Prostatitis (inflammation of the prostate gland) is the second most common prostatic disease of sexually intact male dogs. In neutered dogs, prostatitis is uncommon.
Prostatitis in dogs can be either acute or chronic (with the latter being the more common form). Acute prostatitis and chronic prostatitis differ based on progression and severity of clinical signs.
Cats have a rudimentary prostate, and both acute and chronic bacterial prostatitis have been very rarely reported in cats.
Etiology and Pathophysiology of Prostatitis in Dogs
Prostatitis in dogs typically occurs due to bacterial infection. Aseptic prostatitis is extremely rare in dogs. Various organisms, including Escherichia coli, Staphylococcus, Streptococcus, and Mycoplasma spp, have been implicated.
Infection may be from hematogenous spread of bacteria (typical of acute prostatitis) or ascending migration of bacteria from the urethra (typical of chronic prostatitis).
Prostatitis in dogs usually involves suppurative inflammation.
Acute prostatitis may result in abscesses.
Chronic prostatitis develops in association with benign prostatic hyperplasia (BPH).
Because prostatic fluid normally refluxes into the bladder, a secondary urinary tract infection often accompanies prostatic infection.
Clinical Findings of Prostatitis in Dogs
Clinical signs of acute prostatitis are nonspecific and include malaise,severe abdominal pain, and fever.Dehydration, septicemia, and shock can occur in severe cases.
Chronic bacterial prostatitis may cause no clinical signs except recurrent urinary tract infection. Clinical signs may also be similar to those of BPH. Physical abnormalities may be limited to the urinary tract. Rarely, prostatic size and shape may be normal.
Diagnosis of Prostatitis in Dogs
With acute prostatitis, clinicopathological findings may include monocytosis and neutrophilia with toxic changes and a left shift.
Ultrasonography may show changes in the normal homogeneous echotexture of the prostatic parenchyma (see images of Inflammation, prostate). With prostatitis, the parenchymal echotexture is more heterogeneous with multifocal hypoechoic areas consistent with small pockets of fluid (see video illustrating transabdominal ultrasonography of the prostate in a dog).
Courtesy of Dr. Michelle Kutzler.
Ideally, prostatic material should be obtained by prostatic massage for both cytological examination and for culture and antimicrobial susceptibility testing (see ). However, massage of an acutely infected prostate may release organisms into the blood and cause septicemia and is therefore contraindicated.
Urinalysis shows hematuria, pyuria, and bacteriuria in affected animals. Urine should be submitted for culture and antimicrobial susceptibility testing. Often, cultures of urine and prostatic material yield the same organisms.
For assessment of chronic bacterial prostatitis, microbiological examination of the third (prostatic) fraction of the ejaculate is more accurate than examination of prostatic massage specimens. Dogs with chronic bacterial prostatitis are usually willing to ejaculate. Prostatic fluid and urine should be submitted for cytological and microbiological examination.
Treatment of Prostatitis in Dogs
IV fluid therapy is indicated when acute prostatitis is associated with dehydration or shock.
Because the prostate-blood barrier is disrupted in acute prostatitis, antimicrobials should be selected on the basis of antimicrobial susceptibility testing and administered for ≥ 4 weeks. Many antimicrobials do not diffuse easily into the prostatic parenchyma because of the presence of the blood-prostate barrier. The mild inflammation associated with chronic prostatitis may not impair the blood-prostate barrier, so antimicrobials that are nonionized at neutral pH with high fat solubility (eg, enrofloxacin, trimethoprim-sulfamethoxazole, clindamycin, or azithromycin, ) are most effective. Enrofloxacin (5 mg/kg, PO, every 12 hours) is a good empirical treatment choice while awaiting results of microbiological testing.
Antimicrobial therapy alone is unrewarding. 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 intracapsular omentalization. Urine or prostatic fluid (or both) should be cultured again 2–4 weeks after antimicrobial therapy to be certain that infection has resolved.
Chronic bacterial prostatitis will not resolve without also treating for BPH. In fact, most cases of chronic bacterial prostatitis will resolve with treatment only for BPH, whether surgical (castration) or medical (finasteride).
Pearls & Pitfalls
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See Pharmacotherapeutics in Bacterial Prostatitis in Dogs and Cats for pharmacological considerations.
Key Points
Canine bacterial prostatitis can be either acute or chronic.
Clinical signs of chronic prostatitis may be absent or similar to those of benign prostatic hyperplasia, whereas clinical signs of acute prostatitis include severe abdominal pain and fever.
Urine or prostatic fluid (or both) should be evaluated cytologically and with culture and antimicrobial susceptibility testing.
Many antimicrobials do not diffuse easily into the prostatic parenchyma because of the presence of the blood-prostate barrier.
For More Information
Kutzler M. Reproductive microbiome alterations: canine prostatitis. Clin Theriogenology. 2019;11(4):649-658.
Phongphaew W, Kongtia M, Kim K, Sirinarumitr K, Sirinarumitr T. Association of bacterial isolates and antimicrobial susceptibility between prostatic fluid and urine samples in canine prostatitis with concurrent cystitis. Theriogenology. 2021;173:202-210.
Also see pet owner content regarding prostatic diseases in dogs and prostatic diseases in cats.
