What are gases in the intestines, symptoms of their accumulation
Gas in the intestines is an unpleasant phenomenon
Gas formation in the intestinal tract is a consequence of the activity of microscopic bacteria and other organisms that make up the intestinal microflora.
The importance of these organisms is extremely important for normal digestion and the functioning of the gastrointestinal tract.
The human digestive organs are home to about 50 trillion different microorganisms, according to various estimates, ranging from 300 to 1000 species. The intestinal microflora is predominantly composed of bacteria belonging to only 35-40 species categories.
Based on medical research, it has been established that a person is able to exist without bacteria living inside him. But the relationship between microflora and the digestive tract is mutually beneficial.
Microorganisms live, feed and reproduce due to nutrients that are taken from the human body, and in return they help speed up digestion, train the immune system, and prevent the proliferation of harmful microflora.
However, not only beneficial bacteria live in the human body. Part of the intestinal microflora is represented by harmful and even dangerous microorganisms, which under certain circumstances can cause serious diseases.
The process of bacterial reproduction is controlled by the human body, due to which they cannot multiply unhindered, but exist within normal limits if the person is healthy.
Bloating is one of the common complaints presented by patients with diseases of the digestive tract. Patients often attribute various symptoms to increased gas production, but in clinical practice neither the volume nor the rate of gas excretion can be measured. The only guideline for the doctor is the subjective perception of excess gas. Understanding the causes and mechanisms of gastrointestinal disorders and finding the right approach to treatment is not so easy. Let's try to consider the problems associated with gas homeostasis disorders from physiological and clinical positions.
Despite the large capacity of the digestive tract, the intestines contain on average about 200 ml of gas [1, 2]. Sources and at the same time regulators of gas content are motility (swallowing, belching, passage through the rectum), diffusion into the blood and/or from the bloodstream, chemical reactions, bacterial fermentation and absorption. The main gases present in variable amounts in different parts of the gastrointestinal tract are nitrogen, oxygen, carbon dioxide, hydrogen and methane. The events associated with these gases differ significantly in the stomach, small intestine and large intestine.
Stomach
Swallowing air is the main source of gastric gas. Ultrafast computed tomography measurements show that with each 10 ml serving of water, 17.7 ml of atmospheric air is ingested [3]. Extrapolating these data to a daily intake of 1500 ml of liquid suggests that at least 2.5 liters of gases, mainly nitrogen, enter the stomach. To this must be added the air swallowed with food and saliva. If we consider that out of 2 liters of nitrogen, only a quarter is released in the intestines with low absorption during the passage, it becomes clear that the bulk of the air is regurgitated. This happens on average 14 times a day, although many healthy people do not feel this. The composition of gastric gas is influenced by their diffusion between the lumen and blood. Gases move passively under the influence of a pressure gradient. Absorption of oxygen and a small part of nitrogen occurs in the stomach. In return, they receive carbon dioxide, the content of which in atmospheric air is lower than in venous blood.
Thus, unconscious and accidental burping after eating is quite normal. Retrograde expulsion of gastric gas through the mouth is caused by gastric distension and may be exacerbated by foods that reduce the tone of the lower esophageal sphincter. Magenblase syndrome is diagnosed already when epigastric fullness and bloating are relieved by belching. Manometric studies of regurgitation show a decrease in the tone of the lower esophageal sphincter following relaxation of the upper [4]. A similar regurgitation mechanism is observed with hiatal hernia, gastroesophageal reflux disease, gastroparesis and duodenal-gastric reflux. Some people experience repeated, noisy regurgitation without bloating. Its reasons are different: this removes air from the retropharyngeal space, which never enters the stomach. Sometimes patients experiencing emotional stress or abdominal discomfort complain of frequent involuntary regurgitation. This temporarily helps relieve the condition. Aerophagia is well known. Patients are convinced that the cause of what is happening is severe digestive disorders. These fears further intensify the swallowing phenomenon [5]. There are also opposite situations when there is no air bubble in the stomach or regurgitation is difficult. An example would be severe achalasia. The fluid level in the esophagus acts as a barrier to gases. The fraction of swallowed air entering the duodenum varies with body position. If a person is lying on his back, regurgitation becomes more difficult. Gas becomes trapped from fluid at the gastroesophageal junction. Thus, most of the air from the stomach enters the small intestine. Difficulties in regurgitation are demonstrated by patients after fundoplication [6].
Different measures are recommended for these conditions. In case of chronic regurgitation, you should use fractional meals, exclude foods that require long-term processing in the stomach, reduce the tone of the lower esophageal sphincter, and take prokinetics. Psychotherapeutic influences are applicable to patients with aerophagia. To reduce air intake, they are advised to drink and eat food slowly, chew it thoroughly, swallow with their mouth closed, and avoid chewing gum.
Small intestine
In the upper intestine, carbon dioxide is released through the interaction of hydrogen ions and bicarbonate. On average, after eating, about 30 mEq/h of hydrochloric acid is released in the stomach [7]. To this are added fatty acids obtained during the digestion of triglycerides. Their amount reaches 100 meq per 30 g of fat. Neutralization with bicarbonate gives almost 22.4 ml of carbon dioxide per 1 mmol of substance. Typically, carbon dioxide makes up about 40% of the volume of duodenal gases, but in patients with duodenal ulcer it is higher (70%), and its pressure is 2 times higher than normal [8]. The gas is highly soluble and quickly absorbed, being replaced by nitrogen. Nevertheless, it is obvious that bloating caused by excessive secretion of hydrochloric acid in patients with duodenal ulcer will be successfully controlled with hydrogen pump inhibitors.
In the jejunum and ileum, changes in gas composition occur due to bacterial overgrowth. Traditionally it is characterized by symptoms of diarrhea, bloating and sometimes signs of malabsorption. Excessive bacterial growth is established when more than 105 colony forming units per 1 ml of contents are detected in small intestinal aspirates [9]. This condition is usually diagnosed in patients with pre-existing dysfunction of the small intestine. For example, this may result from decreased small bowel motility, hypochlorhydria, or a resected ileocecal valve. Bacterial overgrowth is often present in irritable bowel syndrome (IBS). Depending on the cause, heavy microbial colonization may be observed in the proximal small intestine, with a predominance of Gram-positive bacteria [10]. However, more often we see bacterial overgrowth distally. And here it is represented by gram-negative flora - strict anaerobes and enterococci. In order to eliminate bloating, you need to choose the right antibacterial drug. In the case of distal bacterial overgrowth, the advantages will obviously be on the side of metronidazole, which acts on anaerobic microorganisms. Changing your diet may also help. Since the ileum is filled with hydrogen-producing bacteria [11], they can be deprived of fermentable exogenous substrates, primarily incompletely absorbed carbohydrates. These include dairy products, honey, legumes, cereals and potatoes. Most individuals with lactase deficiency retain little enzyme activity. Thus, yogurt with an active culture may be better tolerated due to bacterial beta-galactosidase. Dairy products with lactobacilli and bifidobacteria reduce bloating in a number of patients with lactose intolerance [12]. The tendency to produce gas can also be reduced by cooking. Soaking peas and beans for 12 hours and cooking for 30 minutes removes most of the non-absorbable oligosaccharides raffinose and stachyose [13]. Moderate physical activity accelerates the transit of gases through the small intestine [14].
Actions to reduce bacterial fermentation with the formation of gases in the small and large intestines are largely the same.
Colon
In the colon, the bacterial flora utilizes undigested food debris - lactose, fructose, melitose, stachyose, sorbitol, resistant starch and fiber. The distribution features of the bacterial flora are such that in the right parts of the colon there are bacteria that produce hydrogen, and in the left parts - methane. Hydrogen is absorbed into the blood, but most of it is used by the same bacteria to reduce sulfate to sulfide and convert carbon dioxide to acetate. In addition, in the left colon, hydrogen is consumed by methanogens to reduce carbon dioxide to methane. Nitrogen and oxygen diffuse from the blood into the intestinal lumen, reducing the gradient created by bacterial gas production. The rate of gas excretion through the rectum in healthy people varies from 400 to 1500 ml/day and averages 705 ml/day [15]. In this case, the passage of gases occurs from 10 to 20 times a day [16, 17]. Neither age nor gender has an effect on this. Metabolism of gases in the colon is regulated by the ratio of sulfide-producing bacteria and methanogens. The main pathway of hydrogen absorption, as a rule, does not change during life. Therefore, at the “output”, 1/3 of people will have noticeable concentrations of methane [18]. Clinically, this can be easily recognized by the density of the feces. The inclusion of methane in their composition leads to the fact that feces become lighter than water and float to the surface. None of the quantitatively important gases have an odor. The unpleasant odor of feces is caused by trace amounts of sulfur-containing gases—hydrogen sulfide and methanethiol [19]. They are released during bacterial metabolism of sulfates, cysteines and mucins. In addition to the noxious odor, these gases are toxic, and the colon has an extensive detoxification system. It acts virtually without failure, protecting the mucous membrane from the damaging effects of these compounds. Sulfur-containing gases are quickly metabolized into thiosulfate [20]. Thus, they practically do not enter the bloodstream and are not excreted in the breath. The only exception is one “odorous” sulfur-containing gas - allyl histyl sulfide, a derivative of garlic. It does not undergo transformations in the mucous membrane, is absorbed and is present in exhaled air [21].
Let's look at the clinical problems associated with gas in the colon. Bloating is a companion to many diseases, but this symptom can occur due to various reasons. This is not always excess production. The feeling of bloating may occur due to impaired transit of gases with the generation of delayed motility patterns, increased perception of normal amounts of gas in the intestine, and altered somatic muscle activity in the abdominal wall. Isolated or in combination, these causes of bloating are observed in IBS. Retention of intestinal contents and gases in the small intestine as a result of slow motility or colonic reflux is responsible for generating abdominal distension in many patients with irritable bowel syndrome. A localized air trap in patients with a high splenic flexure causes swelling and pain in the left hypochondrium. However, in both the first and second cases, the total amount of gases may be normal. Abdominal bloating in the absence of excess gas production occurs due to visceral hypersensitivity [22]. Bloating and abdominal enlargement are not necessarily related [23]. A thorough study of abdominal distension made it possible to establish its occurrence only in patients with a perverted viscero-somatic reflex coming from the intestines. Instead of the normal tension of the muscles of the anterior abdominal wall and relaxation of the diaphragm, the opposite effect was observed, and the gas was distributed not in the vertical, but in the horizontal direction [24, 25]. The enlargement of the abdomen increased after eating and decreased when the patient moved to a horizontal position and during sleep. Thus, bloat is a heterogeneous condition caused by a combination of pathophysiological mechanisms that vary between individuals and in most cases are not identified by traditional methods. From a clinical point of view, it is important to note that with increased perception and impaired viscero-somatic reflexes, one cannot expect success from diet, motor regulators, or antibacterial drugs. Psychotherapy methods and antidepressants are useful here. Similarly, biofeedback therapy should be recommended for patients with dyssynergia of the pelvic floor muscles. Obstruction of the outlet leads not only to constipation, but also to impaired gas evacuation. The role of some still popular medications for the treatment of bloating should be viewed with great skepticism. This applies to absorbents and agents that reduce the surface tension of gas bubbles. Simethicone facilitates the breaking of thick foam films, but its effect on hydrogen production is controversial. Results from a well-controlled study suggest that simethicone does not improve lactulose-induced gas symptoms [26]. Activated carbon behaves the same way. Along with studies that demonstrate its benefits, there are many studies that have not confirmed changes in the total volume of gases with its use [27, 28]. There is no strong evidence base for the use of enzyme and anticholinergic drugs to reduce bloating. Rapid expulsion of gases after taking neostigmine in patients with IBS was always combined with increased abdominal discomfort, i.e. acceleration of motor activity led to even more intense pain than the accumulation of gas itself [29].
Passage of foul-smelling gases can be a serious problem for many patients. However, this issue has been little studied scientifically. Although the role of sulfur-containing gases can be considered proven, what exactly happens in the intestines is not known for certain: whether there is an excess of sulfur-containing substrates, whether their transit is accelerated, or whether the flora is oriented towards the production of such gases. The importance of various sulfur-containing substrates has never been assessed, but there are strong recommendations to avoid cabbage, beer and cheeses. Special coal-impregnated gaskets were advertised. However, they turned out to be impractical and adsorbed less than 10% of the gases [30]. Activated carbon didn't help. The only drug that eliminates hydrogen sulfide was bismuth subsalicylate (8-262 mg/day) [31]. Bismuth bound the sulfide and eliminated the odor, but how long it can be used remains unclear.
Two gases produced in the colon, hydrogen and methane, are flammable and can catch fire. Such outbreaks, leading to severe burns and perforation, have been described during electrocoagulation of polyps through a recto- and colonoscope [32], as well as after colon cleansing with mannitol [33]. It served as a substrate for hydrogen-producing bacteria. Currently used polyethylene glycol-based cleaning solutions are not fermented by bacterial flora and are therefore safe. Measurements show that when they are used, the intraluminal concentrations of hydrogen and methane are much lower than “explosive” levels.
A specific condition associated with intestinal gas is pneumatosis cystosus intestinalis, a condition characterized by the presence of gas-filled cysts in the wall of the small and large intestines. They may be asymptomatic or accompanied by pain, diarrhea and bloating. Back in the late 1970s, it was found that patients with pneumatosis intestinalis have very high concentrations of hydrogen in their exhaled air [34]. This happened because bacteria produced but did not utilize hydrogen [35]. Inadequate hydrogen consumption can be provoked by chloral hydrate enemas, but how cysts form is not yet clear. It has been suggested that counterperfusion, the process responsible for the tissue accumulation of gas in divers, is to blame. It is possible that small intramural gas collections occur with some frequency and are normal, but they are quickly absorbed into the circulation. In patients with pneumatosis, very high luminal concentrations of hydrogen by diffusion will maintain gas pressure in the cystic formations, so they persist. The only way to influence the course of the disease was the use of oxygen in high concentrations in inhalation. This maneuver reduces the nitrogen tension in the blood and thereby removes gases from the cysts into the bloodstream [36]. This treatment is combined with diet and ciprofloxacin to reduce hydrogen production by intestinal bacteria.
The purpose of this publication was not to discuss all possible clinical problems associated with gases. Rather, I wanted to emphasize their complexity and versatility. There cannot be a single approach to the management of patients with bloating, and therefore the search for optimal solutions should be based on both an understanding of the mechanisms of disease development and ideas about gas homeostasis.
Diagnostics
Proper nutrition - for normal gastrointestinal function
If discomfort in the digestive tract and flatulation continue for several days, this is a serious reason to contact a qualified specialist - a gastroenterologist.
At the appointment, the doctor collects and analyzes the patient’s life history, his regimen and eating habits, as well as existing diseases, including chronic ones.
Then a physical examination of the patient is performed by palpating and percussing the abdominal area.
The patient is then referred for laboratory tests, which include:
- General blood analysis. The presence of pathology is indicated by an increased level of leukocytes.
- Blood chemistry. One of the factors indicating the presence of pathology is hypoalbunemia - a reduced concentration of albumin protein compared to the norm.
- Coprogram. Examination of feces makes it possible to establish the presence of parasites (helminths), inflammatory processes in the intestines, and assess the state of the microflora.
If there is insufficient information obtained through laboratory tests, instrumental diagnostic studies are performed. These include:
- Ultrasound – examination of organs and tissues using ultrasound. The method is used to determine tumors, cysts, inflammatory diseases, vascular disorders and diverticulosis.
- X-ray examination is the study of organs and tissues using images obtained as a result of their irradiation with x-rays. The technique is useful in assessing the structure and functioning of the gastrointestinal tract, the condition of the mucous membranes, and allows identifying tumors, inflammatory processes (duodenitis, gastritis, colitis, cholecystitis), and developmental anomalies.
- Endoscopy is an internal examination of organs. There are several varieties of this technique depending on the organ being studied:
- during sigmoidoscopy, the rectum is examined;
- during gastroscopy – stomach;
- with duodenoscopy - duodenum;
- during colonoscopy - the large intestine.
Endoscopy allows you to determine inflammation and tumors, and identify intestinal obstruction syndrome.
