Will this stone pass on its own?

What decides whether it passes

Two things, in this order: how big it is, and where it is.

Stones under 5mm pass spontaneously in the large majority of cases. Between 5 and 10mm the odds fall steeply. Above 10mm, spontaneous passage is uncommon enough that waiting is usually the wrong plan.²³ Position matters alongside size: a stone already at the bottom of the ureter, close to the bladder, is far more likely to pass than one sitting at the top.⁴

Pain is a poor guide. A small stone in a bad position can be agonising; a large stone sitting quietly in the kidney may cause nothing at all until it moves or obstructs. How much it hurts tells you very little about whether it will pass, and nothing about whether the kidney behind it is under pressure.

The finding that changes everything

If you have a stone and you develop a fever, the situation is no longer about pain relief.

An obstructed, infected kidney is a surgical emergency. The kidney is blocked and infected behind the blockage, pressure rises, and bacteria are driven into the bloodstream. Obstructive nephropathy causes acute kidney injury that is common and, in the words of one review, routinely undervalued.⁵ The treatment is not antibiotics and hope — it is drainage, urgently, either with a stent or a nephrostomy, and the antibiotics work properly only once the pressure is off.

So the rule is simple and worth memorising: stone pain plus fever means hospital today, not a clinic appointment next week. Kidney stones and urinary infection also feed each other — the relationship is reciprocal, with stones seeding infection and infection promoting stone formation, and the systematic review on this concludes that clearing the stone is part of treating the infection rather than something to consider afterwards.⁶

Delay costs outcomes more generally. In that same emergency cohort, presenting within a month of symptom onset was associated with roughly 4.3-fold higher odds of a good outcome than presenting later.¹

"But my urine test was clear"

This is the misconception I correct most often, and it sends people home reassured when they should not be.

Blood in the urine is common with stones but not universal. In a cross-sectional study of symptomatic stone patients, around 6% had no microscopic blood at all — and the absence of blood was associated with a lower stone position and with raised urea, not with a milder problem.⁷ A comparison study went further: patients with ureteric stones and no microscopic blood had a higher risk of moderate-to-severe hydronephrosis — more obstruction, not less.⁸

The practical consequence: a normal dipstick does not exclude a stone, and it certainly does not exclude an obstructed kidney. Imaging decides this, not urinalysis. Non-contrast CT is the most accurate test and remains the reference standard.⁹¹⁰

What the treatments actually are

If the stone will not pass, there are three routes, and the choice is mostly about size and position.

• Shockwave lithotripsy — sound waves focused on the stone from outside the body. No incision, no telescope, often no anaesthetic beyond sedation. Best for smaller stones in favourable positions; may need repeating.
• Ureteroscopy and laser — a fine telescope passed up to the stone and the stone fragmented with a laser. The workhorse for ureteric stones and for many kidney stones.
• Percutaneous nephrolithotomy (PCNL) — a track made through the flank directly into the kidney. Reserved for large or complex stone burdens.

For kidney stones in the 10–20mm range, miniaturised PCNL and retrograde intrarenal surgery show comparable effectiveness, so the decision turns on bleeding risk and recovery rather than on clearance alone.¹¹ Where bleeding is the concern in complex PCNL, tranexamic acid reduced the need for transfusion roughly five-fold in a randomised trial.¹²

Guidance from the American and European associations is broadly aligned on all of this, though both stress that the plan should still be individualised rather than read off a chart.³

Stopping the next one

This is the part that gets skipped, and it is the part that determines whether you are back in a year.

Stone disease is recurrent by nature — it behaves as a systemic metabolic condition affecting the urinary tract rather than as a one-off plumbing accident.² The single most effective intervention is unglamorous: drink enough to produce 2 to 2.5 litres of urine a day, which for most people means pale urine throughout the day rather than a fixed number of glasses.

Beyond that, generic advice stops being enough. If you have had more than one stone, you should have the stone analysed and a metabolic assessment done — a 24-hour urine collection and blood chemistry — because the right prevention depends entirely on what kind of stone you make.³² More than half of stone formers in one cross-sectional series had a demonstrable metabolic abnormality.¹³

Two cautions worth stating plainly. Do not cut dietary calcium to prevent calcium stones — it is counterintuitive but restricting calcium increases oxalate absorption and can make stones more likely, not less. And beer, cider and "flushing" teas are not treatment; they are the folk remedy most likely to delay a scan.

Stones in the bladder are a different problem

A stone that forms in the bladder rather than passing into it usually means the bladder is not emptying — which in men most often means the prostate.

In a series of men with bladder stones, acute urinary retention was the commonest presentation, and younger age, recent renal colic and smaller stones all raised the likelihood the stone had come down from the kidney rather than formed in place.¹⁴ The distinction matters, because treating the stone without treating the obstruction behind it guarantees a recurrence.

Bottom line

Under 5mm, most stones pass and waiting is reasonable with proper pain relief. Over 10mm, waiting usually wastes time. In between, position and symptoms decide.

Fever with stone pain is an emergency, and a clear urine test does not rule anything out. And if this is your second stone, the conversation should be about why you are making them — not just about removing this one.

Worth reading alongside: blood in the urine, and what happens at a first appointment.