William H Wildgoose MRCVS
Pet fish vet
Internal tumours in koi
Koi and other carp commonly develop internal tumours, often from 4years of age. These usually develop in the liver or gonad (ovary/testes), but in many the cells are hard to identify and are called a sarcoma. They often cause swelling of the belly with lethargy and progressive loss of appetite and other complications over the following weeks or months. A physical examination and palpation of the swelling may reveal areas of an irregular solid mass internally. This can be confirmed by X-ray or using an ultrasound scan, but most are inoperable, and the outlook is usually hopeless.
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This 12year old koi developed progressive swelling for over a year, before becoming seriously ill. Half of its final bodyweight was due to free fluid in the body cavity along with two large cystic tumours.
This adult koi had a more localised swelling of the body cavity due to a discrete solid internal tumour. Although this was visible when the fish was examined under an anaesthetic, simple physical palpation of the belly confirmed its presence.
This adult koi had progressive swelling of the belly for 6months. In addition to the large solid liver tumour (black asterisk), the twin-lobed sacks of the ovary (white asterisks) were filled with abnormal translucent yellow fluid.
This 12year old koi developed progressive swelling for over a year, before becoming seriously ill. Half of its final bodyweight was due to free fluid in the body cavity along with two large cystic tumours.