Left isomerism with Kommerell diverticulum and interventricular membranous septal diverticulum

Case contributed by Fabien Ho
Diagnosis certain


CT scan requested from cardiologist for aortic aneurysm

Patient Data

Age: 40 years
Gender: Female

The distal aortic arch is dilated with an aneurysmal origin of the retro-esophageal aberrant right subclavian artery (Kommerell diverticulum).

There are thoracic and abdominal anatomic variants and anomalies:

  • atrial situs, atrioventricular and ventriculoarterial connections are normal; one may discuss two atria with left morphology. No abnormal pulmonary venous return. There is absence of the hepatic segment of the IVC with azygos continuation.  No persistent left SVC.
  • the bilateral mainstem bronchi show left morphology and each lungs have two lobes and one fissure (bilateral bilobed lungs) 
  • liver and gallbladder are essentially median in position
  • polysplenia 
  • the stomach is on the right, small bowel loops all located on the left, large bowel is located on the right: findings suggestive of a mirrored intestinal nonrotation
  • mesenteric vessels are reversed

There is a pouch-like structure located below the level of the aortic valve annulus, consistent with a membranous diverticulum of the interventricular septum, while the sinus of Valsalva and aortic valve cusps are grossly normal.

This case is a joint interpretation of imaging with Dr P. Mascarel, who is the prime reporter.

Case Discussion

This case is exceptional through association of three findings:

Case uploaded with the permission of referring radiologist Dr. Patrick Mascarel.

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