Lithotripsy

Lithotripsy is a medical procedure involving the physical destruction of hardened masses like kidney stones,bezoars or gallstones. The term is derived from the Greek words meaning "breaking (or pulverizing) stones" (litho- + τρίψω [tripso]).

Techniques

History

Surgery was the only method to remove stones too large to pass until lithotripsy was developed and replaced it as the most frequent treatment beginning the 1980s. In ESWL, external shockwaves are focused at the stone to pulverize it. Ureteroscopic methods use a rigid or flexible scope to reach the stone and direct mechanical or light energy is applied. Endoscopy can use different energy sources: ultrasound, electrohydraulic, mechanical and lasers.

Extracorporal shock wave therapy (ESWL) was first used on kidney stones in 1980 and is applied to gallstones and pancreatic stones. External shockwaves are focused and pulverize the stone which is located by imaging. The first shockwave lithotriptor was the Dornier HM3, a device for testing aircraft parts. Second generation devices used piezoelectric or electromagnetic generators. American Urological Association guidelines consider ESWL a potential primary treatment for stones less than 2 cm.

Shock wave

In physics, a shock wave or shock is a type of propagating disturbance. When a wave moves faster than the local speed of sound in a fluid it is a shock wave. Like an ordinary wave, a shock wave carries energy, and can propagate through a medium; however it is characterized by an abrupt, nearly discontinuous change in pressure, temperature and density of the medium. In supersonic flows, expansion is achieved through an expansion fan also known as a Prandtl-Meyer expansion fan.

Unlike solitons (another kind of nonlinear wave), the energy of a shock wave dissipates relatively quickly with distance. Also, the accompanying expansion wave approaches and eventually merges with the shock wave, partially cancelling it out. Thus the sonic boom associated with the passage of a supersonic aircraft is the sound wave resulting from the degradation and merging of the shock wave and the expansion wave produced by the aircraft.

When a shock wave passes through matter, energy is preserved but entropy increases. This change in the matter's properties manifests itself as a decrease in the energy which can be extracted as work, and as a drag force on supersonic objects; shock waves are strongly irreversible processes.

Kidney stone

A kidney stone, also known as a renal calculus or nephrolith, is a solid piece of material which is formed in the kidneys from minerals in urine. Kidney stones typically leave the body in the urine stream, and a small stone may pass without causing symptoms. If stones grow to sufficient size (usually at least 3 millimeters (0.1 in)) they can cause blockage of the ureter. This leads to pain, most commonly beginning in the flank or lower back and often radiating to the groin. This pain is often known as renal colic and typically comes in waves lasting 20 to 60 minutes. Other associated symptoms include: nausea, vomiting, fever, blood in the urine, pus in the urine, and painful urination. Blockage of the ureter can cause decreased kidney function and dilation of the kidney.

Most stones form due to a combination of genetics and environmental factors. Risk factors include being overweight, certain foods, some medications, and not drinking enough fluids. The diagnosis is usually based on symptoms, urine testing, and medical imaging.Blood tests may also be useful.Urinary stones are typically classified by their location in the kidney (nephrolithiasis), ureter (ureterolithiasis), or bladder (cystolithiasis), or by their chemical composition (calcium-containing, struvite, uric acid, or other compounds).