Not all kidney stones are the same. A stone's composition and how dense it looks on a CT scan strongly influence which treatment will work best — which is why we work that out before treating.
Large population studies consistently find that the great majority of kidney stones are calcium-based, with calcium oxalate the single most common type, followed by calcium phosphate, then uric acid, and smaller numbers of struvite and cystine stones. The exact mix matters because different stone types behave very differently under treatment.
By far the most common stone type — the large majority of all kidney stones are calcium-based. The dihydrate form generally fragments well with shockwave lithotripsy. The monohydrate form is the hardest of the calcium stones and may need more shocks or more than one session, depending on its density.
Common and usually treatable, though response varies. One variant, brushite, is notably hard and tends to resist shockwave lithotripsy — a case where we may recommend another approach.
Accounts for roughly 8–10% of stones and is rising, often linked to obesity or metabolic syndrome. These stones are radiolucent — invisible on a plain X-ray — but show up on CT, where they have a low density and tend to fragment easily. Uniquely, uric acid stones can sometimes be dissolved by alkalinizing the urine, without any procedure at all.
Associated with urinary infections and can grow into large, branching 'staghorn' shapes. These are usually best managed with percutaneous surgery (PCNL) rather than ESWL.
Caused by an inherited metabolic condition. Cystine stones are characteristically hard and resistant to shockwaves, so they often call for a different treatment.
A non-contrast CT scan does more than show that a stone is there. The scan reports a density value in Hounsfield units (HU), and that number helps predict both what the stone is made of and how well it is likely to respond to shockwave lithotripsy. As a rough guide, uric acid stones tend to register at lower densities, struvite somewhat higher, and mixed calcium stones higher still.
Density is one of the strongest predictors of ESWL success: lower-density stones generally fragment more readily, while very dense stones may resist shockwaves and be better treated another way. This is why we review your actual CT rather than relying on stone size alone.
Because uric acid stones don't show up on a plain X-ray, they require a little more sophistication to treat with image guidance — we localize them using contrast or ultrasound. They also tend to be low-density and fragment well, and in some cases they can be dissolved with urine alkalinization rather than any procedure at all. Identifying a uric acid stone early can genuinely change the plan.
If you've had a CT scan, sharing it lets us assess your stone's size, location, and density — and give you a treatment recommendation grounded in your actual imaging.