Once a stone causes blockage, it very often causes problems. The urine gets trapped behind the stone and builds up, increasing the pressure on your kidney. This usually leads to very severe pain, often requiring hospitalisation. The pain often comes in waves. It is frequently descibed as “loin to groin” pain. Small stones, less that 4mm, often will pass with time. However, others must be removed surgically. This mostly involves tiny telescopic instruments, that are minimally invasive. These instruments enable internal access to the stones, where they are usually fragmented using laser and removed. This is often performed as day surgery.