For each of the following links, you will be taken either to selected CT images or to a movie constructed from CT scans. If fixed images, look at them, then come back to this page for the
answer. If the link takes you to a movie, look at it frame by frame, then come back to this page for the
answer. In either case, if you don't want to guess what's wrong, you can look at the answer beforehand.
Thoracic Anomaly or Pathology 1 (The patient has received intravascular contrast.)
Not only does this patient have many calcifications in the wall of the aorta, but there is also a dissecting
aneurysm of the descending aorta. A dissecting aneurysm is said to occur when blood infiltrates into the wall of the
vessel, separating it into two layers. The radiologist said the blood within the dissecting aneurysm was partially
thrombosed.
Thoracic Anomaly or Pathology 2 (The patient is recovering from mitral valve surgery.)
There is considerable bleeding into the pericardial cavity, posing the threat of pericardial tamponade. The patient
also has pleural effusions on both sides.
Thoracic Anomaly or Pathology 3 (I could not have answered this myself.)
This is an example of a persistent left SVC. It was an incidental finding made by one of Stony Brook's very astute
radiologists, Dr. William Moore. When I saw his write-up, I had to refer to an embryology text to be reminded not
only that such a thing can occur, but how it happens. I will explain how a persistent left SVC arises, but it will
be pretty hard to understand without referring to illustrations (such as Figs. 14-3 and 14-4 in Before We Are
Born , by K. L. Moore and T. V. N. Persaud, 7th ed., or Fig. 12.44 in Langman's Medical Embryology , by T.
W. Sadler, 11th ed.). Normally, a large shunt develops betweeen the left and right anterior cardinal veins. This
shunt is the l. brachiocephalic vein, which as you know carries blood from the left internal jugular and subclavian
vv. to the right side. After the shunt develops, the left common cardinal vein becomes deprived of most of its blood
flow (the l. posterior cardinal v. having previously degenerated) and usually becomes fibrous. The part of the l.
anterior cardinal vein inferior to the shunt persists as the l. superior intercostal vein, now carrying blood upward
to the l. brachiocephalic vein. The part of the r. anterior cardinal v. inferior to the shunt, along with the r.
common cardinal v., become the normal right-sided SVC. It empties into the smooth-walled part of the right atrium,
derived from the right horn of the sinus venosus. The left horn of the sinus venosus becomes the coronary sinus. How
then can one get a second SVC on the left side? It happens if the shunt between anterior cardinal veins fails to
develop. As a result, the inferior part of the l. anterior cardinal v. and the l. common cardinal v. both stay big
because they are carrying all the blood from the l. internal jugular and subclavian veins. Since the l. common
cardinal vein empties into the l. horn of the sinus venosus, which has become the coronary sinus, the latter too is
also much larger than normal. The full length of the l. anterior cardinal v., along with the l. common cardinal v.
into which it empties, are said to constitute a left SVC. This left SVC in turn empties into the large coronary
sinus. I don't expect anyone to remember this, but it was fun for me to review something I had long forgotten.
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