|Reports have been published using minimally invasive surgery to perform cryptorchidectomy, ovariectomy, abdominal exploration, bladder surgery, nephrectomy, nephrosplenic space ablation and thora-coscopy.
The major benefits of minimally invasive surgery include: smaller incisions, tension-free dissections, better visualization, and in many cases, more rapid return to function.
The challenges of minimally invasive surgery include: expensive equipment, increased level of necessary skills, and in some cases, instrument limitations. The purpose of this report is to describe some of the recent advances in equine laparoscopy.
Standing laparoscopic ovariectomy is used to remove ovaries bilaterally in mares with behavioral problems and unilaterally in mares with granulosa-thecal cell tumors (Dechant et al). The main challenge with this technique has been finding the best way to ligate the ovarian pedicle and provide hemostasis.
Successful techniques include chain ecraseurs, lasers, staples, loop ligatures, ultrasonic devices Â— and more recently, radio-frequency devices.
Most of the current literature has reported on the use of loop ligatures, ultrasonic devices and the radio-frequency devices.
Loop ligatures obviously are the most cost effective of the latter options. The loop ligatures are available commercially as Endo-Loops (Ethicon) in many different suture materials in sizes two to zero.
The major drawback of the commercially available loops is that the loop diameter is fixed and often too small for active ovaries, and the knot pusher is too short for use in 20-cm cannulas. In human laparoscopy, a variety of knots have been used. In a study by Shettko, the best knot type, suture type and suture-size combination for knot security was found using size No. 1 Maxon (Kendall/Tyco Healthcare) and a 4-S modified Roeder knot.
The main benefit of hand-tied knots is the ability to make a large loop and use a long knot pusher.
However, in some cases of granulosa-thecal cell tumors, the ovary is too large to get a ligating loop around. Fortunately, other devices are available for dissection and coagulation. The ultrasonic cutting coagulating devices, such as the Autosonix (Kendall/Tyco Healthcare) have been designed to cut tissue and coagulate vessels up to 3 mm in diameter effectively. While there have been successful reports of using ultrasonic devices for equine ovariectomy, the ovarian vessels are very close to the maximum vessel diameter suggested and would not be effective in horses with large granulosa-thecal cell tumors. (Alldredge) Radio-frequency devices, such as the Ligasure (Valley Lab/Tyco Healthcare), have been designed to cauterize vessels up to 7 mm in diameter.
The Atlas wand is a 10-mm-diameter, 35-cm-long instrument that is used to coagulate tissue, including vessels.
It has a built-in knife blade that is used to cut the tissue after the coagulation is complete. This device is very effective in cutting and coagulating the ovarian pedicle even in cases of large granulosa-thecal cell tumors.
The author has successfully removed a 20 cm x 15 cm x 15 cm ovary using a standing flank laparoscopic approach. The main drawback of the Ligasure device is the equipment cost.
The least expensive alternative for ovarian ligation is a hand-tied ligating loop. However, if a granulosa-thecal cell tumor is present, a radio-frequency device, such as the Ligasure, might provide better hemostasis and require less manual dexterity. Regardless, the tension-free dissection causes much less post-operative morbidity than do the other techniques that have been described.
Source: Dr. Dean A. Hendrickson (2005): Advances in minimally invasive surgery for equines . In: DVM InFocus Mar 1, 2005; www.dvmnewsmagazine.com/dvm/
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