Found this on Mumsnet, and the person who posted it there found it somewhere else ...
One day, leaning on the bar, Jack says to Mike "My elbow hurts like ****. I suppose I'd better see a Doctor!"
Listen, don't waste your time down at the doctor's," Mike replies. "There's a new diagnostic computer at Walgreen's. Just give it a urine sample and the computer will tell you what's wrong, and what to do about it. It takes ten seconds and only costs five bucks.....a lot quicker and better than a doctor and you get Club card points".
So Jack collects a urine sample in a small jar and takes it to Walgreen's. He deposits $5 and the computer lights up and asks for the urine sample. He pours the sample into the slot and waits. Ten seconds later, the computer ejects a printout: "You have tennis elbow. Soak your arm in warm water and avoid heavy activity. It will improve in two weeks".
That evening while thinking how amazing this new technology was, Jack began wondering if the computer could be fooled. He mixed some tap water, a stool sample from his dog, urine samples from his wife and daughter and the cat, and masturbated into the mixture for good measure. Jack hurried back to Walgreen's, eager to check what would happen. He deposits $5, pours in his concoction, and awaits the results. The computer printed the following:
1) Your tap water is too hard. Get a water softener.
2) Your cat's having kittens. Get a vet
3) Your dog has ringworm. Bathe him with anti-fungal shampoo.
4) Your daughter has a cocaine habit. Get her into rehab.
5) Your wife is pregnant. Twins. They aren't yours. Get a lawyer.
6) And if you don't stop playing with yourself, your elbow will never get better
Thank you for shopping at Walgreen's
that was cute