Pooling of urine in the anterior vagina is a fairly common cause of infertility in the mare. It is a problem of either poor conformation or poor muscle tone and incomplete involution of the tubular genital tract. A simple method of surgical correction consists of retracing the transverse fold, a mucosal fold overlying the external urethral orifice, caudally approximately 5 cm. (two inches) and suturing it to the vestibular floor.
Engle, Mark J. and Clark, Tracy
"Urine Pooling in the Mare,"
Iowa State University Veterinarian: Vol. 42
, Article 2.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol42/iss1/2