Pathology in Practice

Jelena Palić Vet Med Labor GmbH, Division of Idexx Laboratories, Kornwestheim, Germany

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 DVM, PhD, DACVM, DACVP
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Franziska Hergt Vet Med Labor GmbH, Division of Idexx Laboratories, Kornwestheim, Germany

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 Dr med vet, DECVIM

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History

A 12-year-old 7-kg sexually intact male Miniature Dachshund was evaluated for constipation and tenesmus.

Clinical and Gross Findings

On presentation, a grape-sized swelling and soft palpable mass were present in the right perineal area. The rest of the clinical examination was unremarkable.

Ultrasonographic examination of the perineal area revealed a hyperechoic mass surrounded by a small amount of free fluid (Figure 1). The exact origin of the mass could not be determined. Ultrasound-guided fine-needle aspiration (FNA) samples were collected for cytologic analysis.

Figure 1
Figure 1

Perineal mass in a 12-year-old intact male dog. A—Ultrasonographic image illustrating a hyperechoic soft tissue mass surrounded by a small amount of free fluid. B—Photomicrograph of a fine-needle aspirate preparation of the perineal mass showing tightly packed, uniform-appearing epithelial cells with a honeycomb arrangement. May-Grünwald-Giemsa stain; bar = 20 μm.

Citation: Journal of the American Veterinary Medical Association 260, 15; 10.2460/javma.22.04.0170

Cytologic Findings

The FNA preparations were of high cellularity with low numbers of erythrocytes in the background. Uniform clusters of epithelial cells were present (Figure 1). Cells had round nuclei with stippled chromatin and lacked prominent nucleoli. They exhibited mild anisocytosis and anisokaryosis. The nuclear-to-cytoplasmic ratio (N:C) was moderate, and the cytoplasm was pale basophilic. Cell clusters showed a characteristic honeycomb arrangement.

Morphologic Diagnosis and Case Summary

Cytologic diagnosis: benign prostatic hyperplasia.

Case summary: perineal hernia with prostatic herniation in a dog.

Comments

Perineal hernias occur due to weakening or complete failure of the muscular diaphragm of the pelvis resulting in herniation of pelvic and sometimes abdominal viscera into the subcutaneous perineal region.1,2 In dogs, a common presentation of perineal hernia is a nonpainful unilateral (more often described on the right side3) or bilateral perineal swelling.1 Because perineal hernias can contain prostate, urinary bladder, rectum, or small intestine, additional clinical signs can include constipation, obstipation, dyschezia, tenesmus, rectal prolapse, stranguria, anuria, vomiting, or fecal incontinence, alone or in combination.1,3 Perineal hernias occur most commonly in mature sexually intact male dogs.1 Proposed causes of the muscular pelvic diaphragm weakness are tenesmus associated with chronic prostatic disease or constipation, myopathy, rectal abnormalities, hormonal imbalances, and effect of relaxin on muscle fiber weakening.1 Prostatic disease can contribute to the formation of perineal hernia due to increased pressure that can be caused by prostatic hyperplasia,4 paraprostatic cyst,3 and prostatic B-cell lymphoma5 as well as inflammation and pain.1 The prostate can herniate into the hernial sac with or without retroflexion of the urinary bladder.4 Prostate was detected within the hernial contents in 13% (4/32)6 and 41% (14/34)7 of dogs; other studies reported that 43% (13/30),8 51% (21/41),9 and 59% (19/32)10 of dogs with perineal hernia show concurrent prostatic disease. Furthermore, it was proposed that relaxin, a hormone synthesized primarily in the prostate of intact male dogs, may leak from hyperplastic prostatic gland, causing local muscle atrophy and softening of connective tissue, therefore leading to perineal hernia.11 An in vivo study12 demonstrated that dogs with prostatic hyperplasia also had significantly higher expression levels of canine relaxin receptors in the musculature of the pelvic diaphragm and internal obturator muscle, compared with control dogs, which likely led to increased relaxin activity and higher likelihood of perineal hernia development.

The definitive diagnosis of a perineal hernia is based on clinical signs and findings of a weakened pelvic diaphragm during a digital rectal examination.1,2 Other diagnostic tests that can be performed include abdominal radiography and ultrasonography, which may help in the size assessment of the prostate and determination of whether the bladder is displaced into the hernia sac.1,2 Findings in the dog of the present report and a dog with mineralized paraprostatic cyst in the perineal region described in a previous case report3 are examples that FNA is also a useful diagnostic tool. Two cases of inadvertent iatrogenic total prostatectomy and urethrectomy with subsequent dysuria were reported in dogs.4 In both cases, existing perineal hernias were not recognized by the referring veterinarians during clinical examination, and the caudally herniated prostate was erroneously diagnosed as perianal neoplasia and excised without performing FNA prior to surgery.4

Perineal hernias are treated by surgical intervention.1 In addition to herniorrhaphy, castration is recommended to decrease the size of the prostate and reduce the recurrence of the perineal hernia.7,13 The dog of the present report was castrated after the initial diagnosis. Surgical repair of the hernia was also recommended and scheduled for a later date; because the patient improved clinically (constipation and tenesmus resolved), the owners decided to postpone the surgical repair of the hernia. Approximately 7 months later, the dog was presented again with constipation. The owners elected not to proceed with the surgical repair of the hernia, and the dog was euthanized.

In summary, cytology is a good diagnostic tool during the workup of the perineal soft tissue masses present in intact male dogs and can direct further examination or aid in presurgical assessment of the origin of the prolapsed tissue.

Acknowledgments

No external funding was used in this case, and the authors declare that there were no conflicts of interest.

The authors thank Dr. Ingvild Blaker Thoresen from Anicura Dyresykehus Oslo AS for providing detailed information regarding the clinical presentation and follow-up.

References

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