เครื่องสลายนิ่ว Extracorporeal Shock wave lithotripsy รุ่นที่ 4 ทำงานอย่างไร?

อัปเดตล่าสุด: 15 สิงหาคม 2569

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Extracorporeal Shockwave Lithotripsy (ESWL) is a minimally invasive treatment for kidney stones. This article explains what the 4th generation of lithotripter technology added over earlier machines. It is written as general education about the technology itself — it does not describe the equipment at any one hospital. For คำแนะนำสำหรับผู้ป่วยหลังการสลายนิ่วด้วยคลื่นเสียงความถี่สูง and the history of all 4 ESWL generations, see the linked articles.

A note on our own equipment: ESWL at Bangkok Hospital Headquarters is currently performed with a third-generation lithotripter, as a daycare procedure with short-acting intravenous analgesia or light sedation for comfort. I introduced 4th-generation ESWL to Cambodia at Royal Phnom Penh Hospital in 2018, after training at Chang Gung Memorial Hospital in Taiwan — but that machine is not the one in use at BHQ today.

• ศูนย์โรคทางเดินปัสสาวะ โรงพยาบาลกรุงเทพ ทำนัด Online 02-310-3009 bhquro@bdms.co.th
• โรงพยาบาลสมิติเวชศรีราชา ชลบุรี 088-022-1445

How does Extracorporeal Shock wave lithotripsy work?

• ESWL technology originated as an incidental breakthrough during World War 2 and has been refined through 4 generations. Each generation offers better pain control and fewer complications
• The shockwave head is placed against the patient’s flank (the area where the kidney lies). The machine generates shockwave pulses that travel through the skin and break kidney stones into small fragments
• Once fragmented, the natural continuous flow of urine from the kidney flushes the stone fragments out through normal urination

What 4th Generation ESWL added over previous generations

• Auto-tracking system — 4th-generation machines use an automated targeting system that continuously tracks and locks onto the stone. This helps shockwaves hit the stone accurately and reduces unnecessary energy delivery to surrounding kidney tissue
• Less need for sedation — because less energy reaches tissue around the stone, the procedure is generally better tolerated, and many centres perform it as a daycare treatment with minimal or no sedation
• Higher reported targeting accuracy — manufacturer and comparative reports describe a hit rate of around 98.5% for 4th-generation systems, against roughly 82.6% for 3rd-generation machines
• Fewer complications — greater targeting precision means less trauma to surrounding renal tissue

None of this means older machines do not work. A 3rd-generation lithotripter remains an effective, well-established treatment for appropriately selected stones; the practical difference is that patients are given short-acting intravenous analgesia or light sedation for comfort during the session.

ESWL success rates by stone size

The European Association of Urology (EAU) 2020 guidelines recommend ESWL for kidney stones under 2 cm. Success is defined as stone fragments < 4 mm on follow-up imaging. Reported outcomes fall broadly in these ranges:

• Stone < 1 cm: around 84% success
• Stone 1–2 cm: around 77% success
• Stone > 2 cm: around 60% success

Stone size is only one factor. Stone density on CT, its position within the kidney, the patient’s body habitus, and the distance from skin to stone all influence how well any lithotripter performs.

Frequently Asked Questions About 4th Generation ESWL

What makes 4th Generation ESWL different from previous generations?

The defining feature of 4th-generation ESWL is its auto-tracking system, which continuously locks onto the kidney stone as it moves with breathing. Reported targeting accuracy is around 98.5%, compared with roughly 82.6% for 3rd-generation machines. Better targeting means less energy reaches the tissue around the stone, which reduces discomfort during the session and allows many centres to treat with minimal or no sedation. Earlier-generation machines remain effective; they simply rely more on operator adjustment and on giving the patient analgesia or light sedation for comfort.

What size kidney stones can ESWL treat?

The European Association of Urology (EAU) guidelines recommend ESWL for kidney stones under 2 cm. Reported success rates are approximately 84% for stones under 1 cm, 77% for 1–2 cm stones, and 60% for stones over 2 cm, where success is defined as residual fragments under 4 mm at follow-up. Stones larger than 2 cm may require additional sessions or an alternative procedure. Guidelines list percutaneous nephrolithotomy (PCNL) as first-line above 2 cm, but PCNL requires a tract created through the flank into the kidney; Dr. Soarawee’s preference is to attempt retrograde intrarenal surgery (RIRS) with the holmium laser wherever it is feasible, since it reaches the stone through the natural urinary passage with no incision and modern flexible ureteroscopy handles stones of almost any size. Stone density, position and body habitus also affect the result.

Is ESWL painful, and is anesthesia required?

This depends on the generation of machine. General anesthesia is not required for ESWL in either case. With a 4th-generation system, the auto-tracking function limits shockwave energy reaching tissue around the stone, so many centres treat with minimal or no sedation. With a 3rd-generation lithotripter — which is what is used at Bangkok Hospital Headquarters — patients are given short-acting intravenous analgesia or light sedation so the session is comfortable. Either way ESWL is a daycare procedure: patients go home the same day, with no post-anesthetic recovery stay.

If you have been diagnosed with kidney stones and would like to discuss ESWL or other kidney stone treatment options, Dr. Soarawee Weerasopone offers specialist consultations at Bangkok Hospital Headquarters. นัดหมายปรึกษาแพทย์. นัดหมายที่โรงพยาบาลสมิติเวช ศรีราชา ได้โดยโทรติดต่อแผนกทางเดินปัสสาวะที่ 088-022-1445.

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