Prostatic Abscess in Dogs
Dr. Douglas Brum
A complete history and physical examination is the first step in obtaining an accurate diagnosis. If large enough the abscess may be palpable (felt) through the abdomen. More commonly, prostatic abscesses may be detected as a softer area on an enlarged, irregular prostate by digital rectal examination. A dog with a prostatic abscess may be quite ill and require a rapid diagnostic assessment. Other times, a critical situation is not present and the diagnostics may proceed in a more orderly manner.
The CBC is a useful test to run when a prostatic abscess is suspected, as it evaluates the red and white blood cells. Elevations in the total white count are commonly seen in cases of infection and prostatic abscessation.
The biochemical profile evaluates the metabolic status of a variety of organ systems. Since prostatic abscesses are a more common occurrence in older animals, and infection can affect other organ systems, it is a useful screening test to rule out other problems and or associated disease. Liver values may be elevated with the infection. If the abscess has compressed the urethra, a partial or complete urinary obstruction may occur, and cause an elevation in kidney values.
A urinalysis will detect inflammation or blood in the urine, and may show signs of a bacterial infection. The urine should be obtained sterilely for accurate interpretation, and the urine should be cultured for bacterial growth. Dogs with prostatic abscesses may have a normal urinalysis, and have no bacterial growth on culture. The bacteria may be sequestered deep within the prostate or abscess and not be present in the urine at the time of sampling.
Cytologic (microscopic) evaluation of seminal fluid is a useful diagnostic tool when testing for prostatic disease. Samples are obtained via an ejaculate, and the fluid is checked for evidence of white blood cells, red blood cells and bacteria. Since the prostatic fluid is concentrated in the last part (third fraction) of the ejaculate, this is the most productive part to analyze. The sample should also be cultured. This test is not often done in a dog with a prostatic abscess since they are generally ill, depressed, and uncomfortable, making obtaining a sample difficult. If a sample is obtained, it usually shows evidence of inflammation and infection.
A prostatic massage and wash is another method for evaluating prostatic fluid. There are several techniques for obtaining this sample. Briefly, a urinary catheter is passed to the level of the prostatic urethra and the prostate is digitally massaged through the rectum. A sample is obtained by flushing fluid into the area. The fluid is then aspirated back through the catheter. This sample is submitted for cytology and culture. Samples may show microscopic evidence of an infection.
Abdominal radiographs are useful in evaluating the abdominal organs and the general size and shape of the prostate. The lymph nodes that drain the prostate (sub-lumbar lymph nodes) are also evaluated for enlargement. The prostate is usually enlarged on radiographs. Occasionally there is a lack of contrast, or detail, in the area of the prostate.
Occasionally the abdominal X-rays may provide ambiguous results as to the nature of the prostatomegaly, especially if a large prostatic abscess or paraprostatic cyst is present. Distention retrograde urethrocystography is a technique where dye and air are injected through the urethra and into the bladder. This technique allows the urethral lining to be visualized and better defines the bladder, prostate and any associated mass lesions that may be present. It may be a useful diagnostic test to use if a compressive or invasive urethral lesion is suspected. This is most commonly seen in cases of prostatic neoplasia, paraprostatic cysts, or prostatic abscessation.
An abdominal ultrasound can evaluate the texture and consistency of the prostate, as well as size and shape. Performing an ultrasound is helpful, even though the appearance of the prostatic abscesses on ultrasound is not specific for the disease. Prostatic cystic hyperplasia, hematomas (blood clots), and hemacysts, which are prostatic cysts that have bled into the cyst cavity, all have a similar appearance. In order to obtain a more specific diagnosis, an area that is identified as abnormal may be aspirated using the ultrasound for guidance.
Fine needle aspiration – inserting a needle into a structure and removing a small amount of cells or fluid with negative pressure using a syringe – may be used to collect fluid from abscess for cytologic evaluation. Extreme care and good judgment are needed when attempting this procedure since infected material from the inside of the abscess may leak out of the aspirated site and into the abdomen. Peritonitis would ensue, requiring rapid therapy. If this procedure is attempted, your veterinarian must be prepared for emergency surgery to flush out the abdomen and to treat the abscess. Even though this procedure caries a degree or risk, it may be the only way to diagnose the abscess other than exploratory surgery. Ultrasound-guided biopsy should not be attempted.
Based on the above diagnostics, a prostatic abscess may be suspected, but the only way to diagnose a prostatic abscess definitively is either by ultrasound-guided aspiration or a surgical exploratory. Surgery becomes both a diagnostic and therapeutic procedure since surgical intervention is needed for treatment.