Equipment

Light is transmitted from a remote light source via a fiberoptic light cable to the rigid fiberoptic laparoscope (telescope). Light transmitted through the light cable passes through incoherent bundles (randomly aligned), whereas light passing through the telescope passes through coherent bundles (spatially oriented). This creates a proper image when the lens system focuses the light at the eyepiece. The fibers in the telescope are delicate, and care must be taken to avoid bending or crimping the shaft. Modern telescopes are constructed so they can be sterilized with a conventional steam autoclave. For purposes of illumination, a light source of 150 to 300 watts is required to adequately illuminate the abdomen, particularly in large- and giant-breed dogs.

Size and viewing angles of laparoscopes vary, some of which are depicted in Figure 28-1. Small-diameter scopes (2.7 to 5.0 mm) have a smaller image with a narrower field of view. Light sources with greater intensity and video cameras with greater light sensitivity are needed with smaller scopes. Scopes up to 10-mm diameter can be used, and although these generate a bigger and brighter image than 5-mm–diameter scopes, this advantage applies only to very large dogs. Scopes are also available in various degrees of angulation of view, from 0° (direct forward viewing) to 70° angle viewing. The 0° angle view has the field of view centered on the long axis of the scope, and thus is easier to use and generally preferred for most procedures. A 30° angle scope can be used to view structures to the side of the tip, and through rotation can be used to expand the field of view. Angled scopes are more difficult for inexperienced operators with regard to spatial orientation, and they pose greater difficulty when using instruments through a second or accessory puncture site. The technique of triangulation to find the tip of the instrument is particularly more difficult with an angled field of view. Taking all these factors into account, a forward-viewing (0°), 5-mm outer diameter, 35-cm long scope is preferred for most dogs and cats. As most laparoscopic instruments are 5 mm in diameter, this provides more versatility by allowing the scope and instruments to be interchangeable with the same cannula. The operator must ensure the scope fits properly through the selected cannula, that the light cable has the appropriate connection to the telescope, and that the video camera fits properly onto the eyepiece.

Figure 28-1 Various rigid telescopes. A, A 5-mm scope with a 0° angle tip. B, A 10-mm scope with a 30° angle tip (insert: close-up of tip). C, An 11-mm operating scope (insert: close-up of tip with 5.5-mm channel).

Most scopes have no biopsy channel. Operating scopes have a 5- to 6-mm channel, with an eyepiece extending from the proximal end (see Fig. 28-1C). These scopes allow introduction of instruments through the same puncture site as the scope. This has the advantages of reducing the number of puncture sites and facilitating identification of the instrument tip for inexperienced operators. The major disadvantage of operating scopes is the limited ability to manipulate instruments passing through the channel. An accessory or secondary puncture technique is usually preferred by more experienced laparoscopists (see “Accessory Puncture Sites” section).

Video capabilities can be achieved with a charge-coupled device (CCD) video camera mounted onto the eyepiece of the telescope. These video cameras have a high resolution, an image magnification by 5 to 15×, and a high image quality. Cameras are constructed with a lens, prism assembly, and one or three chips that convert light to an electronic signal. Cameras with three chips (each representing the primary colors of red, green, or blue) generally produce better images than cameras with just one chip. More recently, high-definition (HD) cameras have become available and produce a superior image quality. Video technology is now essential for interventional or operative laparoscopy.

To visualize abdominal structures, a pneumoperitoneum must be created to lift the abdominal wall away from the viscera. This is accomplished by insufflating gas through tubing attached to a Veress needle (Fig. 28-2). The Veress needle has a spring-loaded blunt inner portion and an outer cannula with a sharp point. The sharp point is used to penetrate the abdominal wall. The inner blunt portion is then protruded past the sharp point and is maintained in that position to avoid traumatizing abdominal organs. Gas can be continually insufflated as needed throughout the procedure. Carbon dioxide gas (CO₂) is recommended because it has the advantage of being rapidly absorbed, thereby minimizing the risk of air embolism. Air embolism is a complication that is more likely to take place if using room air. The disadvantage of CO₂ is that it is slightly more irritating to the peritoneal surface and therefore requires a slightly greater depth of anesthesia. The pneumoperitoneum is maintained throughout the procedure with an automatic insufflator, which continuously administers gas to maintain pressure. Insufflators regulate both flow rate and intraabdominal pressure. Initial gas insufflation should be at a low flow rate (e.g., 1 L/min) to permit accommodation to the increasing intraabdominal pressure. If the pressure suddenly rises during insufflation, it is often a result of omental or mesenteric obstruction, or the incorrect placement of the needle. The position of the needle should be adjusted by gently moving it in and out of the abdomen; occasionally it must be replaced completely. Once optimal insufflation has been achieved, a higher flow rate can be used to maintain desired pressures. Ideally, intraabdominal pressure should not exceed 10 mm Hg (cats and small dogs) to 15 mm Hg (large dogs). Excessive pressure decreases central venous return and reduces diaphragm movement, causing decreased ability to ventilate. These effects are unlikely to occur at recommended abdominal pressures, but should be considered in patients with preexisting cardiopulmonary disease.

Figure 28-2 A, Veress needle. B, Close-up of tip with sharp point in position to penetrate the abdominal wall. C, Close-up of tip with blunt inner obturator protruded in position to avoid trauma to abdominal organs.

After the creation of the pneumoperitoneum, the laparoscope is introduced into the abdomen with the use of a trocar/cannula assembly (Fig. 28-3). The cannula is a metal or hard plastic sleeve with a one-way valve that permits passage of instruments (such as the trocar, laparoscope, and accessory instruments) and prevents the escape of gas. The trocar is a sharp-pointed stylet that is used to penetrate the abdominal wall. Once the trocar/cannula assembly penetrates the body wall, the trocar is then removed, leaving the cannula in place for introduction of the laparoscope.

Figure 28-3 A, Trocar/cannula assembly with threaded shaft. B, Telescope inserted through cannula with smooth shaft.

Trocar/cannula assemblies come in a variety of sizes and styles. Trocars with a pyramidal tip have a cutting edge that penetrates the abdominal wall more readily than trocars with noncutting conical tips, although they are also potentially more traumatic. Some trocars have a retractable blade within the tip. A well-established pneumoperitoneum must be present for this style to be used to avoid the risk of intraabdominal organ trauma. Cannulae are used to allow passage of instruments in and out of the abdominal cavity while maintaining the pneumoperitoneum. They are constructed with a one-way valve to permit introduction of instruments without the escape of abdominal gas. Additionally, there is a rubber seal at the proximal tip to prevent escape of gas when an instrument is in place. Some cannulae have a side port to allow attachment of insufflation lines to introduce gas during the procedure. The shaft of the cannula can be smooth or threaded. A threaded cannula is more stable and unlikely to move within the abdominal wall during the procedure. Sometimes it is desirable for the cannula to move in and out of the abdominal cavity, such as when the cannula is inserted deep into the abdominal cavity for tissue biopsy. In these instances, a smooth nonthreaded shaft is preferred. For imaging purposes, an appropriately sized cannula must be used to ensure adaptation to the telescope and other instrumentation.

Accessory Puncture Sites

Accessory puncture sites are made for introduction of additional trocar/cannula assemblies. Accessory puncture sites permit the introduction of a variety of palpation, biopsy, and surgical instruments. These instruments are elongated, narrower versions of standard surgical instruments. A “basic” laparoscopic accessory pack should consist of a blunt metal probe, “spoon” or “clamshell” style (oval cup) biopsy forceps, grasping forceps, scissors, suction device, cautery instrument, and Babcock forceps (Fig. 28-4). An “advanced” laparoscopic accessory pack should also include retractors, reticulating instruments (which allow the tips to bend or be deflected), clip applicators, suturing devices, advanced hemostasis devices such as the Harmonic scalpel (Ethicon) and the LigaSure device (Covidien), and stapling equipment. The use of stapling equipment permits additional procedures such as vessel ligation and bowel resection.

Figure 28-4 Laparoscopic instruments. From top to bottom: blunt metal probe, “spoon” or “clamshell” style (oval cup) biopsy forceps, grasping forceps, scissors, suction device, cautery instrument, and Babcock forceps.

Indications and Contraindications for Laparoscopy

Common indications for laparoscopy are for the evaluation of hepatobiliary disease. Laparoscopy allows procurement of large specimens (similar in size to surgical biopsies) using a 5-mm “spoon” or “clamshell” forceps (see Fig. 28-4). Samples obtained with these instruments have a superior diagnostic yield compared with needle biopsies, which have a reported 50% concordance with histologic findings from surgical biopsies.¹ Furthermore, the ability to visualize the liver gives the clinician a better feel for the pathologic process present and its distribution. Laparoscopy can also be used to examine and biopsy the right limb of the pancreas, an organ that can be difficult to image with abdominal radiographs and ultrasound. Other organs that can be biopsied via laparoscopy include the kidney, spleen, prostate, intestine, mesentery, omentum, and parietal peritoneum. Laparoscopy can be used to diagnose and stage abdominal tumors through direct visual assessment and biopsy. Laparoscopy can detect lesions less than 1 mm in diameter on the surface of organs. It can guide the aspiration of gallbladder, loculated ascites, and abdominal cysts or abscesses. Laparoscopy can guide transabdominal intrauterine artificial insemination. Laparoscopy can also be used for the evaluation of abdominal trauma. Injuries such as hepatic or splenic laceration, diaphragmatic hernia, bladder rupture, renal rupture, and abdominal hernia can be readily identified. There are also a variety of surgical or interventional procedures that can be accomplished laparoscopically.

Contraindications for laparoscopy include general anesthesia in an unstable patient, coagulopathy, diaphragmatic hernia, abdominal adhesions, and insufficient clinical experience. It must be emphasized that these are all relative contraindications, and the risks of a laparoscopic procedure must be weighed against the benefits of the procedure to the patient.

General Laparoscopic Technique

Several skills are required to perform a successful laparoscopic procedure.² The operator must have a good grasp of abdominal anatomy, surgical principles, anesthetic induction and maintenance, and operative use of laparoscopic equipment. Compared with surgery, laparoscopy poses three additional challenges—two-dimensional imaging, lack of tactile sensation, and problems with depth perception—all of which pose significant challenges for the inexperienced laparoscopist. The operator must be familiar with the general feel of the instruments, and how slight movements of the camera head can result in wide excursions of the image. Tactile sensation can be developed with practice through the use of a blunt probe. Fluctuant structures can usually be distinguished from solid structures using the blunt probe. There is also a fulcrum sensation that occurs with instrument movement. Because the instruments and scope are entering the abdominal cavity through a cannula, movement of the tip is in a direction opposite to that of the handle. Thus, when the hand and handle are moved upward, the tip of the instrument moves downward. When the hand and handle are moved to the left, the tip of the instrument moves to the right. Another necessary skill necessary is triangulation, because the angle of the scope and the angle of the instrument form a triangle. Triangulation permits the operator to find an instrument placed through a secondary or accessory cannula in the field of the scope. The angle of entry of each component of the triangle must be recognized to avoid frustration when attempting to find the instrument tip. One technique that is helpful is to move the scope further away from the anticipated point of the instrument tip. This will increase the field of view. Once the tip of the instrument is located, the scope can be moved closer to the instrument to improve visualization. At this point the instrument and scope are moved in parallel so that the instrument tip never leaves the field of view. This technique will reduce unnecessary anesthesia time. The skill of triangulation becomes more challenging when using an angled scope (such as a 30° telescope). If the viewing angle is directed upward and an instrument is inserted from the side, it appears to come from below and to the side of the field of view.

Laparoscopy is best performed under general anesthesia. The position of the dog or cat and the location of the various puncture sites depend on the procedure, patient’s size, and organ of interest. Because the port placement is so critical to a successful procedure, placement of the ports must be carefully planned and the site marked on the patient ahead of time to ensure a sterile field. In general, ports should not be placed too close together to avoid crowding of instruments with each other or with the scope. Furthermore, triangulation to locate instruments and subsequent manipulation of instruments is more difficult when they are placed too close to the scope. If it is determined that port placement is not acceptable, it is often better to place an additional port to allow completion of the procedure than to struggle through the procedure with suboptimal port location. Prior to starting the procedure, the urinary bladder should be emptied.

A right lateral or right lateral oblique approach is generally preferred for the liver, gallbladder, biliary tract, pancreas, right kidney, and right adrenal gland. The main advantage of this approach is that it avoids the falciform ligament, which is commonly encountered with a midline approach. The main disadvantage of a right-sided approach is the inability to see most left-sided abdominal structures. A midline approach is occasionally used for more complete evaluation of the liver (more of the liver can be seen by this approach than by a right-sided approach) and many interventional surgical procedures. Although the falciform ligament may impede the procedure, it can be avoided by placing the central port just lateral to midline and caudal to the umbilicus. In a lateral approach, the scope is placed several centimeters lateral to midline, depending on the size of the patient. A left-sided approach is seldom used, but is necessary to visualize the left kidney and left adrenal gland.

Complications of Laparoscopy

Potential complications of laparoscopy include those related to general anesthesia, inadvertent organ damage during instrument introduction, excessive bleeding during biopsy or other intervention, other surgical complications, overdistention of the abdomen, air embolism, subcutaneous instillation of gas, tension pneumothorax if the diaphragm is inadvertently punctured, and postoperative infection. Operator experience, good patient planning, and meticulous attention to procedural detail minimizes the probability of these complications. Postoperative pain should be anticipated and should be addressed with appropriate analgesics.

Laparoscopic Surgery

Many laparoscopic surgical procedures are currently being performed on dogs and cats. These include ovariectomy and hysterectomy, adrenalectomy, bile duct exploration, gastropexy, cystotomy with calculus removal, cryptorchid testicle removal, jejunostomy tube placement, splenoportography, cholecystectomy, and others. Limitations of laparoscopic surgery include the two-dimensional image, restricted freedom of movement of the instruments, restricted sense of touch, limited opportunity to move the position of instruments once cannulae have been placed, the need for extensive training, and limitations on instrumentation available for laparoscopy. As clinicians and equipment manufacturers address technical limitations, many surgical procedures should become more amenable to laparoscopic surgery.

Newer Laparoscopic Techniques

One recently developed innovative laparoscopic technique described in human beings is natural orifice transluminal endoscopic surgery (NOTES). This technique involves insertion of an endoscope into a natural orifice (such as the stomach, vagina, or colon), access to which is then used to perforate the wall to gain entrance to the peritoneal cavity. Many interventional procedures can be performed using this technique. The approach is thought to limit postoperative pain, decrease wound problems, and offer improved cosmesis. Transvaginal cholecystectomy is the main procedure being performed to develop the NOTES technique, although other surgical procedures can also be performed with this approach. There are many challenges to overcome to accomplish these procedures successfully. Luminal access can be achieved with new steerable trocar/cannulae. Flexible scopes have been developed with multiple steerable channels to allow introduction and manipulation of a variety of instruments to be used for the surgical procedure. Tissue or organ retraction is also very challenging. This has been overcome by use of special intraluminal retraction devices (Endograb, Ethicon), articulated graspers, and deployable devices (T-tag suture devices). Closure devices also have been developed, including endoscopically deployed clips. These include the Resolution Clip (Boston Scientific) and the QuickClip2 (Olympus).

Another method of overcoming these technical challenges is to combine a single puncture transabdominal laparoscopic port with transluminal access (called hybrid NOTES). This improves retraction and allows more versatile instrumentation.

The single-incision laparoscopic surgery (SILS) is another newly introduced technique. This technique permits the introduction of multiple instruments through one large port into the abdominal cavity. Several manufacturers have developed these devices. Furthermore, gently curved rigid instruments have been developed for this technique. The gentle curve permits better triangulation of instruments despite their insertion into a common port. In addition, reticulated instruments with steerable tips make this technique more versatile.

Intraoperative ultrasound (IOUS) during laparoscopic cholecystectomy is becoming increasingly commonplace in human laparoscopic surgery. High-resolution ultrasound probes are integrated into the tip of laparoscopically deployed instruments. The use of IOUS can help define biliary anatomy, including the entire common bile duct. Abnormalities, such as common bile duct calculi, sludge, or aberrant biliary anatomy, can be identified. The procedure only adds 5 to 7 minutes to a cholecystectomy, and can potentially change the management of the patient.

Only time will tell whether NOTES, SILS, or IOUS will be routinely applied in dogs and cats. Controlled clinical trials will be necessary to define the role of all laparoscopic procedures in veterinary medicine.