GASTROSCOPY

What is it? A fibre-optic camera is passed down into the stomach.

Why you need it Recurring “indigestion” or difficulty swallowing, especially in patients over 40, or a suspected stomach ulcer.

Will it hurt? A mild sedative and some anaesthetic to numb the back of the throat helps to minimise any gag reflex as you swallow the camera tube.

What will it tell you? Usually, everything you need to know. Acid spilling up from the stomach and burning the gullet is easy to see and ulcers are hard to miss. Tissue samples can be taken to diagnose stomach tumours.

BARIUM ENEMA

What is it? An X-ray designed to examine the colon, or “large bowel”, which doesn't normally show up. If a liquid preparation of barium, which does, is squirted up there, then the outline is easy to see.

Why you need it You've noticed some blood on the toilet paper and your GP can't be sure that it isn't just a bad case of piles.

Will it hurt? Discomfort and dizziness, which you may experience as we squirt the liquid in, spin you around to coat the bowel and then pump in some air to inflate things a little to get better-quality pictures.

What will it tell you? Hopefully that you've got something benign and treatable and not a slow-growing tumour.

BRAIN BIOPSY

What is it? A hole is drilled in the skull and a small piece of brain tissue is removed.

Why you need it We don't do these for fun. You either have a suspected malignant tumour or we wonder whether an infection has spread into the brain and its surrounding tissues.

Will it hurt? Amazingly enough, no. It's actually helpful if the patient is wide awake throughout the procedure.

What will it tell you? If it is a tumour, a biopsy will help your cancer specialist and neuro-surgeon tailor your treatment for the best possible outcome. If it's an infection, a tissue sample might tell your doctor which bacteria or virus is responsible.

CARDIAC CATHETERISATION

What is it? A thin plastic pipe is inserted into an artery in the groin and is twiddled and pushed until it reaches the heart.

Why you need it You might be suffering from pains in the chest or the doctor suspects a leaking heart valve.

Will it hurt? A little local anaesthetic over the groin and a smidgen of “vitamin V” (Valium) given just before proceedings takes care of everything.

What will it tell you? X-ray-visible fluid is injected through the pipe and outlines the coronary arteries - the ones that supply the heart muscle itself - and/or the heart's valves and chambers.

LUMBAR PUNCTURE

What is it? A teaspoonful of fluid surrounding the spinal cord is removed using a sterile needle.

Why you need it Probably because you're semi-conscious with a funny rash that doesn't go away when the skin is stretched tight.

Will it hurt? Not if you're semi-conscious. Otherwise you might feel a tingle down a leg if the needle touches a nerve root. The crashing headache that sometimes follows is termed a spinal tap.

What will it tell you? What type of meningitis you have and which antibiotics will treat it most effectively.

URETHRAL SWABBING

What is it? A small cotton bud is inserted into the plumbing between the bladder and the outside world.

Why you need it Because you've turned up at a sexual health clinic with a convincing description of a sexually transmitted infection, usually involving an unpleasant discharge and pain when you pee.

Will it hurt? That depends how sore it is up there to begin with, but stories of men leaping off the exam couch as the swab is passed are usually exaggerated.

What will it tell you? Whether it's chlamydia, gonorrhoea or trichomonas, and which antibiotic you will need to clear it up.

MAMMOGRAM

What is it? Two X-ray pictures are taken of the breast, one from above and one diagonally.

Why you need it. Mammography forms part of the NHS breast- screening programme and is offered to all women over the age of 50 at three-yearly intervals.

Will it hurt? A little. The breast has to be compressed gently between two metal plates to ensure that the images are clear enough to interpret.

What will it tell you?

Mammography is a screening procedure, not a diagnostic test. About one woman in 20 is asked to attend for further investigation and of these seven out of eight will get a clean bill of health.

DC CURRENT CARDIOVERSION

What is it? Nothing fancy. We just, erm, stop your heart for a few seconds and then give you an electric shock to get it going again.

Why you need it Your heartbeat is so irregular that drugs can't control it.

Will it hurt? Unless it's the middle of a cardiac arrest procedure you will be dozing peacefully. It's more likely to hurt us more than you, especially if we don't jump back when the guy with the electrodes shouts, “Clear!”

What will it tell you? Nothing, but it might restore your heart rhythm to normal.

ARTHROSCOPY

What is it? A fibre-optic camera is passed into a joint to allow a surgeon to look inside.

Why you need it You may have an unstable or very painful knee or shoulder.

Will it hurt? Most arthroscopies are performed under general anaesthesia but a few are done under local. A few days wearing a knee support afterwards will help to ease discomfort.

What will it tell you? Whether you have a cartilage problem. If it's only a small tear it's possible to deal with it using tiny scalpels to trim away the damaged tissue and then wash the debris out of the joint.

LIVER BIOPSY

What is it? A hollow combination needle and scalpel is passed through the upper abdomen into the liver and a sample is cut out for microscopy.

Why you need it To find out why your eyes are turning yellow.

Will it hurt? Not if the local anaesthetic works and you hold your breath when the doctor tells you to.

What will it tell you? Either that long years of heavy drinking have taken their toll or that your liver is inflamed - hepatitis - as a result of a viral infection. Very rarely it might diagnose a tumour arising from the liver itself or pick up traces of one that has spread from elsewhere.

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