Kidney Stones: How to Recognise Them, When They Pass on Their Own and How to Stop Them Coming Back

What are kidney stones and why are they so common here?

Kidney stones are hard crystals that form inside the kidney when urine carries more salts and minerals than it can keep dissolved. A stone starts as a tiny grain and grows layer by layer. It can sit quietly in the kidney for years without symptoms, or it can suddenly move into the ureter, the narrow tube that carries urine from the kidney to the bladder. That is when the pain begins, and many people describe it as the worst pain they have ever felt.

The Middle East sits inside what urologists call the stone belt, a band of hot, dry countries running through the Arabian Peninsula, the Gulf, Iraq, the Levant and Egypt. The main reason is simple. In heat the body loses a lot of water through sweat, so less urine is made and what is made is more concentrated, which is exactly the environment in which salts crystallise. Outdoor work, moving between air-conditioned cars and offices without feeling thirsty, and drinking tea and coffee in place of water all add to the risk.

In a 2021 survey of 580 residents of Saudi Arabia, 9.1% said they had already had a kidney stone, and the median age at diagnosis was only 29. The researchers also found that 35.9% of those affected had a first-degree relative with stones, and suggested the region's high rates of cousin marriage may play a part. In other words, stones here are not a disease of old age. They are a problem of working adults living and moving in the heat.

The good news is that most causes of stones can be changed. A first stone is a warning, and if you understand what type it was and why it formed, you can greatly reduce the chance of another one in the years ahead.

Kidney stone symptoms: what does renal colic feel like?

The classic symptom is renal colic: sudden, sharp pain in the side or lower back on one side, just below the ribs. It comes in waves that build, ease slightly and return, because the ureter is squeezing to push the stone along. As the stone moves down, the pain shifts towards the lower abdomen and the groin, and it can spread into the testicle in men or the labia in women.

What sets stone pain apart is that you cannot get comfortable. People with renal colic roll around, stand up, sit down and pace the room, unlike appendicitis, where people tend to lie still. Nausea, vomiting and sweating are common. Blood may appear in the urine, sometimes as an obvious pink or brown colour and sometimes only under the microscope on a urine test (urinalysis).

When the stone reaches the lower end of the ureter, close to the bladder, you may feel an urgent and frequent need to pass urine, burning, and a sense that the bladder never fully empties. These symptoms look very much like a bladder infection, so many people buy an antibiotic from the pharmacy without any test, which can delay the right diagnosis.

Not every stone hurts. A stone sitting still inside the kidney is often found by chance on an ultrasound done for another reason. Finding one does not always mean it needs treatment straight away, but it does mean it is time to start prevention and to keep an eye on it with your doctor.

When is kidney stone pain an emergency?

The most dangerous thing about a stone is not the pain but the combination of blockage and infection. When a stone blocks the ureter, urine builds up behind it. If bacteria get into that trapped urine, the kidney becomes a closed pocket of infection that antibiotics alone cannot clear. This is called obstructive pyelonephritis, and it can progress to blood poisoning (sepsis) within hours. The treatment is not to wait but to open a path for the urine quickly, usually with a stent passed up through the bladder or a tube placed through the back directly into the kidney.

A large American study published in 2020 looked at more than 311,000 hospital admissions for a blocking stone with a urinary infection. Waiting two or more days after admission to drain the kidney raised the odds of death by 29%. So if you have fever or shivering along with stone pain, do not settle for a painkilling injection at a small clinic and go home.

The second serious situation is passing no urine or very little, especially if you have only one kidney or stones on both sides. The same applies to a pregnant woman with pain in her side, to anyone who is vomiting and cannot keep fluids down, and to pain that strong painkillers do not touch. In any of these cases go to the emergency department of a hospital that has a urologist and a CT scanner, not to a local dispensary.

How are kidney stones diagnosed?

A doctor will usually start with a urine test to look for blood and signs of infection, and a blood test for creatinine to check how well the kidneys are working. A full blood count is added if infection is suspected. A raised white cell count, or pus in the urine along with a fever, changes the whole plan, because it suggests infection behind a blockage.

The most accurate way to see a stone is a CT scan without contrast dye, often written on the request as non-contrast CT KUB. It shows stones of every type, measures them in millimetres and pinpoints where they are, and those two facts, size and position, decide the treatment. Many hospitals now use a low radiation dose for this scan.

Ultrasound is a safe and useful choice in pregnancy, in children and for following up known stones, but it is less reliable at spotting small stones inside the ureter. A plain abdominal X-ray (KUB X-ray) may miss uric acid stones completely, because they do not show up on X-ray. If you are told your plain X-ray is clear despite severe typical pain, that does not rule out a stone.

Will my kidney stone pass on its own? Size is the answer

The first question after diagnosis is whether the stone will pass by itself or needs a procedure. The answer depends above all on the width of the stone in millimetres, and then on where it sits. A stone near the bladder passes more easily than one stuck high in the ureter close to the kidney.

A Swedish study followed 392 people with a stone in the ureter for 20 weeks. It found that 98% of stones 3 mm wide or smaller passed on their own, along with 81% of 4 mm stones and 65% of 5 mm stones. Then the numbers fall sharply: only 33% of 6 mm stones passed, and just 9% of stones 6.5 mm or wider. So when a doctor tells you a 3 mm stone will probably pass, that advice rests on real numbers.

While waiting, doctors usually prescribe anti-inflammatory painkillers, and in some cases a medicine that relaxes the muscle of the ureter to help the stone through, especially when it is in the lower part. Ask your doctor how many weeks they plan to wait before stepping in, because a stone that stays stuck for months can quietly damage the kidney even after the pain settles.

If the stone passes, try to catch it by passing urine through a clean tea strainer or a piece of gauze, then keep it dry in a small container. A laboratory analysis of the stone tells you its type, and everything about prevention is built on that.

Treatment for larger kidney stones: shock waves and keyhole surgery

If a stone is large, has not passed after a reasonable wait, causes pain that cannot be controlled, or comes with infection or falling kidney function, a urologist will usually recommend one of three main procedures. The choice depends on the size, position and hardness of the stone, your general health and the equipment the hospital has.

Shock wave lithotripsy (ESWL) focuses strong sound waves on the stone from outside the body, breaking it into fragments that pass in the urine. There is no cut and usually no general anaesthetic. It suits medium-sized stones in the kidney or upper ureter but works less well on very hard stones. Ureteroscopy passes a thin telescope up through the urethra and bladder into the ureter or kidney, where the stone is broken with a laser or pulled out, and its success rate is high. Very large kidney stones may need percutaneous nephrolithotomy (PCNL), in which the stone is removed through a small opening in the back.

After ureteroscopy the surgeon sometimes leaves a temporary stent, a soft tube running from the kidney to the bladder. It can cause burning, a frequent urge to pass urine and some blood, all of which are expected. The important thing is never to miss the appointment to remove it, because a stent forgotten for months can become crusted with minerals and turn into a serious problem of its own.

Types of kidney stones and what a stone analysis tells you

Not all stones are the same, and each type has its own prevention. A study that analysed 1,747 stones over 14 years in the Eastern Province of Saudi Arabia found that about 85% were calcium oxalate in both men and women. Uric acid stones came second at about 10%. Men made up 79% of the patients.

Knowing the type changes the advice completely. A person with calcium oxalate stones does not need to cut out milk and yoghurt, quite the opposite. A person with uric acid stones can sometimes have the stone dissolved, without any surgery, by a medicine that makes the urine less acidic. So always ask for the stone to be analysed, whether it passed on its own or was removed by a surgeon.

If stones keep coming back, appear at a young age, or you have only one kidney, your doctor will usually ask for a 24-hour urine collection. This measures the volume of urine and the amounts of calcium, oxalate, citrate, uric acid and sodium in it, and shows the actual cause in your body rather than relying on general advice.

How to stop kidney stones coming back: water first

The strongest evidence on prevention comes from an Italian randomised trial that followed 199 people for 5 years after their first stone. In the group told only to drink a lot of water, stones returned in 12 of 99 people, compared with 27 of 100 in the group given no advice. Water alone cut recurrence by more than half. The researchers also found that at the start, the stone formers were passing only about one litre of urine a day.

The American Urological Association advises drinking enough to pass at least 2.5 litres of urine a day. In a Gulf or Iraqi summer, or when working outdoors, that usually means well over three litres of fluid, because so much is lost as sweat. The practical test is the colour of your urine: it should stay pale, close to water, throughout the day, and you should need to get up at least once at night to pass urine. During Ramadan, spread your water between iftar and suhoor instead of drinking a large amount at once.

Salt is the second enemy. Sodium pulls calcium into the urine with it, and pickles, salty white cheese, stock cubes, crisps and processed meats carry a great deal of it. Do not cut calcium from your food, however. Calcium in milk and yoghurt binds oxalate in the gut and stops it being absorbed, and a low-calcium diet actually raises the risk of stones. The problem is calcium tablets taken without a medical reason, not a glass of laban.

If your stone was calcium oxalate and a 24-hour urine test shows high oxalate, cut back on spinach, chard, beetroot, almonds, tahini and sesame, chocolate and strong black tea, without banning them entirely. Lemon juice in water adds a little citrate, which discourages crystals, but it is no substitute for potassium citrate if a doctor prescribes it after testing. Folk remedies such as khella or corn silk tea have no strong evidence that they dissolve stones, and some have real side effects, so do not let them delay proper treatment.

Sources

• Safdar OY, Alzahrani WA, Kurdi MA et al: The prevalence of renal stones among local residents in Saudi Arabia, Journal of family medicine and primary care, 2021
• Amir A, Matlaga BR, Ziemba JB et al: Kidney stone composition in the Kingdom of Saudi Arabia , Clinical nephrology, 2018
• Jendeberg J, Geijer H, Alshamari M et al: Size matters: The width and location of a ureteral stone accurately predict the chance of spontaneous passage, European radiology, 2017
• Borghi L, Meschi T, Amato F et al: Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-year randomized prospective study, The Journal of urology, 1996
• Haas CR, Li G, Hyams ES et al: Delayed Decompression of Obstructing Stones with Urinary Tract Infection is Associated with Increased Odds of Death, The Journal of urology, 2020
• Pearle MS, Goldfarb DS, Assimos DG et al: Medical management of kidney stones: AUA guideline, The Journal of urology, 2014