Can Fish Have Surgery?
Dr. Craig Harms
Can you have surgery on your fish? The answer is an emphatic Yes! Removal of masses. The most common surgeries performed on fish are for the removal of masses. These masses may be located externally in the skin or internally in the abdominal cavity. Masses may result from infections (e.g., abscesses), parasitic cysts or from neoplasia (cancer).
Veterinarians perform surgery on fish for many of the same reasons they perform surgeries on other species, along with some that are unique to fish. A few of these are removal of external and internal masses, repair of skin lacerations, removal of a severely damaged eye (enucleation), and swim bladder repair for buoyancy problems. All it takes is a fish that develops a condition that can be repaired surgically, an owner who cares enough to get the highest level if it is in the fish's best interest (sometimes euthanasia is the most humane option) and a veterinarian willing and equipped to perform surgery on some very interesting patients.
The decision to proceed with surgery may be motivated by the economic value of the patient, rarity of the species involved, or the owner's emotional attachment to the fish.
How Is It Done?
Surgery depends first on administering anesthesia to eliminate pain and keep the fish still. Anesthetic is delivered to a fish in the water. Then the fish is removed from the water because performing surgery is difficult in water and can result in contamination of the surgical site. For brief surgeries (e.g., abscess care) lasting less than five minutes, pumping water over the gills is not necessary. For longer surgeries (surgeries lasting more than two hours have been performed with successful recovery), the fish's skin must be kept moist. Water containing anesthetic is pumped over the gills to keep the fish oxygenated and anesthetized.
Once the necessary life-support system is in place, general surgery techniques are similar to surgery in mammals, birds and reptiles. One difference is the skin. Fish skin is very sensitive and contains a protective layer of mucus. Many species have scales. Small scales like those on trout have little effect on the incision, but thick, heavy scales must be removed along the incision line or the scalpel blade will not make a smooth cut, or may not cut at all. The skin and scales of some fish like sharks is very tough - a surgeon goes through a lot of scalpel blades during a shark surgery.
The mucus layer should be disrupted as little as possible because it protects the fish's skin from infections. Therefore, a full surgical scrub preparation of the incision site, as is performed in other species, cannot be performed on fish. Surgical incisions of fish are closed with suture. External sutures should be removed from the skin once it heals.
Specific Surgical Procedures
Because fish skin does not stretch very far, large masses removed from the skin may not be able to be sutured closed. Fish have an amazing capacity to heal large skin defects in time, but they may need some help to prevent the surgical site from becoming infected and to keep their electrolytes (salts) balanced. Your veterinarian may advise some topical treatment with an antibiotic ointment, systemic antibiotic treatment (oral or injection), an immersion treatment for opportunistic parasites, and/or the addition of a small amount of salt to the water-one to three grams per liter.
Lacerations. Cuts or lacerations are common in fish kept outdoors in ponds. If the wound is fresh, it can be treated with a mild disinfectant and sutured. If the laceration is old and contaminated, it is best to treat it as an open wound to scar in gradually. Your veterinarian may also recommend systemic antibiotics.
Lacerations are often inflicted by predatory birds. Provision of protective cover within the pond, steep sides to discourage wading birds, exclusion nets and lawn sprinklers triggered by motion sensors have all been used to reduce the possibility of bird strikes in koi ponds.
The reproductive system. The most common surgeries in dogs and cats – spays (removal of ovaries) and neuters (removal of testes) – are not routinely performed on fish. But sometimes female fish can become egg-bound if they enter reproductive condition when their aquarium conditions are not perfect for egg-laying. The eggs then sit in the abdomen and might not be absorbed, instead becoming hard and possibly infected. At that point, a surgical spay becomes a life-saving procedure. The ovaries of fish are very long, so the suture line for a fish spay is relatively much longer than for a dog or cat.
The eye. Advanced parasitic, infectious or neoplastic (cancerous) diseases of the eye may require surgical removal of the eye (enucleation). One-eyed fish do quite well even though they may not be display quality. The eye socket can be left empty and it will gradually fill with scar tissue. For cosmetic purposes, a procedure to implant a taxidermy glass eye has been described and short-term results are visually appealing, although long-term retention has been problematic.
Swim bladder. Fish experiencing buoyancy problems (floating, sideways or upside-down posture) may have a swim bladder abnormality. This can be diagnosed by your veterinarian by taking an X-ray. The swim bladder is a gas-filled organ that many fish use to maintain their position vertically in the water column. Other causes of buoyancy problems can include gas in the gastrointestinal tract or nervous system disease.
If the swim bladder is the cause of the problem, excess gas can be removed by a needle and syringe for a short-term correction but, often, a surgical reduction in the swim bladder is required. The swim bladder is made up of very fragile tissue, making swim bladder reduction a very delicate surgery. Negative buoyancy (sinking) may result after the surgery, but fish can adapt to this condition by resting on the bottom of the tank and swimming up for food, although a non-abrasive surface may be required to prevent damage to the skin of the belly.
Liver and kidneys. Liver and kidney tissues have often been used to diagnose diseases in fish, by microscopic examination (histopathology) or by culturing for harmful bacteria. Traditionally, these procedures have been performed on a few fish euthanized for this purpose, so that the remaining fish can be treated appropriately. While this procedure is acceptable in aquaculture situations, few people find this approach appropriate for their prized pets. Exploratory surgery of the abdomen is a non-lethal alternative, with small portions of the organs being excised (biopsied) for diagnostic purposes. Endoscopy can also be used to obtain biopsies of specific organs or to examine the gonads and determine sex of fish which cannot be sexed by external characteristics.
Depending on the water temperature, fish skin may heal more slowly than mammal skin, and sutures may be removed by your veterinarian from 10 to 30 days following surgery. If the fish cannot be retrieved for suture removal (those, for instance, in ponds), an absorbable suture may be used. These, however, are more likely to incite an inflammatory reaction and be expelled as foreign bodies than to be actually absorbed.
Following surgery, your fish will likely not be interested in feeding immediately. Gradually re-introduce food (less than usual) the day after surgery, and increase until its full appetite returns. Observe the suture line for signs of inflammation (redness) and secondary infection with water molds (Saprolegnia). Follow your veterinarian's instructions regarding post-surgical antibiotic, antifungal, antiparasitic, and osmotic (salt) treatments if these are needed.