Kidney Stones
A kidney stone is a hard deposit that forms when the salts in urine become too concentrated to stay dissolved. It causes no symptoms while it sits in the kidney; the pain — renal colic — begins when it moves into the ureter and blocks it, and it is a severe, wave-like pain from the loin round to the groin that no position relieves, usually with nausea, vomiting and blood in the urine. Most stones under 5 millimetres pass on their own within a few weeks with fluids and pain relief, larger ones often need a procedure, and the test that settles the question is a non-contrast CT of the kidneys, ureters and bladder, with ultrasound used first in pregnancy and often in younger people. One combination is an emergency: stone pain with fever or shivering means a blocked kidney that is also infected, which can become life-threatening within hours and needs the blockage relieved, not just an antibiotic. Pakistan's climate makes stones common, and prevention works: drink enough to pass about 2.5 litres of urine a day, which in a Punjab summer means well over three litres in, cut salt, keep dietary calcium normal rather than restricting it, and moderate red meat. Around half of people form another stone within ten years without prevention.
Health writers · Aslam Clinic
What a kidney stone is
Urine is water carrying dissolved waste salts. When there is too little water for the amount of salt, crystals come out of solution, stick together, and grow into a stone — exactly as sugar crystallises out of a syrup that is too concentrated. Most stones are made of calcium combined with oxalate; the rest are calcium phosphate, uric acid, struvite formed by infection, or, rarely, cystine from an inherited disorder.
A stone can sit quietly in the kidney for years and cause nothing at all; plenty are found by chance on a scan done for another reason. Trouble begins when it drops into the ureter, the narrow tube to the bladder. The ureter grips and squeezes to move it along, urine backs up behind it, and the kidney swells. That is colic, and it is one of the most severe pains in medicine.
Why stones are so common here
Pakistan sits in the belt of the world where stone disease is most common, and the reasons are unglamorous. Summer temperatures above 40 degrees for months at a time mean large fluid losses through sweat. A great deal of work is done outdoors. Fluid intake often does not rise to match, particularly for people who cannot easily reach a toilet during a working day. Concentrated urine is the single largest risk factor for a stone, and repeated in hot, dry, hard-working conditions produces it reliably.
Beyond climate, the usual contributors are a high-salt diet, a diet heavy in red meat and offal, and excess weight, a family history, recurrent urine infections, and a previous stone — which is the strongest predictor of all.
What it feels like
- Pain that begins suddenly, often at night or early morning, in the loin or flank on one side.
- Waves. The pain builds over minutes to an intense peak, eases somewhat, and builds again. Between waves it does not fully disappear.
- Movement of the pain. As the stone descends, the pain travels from the flank round the abdomen to the groin, and into the testicle or the labia.
- Restlessness. People with renal colic pace, rock and cannot lie still — the opposite of an inflamed appendix or peritonitis, where any movement hurts. This is a genuinely useful distinguishing sign.
- Nausea and vomiting, which are common and can be severe.
- Blood in the urine, visible in about one case in five and detectable on a dipstick in most of the rest.
- Urgency and frequency when the stone reaches the lowest part of the ureter near the bladder, often mistaken for a .
How it is diagnosed
- Non-contrast of the kidneys, ureters and bladder is the reference test. It finds almost every stone, gives the exact size and position, and shows how much the kidney is obstructed. Low-dose protocols keep the radiation modest.
- is first choice in pregnancy and often in children and young adults, and is widely available here. It shows swelling of the kidney and stones within it well, but frequently misses stones in the middle part of the ureter.
- of the abdomen shows most calcium stones but not uric acid ones, and is mainly used to follow a stone already known about.
- for blood and for infection.
- Blood tests — and for kidney function, plus calcium and uric acid.
- Stone analysis. If you pass a stone, catch it: strain your urine through a fine sieve or a piece of muslin and keep whatever comes out. Knowing what the stone was made of changes the prevention advice completely, and it costs nothing to collect.
Will it pass on its own?
Size and position decide it. Stones low in the ureter, near the bladder, pass more readily than those higher up, and small ones pass far more often than large ones.
| Stone size | Chance of passing on its own | Usual approach |
|---|---|---|
| Under 5 mm | Roughly two-thirds to three-quarters | Fluids, pain relief and observation for up to four weeks, with a repeat scan if it has not passed |
| 5-10 mm | Roughly half, less as size increases | As above, often with a medicine to relax the ureter. A procedure if it has not moved in four to six weeks or if pain persists |
| Over 10 mm | Unlikely | A procedure is usually planned from the outset |
| Any size, with fever | Not relevant | Urgent drainage of the kidney, whatever the size. This is an emergency |
Treatment
For a stone that is going to pass, the treatment is pain control, fluids and time. Guidelines recommend an as the first choice for renal colic, because it works better than an opioid for this particular pain and causes less vomiting. Which one, in what form, and whether it is safe for you depends on your kidney function, your stomach and your other medicines, so it is a prescribing decision rather than something to arrange at a pharmacy counter.
- Medicine to help it pass. An alpha-blocker relaxes the lower ureter and modestly improves the chance of passing a stone in the 5 to 10 mm range that is sitting low down. The benefit is real but small, and it is a prescription decision.
- Shockwave lithotripsy. Focused sound waves break the stone from outside the body, and the fragments are passed in the urine. No cuts, usually a day case, best for smaller stones in the kidney or upper ureter. Sometimes more than one session is needed.
- Ureteroscopy. A fine telescope is passed up through the bladder to the stone, which is broken with a laser and removed. Highly effective for ureteric stones. A temporary stent is often left in afterwards, which commonly causes urgency, a dull ache and some blood in the urine until it is removed — uncomfortable but expected.
- Percutaneous nephrolithotomy. For large stones in the kidney, reached through a small track in the back. An inpatient procedure with the highest clearance rate for big stones.
- Urgent drainage. For an infected obstructed kidney, a stent from below or a nephrostomy tube through the back relieves the pressure immediately; the stone itself is dealt with later, once the infection is controlled.
Types of stone, and what drives each
| Type | Roughly how common | What drives it | What helps |
|---|---|---|---|
| Calcium oxalate | About 7 in 10 | Concentrated urine, high salt, high oxalate intake, and — counter-intuitively — a low-calcium diet | Fluids, less salt, normal dietary calcium taken with meals, moderating very high-oxalate foods |
| Calcium phosphate | About 1 in 10 | Alkaline urine, some kidney tubule disorders, overactive parathyroid glands | Fluids, less salt, and treating the underlying cause where there is one |
| Uric acid | About 1 in 10, higher in hot climates | Persistently acidic and concentrated urine, obesity, , gout, high intake of red meat and offal | Fluids, less red meat and offal, weight loss, and alkalinising treatment a doctor prescribes. These stones can sometimes be dissolved |
| Struvite (infection stones) | About 1 in 20 | Repeated urine infections with bacteria that split urea. Can grow very large and fill the kidney | Complete surgical removal plus treating and preventing infection. Rarely managed with medicine alone |
| Cystine | Rare, inherited | An inherited defect that leaks cystine into the urine, usually starting in childhood | Very large fluid intake, alkalinising treatment and specialist follow-up for life |
Stopping the next one
About half of people who form a stone form another within ten years. Prevention is not complicated, and the first item on the list does more than the rest combined.
- Drink enough to pass about 2.5 litres of urine a day. That usually means more than three litres in, and considerably more in summer or with outdoor work. The test is not how much you drink but what comes out: urine should be pale straw, not dark yellow. Keep drinking through the evening, because urine concentrates most overnight.
- Add lemon. Citrate binds calcium in the urine and stops crystals sticking together. Fresh lemon or lime juice in water through the day is a cheap and reasonable way to raise it. Bottled squashes loaded with sugar are not.
- Cut salt to under 5 grams a day. Salt makes the kidney excrete more calcium into the urine. The salt is mostly not in the shaker: it is in pickles, papar, packet masalas, namkeen, bakery items and restaurant food.
- Keep dietary calcium normal. Around 1000 to 1200 mg a day from food — milk, dahi, cheese, and it works best when eaten in the same meal as high-oxalate foods, because the calcium binds the oxalate in the gut instead of in the kidney. Cutting calcium out is the most common piece of wrong advice about stones and it increases the risk.
- Moderate red meat and offal, particularly for uric acid stones. Not elimination; moderation.
- Reduce very high-oxalate foods only if your stones are calcium oxalate. The heavy contributors here are spinach and other saag, nuts, sesame, chocolate, and very strong tea drunk in large amounts. A couple of cups of chai is not the problem; a dozen is worth a thought.
- Avoid high-dose vitamin C supplements, above about 1000 mg a day, which the body converts partly to oxalate. Vitamin C in food is not a concern.
- Lose weight if you are carrying extra, and get treated if you have it.
- Ask for a 24-hour urine collection if you have had two or more stones, or one at a young age, or a strong family history. It measures what your own urine is over-producing and turns general advice into advice for you.
When to see a doctor
See a doctor for any episode of severe one-sided flank pain, for blood in the urine, and for a stone found by chance on a scan, so that its size and position can be judged. If you are waiting for a stone to pass, arrange the follow-up scan rather than assuming silence means it has gone: a stone can obstruct a kidney painlessly and damage it over weeks.
Go to an emergency department for fever or shivering with the pain, for pain that will not settle, for persistent vomiting, if you cannot pass urine, or if you have one kidney or a transplant. And if you pass a stone at home, keep it and take it to your next appointment.
Common questions
Still not sure what to do?
Reading about a symptom only goes so far. A doctor who can ask you questions and examine you will get further in ten minutes than any article can.
