Electrogastrography

Electrogastrography (EGG) is a method for studying the motor function of the stomach, based on the registration of biopotentials of the stomach from the surface of the body. This diagnostic method is non-invasive, as a close relationship between the electrical and contractile activity of the gastrointestinal tract has been proven. In clinical practice, the study of motility is carried out using electrogastrographs – portable devices, the main blocks of which are an amplifier and a recording device. Thanks to this method, without resorting to invasive diagnostics, the attending physician can obtain data on the presence of disorders of the digestive process.

How does the stomach work in our body

The gastrointestinal tract is represented by a complex system, where each organ performs its own, unique functions, and in general, the entire digestive tract is responsible for the processed food entering the body, the absorption of nutrients and the excretion of the processed product – feces. In this case, the process of processing food begins in the oral cavity, and then the lump of food enters the stomach through the esophagus.

The stomach is a hollow organ located in the upper part of the abdominal cavity, between the esophagus and the duodenum. Anatomically, its structure is represented by four sections – the inlet (cardiac), arch, middle part (body), pyloric (antral) section. In the antrum is the pyloric sphincter.

The oblong shape of the organ has two bends – small and large. A small bend is turned towards the liver, a large one – towards the spleen. Outside, the organ is covered with a serous membrane, its walls consist of muscular, submucosal and mucous layers of tissue.

The gastric mucosa contains special digestive glands that produce the enzyme pepsin and hydrochloric acid.

In addition, the antrum contains cells that produce mucus that covers the inner lining of the stomach and performs a protective function. It is thanks to her that the gastric juice cannot digest the internal mucous layer of the organ.

In the human digestive system, the stomach performs several functions:

• motor;
• secretory;
• excretory;
• suction.

Motility of the stomach implies peristaltic contractions of the muscle tissue of the organ, which contribute to the promotion of the food bolus through the gastric cavity towards the intestines. It is the wave-like contraction of the muscles throughout the cavity of the stomach with a certain rhythm and speed that provides the evacuation function and additional grinding of food.

Secretory function is provided by the activity of the glands of the stomach, which produce special enzymes and liquid for digesting the food bolus.

Excretory (excretory) function of the stomach is one of the extrarenal ways of removing metabolites from the bloodstream to ensure homeostasis. Metabolic products are released into the stomach cavity, as well as substances that have entered the body, the presence of which in it is unnecessary or harmful. The excretory function of the stomach promotes the activity of the kidneys, protecting them from excessive stress. The role of this function especially increases in various pathological conditions of the body or under extreme influences on it, causing pronounced changes in metabolism.

Absorption function of the stomach. Under normal conditions, the vast majority of nutrients in the stomach are not absorbed. Due to the motor activity of the stomach, the movement of food masses into the intestine occurs before significant absorption has time to occur. In some diseases of the stomach, accompanied by food retention or severe inflammation of the mucous membrane, the absorption process is greatly enhanced. Consequently, the main part of the beneficial components of food is absorbed in the intestines. The walls of the stomach absorb some of:

• alcohol;
• iodine;
• bromine;
• water;
• glucose

The essence of the electrogastrography method, for which an examination is prescribed

Any disturbances in the contractile activity of the stomach and intestines, disorders of the coordination of peristalsis can provoke or be the result of some pathological processes. Assessment of the level of impairment helps to identify the severity of the patient’s condition, as well as the prognosis of the course of the disease.

Electrography of the stomach refers to methods for assessing the motor function of an organ that use data characterizing the electrical activity of these organs. Such techniques are based on the presence of a relationship between the contractile and electrical activity of the gastrointestinal tract.

In clinical diagnostics, there are two types of electrogastrography:

• straight;
• peripheral.

The first type of procedure involves the placement of fixing electrodes directly on the walls of the organ, so it is used extremely rarely. With peripheral EGG, electrodes are fixed on the anterior abdominal wall, that is, on the skin of the abdomen.

EGG of the stomach is prescribed for:

• the need to establish a primary or confirm an existing diagnosis;
• study of organ motility disorders;
• preoperative preparation;
• the need to differentiate mechanical and functional disorders;
• selection and development of treatment tactics;
• quality control and effectiveness of the treatment.

Indications and contraindications for electrogastrography of the stomach

The basis for the appointment of a diagnostic procedure is the presence of a disease of the stomach. In this case, the attending physician needs to determine the state of peristalsis of the organ, as well as the features of its reaction to various drugs.

Among the indications for the implementation of electrodiagnostics:

• stomach ulcer;
• diseases of the small intestine;
• the presence of adhesions in the abdominal cavity;
• refluxes: deviations in the work of the so-called transition zones;
• diagnosis of intestinal obstruction;
• suspicion of postoperative intestinal paresis.

What are the contraindications for the procedure? Due to its painlessness and harmlessness, gastric EGG has practically no contraindications. If the subject has a pacemaker, electronic devices, implants or shunts, this should be reported to the attending physician in advance.

Requirements for preparation and technique of the procedure

All preparatory measures before electrogastrography are aimed at cleansing the stomach and intestines. For these purposes, 2-3 days before the study, as part of the preparation, the patient is transferred to a slag-free diet. To reduce the level of gas formation in the digestive tract, the following are excluded from the diet:

• fresh fruits and vegetables;
• bread, especially black;
• beans;
• milk and dairy products;
• alcoholic and carbonated drinks;
• fatty fish and meats.

On the evening before the examination, the patient may take a laxative or take a cleansing enema. Dinner should be light.

In the morning before the procedure, it is forbidden to eat and drink, as it is carried out strictly on an empty stomach.

The total duration of EGG of the stomach is about 40-50 minutes. The subject is placed on the couch, in the supine position. Special sensitive electrodes are fixed on the legs and stomach.

The location of the active conductor is determined radiographically – it is located at the intersection of the pyloric part of the stomach and the middle of the abdomen. The second electrode is placed on the right leg.

After recording the data recorded on an empty stomach, a food test is carried out. The patient takes 150 grams of bread, drinks it with a glass of tea with sugar, takes a sip of barium sulfate suspension.

The sensors display a broken line of a certain size with a specific frequency of teeth on the screen of the device. These teeth are a reflection of biocurrents arising from the contractile activity of the muscular tissue of the stomach.

The devices used for the procedure (electrogastrographs) allow recording fluctuations of biocurrents on the body surface, corresponding to the rhythm of gastric peristalsis.

Due to the fact that the frequency bandwidth has a narrow range, the device selectively records vibrations that are synchronous with contractions of the stomach.

Before the start of fixation and after its completion, the diagnostician calibrates the potentials.

Features of decoding the readings of the electrogastrograph

There is a normal range of indicators of electrical oscillations of the biocurrents of the digestive tract organs, with which the result is compared. The EGG norms of the gastrointestinal tract are represented by the following indications of the amplitude of the curve:

• colon: 0,01-0,03 Hz;
• body of the stomach: 0,03-0,07 Hz;
• ileum: 0,07-0,13 Hz;
• jejunum: 0,13-0,18 Hz;
• duodenum: 0,18-0,25 Hz.

According to L.G. Krasilnikov and B.I. Fishzon-Ryssu defines three types of EGG curves in healthy people: the normokinetic curve has an amplitude of 0,2-0,4 mV, the hyperkinetic curve has an amplitude exceeding 0,4 mV. The hypokinetic curve is fixed with an amplitude below 0,2 mV.

Any pathological processes in the stomach and neighboring organs that affect the ability of the stomach to contract are displayed on the electrogastrogram with characteristic changes, for example, a change in the rhythm of contractile movements, a violation of the amplitude of the teeth on the curve.

In addition, EGG provides an opportunity to determine the effect of various drugs and substances on the motor function of the organ. So, the introduction of 2-5 grams of sodium bicarbonate to the patient is displayed by an increase in the amplitude of the electrical oscillations. Hydrochloric acid has the ability to slow down contractions of the stomach, so the amplitude of electrical oscillations decreases.

Atropine, administered to patients with both a healthy stomach and peptic ulcer, also reduces the amplitude of the curve, while morphine increases it. At the same time, the effect of morphine and atropine in patients is expressed much longer than in healthy ones.

According to the results of electrogastrography, a diagnostician can detect a normal contraction rate (2-4 cycles per minute), or the presence of motor disorders.

Bradygastria is diagnosed if the subject has peristalsis hypotension – the frequency of contractions is less than 2 cycles per minute. Tachygastria is characterized by hypertonicity, when from 4 to 10 cycles of contractions are recorded per minute in a patient.

The obtained data are drawn up by the diagnostician in a medical report. The document, together with the fixed images of the curves, is handed over to the patient, who then passes them on to his attending physician. According to the conclusion of the diagnostician, the doctor will be able to determine the patient’s diagnosis, develop treatment tactics for him, select drug therapy, and, if necessary, prescribe other types of diagnostic procedures.

Electrogastrography is a safe and completely painless procedure for examining the functional abilities of the stomach. This diagnostic method does not require complex preparation measures and has no contraindications. It can be performed on children, adults, seriously ill patients, pregnant and lactating women. By studying the results of the EGG, the doctor can establish abnormalities in the digestive tract associated with a disorder of gastric motility.

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