The first couple of times I accompanied my wife had no effect on me but things changed dramatically when she changed Doctors after her original Doctor (a man) retired.
Following an operation she had to have an examination and when we got to the hospital we found that her new Doctor was a woman (attractive brunette around 35 years old). We went into the examination and she asked my wife to remove her dress and sandals so she could check her height and weight. Watching her having to strip to her underwear for this woman was a huge turn-on and I felt myself getting hard!
Next she was asked to remove her bra so she could examine her breasts and I watched with pleasure as she caressed and squeezed my wife's breasts. My wife's breasts are extremely sensitive and i have often made her climax just by caressing them so I knew what this would be doing to her - her breathing had got heavier and to my delight I saw her nipples stiffen and imagined her panties getting damp with her cum. By now I had an absolutely raging erection!
The best was yet to come however as she was then asked to get onto the examination table and remove her panties for the internal exam. She slipped off her pants and spread her legs and I could see that she was already wet with excitement. The Doctor inserted 2 fingers into her vagina and began to feel and probe around. By now my wife was flushed pink and sweating and as the examination continued she occasionally gasped and flexed her legs slightly. The thought that she was responding to the Doctor's touch was fantastic and I suddenly thought how wonderful it would be if she actually climaxed during the exam - my briefs were now damp with precum and for a minute I thought I was going to ejaculate!
Sadly it was over far too soon and she was allowed to put her clothes back on and we went home. When we got back she said she was feeling a little sweaty and went for a shower. While she was in the shower I examined her panties and to my delight the crotch was soaked with her cum from when she was having her breasts examined.
It was one of the most erotic experiences of my life!