There are three main parts of the upper intestinal tract:

• esophagus
• stomach
• duodenum

The esophagus is a long muscular tube connecting your mouth and your stomach. There are muscles at the top and bottom of the esophagus that control things coming and going, much like control valves. These muscles are called the upper and lower esophageal sphincters (pronounced sfink - ters).

The stomach is hollow and surrounded by two very thick layers of muscle. The stomach functions as a reservoir or holding tank for the food we eat. In children, when the stomach is empty, it is about the size of a fist, but it can get much bigger as you put things into it.

The duodenum is the uppermost part of the small intestine. The small intestine is a very long tube where food gets broken into very tiny "microscopic" particles and then absorbed into the blood.

How things work normally:

When things are working normally, after chewing your food, you swallow. When you swallow, you are pushing the food into the back of your throat and then down your esophagus. At the bottom of the esophagus is the lower esophageal sphincter. This muscle works to keep food in the stomach when the stomach is contracting or squeezing. When you swallow food, it doesn't just fall down the esophagus, it is pushed down the esophagus towards the stomach. The esophagus squeezes in a coordinated fashion with the squeeze moving from the top of the esophagus downwards towards the stomach (this coordinated type of squeezing is called peristalsis). As the food gets down to the bottom of the esophagus, the lower esophageal sphincter opens to let the food pass into the stomach and then the sphincter muscle closes again. Every time we swallow food or saliva, our esophagus squeezes in this coordinated fashion and the lower esophageal sphincter temporarily opens.

Once food gets into the stomach, it is mixed with stomach acid and other digestive juices. The stomach works like a blender. It mixes food with acid and digestive juices and mashes the food into very tiny pieces. Once the food is completely mashed, the muscle at the bottom of the stomach called the pylorus opens and closes to very slowly dribble the food into the first part of the small intestine called the duodenum.

In the small intestine, the mashed food is broken into very tiny microscopic pieces by other digestive juices and then the "digested" food is absorbed . . . passed across the lining of the intestine and into the blood.

What happens with gastroesophageal reflux:

As you can see, this is a very complicated process. In children with gastroesophageal reflux, there is some incoordination of the upper intestinal tract that accounts for their problems. Most children with reflux are good eaters . . . in fact, many times they are guzzlers . . . when they are hungry, they cannot be put off. They often become quite frantic, screaming and clawing at their faces. Once they are fed, they tend to gulp down their milk or formula very quickly. They usually don't choke or gag during feedings. This suggests they have no difficulty getting the food from their mouth to their esophagus!

Once the food is in their stomach, the stomach begins contracting - mashing the food and mixing it with acid and digestive juices. In children with reflux, out of the blue, the lower-esophageal sphincter opens so that as the stomach squeezes, there is nothing to keep the food in the stomach and so it comes back up the esophagus. This is gastroesophageal reflux! Sometimes, the food and acid come all the way up the esophagus and out the mouth and the child "spits up" or "vomits". Other times, the food or acid may only come part way up. In you and I, this is what we call heartburn or indigestion.

Anything that increases the pressure in the stomach has a tendency to make reflux worse. This is why many infants with reflux will spit up when they are straining to pass a bowel movement or when they cough, sneeze, or laugh.

Since reflux usually takes place when the stomach is contracting normally, most of the time, when an infant "throws-up" or "spits-up" with reflux, they don't have much pain or discomfort. In fact, many infants with reflux are not bothered at all by their reflux. They will be perfectly content immediately before they throw-up, and seem fine immediately afterwards too. Much of the time, it seems as if the baby isn't aware of any problem before they throw-up! This is very different than when we vomit because we have an intestinal flu-virus or an intestinal blockage. With that type of vomiting, we feel sick beforehand. We become very nauseous, we start sweating, salivating, and swallowing. We do all sorts of things to prepare ourselves for the vomiting including running to the bathroom!

• heartburn
• indigestion
• a feeling of food getting stuck in their throat (the medical term for this is dysphagia)
• recurrent or persistent hiccoughs

While we assume that young infants may have the same symptoms, we don't know for sure. The most common symptoms that young infants seem to experience with gastroesophageal reflux are:

• frequent or recurrent vomiting
• heartburn, gas, or abdominal pain

Many other symptoms are sometimes blamed on gastroesophageal reflux, but much of the time, we really aren't sure whether reflux actually causes them. Some less common problems seen in young infants that are may be blamed on gastroesophageal reflux include:

• colic or recurrent abdominal pain
• recurrent episodes of choking or gagging
• feeding problems
• poor growth
• unusual posturing such as wry-neck (torticollis) or arching (opisthotonus)
• apnea
• recurrent episodes of wheezing or pneumonia 

Colic, abdominal pain, and feeding difficulties and gastroesophageal reflux:

Older children and adults with chronic reflux sometimes  complain of frequent heartburn, chest pain, or indigestion. Some adults experience frequent or recurrent hiccups or complain that food "gets stuck" in their throat (dysphagia). Most of these symptoms are thought to develop when the esophageal lining becomes inflamed or irritated by chronic or repeated exposure to gastric acid and gastric digestive juices (esophagitis).

While we often assume young infants experience similar symptoms with reflux, it is very difficult to know whether a baby's irritability, difficulty sleeping, or feeding problems are caused by reflux.  Thirty-six percent of infants experience daily episodes of hiccups, 17% cry for at least an hour each day, and 10% have at least one episode of arching each day so these behaviors are by no means specific for reflux.   Nevertheless, there are reports of infants with feeding failure or feeding refusal, repeated arching (opisthotonus), or other unusual forms of posturing whose symptoms improve or resolve with treatment for reflux.

Very rarely, infants with chronic and/or severe reflux may develop erosive or bleeding esophagitis. This can result in blood being visible when the child vomits or spits up. If the esophagitis is extremely severe or it persists for a prolonged period of time, it is possible for esophageal scarring to develop. This is termed an esophageal stricture. It is very difficult to determine how many children with chronic reflux develop esophageal strictures, but they are clearly very rare.  Among adults with chronic esophagitis, only three in 1000 will develop esophageal strictures over many years of follow-up.

Poor growth and gastroesophageal reflux:

It is extremely unusual for gastroesophageal reflux to impair or limit a child’s growth as long as an adequate number of calories are being provided.  In most cases, poor growth in a child with gastroesophageal reflux occurs when a family unintentionally limits their child’s intake of calories.  To try and lessen the vomiting, they dilute the formula with water or limit milk/formula intake and substituting water or Pedialyte^®.    

Respiratory symptoms and gastroesophageal reflux:

There is a long list of respiratory symptoms that may be associated with gastroesophageal reflux, however, it is often difficult to know whether the reflux causes the lung problems or the other way around.  Since the windpipe (trachea) and the esophagus are very close together, many people have assumed that aspiration of refluxed stomach contents leads to respiratory symptoms.

Reflux of stomach contents up into the upper esophagus has been demonstrated in some patients with recurrent respiratory symptoms, however this appears to be very uncommon and is probably extemely rare among children who are neurologically normal.

While children with neurological abnormalities may aspirate refluxed stomach contents, more often, these children aspirate while they are eating.  This is called laryngeal penetration and it occurs when swallow-breathe patterns are not well coordinated. Normally, with the initiation of a swallow, there is a pause in breathing and the larynx closes to protect the airway. In children who show no swallowing difficulties, it is reasonable to assume that these protective reflexes will function during an episode of gastroesophageal reflux.

There are reports describing children who suffer from  chronic congestion and chronic hoarseness having gastroesophageal reflux.  It is thought that aspiration of refluxed stomach contents causes inflammation and swelling of the upper airways and results in noisy breathing (stridor) or spasms of the vocal cords (laryngospasm).  If evaluation of the upper airway demonstrates chronic inflammation, it is reasonable to consider GER as a potential source of the symptoms.

The role of GER in apnea (stopping breathing) and bradycardia (slowing of the heart rate) has been of great interest because of the potentially life-threatening nature of these symptoms. Although many studies have demonstrated that infants with apnea may have gastroesophageal reflux, there is usually little or no correlation between apneic episodes and reflux episodes.  Instances in which apnea and GER have been directly associated in a cause-and-effect manner are extremely uncommon.

Both children and adults with chronic asthma have an increased incidence of gastroesophageal reflux. However, it is extremely difficult to know whether reflux causes asthma or asthma causes reflux. Chronic asthma may precipitate reflux since chronic coughing and increased respiratory efforts increase abdominal pressure which tends to force stomach contents upwards. Among children with chronic asthma, the overall incidence of gastroesophageal reflux has been reported to range between 46 and 75%. In one study, 82% of adult asthmatics had evidence of reflux!. Relatively few children with chronic asthma experience significant improvement in their asthma when they are treated for reflux so while reflux should be considered as a possible cause of uncontrolled chronic respiratory symptoms in children, it is important to remember that many of the trigger factors for wheezing also trigger gastroesophageal reflux.