Transurethral needle ablation (TUNA) of the prostate is a procedure used to treat benign prostatic hyperplasia (BPH). It is performed by placing interstitial radiofrequency (RF) needles through the urethra and into the lateral lobes of the prostate, causing heat-induced coagulation necrosis. The tissue is heated to 110°C at an RF power of 456 kHz for approximately 3 minutes per lesion. A coagulation defect is created.
Transurethral resection of the prostate (TURP) was originally developed in the United States between 1920 and 1930 and was generally considered the criterion standard for surgical management of BPH.
Advances in the surgical treatment of BPH have come via applications of traditional electrosurgical current. TUNA is one of these minimally invasive treatments of prostatism. It began as a treatment in the early 1990s, with the first preliminary trials on humans in 1993. The first studies in the United States began in 1994, and the US Food and Drug Administration approved TUNA of the prostate in 1996.
However, a decline in the use of this procedure has occurred as newer techniques to treat BPH (laser ablation/enucleation, thermotherapy) have arisen and become more popular.
The TUNA system produces thermal tissue ablation by applying low-level RF energy to prostate tissue. The generated RF is in the form of electrical energy and is delivered by the 2 electrodes, which are in contact with the patient. As the prostate cells resist passage of the current, thermal energy is produced by friction and by the heating of water molecules. This leads to tissue heating and, ultimately, coagulation necrosis. Thermal lesions occur only in a localized area, because the RF signal is transmitted into tissue only by direct contact.
Although the ideal use of TUNA has been thought to be in patients with large lateral lobes, Naslund and Stitcher reported that TUNA can be used effectively in patients with large median lobes. The key to this form of treatment is to ensure that the needles are in the median lobe and do not protrude into the bladder.
A normal prostate gland is approximately 20 g in volume, 3 cm in length, 4 cm wide, and 2 cm in depth. As men get older, the prostate gland is variable in size secondary to benign prostatic hyperplasia. The gland is located posterior to the pubic symphysis, superior to the perineal membrane, inferior to the bladder, and anterior to the rectum. The base of the prostate is in continuity with the bladder and the prostate ends at the apex before becoming the striated external urethral sphincter. The sphincter is a vertically oriented tubular sheath that surrounds the membranous urethra and prostate. See the images below.