Article about hiatal hernia or as it is often called hiatus hernia.

What is a Hiatal Hernia?

It is where part of the stomach moves up through the muscular diaphragm into the thoracic cavity. Usually the entire stomach is positioned in the abdominal cavity below the diaphragm. A hiatus hernia causes problems such as acid reflux because the lower esophageal junction (LES) is now above the diaphragm and the valve does not work properly. A major component of the lower esophageal junction valve is the muscular crura (or cross) of the diaphragm. There are two types of hiatus hernia: Sliding hiatus hernia and rolling hiatus hernia.

Sliding Hiatal Hernia

It is known that about 95% of hiatus hernias are of the sliding type. In a sliding hiatus hernia the top of the stomach “slides” through the diaphragm.

See picture below.

The top image is of the normal anatomy of the stomach and gastro-esophageal junction (GEJ). The bottom image shows a sliding hiatus hernia. normal stomach and sliding hiatus hernia The esophagus now goes into the stomach at its upper point (at twelve o’clock) rather than at eleven o’clock. This means that no fundal compartment lies in the stomach to collect gas and to maintain a low pressure within the stomach. In a sliding hiatus hernia the, the esophagus enters straight into the top of the stomach, with a round opening, instead of the normal angled oval. There is no flap valve to prevent reflux and there are no diaphragmatic crura to close off the the lower end of the esophagus and no sling mechanism to support the junction between the stomach and esophagus. Some of the stomach is in the thoracic cavity, so that there are cells in the chest directly producing acidic digestive juices, allowing free access to the cells lining the esophagus above.

Rolling Hiatal Hernia

About 5% of hiatus hernias are of the rolling type. These are sometimes known as paraesophageal hernias. With a rolling hiatus hernia the fundus (or top) of the stomach rolls up into the chest to lie alongside the lower part of the esophagus. See diagram. The cardia (the anatomical term for the part of the stomach attached to the esophagus) remains below the diaphragm and still works well. The angle between the lower esophagus and the stomach is still in place. Also so do all the other mechanisms, such as the sphincter and the diaphragmatic crura. For these reasons reflux of stomach contents into the lower esophagus is less likely than with a sliding hiatus hernia.

Symptoms

Many people with a sliding hiatus hernia have no symptoms at all. However, having a hiatus hernia is a risk factor (and increases the likelihood) of esophageal reflux and gastro-esophageal reflux disease (GERD).

Hiatal Hernia in greater detail

What is the relationship between GERD and a hiatal hernia?

This is a question that gastroenterologists have been debating for many decades. In 1951 Dr Allison wrote that there was a very strong connection between having a hiatal hernia and the chance of developing acid reflux disease (1).

In the early 1970’s medical opinion changed to believe that gastroesophageal reflux disease was caused by weakness within the lower esophageal sphincter (2). In 1982 Dodds and others said that transient lower esophageal relaxations (tLESRs), that were not related to swallowing were an important factor in whether people developed GERD (3). A hiatal hernia became thought to be insignificant in its role in causing acid reflux disease. So in the 1980’s and 90’s a hiatus hernia was dismissed as an unimportant incidental finding during a barium swallow or upper GI endoscopy. Research published in 1992 questioned this position (4). Further research has gradually changing medical thinking (5). Now it is thought that both having a hiatal hernia and the strength of the LES are independently important.

There are other factors which lead to acid reflux disease starting such as esophageal acid clearance, tissue resistance of the esophagus, the amount of acid produced by the stomach, slowing down of emptying of the stomach etc.

There is now a two-sphincter hypothesis used by specialists to explain why GERD develops. The two sphincters are the intrinsic LES and the extrinsic pressure applied by the muscular cross (crura) of the diaphragm.

This article concentrates on the important role of a having a hiatal hernia.

Structure of the Gastroesophageal Junction

GERD is thought to develop when there is an imbalance between the aggressive and defensive factors within the esophagus affecting the sensitive lining of the esophagus. See this article for more about the battle within the esophagus: The battle in the esophagus

Aggressive factors are those such as acid produced by the stomach lining (the strength and amount of acid), the bile reflux from the duodenum into the stomach (and then the esophagus), the enzyme peptin from the stomach and delay in emptying of the stomach.

Factors important in defence of the gullet lining are those such as: the gastroesophageal junction (a mechanical anti-reflux barrier), production of alkaline saliva, strength of the mucosal lining, and the clearance and removal of acid.

The gastroesophageal junction is the first and main defence against damage by refluxed stomach contents. Abnormal damaging acid reflux occurs when this barrier weakens.

The gastroesophageal junction is a structurally complicated area and is made up of the lower esophageal sphincter (LES), the muscular cross of the diaphragm, the actual position anatomically within the abdomen of the LES, the sharply angulated angle of His and the phrenoesophageal ligament. The lower esophageal sphincter is the lower portion (measuring 3-4cm) of the gullet that maintains a naturally high muscular tone even at rest. This is the vital and important part of the defences against refluxing acid from the stomach. The pressure at rest within the LES is known to vary from 10-45 mmHG above the pressure inside the stomach. This pressure difference changes during the day and is greatest after a meal and highest at night. The muscle within the LES maintains the tone with its intrinsic muscle tone and this is controlled by the cholinergic nerves (part of the parasympathetic nervous system).

The degree of muscular tone within the LES is also affected by other factors which include:

• the pressure inside the abdominal cavity,
• levels of certain hormones and peptides (short polymers of amino acid monomers linked by peptide bonds – i.e. mini proteins),
• foods consumed and various medications.

Examples of factors that reduce the LES tone (and therefore lead to acid reflux) are:

• a fatty meal,
• chocolate,
• peppermint,
• alcohol,
• progesterone,
• octreotide,
• theophylline and
• anticholinergics.

Gastroesophageal reflux is caused by 3 factors:

1. firstly, transient lower esophageal relaxations (tLESRs),
2. secondly, hypotensive lower esophageal sphincter (LES) and
3. thirdly, an anatomical defect such as a hiatal hernia.

For those patients who do not have a structural abnormality such as a hiatal hernia, the main factor is incorrect tLESRs. These patients tend to have milder GERD. Whereas those sufferers whose mechanism of GERD is mainly due to a hypotonic LES and/or hiatus hernia generally suffer from more severe acid reflux disease.

The causes and anatomy of hiatal hernia

A hiatal hernia is a mechanical anatomical abnormality where components of the abdomen, usually the stomach and gastro-esophageal junction, move up through the diaphragm into the chest. These parts move up through the hiatus (or hole) through which the gullet or esophagus passes. This hiatus is made up of muscular crosses (or crura) of the diaphragm that form a sling, and is shaped like an ellipse.

In normal circumstances the lower part of the gullet is fixed to the esophageal hiatus by a ligament called the phrenoesophageal ligament. This is composed of two fasciae (connective tissue membranes): the endoabdominal fascia and the endothoracic fascia. This ligament, which is also called the fascia of Laimer, is fixed in a circular fashion into the muscle of the gullet close to the area of the squamocolumnar junction. This ligament plays an important role in ensuring that the gastroesophageal junction (GEJ) works properly and stops the stomach and/or GEJ from moving up into the thoracic cavity by closing off the potentially open areas between the lower gullet and the esophageal hiatus.

When we swallow, the gullet becomes shorter. This is due to contractions of the muscles that are arranged longitudinally in the esophagus. The phrenoesophageal ligament and membrane is also stretched. As a result the gastroesophageal junction and a small component of the stomach move up through the esophageal hiatus. When we finish swallowing, the parts that have moved up slide back down again because of the elastic nature of the phrenoesophageal ligament.

However, this important ligament can become “worn out” or lax as we get older. This is because of loss of elasticity due to aging and perhaps because of “wear and tear” from the mechanical stress of repeated swallowing. This laxity then increases the chance of a hiatal hernia forming. It is also thought that some of the loss of elasticity is due to shortening or contraction of the longitudinal muscles of the esophagus.

Another factor in loss of elasticity may be the increased abdominal pressure that can occur during pregnancy, in power athletes, in obesity, with previous surgery and genetic factors.

Some gastroenterologists have suggested that rather than a hiatus hernia being a cause of reflux esophagitis, the reflux esophagitis is the main culprit that starts of the process of shortening of the longitudinal muscles which then leads to a hiatus hernia developing.

There was a study carried out in opossums in which it was discovered that exposing the lining of the esophagus to acid lead to contraction of the longitudinal muscles of the esophagus which then lead to the gullet becoming shorter.

Types of hiatal hernia

Most textbooks describe two different types of hiatal hernia. These are the sliding hiatal hernia and the para-oesophageal hiatal hernia.

The para-oesophageal hernia can be further sub-divided into two or three different types, thus making three or four types.

Type 1 - sliding hiatal hernia

The first type is the sliding hiatal hernia. This type is sometimes known as a concentric or axial hiatal hernia. This category accounts for at least 95% of hiatal hernias.Para-oesophageal types make up the remaining 5%. The features of a sliding hiatal hernia are widening of the oesophagus hiatus and looseness of the phrenoesophageal ligament. This enables part of the stomach, in particular the gastric cardia, and the GEJ to pass through the opening in the diaphragm. The opening out of the esophageal orifice leads to the width of the oesophagus increasing to the size of the oesophageal hiatus. This is apparent when doctors visualize the cardia with plenty of insufflations. The orientation of the axis of the stomach is not altered in a sliding hiatal hernia. This type of hernia may be non-reducible or it can be reducible (able to be pushed back into the normal position)./p>

It is normal for the GEJ to move a little bit (up to 2cm) and for a sliding hiatal hernia to be clinically meaningful it should move beyond this 2cm range.

The diagnosis of a sliding hiatal hernia can be made by the following tests:

• an upper GI endoscopy,
• a barium swallow,
• with conventional or high-resolution manometry.

It is important to note that as a sliding hiatal hernia becomes bigger then generally the symptoms of gastroesophageal reflux disease (GERD) worsen.

Type 2 – para-esophageal hernia

he second variety is the classic type of para-esophageal hernia. In this form part of the stomach known as the gastric fundus is displaced through the muscular diaphragm. The GEJ does not pass through the aperture or hiatus. The gastric fundus comes to lie alongside the gullet because there is a defect or hole in the phrenoesophageal ligament or membrane. If the portion of the stomach that moves though the hiatus does not reduce (roll back) then the hernia may become incarcerated.

An incarcerated hernia is one that is so occluded that it cannot be returned by manipulation; it may or may not become strangulated. Incarcerated para-esophageal hernia is very rare and usually causes severe lower chest or upper abdominal pain. It is a medical emergency.

Para-esophageal hernia rarely features on a doctor’s list of differential diagnoses of acute chest or epigastric (upper abdominal) pain. The symptoms can be confused as a heart attack (myocardial infarction) and the outcome could be life-threatening. This diagnosis is easily missed when emergency department doctors do not have a high index of suspicion for this condition.

Multi-slice thoracic-abdominal computed tomography (CT) scanning is an extremely reliable and useful investigation for making the diagnosis and detecting complications.

An incarcerated para-esophageal hernia needs urgent surgical repair. It is documented in the medical literature that surgical repair of PEH results in an excellent outcome and low complication rate when compared with laparoscopic repair.

Making the correct diagnosis and ensuring proper treatment can prevent life-threatening complications.

An anatomical feature of this type of hernia is that the stomach often rotates about its longitudinal axis or rarely around its transverse axis. This is because the GEJ is fixed in its position to the median arcuate ligament and the pre-aortic fascia. Other factors that predispose to this rotation are the laxity of the gastro-colic and gastro-splenic ligaments. The rotation of the stomach leads to a volvulus (Abnormal rotation of a portion of the gastrointestinal tract, usually the intestine, around its mesenteric attachment site, which may impair blood flow to the twisted part). Laxity in the gastro-splenic and gastro-colic ligaments can then increase the risk of a volvulus occurring.

Over time a para-oesophageal hernia tends to enlarge and may need a surgical procedure to return the part of the stomach that has herniated through the diaphragm back to its original anatomical position and to relieve pressure on a segment if it is incarcerated.

Type 3 – a mixture of type 1 and type 2

In this type, there is a para-oesophageal hernia and the gastro-esophageal junction is not fixed in place, but moves through the hiatus in the diaphragm.

Type 4 – the herniation of other abdominal organs through the aperture in the diaphragm

In this type there is movement of abdominal organs (in addition to the stomach and GEJ) through the oesophageal hiatus into the thoracic cavity (into the posterior mediastinum part of the thorax). The organs than may be herniated include the colon, spleen, pancreas etc.). This type occurs because of progressive widening of the aperture and because a large defect has developed in the phrenoesophageal ligament and membrane.

This type is really a worsening of type 3 and some specialists include type 4 into the type 3 group.

The rest of this article will concentrate on the first type of hiatal hernia – the sliding hiatal hernia (type 1), and will from now on use the term “hiatal hernia” to indicate this condition, because this is the variety of hiatus hernia that is a cause of and associated with acid reflux disease.

Diagnosis

It is possible to make the diagnosis of a hiatal hernia in the following ways: radiographically (using xrays) with a barium swallow, via endoscopy and using assessment with manometry. Large hiatal hernias can be identified and diagnosed easily with any of these investigations but small (less than 2cm) hiatal hernias can be difficult to diagnose with each test having its drawbacks. ...to be completed soon

References

1. Allison PR. Reflux esophagitis, sliding hiatal hernia, and the anatomy of repair. Surg Gynecol Obstet.1951;92:419–431
2. Cohen S, Harris LD. The lower esophageal sphincter. Gastroenterology. 1972;63:1066–1073
3. Dodds WJ, Dent J, Hogan WJ, et al. Mechanisms of gastroesophageal reflux in patients with reflux esophagitis. N Engl J Med. 1982;307:1547–1552
4. Sloan S, Rademaker AW, Kahrilas PJ. Determinants of gastroesophageal junction incompetence: hiatal hernia, lower esophageal sphincter, or both? Ann Intern Med. 1992;117:977–982
5. Pandolfino JE, Shi G, Trueworthy B, Kahrilas PJ. Esophagogastric junction opening during relaxation distinguishes nonhernia reflux patients, hernia patients, and normal subjects. Gastroenterology.2003;125:1018–1024