Parvovirus infection in pregnancy

fetus

Q. While doing some reproductive medicine practice questions in a boards question bank I came across one I couldn’t reason through and was hoping you could help: (more…)

Which direction does blood flow through the ductus arteriosus?

Q. I just had a quick question for you. Our notes say that a ductus arteriosus allows flow from the pulmonary artery to the aorta, which I knew.
However, they also say that it’s a left to right shunt, and that it can become right to left. This confuses me, since from what I know, flow would be going from right (pulmonary artery) to left (aorta).

A. When we talk about the ductus allowing flow from the pulmonary artery (right) to aorta (left), we’re talking about intrauterine flow through the ductus. Before birth, the pressure on the right side of the heart is greater than the pressure on the left – so blood flows from pulmonary artery to aorta (through the ductus).

After birth, though, the pressure on the left becomes greater than the pressure on the right. In most babies, the ductus closes (probably in response to the new levels of oxygen in the blood). In some babies it remains patent, in which case flow would now be from the aorta (left; higher pressure) to the pulmonary artery (right; lower pressure).

If the ductus is widely patent, then after a while, that left to right shunt can put enough pressure on the lungs that they react by closing down vessels, effectively making it more difficult to push blood through. Now the right heart has to work really hard to push blood through the lungs – and it can get to the point where the right heart is actually bigger and stronger than the left, making the shunt reverse and go from pulmonary artery (right; higher pressure) to aorta (left; lower pressure).

What is array-based CGH?

Today’s post, authored by a very smart guest cytogeneticist, nicely describes array-based comparative genomic hybridization, a very cool DNA test that gives us a way to detect genetic abnormalities that are too small to be seen under the microscope. (more…)

What the heck is uniparental disomy?

We were talking about developmental pathology the other day in class – trisomies, sex chromosome numerical abnormalities, microdeletion syndromes etc. – and the term “uniparental disomy” came up.  (more…)