Which term describes the normal arrangement of thoracic and abdominal organs?

• A. Situs solitus
• B. Situs inversus
• C. Situs ambiguus
• D. Situs peritoneus

Answer: (A)

Normal left-right organization of the thoracic and abdominal organs is called situs solitus. In this arrangement, the heart sits on the left side with the apex pointing left, the stomach is on the left, and the liver is on the right, with the spleen typically on the left as part of the standard visceral layout. Recognizing situs solitus on a fetal scan helps establish the baseline anatomy for interpreting cardiac and great vessel relationships. When the viscera are a mirror image, with the heart on the right and the stomach on the right, that’s situs inversus. If the arrangement is not clearly one pattern or is inconsistent, that’s situs ambiguus (heterotaxy). The term situs peritoneus isn’t used to describe visceral situs.