Emphysematous Prostatitis and Carcinoma in a Dog

Introduction

Emphysematous prostatitis can be characterized as an inflammatory condition of the prostate with a pathological accumulation of gas within the prostatic tissue. Gas production in the urinary tract can be the result of a gas-forming organism.¹ This needs to be differentiated from secondary causes such as iatrogenic introduction of an instrument into the urogenital tract resulting in the formation of a fistulous connection between the urinary tract and colon. To the authors’ knowledge, there have been no previous reports of emphysematous prostatitis in dogs. The presence of gas within the prostate has been mentioned in one reference as a possible indication of a gas-forming organism.² There also has been documentation of emphysematous prostatitis and cystitis in a human secondary to Candida albicans.³ This report describes the presence of emphysematous prostatitis in a dog with a prostatic abscess and concurrent prostatic carcinoma.

Case Report

A 10-year-old, intact male beagle presented for lethargy, anorexia, straining to urinate, and intermittent urinary incontinence. On physical examination, the dog was cachectic, and a mass was palpated in the caudal abdomen. A urinary catheter was passed easily, and 2 mL of turbid urine was collected. Subjectively, there was no change in the size of the mass on palpation. Urinalysis revealed leukocytes (3+; reference range, 0 to trace), proteinuria (300 mg; reference range, 0 to trace), and positive occult blood (3+; reference range, 0 to trace).

The complete blood count (CBC) revealed a mild, nonregenerative anemia (hematocrit, 32.3%; reference range, 37.0% to 55.0%), neutrophilia with a left shift (segmented neutrophils, 17.89 ×10³/μL [reference range, 3.0 to 11.0 ×10³/μL]; banded neutrophils, 2.17 ×10³/μL [reference range, 0 to 0.3 ×10³/μL]), and a monocytosis (5.15 ×10³/μL; reference range, 0.15 to 1.35 ×10³/μL). These changes were consistent with an inflammatory process. The serum biochemical profile revealed a hyperglobulinemia (4.7 g/dL; reference range, 2.7 to 4.4 g/dL) and hypoalbuminemia (2.3 g/dL; reference range, 2.5 to 3.8 g/dL). The creatinine concentration was also decreased (0.4 mg/dL; reference range, 0.7 to 1.5 mg/dL).

Survey radiographs of the abdomen revealed a bilobed mass in the caudoventral abdominal quadrant, causing dorsal displacement of the descending colon [Figures 1A, 1B]. The mass contained gas. The wall of the mass appeared thickened and irregular. Gas was also present in another structure cranial to this mass. Feces were present in the transverse and descending colon. A metallic projectile was noted in the cranial abdomen, and another was noted in the soft tissues of the prepuce. A retrograde positive-contrast cystogram was performed to determine the location of the bladder relative to the mass [Figure 2]. The study demonstrated that the cranial, gas-filled structure was the bladder and that the other gas-filled mass was caudal to it. No evidence of urethroprostatic reflux was demonstrated. Differential diagnoses for the caudoventral abdominal mass included prostatic abscess, cavitary prostatic neoplasia, and paraprostatic cyst. Cranial migration of gas from the prostatic mass or emphysematous cystitis caused by gas-forming bacteria were possible causes for the intravesicular gas. The feces in the colon were likely due to constipation or obstipation as a result of compression from the mass or pelvic pain.

An exploratory celiotomy was performed. A firm and subjectively enlarged prostate was visualized in the caudal abdomen. The prostate was isolated, lanced, and drained. Approximately 200 mL of purulent material and an undetermined amount of gas were removed from both prostatic lobes. The prostate was then flushed with copious amounts of sterile 0.9% sodium chloride irrigation solution. Surgical exploration of the abdomen revealed no communication between the prostate and colon. Parenchymal tissue was broken down digitally within the body of the prostate. An incision was made on each side of the prostate, and a Penrose drain^a was passed through the prostate. The drain exited the abdomen through incisions made in the ventral body wall on either side of the prepuce. The drain was sutured to the body wall at the incision site. The initial incision in the prostate was closed using an inverting suture pattern, the abdominal cavity was lavaged with warm saline, and a routine abdominal closure was performed. The dog was then castrated. A sample of the purulent material from the abscess was submitted for both an aerobic and anaerobic culture and sensitivity, and a biopsy of the prostatic tissue was submitted for histopathology. The dog was sent home on enrofloxacin^b (5 mg/kg body weight, per os [PO], q 12 hours) and penicillin V potassium^c (11 mg/kg body weight, PO, q 8 hours) for 6 weeks. The drains showed little or no evidence of drainage after 7 days and were removed.

The culture revealed a heavy growth of Eshericia coli (E. coli) sensitive to a number of antimicrobials. The prostatic histopathology revealed a poorly differentiated tubular carcinoma or adenocarcinoma with necrosis and lymphatic invasion. The final diagnosis was prostatic carcinoma or adenocarcinoma with secondary prostatic abscessation and emphysematous prostatitis. Thoracic radiographs, regional lymphnode biopsies, and follow-up urinary cultures were recommended but declined by the owner. Subsequent telephone conversations with the owner revealed that the dog did well for about 2 weeks and then became anorexic and lethargic. The dog died at home approximately 1 month after surgery. Necropsy examination was not permitted.

Discussion

Emphysematous prostatitis is an unusual manifestation of prostatic disease. A prostatic infection by a gas-forming organism should be suspected, but iatrogenic causes and fistulas need to be ruled out. The most common mechanism of gas formation is the bacterial fermentation of glucose, resulting in the formation of carbon dioxide with butyric and lactic acid.^4–6 Dogs with diabetes mellitus have a high incidence of bacteruria and glucosuria, subsequently predisposing these animals to gas formation in the urinary tract by glucose fermentation.⁷ Other cases of gas-forming infections of the urinary tract have been documented in nondiabetic dogs without evidence of glucosuria.⁴ The production of gas in these cases is thought to be due to the breakdown of urine albumin by E. coli, the most commonly isolated microorganism in gas-forming infections.^4–6 Other pathogens include Aerobacter aerogenes, Staphylococcus aureus, Streptococcus spp., Proteus spp., Nocardia spp., and Candida albicans.^3–6

Histopathological diagnosis in this case was a poorly differentiated tubular carcinoma or adenocarcinoma. Adenocarcinoma is the most frequent prostatic cancer, although undifferentiated carcinoma, transitional cell carcinoma, leiomyosarcoma, and hemangiosarcoma have also been diagnosed.^8–11 It has been estimated that the incidence of prostatic carcinoma in dogs is <1% of the canine population; however, it has also been suggested that the low incidence may be due to the difficulty in clinically differentiating carcinoma from other diseases of the prostate.⁸¹² Treatment of primary prostatic adenocarcinoma is historically unrewarding, and prognosis is poor.⁹¹³

This case also presented with a prostatic abscess. Prostatic abscesses are usually secondary to a primary disorder. Benign prostatic hyperplasia, squamous metaplasia, and prostatic neoplasia predispose the gland to infection by altering normal defense mechanisms that prevent retrograde movement of bacteria.⁹¹⁴ Organisms most commonly isolated include E. coli, Mycoplasma spp., Staphylococcus spp., Streptococcus spp., Klebsiella spp., Proteus spp., and Pseudomonas spp.⁹¹⁴ Some of these organisms, such as E. coli, are also capable of gas production. Gas-producing bacteria were considered to be the logical cause of the collection of gas in the prostate of this case, because a fistula between the colon and prostate was not identified prior to or at surgery. Surgery is often recommended to drain or excise prostatic abscesses, but complications are common.¹⁵ Ventral drainage by means of Penrose drains was chosen in this case. Other proposed treatments include marsupialization of the abscess, local resection, subtotal and excisional prostatectomy, and intracapsular prostatic omentalization.¹⁵¹⁶ Additional treatments include castration and proper antibiotic therapy based on culture and sensitivity. It has been recommended that antibiotic therapy be given for a minimum of 3 to 6 weeks.⁹

It is likely that the prostatic carcinoma was the inciting cause of this dog’s problems, and the prostatic abscess and gas formations were secondary complications. However, the relationship between prostatic neoplasms and prostatic abscessation is not fully understood.¹⁷ It is not known if chronic inflammatory prostatic disease can lead to malignant transformation of prostatic tissues, as has been hypothesized in another case of prostatic disease and reported to occur in other tissues.¹⁷

Conclusion

This report describes the presence of emphysematous changes within the prostate associated with inflammatory and neoplastic processes. The presence of concurrent disease processes in the prostate can make definitive diagnosis difficult. Diagnosis in this case was based on exploratory celiotomy and biopsy of the prostate. However, published literature on prostatic neoplasia suggests that a biopsy sample may miss prostatic neoplasia.⁸ Therefore, biopsy of the medial iliac lymph nodes and thoracic radiographs are recommended.⁸⁹¹²

Acknowledgments

The authors recognize Dr. Bill Weber for his participation in the clinical diagnosis of the case and Dr. Barbara Lightner for her participation in the clinical assessment and treatment of the case.