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Kidney stone

Kevin Mackenzie

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Scanning electron micrograph of a kidney stone removed from Kevin Mackenzie, the creator of the image. Kidney stones form when salts, minerals and chemicals in the urine (for example calcium oxalate and uric acid) clump together and solidify. Kidney stones vary in size. Small kidney stones are often passed naturally, but larger stones sometimes get stuck in the kidney or in the tubes that carry urine out of the body. Kidney stones can cause a lot of discomfort and pain, and in some cases can lead to infection. If a stone cannot be passed naturally it may need to be surgically removed or broken up. The size of the stone in this image is 2 mm.

Why was this image chosen by the judges?

Catherine Draycott, Head of Wellcome Images, said: "The beautiful image of the kidney stone looks paradoxically like something from another galaxy with its dark and subtle colours and sense of floating weightless in space. In reality, far from floating, these jagged particles can make an excruciating path through the tiny vessels in the body."

How big can kidney stones get?

Kidney stones are normally millimetres in size; however, according to the 'Guinness Book of Records', the largest recorded kidney stone measured 13 cm at its widest point. It was removed from the left kidney of Vilas Ghuge by Dr Hemendra Shah on 18 February 2004 in Mumbai, India.