropathy ( dysmotility syndromes.

o Cachexia, jaundice, or palpable masses ( malignant obstruction.

• Abdominal inspection may reveal scars from prior fundoplication, vagotomy, or other operations that can cause adhesions.

• Auscultation

o Absent bowel sounds ( ileus or myopathic dysmotility.

o High-pitched bowel sounds ( intestinal obstruction.

o Succussion splash ( gastric obstruction or gastroparesis.

• Abdominal percussion and palpation ( tympany and distention in the patient with mechanical obstruction or intestinal dysmotility.

• Rectal examination: exclude occult fecal blood, which would suggest lumenal inflammation or neoplasm.

Investigations

• Used to exclude organic disease.

• Routine: CBC, electrolyte, glucose, albumin, and total protein levels, and ESR exclude most inflammatory or neoplastic conditions.

• Calcium and phosphate levels, parameters of renal and thyroid function, liver chemistries, and fasting morning cortisol levels may be needed.

• Amylase may be elevated in patients with ischemic gut segments.

• Stool examination: for ova, parasites, blood and fat.

• Serology

o Endomysial or tissue transglutaminase antibody levels ( celiac disease.

o Antinuclear antibodies and scleroderma antibodies.

o Antinuclear neuronal antibodies ( paraneoplastic visceral neuropathy.

• Imaging techniques

• Upright abdominal radiographs ( diffuse distention consistent with ileus or pseudo-obstruction, or air-fluid levels in the patient with intestinal obstruction.

• Contrast enema radiography ( colonic or distal small intestinal obstruction.

• BMFT ( partial gastric outlet or small intestinal obstruction.

• Upper or lower endoscopy and biopsy of lesions producing partial blockage.

• Functional Testing ( when results of structural testing are unrevealing.

• Tests of Gut Motor Function ( suspected gastrointestinal dysmotility

o Gastric-emptying scanning & small intestinal or colonic transit.

▪ Scintigraphic measures of the emptying of liquid (111In-DTPA in water) or solid (99mTc-sulfur colloid in eggs) radionuclides

▪ Radiopaque marker techniques ( slow transit constipation.

o Gastrointestinal manometry.

▪ Smooth muscle dysfunction ( scleroderma (low amplitude contractions.

• Breath Testing

o Hydrogen breath testing may be used to confirm carbohydrate maldigestion or malabsorption as a cause of gas and bloating.

• Flatus Analysis

• Counting the number of flatus passages over 24 hours to determine if increased flatulence is present (normal, ................
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