Dr. Craig Harms
The most common surgery performed on fish is for the removal of masses, usually located externally on the skin or internally in the abdominal cavity. Masses may be the result of infections such as abscesses, parasitic cysts, or from cancer. Because fish skin does not stretch very far, incisions from removal of large masses may not be able to be closed by sutures.
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 addition of a small amount of salt to the water, one to three grams per liter.
Lacerations (cuts) are common in fish kept outdoors in ponds and are often inflicted by predatory birds. 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. Systemic antibiotics may be advised. 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.
Spaying (removal of ovaries) and neutering (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 are not absorbed; instead they become hard and possibly infected. At this point, spaying 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.
Advanced parasitic, infectious or cancerous diseases of the eye may require enucleation, which is surgical removal of the eye. 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 in 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.
Fish experiencing buoyancy problems, such as floating sideways or upside-down, may have an abnormality of the swim bladder, a gas-filled organ that helps maintain their position vertically in the water column. Your veterinarian can diagnose this by taking a radiograph (X-ray), and excess gas can be removed by a needle and syringe for a short-term correction. Often, though, a surgical reduction in the swim bladder is required, and this is a delicate surgery because the swim bladder is made up of very fragile tissue. Negative buoyancy (sinking) may result following the surgery, but fish adapt to this condition by resting on the bottom of the tank and swimming up for food. A non-abrasive surface may be required to prevent damage to the skin of the belly. Other causes of buoyancy problems can include gas in the gastrointestinal tract or nervous system disease.
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 for biopsy. 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.
Following surgery, your fish will not likely be interested in feeding immediately. Gradually re-introduce feeding the day after surgery, feeding at a lower level than usual until 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, and be sure to maintain the water quality at an optimal level during the healing phase. Have the sutures removed when healing is complete, in 10 to 30 days.