Inflammation of the canine prostate gland usually is suppurative and may result in abscesses. It is commonly associated with benign prostatic hyperplasia (see Prostatic Diseases: Benign Prostatic Hyperplasia in Small Animals). Various organisms, including Escherichia coli, Staphylococcus, Streptococcus, and Mycoplasma spp, have been incriminated. Infection may be hematogenous or ascend from the urethra. Because prostatic fluid normally refluxes into the bladder, urinary tract infection often accompanies prostatic infection. Canine prostatic infection can be divided into 2 types, acute prostatitis and chronic prostatitis, based on progression and severity of clinical signs.

Acute prostatitis is associated with malaise, pain, and fever. Dehydration, septicemia, and shock may occur in severe cases. Neutrophilia with a left shift, monocytosis, and/or toxic WBC may be seen. Ultrasonography shows hypoechoic areas consistent with small pockets of fluid. Ideally, prostatic material is obtained by prostatic massage, ejaculation, or fine-needle aspiration for cytologic examination and for culture and sensitivity testing. Massage of an acutely infected prostate may liberate organisms into the blood and cause septicemia. For this reason, other methods are preferred. However, dogs with acute bacterial prostatitis or abscesses may be reluctant to ejaculate, and fine-needle aspiration may release organisms into the peritoneal cavity. Urinalysis shows hematuria, pyuria, and bacteriuria. The urine should be submitted for culture and sensitivity testing. Often, the urine and prostatic material yield the same organisms.

IV fluid therapy is indicated when acute prostatitis is associated with dehydration or shock. Antibiotics should be selected on the basis of sensitivity testing and given for 3–4 wk. After the infection is controlled, castration should be considered. In some instances multiple microabscesses within an infected prostate gland may coalesce into a solitary abscess. Large prostatic abscesses are best treated by surgical drainage and castration. Urine or prostatic fluid (or both) should be cultured again after antibiotic therapy and 2–4 wk later to be certain that the infection has resolved.

Chronic bacterial prostatitis may cause no clinical signs except recurrent urinary tract infection. Physical abnormalities may be limited to the urinary tract. Rarely, prostatic size and shape may be normal. Dogs with chronic bacterial prostatitis are usually willing to ejaculate. Prostatic massage or fine-needle aspiration could also be used to obtain specimens. Prostatic fluid and urine should be submitted for cytologic and microbiologic examination.

Chronic bacterial prostatitis may be difficult to resolve. Many antibiotics do not diffuse easily into the prostatic parenchyma due to the presence of the blood-prostate barrier. The mild inflammation associated with chronic prostatitis may not impair the blood-prostate barrier, so antibiotics that are non-ionized at neutral pH with high fat solubility (ie, erythromycin, clindamycin, trimethoprim-sulfamethoxazole, or enrofloxacin) are most effective. Antibiotic therapy should continue for ≥4 wk. Cultures should be repeated during, and for several months after, antibiotic therapy to ascertain whether resistance or persistent infection has developed. The benefits of castration for treatment of chronic bacterial prostatitis are uncertain; however, it seems reasonable that the prostatic involution after castration would at least help prevent recurrence of infection.

Last full review/revision July 2011 by James A. Flanders, DVM, DACVS