Laparoscopy has become an integral diagnostic and surgical tool in human and veterinary medicine. Its use in non-domestic animal medicine has primarily been focused on avian medicine and more recently in reptiles. Although rigid laparoscopy has been performed with fish, its use is still fairly uncommon and there are few citations in the literature.1,2,3
Fish pose a variety of diagnostic challenges. Many of the diagnostic techniques commonly utilized in domestic animal medicine are less useful in fish. In some cases, the clinician may need to sacrifice individual fish in order to collect diagnostic material. Because laparoscopic surgery allows the clinician to directly image the various visceral organs and collect diagnostic samples, laparoscopy can improve the clinician's diagnostic capabilities and may reduce the need to sacrifice fish.
In this study, food fish carcasses were initially utilized to develop a variety of surgical laparoscopic techniques. These techniques included: sample collection, location of incision sites, trocar placement and determining appropriate insufflation pressures. After these techniques had been established in cadaver specimens, laparoscopic surgery was performed on clinical cases that required surgical intervention. In all cases, general anesthesia was accomplished using MS-222 and the animals underwent standard surgical positioning and preparation.
For evaluation of coelomic organs, a foam wedge was used to place the animal in dorsal recumbency and a paramedian incision was made cranial to the vent. Once the incision site is determined, the scales over the area are removed and a stab incision is made into the body wall. A blunt, curved hemostat was used to enter the coelomic cavity and to enlarge the hole for sheath placement. Depending upon the procedure and the size of the patient, 1 to 3 incisions were made for camera and/or instrument placement. In small animals (<200grams), a single incision was made and a small (14.5 Fr.) laparoscopic examination sheath was placed within the coelom. This trocar sheath has two lumens; one for the laparoscope (2.7mm, 18cm. slender telescope) and the other acts as an instrument portal (5 Fr.). For larger animals, especially if extensive organ manipulation is required, other trocar ports for additional instrumentation may be required. From a single incision, the clinician can commonly visualize and sample the following organs: liver, spleen, intestines, stomach, gonads, pericardium and the serosal surface of the swim bladder.
For evaluation of the swim bladder or for renal biopsy, the animal was placed in lateral recumbency and an incision was made on the lateral body wall, in the lower 2/3 of the swim bladder. Due to the tremendous anatomical species variation in fish, a radiograph was taken prior to surgery to help confirm the exact location of the swim bladder. Once the incision site was determined, a #11 scalpel blade was used to penetrate the muscular lateral body wall and enter the swim bladder. With the laparoscope inside the air bladder, good visualization of the entire internal lining can be accomplished. For renal biopsy, a 34 cm, 4 Fr. laparoscopic scissor was used to incise the air bladder just over the dorso-cranial aspect of the swim bladder. Care should be taken to avoid large vessels which may travel along the dorsal midline and are adherent to the air bladder. Biopsy forceps (5 Fr.) were then inserted into the instrument channel and fed into the incision site over the kidney. The renal tissue is often not directly visualized, but lies directly underneath the cranial aspect of the air bladder. Once the biopsy sample has been collected, a surgical gelatin sponge (Gelfoam®) can be placed at the renal biopsy site to help minimize hemorrhage.
Distension of the coelomic cavity is facilitated by using carbon dioxide insufflation. Pressures of 4-6 mm Hg provided adequate dilation and no apparent interoperative or postoperative problems. As with a conventional coeliotomy, it is recommended that attempts should be made to remove as much gas as possible prior to closing. No buoyancy problems were noted after these laparoscopic procedures. A varess needle is commonly used in human and domestic animal laparoscopic procedures to provide insufflation prior to trocar placement. This technique has been described in fish2 and works best in those animals which may have a thin body wall. Due to concerns of possible iatrogenic trauma, the author elected to not use a varess needle and instead attached the insufflation hose directly to a port in the instrument sheath. Sterile saline can also be used to dilate the coelom and in additional to allowing organ visualization, this method may also provide supplemental hydration and electrolytes.
Rigid laparoscopic surgery was done on seven species of fish including both fresh water and marine species. It was found to be a very effective method to directly visualize visceral organs. Although surgical techniques were limited to the collection of biopsies, it is expected that additional surgical procedures would be possible.
The author would like to acknowledge Dr. Andy Stamper, Jane Davis and Jane Capobianco for their support of this work. I would also like to thank the dedicated staff at The Living Seas and the veterinarians at Disney's Animal Programs who helped and supported this project.
1. Moccia RD, Wilkie EJ, Munkittrick KR, Thompson WD. 1984. The use of fine needle fibre endoscopy in fish for in vivo examination of visceral organs, with special reference to ovarian evaluation. Aquaculture 40: 255-259.
2. Murray MJ. 1998. Endoscopy in fish. In: Murray MJ, Schildger B, Taylor M (eds.). Endoscopy in birds, reptiles, amphibians and fish. Endo-Press, Tuttlingen, Germany, pp 59-75.
3. Ortenberger AL, Jansen ME, Whyte SK. 1996. Nonsurgical videolaparoscopy for determination of reproductive status of the Arctic charr. Can Vet J 37: 96-100.