Descriptions of different techniques and approaches for veterinary laparoscopic surgical procedures

Introduction
Laparoscopy is alternatively referred to as minimally invasive surgery, minimal access surgery, video surgery, endosurgery, and endoscopic surgery. It is commonly referred to as "keyhole surgery" by the public. It is perhaps best for veterinary surgeons to avoid the use of the term "keyhole surgery" when dealing with clients, as there is much ambiguity surrounding its use. It is not uncommon for vets to refer to open surgery simply performed through small incisions also as "keyhole surgery". While this may appear pedantic, this gets to the crux of what endosurgery is actually about. While small wounds are a clearly recognisable feature and an obvious benefit, these small wounds are not the only, or probably even the main benefit of this type of surgery. The real benefit is really the markedly enhanced visualisation (helped by the marked magnification allowed by the endoscope, which is really a mini-telescope), which, if used correctly leads to safer surgery. The ultimate aim of laparoscopy should be safe, visual surgery, with the secondary benefit of small wounds, while small open abdominal surgery incisions lead to poor visualisation, and resultant unsafe surgery.

What is possible, versus what is sensible
Successful laparoscopic surgery of congenital anomalies has even been performed on the foetus in utero in experimental animal studies. Even hand-access ports are available to allow entry of the entire hand into a laparoscopic surgery field without loss of insufflations. However, it is possible to loose sight of what is truly in a patients best interests in ones newly acquired zeal for laparoscopic surgery. One should always consider if the laparoscopic approach to a procedure does indeed offer a benefit to the patient. It is well recognised in human surgery that in a small number of specific procedures the traditional open abdominal surgical approach actually has better surgical outcomes than laparoscopic approaches, even if performed by extremely accurate robotic laparoscopic surgery. The best example is prostatectomy for prostate cancer, where open surgery has a slightly lower risk of post-operative adverse consequences such as incontinence and impotence (when performed by very experienced urological surgeons). It may also be simpler, less expensive, quicker, and safer to perfrom a laparoscopic-assisted rather than "pure" laparoscopic procedure Good examples of this are laparoscopic-assisted cryptorchidetomy, full thickness intestinal biopsy, enterotomy, enterectomy, etc. While a laparoscopic procedure in its strictest sense means the entire procedure should be completed intra-abdominally, whereas laparoscopic-assisted means part of the procedure is completed outside the abdomen. As an example a loop of small intestine is exteriorised to allow an enterotomy, allowing simple routine suturing and leakage testing, with the benefit of less risk of abdominal contamination. In contrast the completely laparoscopic technique requires expensive disposable laparoscopic stapling units or intra-corporeal laparoscopic suturing which has a steep learning curve, and increased operative time.

Laparoscopic Access - safe approaches to the abdomen
Safe access to the abdomen is perhaps the most difficult part of any laparoscopic procedure, and no matter how much care is taken, and whatever technique used, injuries to underlying abdominal structures can occur. Despite differing opinions, a large Cochrane review of human laparoscopy studies did not demonstrate that veress needle use was more dangerous than open approach access, which is currently in favour by general surgeons in the UK.

Blind approach using the veress needle
Blind sharp trocar entry using prior insufflation of the abdomen with a special guarded double lumen needle (originally designed for thoracocentesis in humans with tuberculosis), is still the most commonly employed access technique by veterinary surgeons, and is also still popular with gynaecologists. The technique has fallen out of favour with general surgeons in the UK, and open access is generally taught to surgery residents due to the lower risk of major vascular trauma. The spleen of carnivores is much larger than in humans and is at increased risk of trauma by the verres needle. Even if haemorrhage is minor and self limiting, relatively small amounts of haemorrhage do obscure vision, and interfere with optimal visualisation, and may require suction and lavage, increasing operative time. There is also the risk of gas embolism if the veress needle punctures the spleen or major vessel. Different authors recommend different sites, such as umbilical right lower quadrant, and the right upper quadrant, just below the costal arch. The needle usually gives a distinctive double click once it enters the peritoneal cavity, and pressure should rise slowly on initial insifflation. A rapid increase in pressure when insufflation is started indicates the needle is inside tissue.

 

A veress needle is a guarded needle, but can still traumatise organs and major vascular structures when placed in the abdomen, and the entry site must always be examined at the begining of laparoscopy to detect any resultant trauma. Here, note the vicinity to a full bladder. It is advisable to always empty the bladder before laparoscopy.

Open access
Open access is the method of entry currently favoured by most general surgeons in the UK, and is regarded as the safest method, although systematic reviews have not demonstrated this conclusively. An incision is made through the caudal portion of the umbilical scar (as the abdominal wall is thinnest at this point. By means of retraction and careful blunt and sharp dissection with artery forceps or small scissors, the abdominal cavity is entered. The primary (optical) trocar is inserted with a blunt trocar. In many cases the seal is sufficiently tight to prevent any gas leakage, but in larger or obese patients a conical Hasson cannula can be used to seal any gap and maintain a pneumoperitoneum. This is the authors method of choice in dogs, cats, and small pet mammals.  A flexible ring retractor (Lonestar) has a low profile and is perfect fo retraction for open access when performing minor laparoscopic procedures (such as liver biopsy) without an assistant.

Optical controlled access
Optical trocars may also be used for visually controlled access to the abdomen. The Visiport (Covidein) trocar is designed for a 10mm 0 degree laparoscope and is a single use disposable instrument, and hence is not commonly used in small animal laparoscopy. It has a trigger that fires a 1mm depth blade for controlled access into the abdomen, and may be used in the non-insufflated abdomen as well. The Ternamian EndoTip (Karl Storz) is a steel reusable cannula, and is popular with some vets. It is available in 10mm, 5mm, and 3.9mm sizes. It is only suitable for use in the insufflated abdomen, so does not eliminate the risks associated with a veress needles use, but is an improvement of a sharp trocar. It must be used with a 0 degree laparoscope. It is not safe to use in a non-insufflated abdomen. Despite owning a 10mm and 5mm EndoTip cannula, the author has not found them to be particular useful, an still prefers an open approach.

Insufflation
Insufflation is performed with carbon dioxide, and it is recommended at pressures not exceeding 10-12mmHg. Higher flow rate insufflators are advantageous at maintaining an insufflated abdomen, despite possible gas leaks.

On entering the abdomen with the laparoscope it is recommended that a rapid examination of the abdomen is performed before anything else, even when performing an elective procedure such as ovariectomy, etc. Access induced injuries are best visualised immediately, before a small injury may be obscured by organ movement. This also allows one to check for other gross pathology, such as an asymptomatic neoplasm, etc, and an undetected diaphragmatic hernia will definitely affect ventilation due to the insufflation.

Laparoscopy Wound Closure
10mm (and larger) ports site incision, as well as any 5mm ports sites actually placed midline (in the linea alba) should be closed in two layers to prevent the risk of incision site hernias, usually caused by omental fat herniating sub-cutaneously. 5mm non-midline port sites and small port site do not need muscle layer closure, and simply require skin closure with tissue adhesive, intradermal, or routine skin suture.

Laparoscopic suturing techniques
Laparoscopic suturing is more technically difficult that suturing in open surgery, with a steep learning curve. It is also more difficult in smaller patients. Due to the time involved numerous single use stapling aids are available in laparoscopic surgery, but none are ideal and it is well worth the surgeons while becoming proficient with these techniques. For suturing of larger structures such as an intracorporeal enterectomy, 12mm endo gia stapling devices (Covidien or Ethicon) are more commonly used, but are again unsuitable for small canine patients, cats, and rabbits. These are also relatively expensive, and although hand pieces can be reused, cartridges cost approximately £100 each. (see instruments and equipment section)

Extracorporeal  suturing
Laparoscopic locking slip knots, formed outside the body, and then positioned and tighten internally with a knot pusher are an extremely useful technique to master in veterinary laparoscopy. While commercially prepared loops are available (surgitie, endoloop, etc), it is far more economical to prepare these oneself. They can be used to ligate vessels and structures, and can be used to perform ovaroiectomies should electrosurgery not be available, or should a problem occur during surgery with the unit. Although it is often recommended that this is not suitable for vessles larger than 3mm diameter, this may be safely accomplished by means of double ligation. There are numerous different knots demonstrated in books that are suitable. The original laparoscopic extracorporeal knot was the Roeder knot. Originally implemented for tonsillectomies, it was lso sed initially inlapaoscopic surgery, but is unreliable unless used with catgut, and so has fallen out of favour. There are several modified Roeder knots that are still in use, as well as the Meltzer (below) and Tayside knots. They do take some practice before use, and it is also possible to prepare several loops and sterilise them so they are ready for use in surgery. While these knots can be performed with monofilament sutures, they are easiest to prepare and use when made with braided suture materials such as Vicryl (Ethicon) or Polysorb (Tyco).

 

Intracorporeal Suturing techniques
Internal suturing is more difficult, but useful fr more advanced techniques such as laparoscopic colposuspension, etc. Half-curved cutting or specially designed endoski needles are most suitable. Suture length should also be limited to about 20cm in length to allow manipulation and knot tying. Laparoscopic needle holders are needed, and a pair is recommended to allow ease of suturing with both hands handling the needle. Simple interrupted sutures with a 3-throw surgeons knot are most commonly used. Tumbling square knots are also a useful technique. Continuous sutures may also be knotted with an Aberdeen knot.  

Canine laparoscopic ovariectomy (2 ports)
Canine laparoscopic ovariectomy is one of the most common laparoscopic procedures currently performed in dogs. The 2 port technique and use of bipolar electrocautery illustrated here is one of the most popular (the others being 3 ports, and a single port technique using an operating laparoscope). In this video primary port placement is by an open approach rather than verres needle and blind sharp trocar insertion, in keeping with current trends in human laparoscopic access (Romain Pizzi).

Single port canine laparoscopic ovariectomy
A single port laparoscopic ovariectomy technique is favoured by some veterinarians. The main difference is that a 10mm or 12mm operating laparoscope is used, via a single midline (linea alba) caudal umbilical port, with a graspers inserted through this to mobilise the ovary and position this against the abdominal wall. The ovary is fixed to the abdominal wall with a large circular cutting needle and suture. Bipolar forceps and scissors are inserted alternately through the operating cannel of the laparoscope to complete the procedure. The procedure can be a little more akward, as less manipulation is possible in comparison to the 2 port technique. One benefit of this approach is that instrument entry is always under visualisation.

Laparoscopic cryptorchidectomy
This is arguably the simplest elective veterinary laparoscopic procedure and holds marked advantages over open abdominal exploration, in terms of not only post-operative recovery and healing due to the small wounds, but can actually work out less expensive for the practice due to the savings in operating time and consumables such as sutures etc. Laparoscopic-assisted cryptorchidectomy also only necessitates 2 ports and can be performed with small instruments, and there is arguably little advantage on performing a true laparoscopic cryptorchidectomy instead.

  

The patient may be positioned in dorsal recombency in a slight (less than 30 degree) head down "Trendelenburg" position, but this is not essential. The stack and screen are positioned at the patient's feet. The primary 5mm sub-umbilical optical port is inserted as standard (see section on access). After insufflation of the abdomen, the laparoscope is inserted and the caudal abdominal cavity and pelvis examined. In many cases the cryptorchid testicle is immediately evident. If not, examine both internal inguinal rings. The vas deferens and testicular will normally be clearly evident entering the ring in the case of scrotal or inguinal testicles. If the vas is seen not entering the inguinal canal, the gubernaculums testis can be visualised and followed back from the inguinal ring into the abdomen to locate the retained testicle. Viscera may usually be sufficiently retracted without the need for instrumentation by simply tilting the body laterally. A trocar and port is inserted as close to the retained testicle as possible, and this retained testicle grasped with toothed (traumatic) forceps and exteriorised through this secondary port. The incision can be enlarged with a scalpel, or fascia cutter. A 13 scalpel bladder (commonly used for removing sutures) is ideal for this purpose (under visualisation). The vas deferens and testicular vessels are ligated externally as routine, and the testicle removed. The ligated stumps are returned to the abdomen. A finger can be used to block the secondary port site, while the abdomen in insufflated again, and the abdominal given a final examination for any signs of haemorrhage. Ports sites are closed as routine.   

The safe use of electrosurgery in laparoscopy
It is important to distinguish between electrosurgery and electrocautery. Electrocautery uses direct current (DC), the current does not enter patient's body and only provides a heated wire. Electrosurgery works by passing a high voltage and a relatively high current through the patient's tissues. In the UK, mains current is 240 Volts and surgical diathermy units are powered by this current, so how is it that the patient does not receive an electric shock? The answer is in the frequency of alternating current used. UK mains frequency is 50 Hertz, neuromuscular stimulation ceases at 100 Kilohertz and the range of frequency used by electrosurgical generators is between 200 Kilohertz to 3 Megahertz. So how is the clinical effect achieved at the tip of the electrosurgical instrument? The answer lies in the principle of current density: When current passes through a smaller volume of conductor, energy is lost as heat. This explains why the tip of the electrosurgical instrument heats up when activated touching the patients tissues. The surface area at the point of contact is relatively tiny compared to the surface area at the patient return electrode (where no heating effect should occur).

Monopolar surgery
While monopolar surgery is widely used in human surgery, it does carry a higher risk of inadvertent injuries than bipolar surgery, or ultrasonic scalpels. Care is especially needed in veterinary patients with their thick coats that there is extremely good contact with the ground plate, otherwise severe burn injuries may result. The monopolar hook is a useful instrument for fine haemostatic dissection and dissection of fat, but is generally not suitable for ovariectomies. It's function is being replaced in human surgery by ultrasonic scalpels (Harmonic ACE, Ethicon), which coagulate and cut tissues via ultrasound, with little collateral heat generation, and no risk of distant burns.

 

The monopolar active electrode is in the wound and the patient return electrode is attached elsewhere on the patient. Therefore the current must flow through the patient to the patient return electrode. The varying thermal effects of the different diathermy modes are mainly caused by the different waveforms used. Pure cutting and bipolar currents have a constant, un-modulated waveform with a relatively low voltage. The opposite end of the scale is pure coagulation current, which is highly modulated and is only 'on' around 6% of the time. Pure monopolar coagulation current has a much higher voltage than monopolar cut or bipolar electrosurgery. The mechanism of pure cutting monopolar current is that tissue is divided with electric sparks. The electrode held slightly away from tissue, with intense heat focused at the surgical site. Cutting generates the greatest amount of heat over a very short period of time and vaporises tissue. Tissue desiccation is most efficiently achieved with the CUT current, but the electrode must be in direct contact with the tissue. The current concentration is reduced and less heat is generated, causing the cells to dry out and form a coagulum rather than vaporize and explode. Fulguration is caused by sparking with the COAG wave form (higher voltage). This coagulates and chars the tissue over a wide area. Less heat is produced due to short duty cycles and causes the creation of coagulum rather than cellular vaporization. The function of the patient return electrode, or ground plate, is to remove current from the patient safely. A return electrode burn occurs when the heat produced is not safely dissipated by the size or conductivity of the patient return electrode.

BURN  = (HEAT X TIME) / AREA

When choosing the position for the return electrode, one should choose a well vascularised muscle mass, avoid areas of vascular insufficiency, irregular body contours or bony prominences, and also consider the incision site or prepared area, the patient position and the presence of other equipment attached to the patient. In our veterinary patients a very important consideration is their fur. Light animals with a dense fur coat such as rabbits are particularly at risk of return electrode burns. The risk is less in larger animals, and may also be helped by clipping the site for placement of the retrun electrode, as well as apply a large wet laparotomy swab over the return electrode.

70% of electrosurgical burns are caused by poor contact at the return electrode site.

When electrosurgery is used in the context of minimal access surgery, it raises a new set of safety concerns, specific to laparoscopic surgery.

Direct Coupling is caused by accidental activation of the electrosurgical generator while the active electrode is near another metal instrument. The secondary instrument becomes energized and the energy seeks a pathway to complete the circuit to the patient return electrode. There is potential for significant patient injury.

Insulation Failure allows voltage to spark through compromised insulation (especially when in COAG mode). High voltage can also "blow holes" in weak insulation. An alternative route is sought for the current to flow via breaks in the insulation and if this current is concentrated it can cause significant injury.

 

Capacitive Coupling occurs whenever two conductors are separated by a non-conductor. An electrostatic field is created between the two conductors. As a result, a current in one conductor can, through this electrostatic field, induce a current in the second conductor. An "inadvertent capacitor" may be created by the composition and placement of surgical instruments:

Electrode (conductor)  +  Electrode Insulation (non-conductor)  +  Metal Cannula (conductor) =  CAPACITOR

If we consider a metal cannula system, a capacitor occurs whenever a non-conductor separates two conductors. The conductive active electrode is surrounded by nonconductive insulation - in turn surrounded by a conductive metal cannula. An "inadvertent capacitor" may be created by the surgical instruments. If we consider a plastic cannula system, capacitance cannot be entirely eliminated with an all plastic cannula. The patient's conductive tissue completes the definition of a capacitor; capacitance is reduced, but is not entirely eliminated. Finally, if we finally consider a hybrid cannula system, this is the worst combination and occurs when metal cannula held in place by a plastic anchor, or when a metal reducing tube is placed through a plastic cannula. The metal cannula or reducer still creates a capacitor with the active electrode. However the plastic port prevents the current from dissipating through the abdominal wall. Capacitively coupled current may exit to adjacent tissue on its way to the patient return electrode can cause significant injury.

 

One method of increasing the safety of monopolar surgery in laparoscopy is using higher frequency current, also referred to as radiosurgery (eg. Surgitron, Ellman), in the order of 3.8-4.0MHz. This is less reliance on good contact with the return electrode (ground plate).

Video on the principles and safe use of electrosurgery in laparoscopy

Bipolar electrosurgery
Bipolar electrosurgery provides precise controlled desiccation with a limited amount of tissue impacted by the current. This modality also works well in irrigated environments. The active output and patient return functions are both accomplished at the site of surgery - current path is confined to tissue grasped between the instrument tips. The patient return electrode does not need to be applied for bipolar only procedures. Bipolar electrosurgery is the most widely used modality in veterinary laparoscopy, and ideally suited to simple procedures such as laparoscopic ovariectomy.

Do you actually need electrosurgery for laparoscopy?
The Editor is aware of a human consultant surgeon in India that has performed over 500 cholecystectomies without any electrosurgery, simply using meticulous careful sharp and blunt dissection of the gallbladder from the hepatic bed. The author has also performed several canine ovariectomies using loop ligatures instead of electrosurgery, and many other minor laparoscopic procedures such as biopsy, do not require electrosurgery. Electrosurgery is however undeniably useful and can enable one to complete procedures more rapidly and limit minor haemorrhage, and so is recommended for veterinary laparoscopy. Despite some veterinary authors insistence that more advanced electrosurgery modalities (Ligasure, Valleylab; Harmonic scalpel, Ethicon) are essential, bipolar surgery is more than sufficient for most veterinary applications, and many human surgeons only ever use monopolar and bipolar modalities.

Tissue feedback controlled bipolar surgery (Ligasure, Valleylab; Enseal, Ethicon)
This advanced electrosurgical modality has gained popularity amongst vets, due to its ease of use for procedures such as laparoscopic ovariectomy. It can be used to seal blood vessels up to 7mm in diameter. The control unit measures tissue impedance and gives an audible signal once tissue has been sealed. This also prevents overlong application with char formation (leading to increased inflammatory response. 5mm and 10mm diameter handpieces are available, and may have an integrated blade, allowing one to seal and cut tissue without having to change instruments, hence shortening surgery time. The main disadvantage of this system is that the instruments are disposable and relatively expensive, making them unsuitable for single use in procedures such as canine laparoscopic ovariectomy. While handpieces are commonly re-used by cleaning and liquid or ethylene oxide sterilisation, they are not particularly robust, with the insulating plastic snapping off after a repeated use (they are after all designed for single use). Some human surgeons also do not favour them, as the jaws can become sticky with coagulum during surgery, and laparoscopic clip applicators are generally favoured for haemostasis of important vascular structures in human surgery.

Ultrasonic scalpel (Harmonic ACE, Ethicon; AutoSonix, Covidien; Sonosurg, Olympus)
Unlike electrosurgery, this uses and ultrasound transducer in the handpiece to transmit vibrations down the shaft of the instruments to the tip. This generates heat, which coagulates vessels in a similar way to electrosurgery. Ultrasonic scalpels are regarded as effectively sealing vessels up to 3mm in diameter. They  generate lss heat that electrosurgery, with minimal collateral heat propogation, and are useful for dissection around delicate structures. Unfortunately, they also single use handpieces that are expnsive for veterinary procedures.