Welcome to HCM,
You are concerned about your father and rightly so, after going through history and treatment, he suffered a infection and septicemia
which caused his renal function to worsen, it is true that he survived serious condition and treating doctors must be compimented for it.
It felt bad as he required amputation
.Actually diabetic have to to take very special care of feet.
Now when he has recovered and regaining health, please take care of his diabetes
and medicines so he improves continuously, diabetic take long time to heal wounds so take utmost care, as far as urinary catheter is concerned check for any prostate
problem with USG and PSA so it can be treated and if any neurological cause is there it should be taken care of.
If catheter can not be removed a suprapubic catheter is better option please discuss with your treating surgeon.
Take care of his diet antibiotics, vitamin supplementation and proper medical and surgical check up with dressing his wound s will heal.
Take very good care.