Dr. Jeff Hersh: Organs can be inverted

Q: Is it possible for some people to have their heart on the right side of the chest instead of the left?

A: Yes, this is called dextrocardia. To really understand what this means we need to understand a bit more about how the heart - and other body organs - develop.

When an embryo is developing very early in pregnancy, a structure called a gut tube and another called a heart tube are formed. These long hollow tubes have areas that widen and form pouches to become various body organs, as well as move and rotate to define the final locations of these structures. Cilia (small hair-like organelles that protrude from cells) help direct and guide this complex development.

The gut tube forms inside the abdominal cavity, rotating, widening (in some parts) and developing extensions that eventually become the stomach, intestines and other abdominal organs (liver, gall bladder, pancreas, etc.).

The heart tube also twists and folds as it develops, forming the great vessels (the aorta and vena cava) that will carry blood to and from the heart and lungs, as well as the different chambers of the heart to pump this blood once the baby is born.

In normal orientation and location of the various organs (situs solitus) the heart is mostly centered in the chest, but the base of the left ventricle (which pumps the oxygenated blood to the body) points and extends toward the left side of the chest. To make room for this, only two lobes of left lung develop; there are three right lung lobes.

Normal development of the abdominal organs situates the liver and gallbladder in the upper right and the stomach, pancreas and spleen on the left. The orientation of the large and small intestines is also well defined.

Complete situs inversus (totalis) is when all the organs are located in the mirror image location. This occurs in about one in every 10,000 people, and is usually not identified until some routine test is done since these people usually have normally functioning organs -- and, hence, a normal life expectancy. There is an X-linked hereditary component to this, with equal incidence in males and females.

Many other abnormal variations are possible. For example, the abdominal organs may have a mirror image location but the heart is in the normal left configuration, or there can be mirror image of the abdominal organs and the heart, but the great vessels may be reversed. Whenever there is an abnormal orientation that is not complete situs inversus, abnormalities of some of the organs are usually present. These are often identified when they cause symptoms during the newborn period.

The required treatment and the prognosis depend on the specific abnormalities. For example, abnormalities of the heart can be life-threatening and may require open heart surgery. Problems with development of the stomach and/or intestines can cause nutrition issues and/or other problems. Lack of development of the spleen can limit the patient's ability to fight infections.

The presence of normally functional cilia is important to guide the correct rotational development of the gut and heart tubes. The hair-like cilia within the respiratory system help sweep foreign objects away. From this we can understand why 25 percent of patients with situs inversus also have "primary ciliary dsykenesia" where malfunctioning cilia predispose the patient to sinus and lung infections (Kartagener syndrome).

Dextrocardia may be suspected when a chest X-ray (or other test) is done for unrelated reasons (for example, to look for a possible pneumonia). If this happens, the first step is to ensure that the X-ray is labeled correctly since incorrect labeling can make it appear the heart is on the "wrong" side.

Other disease states that can "push" the heart out of its expected location may also make it appear that a patient has dextrocardia. Once dextrocardia is confirmed, other tests (for example a CT scan) may be done to verify whether the patient has situs inversus or some other issue.

Even in those patients with complete situs inversus and normally functioning organs, it is useful to make the diagnosis because certain diseases may present with atypical symptoms. For example, classic appendicitis would have left (rather than right) lower abdominal tenderness. Gallbladder symptoms would manifest in the left (rather than right) upper quadrant.

Finally, the mirror image shape of the organs may cause challenges if the patient needs an organ transplant.

The very complex development of the human embryo early in pregnancy offers the possibility for many different "abnormal" variations. This is one of the many things that continually make the art of medicine challenging, since one must constantly question even the most basic assumptions.

Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P., can be reached at DrHersh@juno.com.