Priapism in a Quarter Horse gelding

Priapism is an uncommon finding in domestic animals; however, it is reported in horses. It has multiple etiologies, including use of phenothiazine tranquilizers for routine procedures such as sheath cleaning and dentistry. 1 Priapism results in a selective engorgement of corpus cavernosum and corpus spongiosum that ultimately leads to venous occlusion. 2 Exact mechanism for initial failure of detumescence is not known, but ultimately, red blood cells become sickle shaped in response to increased partial pressure of CO2 . 3 This deformation in red blood cells can lead to permanent obstruction of venous drainage. A 25 year old, Quarter Horse gelding was presented with paraphimosis (noticed 2 days prior to presentation) secondary to priapism. His teeth had been floated 1 week earlier, under acepromazine sedation. Initial efforts to address priapism included placement of 12 gauge trocar needles, 1 dorsally and 1 ventrally within corpus cavernosum for irrigation with heparinized saline. Egress fluid from ventral trocar needles were thick, dark, and serosanguineous. As flush continued, fluid consistency changed to thin, bright red, serosanguineous to sanguineous, suggesting intact arterial supply. Phenylephrine was also administered directly into corpus cavernosum to promote vasoconstriction and reduction of priapism. Complete detumescence was not achieved by flush or phenylephrine treatment. A vascular shunt was established from corpus cavernosum to corpus spongiosum to relieve venous obstruction. Two days after the procedure, there was minimal improvement. Humane euthanasia was performed due to quality of life and financial constraints. At necropsy, vascular shunt (communication between corpus spongiosum and corpus cavernosum) appeared intact. Chronicity of the disease might have prevented full resolution and recovery, despite creation of a functional vascular shunt.

Keywords: Equine, gelding, priapism, acepromazine, corpus cavernosum, corpus spongiosum

References

1. Brinsko SP, Blanchard TL, Varner DD, et al: Surgery of the Stallion Reproductive Tract. In: Brinsko SP, Blanchard TL, Varner DD, et al: editors. Manual of Equine Reproduction. 3 rd edition, Mary Land Heights; Elsevier:2011. p. 263-272.
2. Rochat, MC. Priapism: A Review. Department of Veterinary Clinical Sciences, College of Veterinary Medicine Oklahoma State University. 2001.
3. Hinman F. Priapism: Reasons for failure of therapy. J Urol 1960;83:420.

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.