Kidney Stones: Types, Symptoms and Causes
If you've had sudden pain in your side or back, blood in your urine, or you've been told a scan picked up a stone, it helps to understand what kidney stones actually are before thinking about treatment. This page covers how stones form, the different types, the symptoms to watch for, and what genuinely helps prevent them. If you've already been advised that a stone needs treatment, the kidney stones surgery page covers the options in detail.
Kidney stones are hard deposits of minerals and salts that form inside the kidney when urine becomes concentrated. They range from specks that pass unnoticed to stones large enough to block the flow of urine.
The different types of stones
Not all stones are the same, and the type matters because it points to the cause — and to what might prevent the next one.
Calcium stones are by far the most common, usually calcium oxalate. They form when calcium binds with oxalate in concentrated urine. They're often linked to dietary and fluid factors, though the relationship is more complicated than simply "too much calcium" — cutting calcium out is usually the wrong response.
Uric acid stones form when urine is persistently too acidic. They're more common in people with gout, persistently acidic urine, high purine or animal-protein intake, or certain metabolic conditions, and unlike most stones they can sometimes be dissolved with treatment that makes the urine less acidic.
Struvite stones form in response to certain urinary tract infections. They can grow quickly and become large, and because they're driven by infection they usually need specialist management and often need to be removed completely rather than left to pass.
Cystine stones are rare and run in families, caused by an inherited condition called cystinuria that makes the kidneys leak excess cystine into the urine. They tend to recur and need ongoing management.
Knowing which type you've had is part of preventing the next one, which is why stones are often sent for analysis after they're passed or removed.
Symptoms to watch for
The classic symptom is sudden, severe pain in the side or back that radiates toward the lower abdomen and groin, often coming in waves. This is renal colic, and it's frequently described as one of the most intense pains there is. It can come with nausea, vomiting, a frequent or urgent need to pass urine, and blood in the urine.
Not every stone announces itself this way. Some sit quietly and are found incidentally on a scan done for another reason. And the symptoms above aren't unique to stones — they can point to other conditions too, which is why diagnosis matters rather than self-diagnosis.
One situation is genuinely time-critical: a stone blocking the flow of urine alongside fever, rigors, or other signs of infection. That combination can become serious quickly and needs urgent medical care, not a wait-and-see approach.
Kidney Stone Symptoms in Women
Kidney stones have historically been more common in men, but they are increasingly recognised in women as well. Stones can present and behave similarly in both sexes, but pregnancy introduces specific assessment and management considerations that are important to understand.
One important difference relates to pregnancy. If you're pregnant and diagnosed with a kidney stone, the assessment and management approach changes. Ultrasound is usually first-line imaging (CT is generally avoided unless clearly necessary), and both pain relief and any antibiotics must be pregnancy-safe. The timing of any intervention depends on the stage of pregnancy, whether there is obstruction or infection, and how well pain is controlled. Physiological hydronephrosis (mild kidney swelling) is normal in pregnancy and can complicate diagnosis, since it may be visible on imaging but unrelated to a stone.
Symptoms in women can sometimes overlap with other pregnancy-related, gynaecological, or urinary tract causes. The classic pain of renal colic — severe side or back pain radiating to the lower abdomen — is the same in women as in men, so imaging and specialist assessment are important to confirm the diagnosis.
For women planning pregnancy or currently pregnant, discussing any history of kidney stones with your healthcare provider is important — both for understanding the risks if a stone recurs during pregnancy and for considering whether any necessary treatment should be done before conception.
Stone recurrence depends on multiple factors including stone type, underlying metabolic risk factors, infection history, obesity and metabolic syndrome, and pregnancy-related changes. Outside pregnancy, the broad diagnostic and treatment principles are similar. If pregnancy is a consideration, the conversation around timing, imaging choices and medication safety becomes more specific.
How stones are diagnosed
Diagnosis combines your history and symptoms with imaging — most often a low-dose, non-contrast CT scan, and sometimes ultrasound — to confirm the size and location of the stone. Urine and blood tests check for infection, kidney function changes, and metabolic factors that may have contributed to stone formation. Size and position do most of the work in deciding what happens next: they largely determine whether a stone will pass on its own or needs treatment.
What actually helps prevent stones
Prevention is where a lot of well-meaning advice goes wrong, so it's worth being precise.
The single most effective thing is drinking enough fluid to keep urine dilute — this matters more than any single dietary change. Beyond that, reducing salt and not over-doing animal protein both help for the most common stone types.
The counter-intuitive one: for most people, cutting dietary calcium is the wrong move and can make calcium oxalate stones more likely, not less. Calcium from food binds oxalate in the gut before it reaches the kidneys. The aim is normal dietary calcium, not calcium avoidance. Calcium supplements are a different matter and are worth discussing with a doctor if you form stones.
That said, prevention isn't one-size-fits-all. The right strategy depends on the type of stone and, in people who form them repeatedly, on what urine and blood tests reveal about the underlying driver. Recurrent stones often have a preventable cause worth investigating properly rather than guessing at.
If you've been told you need treatment
Whether a stone needs treatment — and which treatment — depends on its size, position, and what's causing the obstruction or symptoms. The options range from minimally invasive approaches to surgery for larger stones. These are covered in full, along with what recovery involves, on the kidney stones surgery in Melbourne page.
About the author
Dr Deanne Soares is a Melbourne-based urologist who assesses and manages a wide range of urological conditions, with an emphasis on thoughtful, individualised care.
