I am 31 years old. I have gone urinate when i noticed the size (width) of penis has swollen but the head is not affected. The swollen stops at the neck. i never engage in any sexual activities as long as i can remember and most the symptoms listed from other complains and responses are absent.

i have diagnose of a kidney stone whose size is below 4mm and i have advised by my doctor go on water therapy to flush it out. i drink approximately 5 litres of water a day. 

There not inching, no pain except a very subtle sensation which i feel when conscious of it.

Please i want to know what could likely be the cause.