I and other friends have the problem given below:He sits for duration double the normal time while urinating so that not a single drop remains, but when he gets up there is a feeling or perhaps a clear doubt that one or little less or little more drop has come out from Penis, this sometimes happens because of high temperature in the body mainly due to fever, illness, etc. So what is the ruling regarding such problem? Can He pray Salah in such doubtful or helpless condition? Please reply in detail if 'Yes' and in detail if 'No'?

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

If the person is certain or has clear doubts that some urine - no matter how little it is - has come out after having purified oneself from urinating he has to wash it completely from his body and clothes. But if the person has only a mere doubt which is negligible, he does not have to do any washing.
On the other hand, the person should try to cut all ways that lead to doubt and suspicion. Normally, the person could easily determine whether something has actually come out or not, just by checking and this will remove all doubts.
Allah knows best.