Frequently asked questions about kidney stones

1. Why do kidney stones form?

Kidney stones have many causes. Broadly they fall into three groups: metabolic (how your body handles minerals), anatomical (structural issues in the urinary tract) and infection-related. The common pathway is crystals forming in urine when it is too concentrated or when certain substances are present in high amounts. These crystals can clump together and become stones. The most common are calcium-based stones. Others include uric acid, cystine and struvite (infection-related) stones.

1. Can kidney stones be prevented?

Many can. The first step is to work out why they formed. This usually means analysing any passed stone if available, blood tests, and often a 24-hour urine test to check volume and the levels of substances such as calcium, oxalate, citrate, uric acid, sodium and pH. If a metabolic cause is found, targeted measures can reduce the risk of further stones.

General prevention measures
• Fluids: aim for at least 2–2.5 litres of urine output per day (usually 2.5–3 litres of fluid intake), spread through the day; more in hot weather or with exercise
• Salt: keep dietary salt low (ideally under 5–6 g/day)
• Calcium: keep normal dietary calcium rather than restricting it, unless advised otherwise
• Protein: moderate animal protein; increase fruit and vegetables
• Oxalate: if advised, reduce high-oxalate foods (e.g. large amounts of spinach, nuts) and pair oxalate with calcium at meals
• Weight, exercise and managing conditions such as diabetes, gout and bowel disease help reduce risk
• Infection stones require treatment of the infection and, where possible, complete stone clearance

1. Is laser stone treatment an operation?

Yes. Laser stone surgery is an endoscopic operation, most often called ureteroscopy or retrograde intrarenal surgery (RIRS). A fine telescope is passed via the urethra into the ureter or kidney; the stone is fragmented with a laser and pieces are removed or passed naturally. It is usually a day case under general anaesthetic. A temporary stent may be placed to help drainage and is removed later.

1. Can every stone be treated endoscopically?

Most ureteric and kidney stones can be managed with minimally invasive techniques, but the best option depends on stone size, location, hardness, anatomy and patient factors. Broadly:

Observation
Small, symptom-free kidney stones can sometimes be monitored with imaging, especially if under about 5 mm and not obstructing.

Shockwave lithotripsy (ESWL)
External shockwaves break the stone into passable fragments. Best for selected stones, typically up to about 10–15 mm and in favourable positions and body habitus.

Ureteroscopy/RIRS (laser)
Highly effective for ureteric stones and many kidney stones, including lower-pole stones when anatomy allows.

Percutaneous nephrolithotomy (PCNL)
Used for larger or complex kidney stones via a small keyhole in the back directly into the kidney. Variants include mini-PCNL and ultra-mini techniques that use smaller instruments and may reduce bleeding and discomfort. ECIRS (combined antegrade and retrograde endoscopic surgery) can be considered in selected complex cases.

1. When is percutaneous surgery (PCNL) used?

PCNL is generally recommended when:
• Stones are large (commonly over 20 mm), staghorn, or multiple with a high total stone burden
• Lower-pole stones are larger or unfavourably sited for ESWL or ureteroscopy
• Stones are very hard or have failed other treatments
• Infection stones require complete clearance

PCNL is done under general anaesthetic. A needle puncture is made into the kidney under imaging, a tract is dilated and instruments are passed to fragment and remove stones. Hospital stay is typically 1–3 days depending on stone burden and technique; a nephrostomy tube or internal stent may be used temporarily.

Additional points patients often ask about

Pain and safety
Renal colic can usually be managed with anti-inflammatory pain relief and fluids. Seek urgent care if you develop fever with a stone, uncontrolled pain or vomiting, or reduced urine output, as these can indicate infection or obstruction.

Imaging and follow-up
Ultrasound, low-dose CT or X-ray may be used to diagnose and track stones depending on type and location. After treatment, follow-up checks for clearance and prevention planning are important.

Stents
A temporary ureteric stent can cause frequency, urgency, flank discomfort or blood in the urine. These symptoms usually settle after removal.

Recurrence
Without prevention, many people form further stones. With tailored advice and, where indicated, medication such as potassium citrate, thiazides or allopurinol, recurrence risk can be reduced substantially.

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