According to the A.D.A.M. Medical Encyclopedia, a Biliary Atresia "is a blockage in the tubes (ducts) that carry a liquid called bile from the liver to the gallbladder," and is caused by an abnormal development of the bile ducts. If not treated, it can lead to fatal liver damage.
This is a problem that develops in infants, and while a surgery called the Kasai procedure — which connects the liver directly to the small intestine, bypassing the ducts — can sometimes solve the problem, liver transplants can be required, as was the case with Jax.
Of course, a liver transplant is no easy thing, especially in a child that young. As we saw on the show, Jax's immune system is compromised, and he has to take weekly trips to the doctor to check up on the status of his liver. Thankfully, getting to the seven year milestone is a great sign for his continued health.
In her Bravo blog Heather encourages those of you who have been moved by Jax's story to check out DonateLifeNY.org to learn more about the New York Organ Donor Network.
The Real Housewives of New York airs Mondays at 9 p.m. ET/PT on Bravo.