A congenital abnormality in which organs in the thorax and the abdomen are opposite to their normal positions (situs solitus) due to lateral transposition. Normally the stomach and spleen are on the left, liver on the right, the three-lobed right lung is on the right, and the two-lobed left lung on the left. situs inversus has a familial pattern and has been associated with a number of genes related to microtubule-associated proteins.