Vent Prolapse - Fish

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Prolapse through the vent can be quite common in fish. This can occur secondary to an infective process or due to straining from passing eggs or constipation.

Potential prolapsed organs include:

cloacal prolapse through the anal pore
intestinal prolapse through the anal pore
rectal prolapse through the anal pore
intestinal prolapse through the genital pore
ovarian prolapse through the genital pore

Clinical Signs

The most obvious clinical sign will be of a mass protruding from the vent of the fish.

The fish may appear depressed, lethargic and anorexic. Dropsy may occur.


The nature of the prolapse may become apparent after a careful physical examination.

Intestine will have a smooth surface whereas ovarian tissue appears grainy with small white to yellow follicles.

Cytology may help differentiate the tissue and provide a definitive diagnosis.


In the case of ovarian tissue, surgical resection is recommended. An encircling ligature can be placed or a CO2 laser can be used to remove the mass. Further eggs can be milked from the fish by inserting a syringe into the genital pore and exerting gentle "milking" pressure on the fish's abdomen.

Prolapsed intestine or rectum should be reduced if possible, and suture material can be used to anchor the tissue to the vent.

Conservative treatment is also possible and some prolapses reduce on their own if the fish is in otherwise good condition.

A purse-string suture can be placed around the genital pore or the anal pore to prevent further prolapses whilst also allowing the passage of eggs or faeces.

Care should be taken to provide optimum water quality and to avoid unnecessary stress to the fish.

Vent Prolapse - Fish Learning Resources
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Ornamental Fish Q&A 02


Campbell, T. (2011) Clinical Cases in Avian and Exotic Animal Hematology and Cytology John Wiley and Sons

Lewbart, G. (1998) Ornamental Fish: Self-assessment colour review Manson Publishing

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