What is Situs Inversus?

Situs inversus is a rare condition resulting in a mirror image arrangement of the organs in the chest and stomach. It may be called mirror image dextrocardia, though in rare cases the heart is not fully moved to the opposite side of the chest and is called levocardia. As peculiar as this arrangement might sound, it is not necessarily indicative of medical problems, and there are many people who are unaware that they have this condition unless they receive a thorough medical examination.

If people were able to fully visualize their organs in a mirror, they would essentially see what it might look like to have situs inversus. Everything is switched to the opposite side with the heart present in the right of the chest next to the lung that should be on the left side of the chest. Liver, spleen and other organs are generally flipped too, creating the mirror image.

It’s advantageous that all organs are on the wrong side because this maintains the way the organs behave with each other. The majority of people who have situs inversus do not have problems or health issues. What becomes problematic is when only some of the organs switch. Dextrocardia, heart in the right side of the chest with no other organ involvement, tends to mean a much greater likelihood of heart defects being present. If situs inversus occurs without dextrocardia, this can be an issue too.

While many people with situs inversus have completely healthy and normal lives, there can be a few who have additional problems. It is possible for heart defects to occur, though rate of occurrence is only slightly higher than rates in people with normal organ arrangement. About a fourth of people with mirror image dextrocardia also have a condition affecting the cilia, which causes it to beat backward, and makes people much more susceptible to illness. When situs inversus and primary ciliary dyskinesia occur together, this may be called Kartagener’s syndrome.

There is no treatment for situs inversus, unless additional problems are present. With better imaging technology, this peculiar organ arrangement may first be noticed in utero with a sonogram. Since many of the organs are tiny, it isn’t always clear that dextrocardia in a fetus means mirror image dextrocardia. It can mean more serious conditions and might suggest making certain that mothers delivery at a tertiary hospital. It should be pointed out that many heart defects could be noted halfway into a pregnancy with scans like fetal echocardiogram.

Many wonder why situs inversus occurs, and while it’s known that this is a looping defect, a clear cause isn’t always defined. In some cases, genetics may play a role, but this isn’t always true. If the condition is genetically inherited it’s thought to occur in an autosomal recessive pattern, which means both parents would need to carry a gene for it. Even when both parents do have this gene, each child would only have a 25% chance of developing mirror image dextrocardia.