Situs inversus is a condition in which the internal organs of the abdomen and thorax lie in mirror image of their normal body position. It can occur alone, without any other anomalies, or it can be a part of a syndrome with various other defects. The prevalence of situs inversus varies among different populations but is less than 1 in 10,000 people.
Although this condition may not create any health issues, it can create a great amount of medical confusion if the patient is unaware they have it. For example, if an individual with situs inversus develops appendicitis, they will present to the physician with lower left abdominal pain, since that is where their appendix lies.
Situs inversus also complicates organ transplantation operations as donor organs will almost certainly come from unaffected donors. As hearts and livers are asymmetric, geometric problems arise placing an organ into a cavity shaped in the mirror image.