Procedure guide · 8 min read

Mini-PCNL: keyhole surgery for kidney stones

Last updated: 4 May 2026 · Reviewed by Mr Sanjay Rajpal, Consultant Urological Surgeon · GMC 6106646

Mini-PCNL — miniaturised percutaneous nephrolithotomy — is a keyhole operation that reaches the kidney through a small incision in the flank, around the size of a drinking straw. It is the most reliable way to clear large or complex kidney stones in a single sitting.

Key point: Mini-PCNL is reserved for larger stones (typically over 2 cm), complex staghorn stones, or hard stones that have not responded to other approaches. The aim is a stone-free kidney with the smallest possible track.

How the procedure works

Under general anaesthetic, a fine needle is guided into the kidney using x-ray and ultrasound. The track is gently dilated to a few millimetres — much smaller than traditional PCNL — and a miniaturised telescope is passed in. A laser breaks the stone, and fragments are washed out. A small drain or a stent is usually left in place for a short period to allow the kidney to heal.

Who it suits

Kidney stones larger than 2 cm.
Lower-pole stones that do not respond to ureteroscopy or shockwave.
Hard stones (e.g. cystine, calcium oxalate monohydrate).
Patients with a history of multiple failed less-invasive procedures.

Alternatives

Smaller stones may be treated with flexible ureteroscopy and laser. Shockwave lithotripsy is non-invasive but less reliable for large or hard stones. The choice between mini-PCNL and ureteroscopy depends on stone size, position, density and the patient's anatomy and preferences.

What happens on the day

You will be admitted on the day of surgery. The operation lasts 60–120 minutes depending on stone burden. You will wake with a small dressing on the flank, often a urinary catheter overnight, and sometimes a thin drain. Most patients stay one to two nights in hospital.

Recovery

First 48 hours: mild flank discomfort, controlled with painkillers.
First week: rest, hydrate, avoid heavy lifting.
Stent removal: if used, usually 1–2 weeks later under local anaesthetic.
Four to six weeks: imaging confirms stone clearance.

Risks and side-effects

The main risks are bleeding (occasionally needing transfusion or, very rarely, embolisation), infection or sepsis, injury to surrounding structures, and the need for a second procedure if stone clearance is incomplete. Long-term kidney function is preserved in the vast majority of patients. Stent-related discomfort is common and short-lived.

When to seek help

Fever, shaking chills or worsening flank pain.
Heavy fresh bleeding or large clots in the urine.
Increasing redness, discharge or pain at the wound.
Inability to pass urine after stent or catheter removal.

Preventing future stones

Stone analysis combined with a 24-hour urine test guides long-term prevention: hydration targets, dietary changes for sodium, animal protein and oxalate, and where indicated medication such as potassium citrate or thiazides. Mr Rajpal will discuss whether a metabolic stone clinic referral is right for you.