William H Wildgoose MRCVS
Pet fish vet
Overgrown wen in goldfish
The wen, head growth or ‘cap’, is a growth of soft fleshy tissue on the head of some goldfish varieties such as the oranda, lionhead and ranchu. It has been selected genetically over the years, but in some cases, excessive growth of the tissue can obscure vision, restrict breathing or affect buoyancy. This common problem requires surgical trimming when severe and may need repeating on a regular basis, every 3 to 6 months. The procedure should be carried out under an anaesthetic, with care taken to avoid infection and damage to the eyes. Click here for a scientific report of cases in America.
The wen is composed of myxomatous (gelatinous) soft tissue covered with a layer of epithelium (skin). The cause of overgrowth is poorly understood and presumed to be due to several factors which may include a genetic or environmental origin, in addition to inflammation from trauma and infection.
This is the same fish following removal of some overgrown tissue above the eye, which improved its vision. Tissue was also removed from the part above the operculum (gill flap). Bleeding is usually minimal as seen where a few capillaries have been cut, with no blood control measures applied.
The image on the left is the side view of the head of a normal common goldfish. The other image is that of an oranda with a similar-sized skull, revealing the irregular bony outline at the top of the skull under a large fleshy wen. This shows the significant bone changes deep beneath the soft outer surface of the wen.
The wen is composed of myxomatous (gelatinous) soft tissue covered with a layer of epithelium (skin). The cause of overgrowth is poorly understood and presumed to be due to several factors which may include a genetic or environmental origin, in addition to inflammation from trauma and infection.