Situs Inversus - Case 1 6/7/2009

Great job - Elisha - you got it within 5 minutes of posting.

So the first image shows dextrocardia. In the original set, the second image shows the stomach bubble on the scout film on the right. In the second image shown here, the stomach is clearly on the right and the ileocecal valve is noted on the left (best seen at the left iliac crest).

This patient has situs inversus.

• Situs - describes position of cardiac atria and viscera
• Situs solitus - normal position
• Situs inversus - mirror image of situs solitus
• Cardiac situs - dictated by atria. (but not the apex - i.e. you can have reversal of left and right atria but apex still points to left)
• Can have situs inversus with cardiac in normal axis (levocardia) or dextrocardia.
• When there is situs inversus - the lungs are often inverted as well - the left has 3 lobes and the right has 2 lobes.
• Dextrocardia may be present but viscera is in the correct position.
• When mirror image is exact - called situs inversus totalis.
• When can't tell - situs ambiguous - heterotaxy - liver may be midline, spleen absent or multiple, atrial morphology unclear, and possibly malrotated bowel.
• 2 primary types of situs ambiguous - asplenia syndrome (right isomerism) and polysplenia syndrome (left isomerism)
• Classic asplenia - double right sidedness - bilateral right atria, absent speen, both lungs have 3 lobes, central liver, aorta and IVC on same side of spine
• Classic polyspenia - double left sidedness - multiple spleens, bilateral left atria, IVC dicontinuity with azygos or hemiazygos continuation, both lobes of lungs have 2 lobes
• All the different varieties are rare - with situs inversus - 0.01%
• Situs inversus totalis - associated with Kartagener syndrome (primary ciliary dyskinesia) (my patient didn't have it).
• Kartagener's - repeated sinus and pulmonary infections - with pulmonary sometimes leading to bronchiectasis (esp lower lobes); 20% of patients with situs inversus; transmitted by Auto Recessive; only 50% of those with Kartagener's have situs inversus; also reduced fertility or infertility is common
• Situs inversus - normal life expectancy (except for those with severe pulmonary complications and those with cardiac anomalies)
• False positive and negative results are usually due to human error with labeling - that is why quality assurance is so important.

Reference - http://www.emedicine.com/ - Dr. Annamaria Wilhelm from Mayo Clinic