I received Shadow’s necropsy report today.  Similar to Malik, he had a ruptured mass that led to some internal bleeding and without euthanasia, he would have likely succumb to blood loss.  Differing from Malik, Shadow’s mass was cancerous and had spread from his kidney to his lungs.  The cancer is called a Hemangiosarcoma, known for rapid growth, with limited clinical signs until the tumor has become very large and spreads between organs.