Thanks for your query.Based on the facts that you have posted it appears that your father has developed stricture urethra
after endoscopic procedure of TURP .This is not uncommon to develop stricture after instrumentation of urethral passage.If the stricture is flimsy and negotiable you can go for endoscopic procedure to cut the stricture what is called as Optical Urethrotomy
If the stricture is dense then it will be better to go for open surgery of Urethroplasty
. Consult some well trained Urologist
and let the him take the decision regarding the mode of treatment.Urethroplsty is safe procedure and result are commanding in best hands.