INSTRUMENTATION

Laparoscopy is an operative procedure designed for the visual inspection and biopsy of the peritoneal cavity and its organs. The basic equipment for laparoscopy includes the laparoscope (telescope) and corresponding trocar-cannula unit, a light source, the Veress (insufflation) needle, and a gas insufflator. A 5-to7-mm-diameter laparoscope is versatile and can be used in dogs and cats of almost any size.

For veterinarians interested in performing a variety of rigid endoscopic procedures (e.g., cystoscopy in female dogs, vaginoscopy, rhinoscopy, avian endoscopy), purchase of both a 2.7-mm oblique-viewing and a 5-mm forward-viewing scope is recommended. The 2.7-mm scope is very versatile; in small patients (e.g., small dogs and cats, iguanas, birds), laparoscopy can easily be performed with this scope, especially if a video camera is used to enhance the image. The 5-mm scope is an excellent instrument for performing laparoscopy in dogs and cats of any size. Laparoscopes with various directions of vision are also available. A 0- or 180-degree direction of vision provides the operator with a "normal" field of view and in our experience has proved most useful for laparoscopy. Oblique-angle and retrograde-view laparoscopes are also available and are preferred by some endoscopists. A light source containing a 150-W lamp is sufficient for routine diagnostic laparoscopy, but photographic documentation requires either a 300-W lamp or a flash generator. The Veress needle is a spring-loaded, blunt-tipped needle used to establish a pneumoperitoneum.

Various types of automatic gas insufflators are available. These units are called either laparoflators or endoflators. The ideal gas for pneumoperitoneum should be nontoxic, colorless, readily soluble in blood, easily ventilated through the lungs, nonflammable, and inexpensive. Carbon dioxide most closely fits these requirements. A carbon dioxide tank ("E" tank) is attached to the laparoflator, and gas is channeled through the unit. Although an automatic insufflator adds to the expense of the total system, it provides a great deal of convenience and safety during a procedure because it allows measurement of both the total gas volume delivered and the intraabdominal pressure and provides automatic insufflation. The unit detects the pressure in the gas hose that is connected to the Veress needle (or insertion cannula after the Veress needle has been removed), and gas is insufflated if the abdominal pressure level is below the level that has been preset on the insufflation unit. We typically set a maximum abdominal pressure of 12 to 13 mm Hg in cats and 15 mm Hg in dogs. Once the preset pressure level has been reached, the laparoflator will not pump any more gas until the abdominal pressure level drops below the preset level. During laparoscopy some gas typically leaks out of the abdominal cavity.

Accessory Instruments for Biopsy Procedures

Organ biopsy procedures require several accessory instruments. We prefer either a grasping-type biopsy forceps or a Tru-Cut type needle and routinely use both of these instruments to obtain tissue samples from liver, kidneys, pancreas, spleen, and adrenal glands, and intraabdominal masses. Palmer forceps (for manipulation and electrocoagulation) and scissors-type forceps are also available. Most accessory instruments are insulated and equipped for use with electrocoagulation units.

LAPAROSCOPIC TECHNIQUE

Preparation and Restraint

Animals should be fasted for 12 to 24 hours before laparoscopy. Ideally, the urinary bladder, stomach, and colon should be empty. Laparoscopic procedures are most commonly performed using general gas anesthesia, with isoflurane or sevoflurane as the preferred agents. Propofol is commonly used for induction of anesthesia. In severely depressed patients, a local anesthetic agent may be sufficient, used either alone or in conjunction with a combination of diazepam and butorphanol or propofol. Oxymorphone or butorphanol provides analgesia, which is often beneficial to the patient during recovery.

Procedure

For laparoscopy, the selection of a midline, right, or left lateral abdominal approach depends on several factors. The right lateral approach is used for diffuse or multifocal hepatopathies, right-sided liver masses, and biopsy of the pancreas, right kidney, or adrenal gland. This approach allows visualization of the caudate, right lateral, right medial, and quadrate lobes of the liver, as well as the gallbladder, common bile duct, descending duodenum, right limb of the pancreas, pylorus, diaphragm, right kidney, and small intestine. For laparoscopy the animal is placed on the table in either a left or right lateral recumbent position. A table that can be tilted is recommended because shifting the abdominal viscera can enhance visualization in some patients. Surgical sterility is maintained throughout the procedure. The lateral abdominal region is clipped from approximately the 10^th intercostal space caudally to the flank and from the dorsal to ventral midlines.

The first step is the establishment of a pneumoperitoneum to produce a gas layer that separates the abdominal wall from the underlying viscera. The internal blunt tip of the Veress needle is retracted; this exposes the sharper outer stylet point, which is used to facilitate abdominal wall penetration. Before the Veress needle is inserted, the underlying area should be palpated to avoid puncture of masses or organs. Once the needle has penetrated the abdominal wall, the spring is released, allowing the blunt tip to protrude. The gas hose from the insufflator is then attached to the Luer-lock of the Veress needle, and a moderate pneumoperitoneum is established using a flow rate of approximately 1 L/min to a final intraabdominal pressure of approximately 12 to 13 mm Hg in cats and 13 to 15 mm Hg in dogs. With experience the operator can assess the pneumoperitoneum by ballottement and the degree of abdominal distension. Respirations and capillary perfusion should be closely monitored because overdistension of the abdomen can lead to cardiopulmonary compromise and even death.

Once the appropriate pneumoperitoneum has been established, the Veress needle is withdrawn and, depending on trocar size, a 1- to 2-cm skin incision is made on the ventrolateral abdominal wall at a variable distance caudal to the ribs. A typical entry site is 3 to 4 cm caudal to the last rib and halfway between the ventral midline and the lumbar vertebral transverse processes. In animals with microhepatica (e.g., cirrhosis) the puncture site should be closer to the ribs and more ventrally placed, whereas in animals with hepatomegaly a more caudal site is preferred. The size of the skin incision and blunt dissection should be kept to a minimum to avoid gas leakage around the cannula. The trocar-cannula unit is held with the base of the trocar seated against the heel of the hand and the fingers grasping the cannula. The trocar-cannula unit is inserted with a quick, steady twisting motion of the hand and wrist; an audible "pop" is usually heard on penetration of the abdominal wall. Ramming or stabbing motions should be avoided!

After the sleeve has fully penetrated the abdominal wall, the trocar is immediately withdrawn to avoid trauma to underlying organs. Once the trocar is removed from the sleeve, the operator can easily insert the sleeve farther, using gentle forward force and slight left-right axial rotation. Before the laparoscope is inserted, it should be warmed to prevent fogging of the distal lens. When a cold optics instrument enters the abdominal cavity, where the temperature is higher and humidity is 100%, the vapor tends to condense on its glass surfaces. Warming can be easily and most economically accomplished by inserting the laparoscope tip into sterile saline or water that is slightly warmer than body temperature or by holding the tip of the laparoscope in the palm for several minutes just before the scope is inserted through the cannula. The operator should begin viewing as soon as the laparoscope is moved into the cannula. Viscera immediately underlying the puncture site are inspected to identify any traumatic injury or hemorrhage caused by trocar insertion. The entire abdomen should then be systematically examined to detect any abnormalities. A blunt probe may be used to manipulate organs or retract omentum to improve visualization.

Tissue specimens can be obtained by passing a biopsy needle (e.g., a Tru-Cut needle) through a small skin incision at a site close to the organ to be sampled. The laparoscope is retracted so that the biopsy needle can be visualized as it enters the abdominal cavity and is directed to the biopsy site. Caution must be exercised to prevent-inadvertent puncture of underlying structures. Grasping biopsy forceps may also be used to obtain tissue samples. The instrument is inserted through an accessory cannula (second puncture) or through the channel of an operating laparoscope. Because of the length of grasping biopsy forceps, we have found this instrument to be particularly useful in larger dogs, especially those with microhepatica. Biopsy sites are observed for several minutes after the biopsy procedure to check for excessive bleeding. Excessive post-biopsy hemorrhage is rare. If excessive bleeding occurs, it can usually be controlled by applying direct pressure with the laparoscope tip or by inserting a blunt probe through the accessory cannula. If direct pressure fails to control hemorrhage, topical hemostatic agents such as absorbable gelatin sponge (e.g., Gelfoam) can be directly applied or electrocoagulation can be performed at the biopsy site.

A distinct advantage of laparoscopy is the clarity of the views and the fact that excellent size biopsies can be obtained under direct visualization. Ancillary procedures that may be performed during laparoscopy include gastropexy, J tube placement, and full thickness intestinal biopsy. When the laparoscopic examination is completed, the pneumoperitoneum is completely evacuated through the cannula, and the abdominal wall and skin incisions are closed with synthetic suture material.

CONTRAINDICATIONS

Laparoscopy is contraindicated in several situations. Cardiopulmonary decompensation precludes the use of this procedure until clinical control of the underlying disorder has been achieved. For obvious reasons, laparoscopy and organ biopsy should not be performed in animals with coagulopathies, and we routinely evaluate coagulation function before laparoscopy. Because visceral puncture may occur during laparoscopy in animals with extensive intraabdominal adhesions from previous surgery or disease, exploratory laparotomy is recommended in these patients. Profound ascites can complicate laparoscopy and increase the likelihood of visceral puncture. Consequently, ascites should be reduced by medical management or abdominocentesis before laparoscopy is performed.

References

1.  Freeman LJ, Kolata RJ, Trostle S. Minimally invasive surgery of the gastrointestinal system. In Freeman LJ, editor: Veterinary Endosurgery, St. Louis, 1999, Mosby.

2.  Magne ML and Tams TR. Laparoscopy: instrumentation and technique. In Tams TR, editor: Small Animal Endoscopy, ed 2, St. Louis, 1999, Mosby.

3.  Twedt DC. Laparoscopy of the liver and pancreas. In Tams TR, editor: Small Animal Endoscopy, ed 2, St. Louis, 1999, Mosby.