Situs inversus is a rare condition that results in a mirror image arrangement of the organs in the chest and stomach. It may be called mirror image dextrocardia, although in rare cases the heart does not move completely to the opposite side of the chest and is called levocardia. As strange as this arrangement may sound, it is not necessarily indicative of medical problems, and there are many people who do not know they have this condition unless they receive a thorough medical examination.

If people could fully visualize their organs in a mirror, they would essentially see what it would be like to have situs inversus. Everything is switched to the opposite side with the heart present on the right side of the chest next to the lung which should be on the left side of the chest. The liver, spleen, and other organs are usually flipped over as well, creating the mirror image.

It is advantageous that all the organs are on the wrong side because this maintains the way the organs behave with each other. Most people who have situs inversus have no health problems or problems. What becomes problematic is when only some of the organs change. Dextrocardia, a heart on the right side of the chest with no other organ involvement, tends to have a much higher chance of heart defects. If situs inversus occurs without dextrocardia, this can also be a problem.

While many people with situs inversus lead completely healthy and normal lives, there may be some who have additional problems. Heart defects are possible, although the rate of occurrence is only slightly higher than rates in people with a normal organ arrangement. About a quarter of people with mirror-image dextrocardia also have a condition that affects the cilia, causing it to knock backwards and making people much more susceptible to the disease. When situs inversus and primary ciliary dyskinesia occur together, this may be called Kartagener syndrome.

There is no treatment for situs inversus, unless there are additional problems. With better imaging technology, this peculiar arrangement of organs can first be noticed in utero with a sonogram. Since many of the organs are small, it is not always clear that dextrocardia in a fetus means mirror image dextrocardia. It can signify more serious conditions and may suggest that mothers be ensured that they deliver in a tertiary hospital. It should be noted that many heart defects could be noticed in the middle of a pregnancy with scans such as the fetal echocardiogram.

Many wonder why situs inversus occurs, and while this is known to be a loop defect, a clear cause is not always defined. In some cases, genetics can play a role, but this is not always true. If the condition is inherited genetically, it is believed to occur in an autosomal recessive pattern, meaning that both parents would need to carry a gene for it. Even when both parents have this gene, each child would only have a 25% chance of developing mirror image dextrocardia.