Situs classification

Last revised by Daniel J Bell on 14 Aug 2020

Situs classification (plural: sitūs) or body situs can be a daunting topic, but it falls into three main groups:

  1. situs solitus: the normal configuration of thoracic and abdominal organs
  2. situs inversus: mirror image of the normal configuration
  3. situs ambiguus (heterotaxy): an intermediate configuration with duplication (isomerism)

Situs is best thought of as a spectrum with situs solitus and situs inversus at either end of the spectrum. Situs ambiguus, as the name suggests, falls somewhere between the two ends of the spectrum.

When situs solitus and situs inversus occur, the atrial situs always corresponds to the visceral situs. In situs ambiguus, the bronchial anatomy always corresponds to the atrial situs.

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