My Father Is 78 Years Old, Has Some Kidney Issues.

My father is 78 years old, has some kidney issues. Otherwise fairly healthy. Tonight he showed me both his feet and ankles are swollen, red, warm to the touch. He has mobility challenge caused by a fracture in his neck several years ago. He uses a walker. He has been getting frustrated more often and is forgetting things. Could the ankle/foot redness and swelling be a serious condition?