The stomach, like every organ of the body, has specific functions that it has to fulfill. When there is a dysfunction of the stomach, the process of digestion and absorption of nutrients are compromised even beyond the stomach. This can lead to a host of problems that can be encompassed under maldigestion and malabsorption. As the digestive tract functions collectively, the symptoms may not only be isolated to the stomach but extend to the end of the digestive tract and even have systemic effects.
Meaning of Stomach Dysfunction
The stomach’s main function is to digest food both mechanically and chemically. The stomach has several other roles that plays an integral part in digestion and absorption of nutrients which may not occur in the stomach itself. Therefore a stomach dysfunction may refer to any problem where the stomach cannot effectively complete one or more of these functions. The effects and symptoms may therefore extend further down the digestive tract.
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Causes of Stomach Dysfunction
The causes of stomach dysfunction focuses on the main functions of the stomach. This includes allowing food to enter the stomach from the esophagus, mechanical and chemical digestion of food in the stomach and emptying of gastric chyme (a combination of food and stomach secretions) into the duodenum of the small intestine.
Stomach Entry Problems
Food and fluids from the esophagus enter into the cardia of the stomach, the area of the stomach where the esophagus joins the stomach. This is regulated by the lower esophageal sphincter (LES), a circular band of muscles. The sphincter also prevents the stomach contents from flowing backward into the esophagus.
Although the sphincter is not part of the stomach, problems with the LES can affect stomach function. It may not close properly thereby allowing for the backward flow of the stomach contents into the esophagus. Conversely it may remain closed and not allow food and fluids to enter the stomach from the esophagus.
The stomach wall secretes a number of different substances that aids with digestion. Acid and digestive enzymes are some of these substances, along with mucus and the hormone known as gastrin. The acid and enzymes chemically digest food partially before it is passed out into the small intestine.
The mucus forms a barrier to protect the stomach wall from acid and enzymes. Gastrin stimulates the stomach wall to secrete gastric acid. Depending on the type of problem, these secretions may be abnormally high or low thereby leading to a host of different stomach problems.
Impaired Muscle Activity
The muscles of the stomach are responsible for movement of food through the stomach as well as pushing out partially digested food along with the stomach secretions into the small intestine. The stomach wall muscles also contract strongly to crush food and mix it with the digestive juices. Various problems can arise with the muscles or with the nerves that control these muscles. This can affect mechanical digestion or the pumping of gastric chyme out of the stomach.
Abnormal Stomach Emptying
Once food is sufficiently digested, it is released as gastric chyme through the pylorus. The muscles of the pylorus form a sphincter (pyloric sphincter) which regulates the outflow of the gastric chyme. Problems with the sphincter and the nerves controlling it can cause delayed or rapid stomach emptying. This may in turn affect digestion further down the tract in the small intestine.
Types of Stomach Dysfunction
A host of different types of stomach conditions may arise due to the various causes of stomach dysfunction. Some of the conditions that arise as a result of stomach dysfunction are discussed further.
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Achalasia is a condition where the lower esophageal sphincter (LES) fails to open. This prevents entry of food into the stomach. Although it is technically an esophageal problem, food cannot enter the stomach. It therefore impacts on the stomach’s ability to receive and digest food. Achalasia is mainly due to a problem with the nerves that control the muscles of the esophagus including the lower esophageal sphincter (LES).
Gastritis and Stomach Ulcers
Gastritis is a condition where the stomach wall becomes inflamed. It is mainly associated with failure of the mucus barrier to protect the stomach wall from the acid and digestive enzymes. This is usually due to H.pylori infection and the excessive use of NSAIDs, both of which counteract the mucus barrier in different ways. Stomach ulcers are open sores in the stomach wall that occur for many of the same reasons as gastritis.
Achlorhydria is a condition where the stomach produces little to no stomach acid. This may occur when the acid-producing cells in the stomach wall become underactive due to lower levels of stimulation or when these glands are damaged. Acid-suppressing drugs are one possible cause, along with H.pylori infection, stomach tumors and atrophy of the stomach wall.
Zollinger-Ellison syndrome is a problem with excessive gastrin. High levels of this hormone results in increased gastric acid production. Zollinger-Ellison syndrome is rare and occurs due to gastrin-secreting tumors (gastrinomas) that occur in the pancreas or duodenum (small intestine). The high levels of stomach acid can lead to gastritis and peptic ulcers as the mucus barrier is unable to cope.
Gastroparesis is where stomach muscle activity is impaired. This causes weak muscle contractions or a lack of stomach muscle activity. Gastroparesis is due to the a damage of the vagus nerve, which controls the stomach muscles. The condition affects mechanical digestion, mixing of the food with stomach acid and enzymes as well as pushing out of the partially digested food into the small intestine.
Gastric Outlet Obstruction
Gastric outlet obstruction includes a host of different conditions where emptying of gastric chyme is impaired. This may occur for many different reasons such as narrowing of the pylorus (pyloric stenosis), tumors, peptic ulcers, infections, obstruction caused by pancreatic pseudocysts or gallstones and muscle or nerve problems. Gastric outlet obstruction contributes to delayed gastric emptying.
Dumping syndrome is where food rapidly empties out of the stomach into the small intestine. It may bypass the stomach altogether in some instances. The main reason for dumping syndrome is surgery to the stomach usually as a means to lose weight (bariatric surgery). This phenomena is also referred to as rapid gastric emptying. With insufficient digestion occurring in the stomach, there may be further problems with digestion and absorption of nutrients further down the gastrointestinal tract.