The disease Katie suffers from is Polycystic Kidney Disease (PKD). It is a genetic condition that causes cysts to grown in the kidneys, decreasing the kidney's function over time. Approximately 60% of patients with PKD will suffer end stage renal disease and need a transplant.
Chad Lowe reprises his role as Dr. George Henry after having guest starred in the role for 3 episodes of the 4th season in 1997.