How is it that a kidney must be transplanted along with a pancreas?

Benefit of K/P Tx: Pancreas transplant survival rates have been improving for the past decade but still have the best long term survival when transplanted with a kidney from the same donor. The ability to monitor kidney function and biopsy the kidney allows us to detect earlier signs of graft function abnormalities than waiting for signs that the pancreas is in trouble, which is often too late.