An embarrassing ailment
A man goes to the doctors and says, "Doctor, I have a problem. It's very embarrassing. I beg you to promise not to laugh."
The doctor answers, "Of course I won't laugh. That would be entirely unprofessional. In over twenty years of being a doctor, I've never laughed at a patient. And I have to say, in that time I've seen any number of highly embarrassing ailments. You can't surprise me."
"Alright," says the man, and he drops his trousers.
The doctor is greeted by the sight of the smallest penis he has ever seen in his life. And as his patient is a very big man, the sight is completely ludicrous. Totally unable to control himself, the doctor falls laughing to the floor.
Ten minutes later he is able to struggle up to his feet and wipe the tears from his eyes. "I'm so sorry," he says to the patient, "I don't know what came over me, I won't let it happen again. Now what seems to be the problem?"
The man sadly looks up at the doctor and says, "It's swollen."