I realise that many of you regard Dr C's articles as catheters rather than columns, in that I seem to do nothing but extract the urine from patients. That may be no bad thing, though. After all, scientists at Imperial College this week reported a groundbreaking study of urine metabolites. Apparently, each analysis gives masses of useful information about an individual's diet, inheritance and lifestyle.

As ever, though, the Japanese have probably beaten us to it. Because I'm sure I remember reading somewhere - possibly in Reader's Digest - that they've developed a “super-loo”. This not only analyses the constituents of your wee, it automatically sends the results, electronically, to your doctor. It's only a matter of time before the Government latches on to this as part of its proactive healthcare push. So you can look forward to taking a leak in the polyclinic pissoir and I can anticipate ploughing through a load of pee-mails.

We GPs really don't need these futuristic novelties. We're already at the cutting edge of thin-strip-of-plastic- with-multicoloured-patches urine-testing technology. They're called dipsticks, partly because that's what they are, but mainly because that's what I look like when I accidentally knock your specimen over my computer keyboard.

They provide an amazing amount of helpful information, though, including clues about urinary infections, kidney disease and diabetes. But they have their limitations, as one woman pointed out to me when I dipsticked her sample. “All normal,” I beamed. “I find that hard to believe,” she scoffed, “because my cat died yesterday.” Good point: they aren't great at picking up recent pet bereavement. I'll get the boffins at Imperial on to it.

Of course, urine isn't the only thing patients bring for us to test or scrutinise. And it's certainly not the most revolting. That accolade is a dead heat between two other bodily excretions. One is phlegm. Elderly bronchitics derive perverse pleasure from sharing with us something green and glutinous, preferably with the words: “You won't believe what I coughed up this morning, doctor.” The one saving grace is the “sputum sign”, a hand rummaging in the pocket for a tissue that is to be unfolded, in awestruck silence, before the physician. This telltale manoeuvre gives me time to back out of the door as urgently as I would if the patient had drawn a gun.

The other item best kept under wraps is baby poo. This is presented in a nappy, specially kept for the occasion, with the accompanying parental concern that the poo is too big, too small, too runny, too hard, or, and, this is the real killer, too smelly. “What do you think, doctor?” Well, I'd love to tell you, but I'm trying to suppress an evacuation of my own - my lunch.

No wonder then, that we GPs sometimes seek revenge. For example, on occasions, we'll request a stool sample. This may be to check for bugs in the dyspeptic stomach or blood in the dodgy bowel. Or it may simply be punishment because we're fed up with you. You'll know if it's the latter, because I'll pass you the bottle with the twee plastic spoon, offer no explanation and smile malevolently.

The other bodily sample that causes real problems is sperm. Of course, it's no joke being an infertile couple, so I'm not being punitive here, I'm being embarrassed. I know: as a rough, tough GP, I should be more professional. But the truth is, the minutiae of how to produce the sample don't fit easily into the ten- minute consultation, not even after we've broken the ice with your ingrowing toenail. That's why I have a “How to produce your sperm sample” leaflet, which I hand out with a furtive wink.

Fine until I muddle it with one on “How to relax”. So infertile man receives instructions on chilling out. And stressed bloke receives graphic detail on...well, he probably thinks I'm taking the piss.

Dr Copperfield is a GP in Essex. He also writes for Pulse magazine and Pulsetoday.co.uk

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