William H Wildgoose MRCVS
Pet fish vet
Polycystic kidney disease
This is a common disease in goldfish that causes a slow progressive swelling of the belly over many months or years. In some cases, the fish may swell up so much that they look like they may burst. It is thought to be due to a developmental /genetic abnormality or a parasite that damages the kidneys. Large cysts develop in the kidney which enlarge and occupy a large part of the body cavity. Although it is easily confirmed on an ultrasound scan, there is no treatment for the disease.
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Severely swollen belly is common in fish and although there can be several different causes, polycystic kidneys are common in goldfish
Side view X-ray showing moderate swelling of the belly and increased distance between the two swim bladder chambers (2 black central areas). The presence of fluid in the cystic kidneys gives a radiographic homogeneous appearance and conceals subtle detail in the body cavity. It is often possible to see the margins of both affected kidneys (smaller right kidney black arrows; larger left kidney white arrows)
Low power (x40 mag) of affected goldfish kidney tissue reveals large cystic cavities (asterisks) caused by severe dilation of the renal tubules, and a glomerulus (arrow) in among some interstitial tissue.
Severely swollen belly is common in fish and although there can be several different causes, polycystic kidneys are common in goldfish