William H Wildgoose MRCVS
Pet fish vet
Kidney tumours in oscars
In general, kidney tumours are uncommon in fish although they are quite common in oscars, a large south American cichlid. Clinical signs vary but there is usually a distinct swelling of the body just above the vent, which gets progressively larger as the tumour grows in size. Affected fish are often less active, eat less and occasionally have buoyancy problems. Diagnosis can be confirmed by X-ray or an ultrasound scan. There is no treatment and euthanasia should be carried out when the fish has a poor quality of life.
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Externally, there is often a localised swelling of the belly (arrow) above the vent, depending on the size of the tumour. This oscar also has severe protrusion of the eyes (pop-eye).
This X-ray of the oscar in the previous image shows the lower position of the kidney tumour (asterisk). However, the appearance of the tumour can vary depending on its size and direction of growth.
The kidney tumour (asterisk) has grown to an enormous size at the rear of the body cavity of the previous fish. The normal kidney is a thin strip of brownish tissue (arrow) lying against the spine and visible within the enlarged swim bladder.
Externally, there is often a localised swelling of the belly (arrow) above the vent, depending on the size of the tumour. This oscar also has severe protrusion of the eyes (pop-eye).