Semen matrix calculi in a rhesus monkey (Macaca mulatta)

An 8.5 yr old male rhesus monkey (Macaca mulatta) died unexpectedly from Streptococcus pneumoniae septicemia. At necropsy the animal had severe ulcerative cystitis, and a rent in the bladder wall resulted in leakage of urine into the abdominal cavity. Seven soft calculi were loosely attached to the mucosa of the urinary bladder. The calculi were resilient, cylindrical, 1-1.5 cm wide, and brown green. Microscopically, they consisted of a bright eosinophilic hyaline matrix that contained spermatozoa. The matrix calculi probably resulted from coagulation of semen after retrograde ejaculation into the urinary bladder. A chronic penile urethritis appeared to be responsible for retrograde ejaculation.