There are several contenders for the miserable distinction of the worst pain known to humans. Although all pain is individual, and bearable or not according to many criteria other than what’s causing it, some conditions are reliably excruciating. Childbirth and toothache tend to score 10 out of 10 on pain, as do two neurological disorders: cluster headache, which can cause pain so bad that sufferers bang their heads against walls in an effort to be rid of it, and trigeminal neuralgia, a facial pain syndrome.

Kidney stones are another famously painful condition. A kidney stone is a clump of mineral salts – the waste products of various metabolic processes – that have dissolved out of the urine and aggregated together. They originate in the kidneys but frequently travel to the bladder. They can be as small as grains of sand or as large as a golf ball (in a variation on the usual fruit analogies, urology prefers sports: for example, in 1658 Samuel Pepys underwent an operation to remove a stone from his bladder that was “as large as a tennis ball”. This would have been a Real Tennis ball, which is smaller than the modern variety but still a terrible object to have in your urinary system).

Kidney stones are usually asymptomatic until they leave the kidney. Any of the body’s contractile tubes will start to hurt if they contract against a blockage. If something obstructs your bowel – a twist, a foreign body, or a tumour – you will get spasms of pain as the bowel tries to squeeze normally against the thing that’s in the way. A gallstone on the move can produce a similar sensation on the right-hand side of your abdomen. Likewise, labour pain can be viewed as a variant on this situation – the muscles of the uterus contracting against the obstruction of a baby. The tubes that lead from the kidneys to the bladder, the ureters, undergo delicate ripples of contraction all the time, helping to flush urine down to the bladder. If a stone gets stuck, the pain of delivering it to the bladder and later the outside world can be extraordinary; urologists sometimes describe it as “male childbirth” (men are about three times more likely to develop kidney stones, in part because their urinary systems are more convoluted).

This kind of pain, generated by a tube clamping down against a blockage, is described as “colicky” in nature. As is often true in medicine, you can learn from watching people as well as from listening to them. If the patient marks out a wave in the air, or opens and closes their fist, that is colicky pain, building to a crescendo before slackening off: it correlates with the action of the muscles. Renal colic is said to be felt “from loin to groin”, but in reality, as it increases in severity, both the nature of the pain and its territory can blur, until the patient ends up perceiving it as an all-encompassing spasm that is making everything hurt. The other giveaway with renal colic is that this is one of the pains that prevents you from lying still. Unlike peritonitis, where sufferers tend to remain immobile so as to avoid aggravating the inflamed tissues, patients with renal colic writhe about in futile pursuit of a comfortable position. A surgeon I worked for told me you could work out the diagnosis from the bedsheets. Neatly tucked-in meant peritonitis; rucked-up and destroyed signalled renal colic. Though few sufferers have demonstrated restlessness as extreme as Ranulph Fiennes, who was halfway to Antarctica before his kidney stones finally forced him to turn back.

Sophie Harrison is a hospital doctor in South Yorkshire

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