Abdominal distension and bloating are a frequent complaint in gastroenterology clinical practice. According to recent results from the Rome Foundation Global Epidemiology Study, up to 18% of the global population experience these bothersome symptoms.1 In this editorial, we will present a practical approach to the patient complaining of these symptoms in the outpatient clinic, focusing on the different mechanisms and associated conditions that should be kept in mind. First, it is important to remember that bloating and distension are not the same. Bloating is the subjective feeling of fullness, pressure in the abdomen or the perception of trapped gas, and abdominal distension refers to the objective increase of the abdominal girth. Cultural aspects play an important role in the evaluation of these symptoms,2 since in Spanish there is no specific word for bloating, instead, Spanish speaking patients will use words like “swelling” or “inflammation” to express both abdominal bloating and/or distension.3 Nonetheless, the pathophysiological mechanisms in both conditions are similar, and they usually coexist,4 therefore it is reasonable to approach both of them in the same manner.
Initial approach to patients complaining of bloating and abdominal distensionA good anamnesis and physical examination can help evaluate different etiopathogenic mechanisms and decide which complementary tests are necessary and plan ahead to offer effective treatments.5 As with many other gastrointestinal symptoms, bloating and distension can be secondary to organic diseases or, as most frequently seen, associated to disorders of gut–brain interaction (DGBI).6,7
Asking for the diurnal variation (intermittent vs continuous), exacerbating and attenuating factors (fasting and/or food intake, relation to bowel movements, or perceived food intolerances), the presence of concomitant gastrointestinal symptoms, including constipation, diarrhea, abdominal pain or post-prandial fullness and associated psychological comorbidities which may points toward a DGBI disorder.6 Among the warning signs that point toward an organic cause are: blood in the stool, unintentional weight loss, onset of symptoms after 50 years age, anemia and/or nutritional deficiencies, palpation of masses during abdominal/rectal examination, succussion splash, fever, abdominal tenderness, recent changes in usual bowel habits and personal and/or family history of cancer, inflammatory bowel disease or celiac disease.8 Patients presenting warning signs should be evaluated with endoscopic and/or imaging studies before stablishing a functional diagnosis (Table 1).
Clinical features useful to differentiate conditions associated with bloating and abdominal distension.
| Secondary organic causes | Severe motility disorder | Obesity | Malabsorption | DGBI | |
|---|---|---|---|---|---|
| Predominant symptom | Distension>bloating | Distension>bloating | Distension>bloating, although bloating is also common | Bloating>distension | Usually bloating>distension, except in cases of abdominophrenic dyssynergia |
| Diurnal variation | Continuous | Intermittent | Continuous | Intermittent | Intermittent |
| Meals | Not related | Worsen after meals | Not related | Worsens after meals, association with specific triggers (lactose, fructans, gluten, etc.) | Worsens after meals, there is no specific association with triggers (all components cause symptoms) |
| Usual bowel habits | Not related | Constipation frequent, diarrhea if SIBO present | Not related | Diarrhea, in cases of severe malabsorption (celiac disease, giardiasis, etc.) steatorrhea | Variable, usually related to DGBI diagnosis (irritable bowel syndrome, functional diarrhea or constipation). Defecatory dyssynergia is common |
| Body weight | Unintentional weight loss | Unintentional weight loss | Previous weight gain | Unintentional weight loss | Usually weight maintained |
| Physical examination | Abdominal tenderness, abdominal masses, shifting dullness, fluid wave | Succussion splash | Central obesity | Normal | Normal |
| Psychological comorbidities | Not related | Not related | Anxiety and depression common | Not related | Anxiety and depression common |
| Main mechanisms: content | Increased extra-intestinal content | Increased intra-intestinal content | Increased extra-intestinal content | Increased intra-intestinal content | Normal intra and extra-intestinal content |
| Main mechanisms: hypersensitivity | Not related | Not related | Visceral hypersensitivity | Not related | Visceral hypersensitivity |
| Treatment options | Specific treatment of underlying causes | Prokinetics, decompression tubes | Low-calorie diet and physical exercise to promote weight loss | In carbohydrate intolerance avoid specific triggers, treat underlying cause | Neuromodulators, biofeedback therapy for defecatory and abdominophrenic dyssynergia |
Bloating and abdominal distension are usually associated with other DGBIs, like functional dyspepsia or irritable bowel syndrome.1 Nonetheless they can be a primary disorder in some patients, according to Rome IV criteria, to stablish the diagnosis of functional bloating/distension, the symptoms must occur at least 1 day per week and without a predominance of pain or abnormal bowel habits fulfilling other DGBI criteria.9 For a practical approach, there are multiple mechanisms involved in the pathogenesis of abdominal bloating and distension that should be kept in mind. Once a secondary cause has been ruled out and a functional diagnosis has been stablished, a tailored approach considering the different mechanisms is recommended.
Mechanisms associated to abdominal distension and bloatingIncreased extra-intestinal content, obesity and other organic diseasesBloating and abdominal distension may be secondary to an organic disease (gastrointestinal or not) and they should be considered in the differential diagnosis. For a personalized approach, warning signs and physical examination are crucial. Common organic causes for abdominal distension include ascites, gastrointestinal or gynecological neoplasms peritoneal metastasis and subacute intestinal ischemia. Bloating and abdominal distension are often present in patients with celiac disease and other conditions associated with malabsorption.5 A detailed dietary history should be obtained to identify a high intake of gas-producing food or specific carbohydrate intolerance. High intake of gas-producing food and carbohydrate intolerance such as lactose, fructose, and polyols may cause symptoms of bloating and distension due to an increased osmotic load, excess fluid retention, and excess fermentation in the colon.10
In the Spanish population the most important sources of carbohydrates intolerance are lactose, excess of fructose and total fructans.11 Therefore, empiric restrictions of lactose for a short duration (2 weeks) may be initially performed.10 A low FODMAP diet (diet low in oligosaccharides, disaccharides, monosaccharides and polyols) has shown beneficial effects on bloating.6 Nevertheless, long-term restrictive diets may cause nutritional deficiencies. For this reason, they should be administered by dietitians trained in gastroenterology. On the other hand, special attention should be paid to patients with risk factors for eating disorders and avoidant or restrictive food intake disorders.12
A common cause of extra-intestinal abdominal distension is obesity. The mechanisms involved are fat accumulation in the abdomen, which may constrain bowel expansion during digestion, and also, adipose tissue accumulation has a pro-inflammatory effect that contributes to intestinal hypersensibility.5 Recent weight gain is associated with new onset bloating,13 and significant weight has shown to improve bloating and abdominal distension symptoms.5
Obesity-associated distension is frequently reported as continuous distension throughout the day, and generally without any dietary trigger or associations with bowel habits. In patients complaining of abdominal distension, recent weight gain must be evaluated in the differential diagnosis, and a low-calorie diet and exercise to promote weight reduction is recommended.
Increased intra-intestinal content, gastrointestinal dysmotility and functional disordersThe main functions of the gastrointestinal tract are to digest and absorb nutrients and to get rid of waste by-products. Normal motility is imperative to achieve these goals. Patients with severe gastrointestinal dysmotility present abnormal flow of ingested food which favors stasis, fermentation by bacteria causing gas which ultimately results in increased in intra-abdominal content.14 Because of this, bloating and abdominal distension are common symptoms in patients with severe motility disorders. In an episode of distention, they present a protrusion of the abdominal wall associated with an increase in total abdominal volume and a cephalic displacement of the diaphragm.15 Patients with motility disorders also frequently complain of post-prandial symptoms like nausea and/or vomiting coupled with abnormal bowel habits, particularly constipation.16
In patients with severe gastrointestinal symptoms unresponsive to treatment, and also in patients with known diseases associated with gastrointestinal dysmotility (systemic sclerosis, Parkinson disease, etc.) upper gastrointestinal motility tests can be performed to rule out motility disorders, gastric emptying scintigraphy for gastroparesis17 and small bowel manometry for enteric dysmotility and chronic idiopathic pseudo-obstruction.18
Constipation and fecal retention increases intraluminal content and promotes colonic distension. Acute colonic distension is associated with increased abdominal girth and alter post-prandial small intestinal motility.19 Patients with constipation-type irritable bowel syndrome who also present slow colonic transit show greater abdominal distension compared to patients without slow transit.20 Abdominal symptoms as bloating, pain, discomfort, and cramping are common in patients with dyssynergic defecation and improve after biofeedback therapy.21 In patients with abdominal distension and bloating complaining of severe constipation, defecatory dyssynergia should be ruled-out, and treatment tailored to improve colonic motility and re-education of the defecatory maneuver with biofeedback if indicated.
Increased visceral hypersensitivity and abnormal viscero-somatic accommodation reflexesAnother important mechanism in the genesis of bloating is visceral hypersensitivity and abnormal viscero-somatic reflexes. In a study22 evaluating colonic content using morphovolumetric analysis of abdominal CT images, there were no differences between the amount of gaseous and non-gaseous colonic content between patients with functional digestive symptoms and healthy subjects, concluding that other factors, such as intestinal hypersensitivity and poor tolerance to small increases in luminal gas may be involved.
Patients with DGBIs, especially irritable bowel syndrome (IBS), present visceral hypersensitivity and hyperalgesia in up to 20–90% of cases.23 Visceral hypersensitivity, in addition to an alteration of the central mechanisms responsible for regulating stimuli perceived as painful as well as psychological states such as anxiety, depression, somatization and hypervigilance, contribute to the development of pain/distension reported by these patients.24 Healthy individuals react to intestinal gas distension by contracting the anterior abdominal muscles and relaxing the diaphragm, which avoids increasing abdominal girth. Patients with functional abdominal distension show an abnormal reaction, characterized by downward displacement of the diaphragm that is associated with an anterior protrusion of the abdominal wall.15
Indeed, in a secondary analysis of studies evaluating patients with abdominal distension using CT scans to objectively quantify the volume of gas between basal conditions and distension episodes, concluded that most patients show a small increase in intestinal gas that does not justify visible abdominal distention, and that abdominophrenic dyssynergia was the most frequent mechanism.4 Since visceral hypersensitivity plays a pivotal role in functional bloating and distension, the use of central neuromodulators to reduce visceral perception, reducing the stimuli that trigger the viscero-somatic reflex generating objective abdominal distension. Neuromodulators that have shown efficacy on bloating are tricyclic antidepressants (amitriptyline), dual serotonin/norepinephrine reuptake inhibitors (venlafaxine, duloxetine),25 and pregabalin.26 In cases were abdominal distension persists, abdominal re-education with biofeedback therapy improves the alteration in viscero-somatic reflexes that occurs in these cases.
ConclusionsAbdominal distension and bloating are prevalent conditions in gastroenterology. These bothersome symptoms impair general well-being and quality of life in patients with organic causes and, more frequently, patients with DGBIs. A tailored approach taking into account the different mechanisms involved can guide individualized therapy targeting, common causes such as; weight, food restrictions, gut motility, visceral hypersensitivity, and, in selected cases, abdominophrenic biofeedback is recommended for holistic care.
FundingNothing to declare.
Conflicts of interestAll authors declare no conflicts of interest.
