Kidney groans

COMIC Peter Kay has revealed he underwent emergency surgery for a huge kidney stone. In his new memoir, the star reveals it was eventually blasted away after a camera was put down his willy.

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What are your kidneys? Your two kidneys are vital organs that filter waste products from your blood.

What are kidney stones? Hard stones made from crystals containing minerals and salts. They form from chemicals like calcium and uric acid and build up into lumps in the kidneys over time. The stones, typically measuring a few millimetres, can appear in one or both kidneys.

What causes them? A diet high in salt and meat but low in fruit and veg can be a factor. Dehydration can also lead to them, as can having a family history of stones and taking certain regular medications like antacids. If you've had one before you have a higher chance of having them again. Stones can be linked to certain medical conditions like diabetes or urine infections.

Who do they affect? One in 10 people will get a kidney stone, and the number is rising. They normally occur in people aged 30-60, and more men than women get them.