Situs inversus totalis is a rare (0.01% of the population) condition where patients have a mirror-image reversal of their internal chest and abdominal organs. For example, the heart is in the right chest, the liver in the left upper abdominal quadrant, and the stomach/spleen in the right upper quadrant. Because this is a complete reversal that doesn’t change the relationship of one organ to another, situs inversus totalis is usually asymptomatic and discovered on physical exam or imaging studies like this coronal slice of a chest CT scan. As a cardiac anesthesiologist, I find it fascinating that even the heart chambers are reversed (a testament to the true “mirror image” description of this disease) whereby the anatomic right atrium is on the left side of the heart, the anatomic left atrium is on the right side of the heart, etc.
In roughly a quarter of cases, situs inversus totalis occurs during embryogenesis due to primary ciliary dyskinesia. Cilia are microscopic, hairlike structures that vibrate to clear secretions, create currents, and even provide mobility to certain organisms. During development, they are also responsible for determining left-right asymmetry through complex signaling pathways.
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