This page is part of the site called Surgical Pathology of the Canine Male Reproductive Tract by

The most important diseases of the epididymis of all species are involve inflammation. Infectious epididymitis is the most important but unlike the ram, is not well studied. One very important and often missed disease is spermatic granuloma of the epididymal head. This is an inflammatory (granulomatous inflammation to spermatozoa) disease with an anomalous and potentially genetic basis.

Inflammation

The presence of spermatozoa, which are antigenic and which also induces a foreign body type disease, within the lumen of the epididymal duct complicates the responses of this organ to injury. Spermatozoa induce a foreign body and immune mediated response and the character is typically granulomatous. Spermatozoa are continuously produced and move through the duct. Any obstruction of the duct of the epididymis results in increased pressure and the likelihood of rupture. A rupture or perforation of the tube will eventually lead to the formation of a cavity containing impacted spermatozoa. In severe cases, the spermatozoa will be released into the cavity surrounded by the vaginal tunics.

Spermatic granulomas thus formed develop anywhere that spermatozoa are found. Most cases occur because of

• blind efferent ductules (see in dogs)
• abberent epididymal ducts
• adenomyosis of the epididymis
• infectious epididymitis (seen in dogs).

 

Infectious epididymitis

Bacterial epididymitis

Bacterial infection of the epididymis usually occurs via two main routes, ascending infection from the urethra via the deferent duct and accessory genital glands, or hematogenous spread. Descending infection from the testis, and direct penetrating injury are both theoretically possible, but much less likely..

Bacteria are the most common causative agent. Brucella canis is a traditional and important cause, but is uncommon except in some specific locales of situations. Infection with Gram negative organisms such as Escherichia coli are the most common in most areas. The macroscopic and microscopic changes in epididymitis are similar, regardless of the cause, so we will outline the changes before examining specific or noteworthy changes for individual causes.

Macroscopic changes

The gross lesions of epididymitis usually involve the tail and sometimes the body of the epididymis. This may be bilateral or unilateral, and the severity can vary tremendously. The severity reflects the degree of damage including necrosis and vascular changes.

In severe acute disease, there is swelling and edema of the epididymis, especially of the tail and sometimes the body. The head of the epididymis is not usually involved. Edema is common, and fluid accumulates within the cavity of the vaginal tunics. Fibrin may be found on the surface of the epididymis and on the tunics. The scrotum will become edematous and swollen also. The inflammation, being neutrophilic in nature, may develop to the stage of abscess formation. Although the lesion looks like an abscess, such a change is often accompanied by release of spermatozoa into the tissues so the liquid resembling pus may be part of a spermatic granuloma. The scrotum is also involved with edema predominating. Self trauma of the scrotum, presumably because of pain, can result in ulceration of the scrotum. The testis can also be involved either with orchitis or with necrosis.

With time, fibrosis becomes the major gross lesion, and there will be a marked interstitial fibrosis visible in the affected areas of the epididymis. Adhesion of the parietal to the visceral vaginal tunic is a common occurrence, and the tunics can become markedly thickened with granulation and fibrous tissue.

Figure : Unilateral epididymitis (lower). The epididymides are viewed from the ventral surface such that the tail of the epididymis is visible and the testis is beneath it.

Microscopic changes

There are no sequential studies of the lesions in dogs. The most acute or recent cases had large numbers of neutrophils within the duct of the epididymis. The epithelium often has degenerative changes including single cell death. The interstitial tissues are expanded with edema and neutrophils and macrophages. Severe cases will have fibrin deposition. Some cases will have whole regions of coagulation necrosis. With time, there may be the formation of abscesses with pools of neutrophils and necrotic debris between the duct or involving the ducts. Rupture of the ducts will allow spermatozoa to enter these areas. The tunics will initially be covered with fibrin and enmeshed neutrophils, but soon develop granulation tissue. With time, there will be infiltrates and accumulations of plasma cells and lymphocytes, especially around vessels and also around the duct.

Organisation of edema and fibrin will eventually cause the formation of fibrous tissue within the interstitium and around areas of necrosis. Spermatic granulomas form where sperm are extravasated.

It is unusual to find bacteria or bacterial colonies within the lesions, even with a Gram stain.

Figure : Histology of epididymitis. The epididymal duct is surrounded by lymphocytes and plasma cells, and there is a spermatic granuloma ventrally.

Canine brucellosis

Brucella canis is the most common Brucella found in dogs. There is a single report of each of Brucella suis (Barr et al 1986) and Brucella abortus (Love et al 2004) causing prostatitis and epididymitis in a dog.

Much has been written about canine brucellosis since Carmichel described the first cases of Brucella canis in 1966. The lesions in the reproductive tract in male dogs is primarily epididymitis. Wanke (2004) reviewed canine brucellosis and noted the pathogenesis involves exposure of mucosa, either genital, conjunctival or oral, with bacteria from urine (especially of male dogs) or vaginal secretions. The bacteria are taken up by macrophages and become bacteremic. They localise in multiple locations including the prostate and epididymis where prostatitis and epididymitis develop. It takes about 5 weeks for lesions to appear, and in the initial phases, the epididymides increase in size, pain develops and there is extra fluid within the cavity of the vaginal tunics. Neutrophils appear in semen, as do bacteria. Spermatic granuloma may develop in time. Gyuranecz et al (2011) reported on a kennel with an outbreak of Brucella abortion and they also reported finding Brucella canis epididymitis in a dog.

Olsen and Palmer (2015) provides a detailed review of the pathogenesis and pathology of brucellosis in all species.

Camargo-Castañeda et al (2021) detailed the histologic lesions and detection of antigen in tissues. The epididymal tubule fills with neutrophils and there is cell death of the epithelium. Antigen was mostly in macrophages.

Barr SC, Eitis BE, Roy AF, Miller R. (1986). Brucella suis biotype 1 infection in a dog. J Amer Vet Med Assoc 189: 686-687.

Brennan SJ, Ngeleka M, Philibert HM, Forbes LB, and Allen AL (2008) Canine brucellosis in a Saskatchewan kennel. Can Vet J. 49(7): 703-708.

Camargo-Castañeda AM, Stranahan LW, Edwards JF, Garcia-Gonzalez DG, Roa L, Avila-Granados LM, Hensel ME, Arenas-Gamboa AM. Characterization of epididymal and testicular histologic lesions and use of immunohistochemistry and PCR on formalin-fixed tissues to detect Brucella canis in male dogs. J Vet Diagn Invest. 2021; 33: 352-356.

Gyuranecz M, Szeredi L, Ronai Z, Denes B, Dencso L, Dan A, Palmai N, Hauser Z, Lami E, Makrai L, Erdelyi K, Janosi S. (2011) Detection of Brucella canis–induced reproductive diseases in a kennel J Vet Diagn Invest 2011, 23:143–147

Love R, Hemphill J Jr, Cooper MS, DeMello GC, Goebel JC. (1952) Epididymitis in a dog caused by Brucella abortus, and treatment with aureomycin. Cornell Vet. 42(1):37-41

Olsen SC, Palmer MV. Advancement of knowledge of Brucella over the past 50 years. Vet Pathol. 2014; 51: 1076-1089.

Wanke MM.(2004) Canine brucellosis. Anim Reprod Sci. 82-83:195-207.

 

Enterobacteriacae

Epididymitis caused by infection with bacteria apart from Brucella canis are the most common in most areas of the world. Surprisingly, little is written about them. Textbooks indicate how common these are, but there were no pubished articles retreived by the electronic search engines. There are 71 cases in the Yager-Best Histovet database that were considered to be from bacterial infection. Where results of serology for Brucella canis were obtained, none were positive. Routine submissions for histopathology are not typically cultured. One case that was cultured had Actinobacillus sp isolated.

It is believed that infection of the epididymis is the result of ascending of bacteria from the penis and prepuce via the accessory genital glands.

Epididymitis, presumably caused by Gram negative organisms such as E. coli, tends to be more severe and necrosuppurative than those seen in canine brucellosis.

Figure : Epididymitis and periorchitis from which an Actinobacillus was isolated. There is concurrent testicular necrosis.

Mycoplasma epididymitis

L'Abee-Lund et al (2003) report culturing Mycoplasma canis from a dog with epididymitis.

L'Abee-Lund TM, Heiene R, Friis NF, Ahrens P, Sorum H (2003) Mycoplasma canis and urogenital disease in dogs in Norway. Vet Rec. 153(8):231-235.

Idiopathic (nonspecific) epididymitis

Olson et al (1992), in reporting 18 dogs with azoospermia found 1 dog had inflammation in the efferent ducts, and 3 had inflammation of the epididymides that varied from mild to severe. Where no cause in found, the cases could be classified as nonspecific, but ascending infection with Gram negative bacteria is likely.

Bloom (1954) reports finding focal interstitial aggregates of lymphoid cells in otherwise normal dogs.

James and Heywood (1979) reported seeing focal chronic inflammatory cell infiltrates in all ages of dog, with an age related trend.

 

Bloom F (1954) Pathology of the dog and cat - The genitourinary system, with clinical considerations. American Veterinary Publications, Inc, Evanston Illinois. p214.

James RW, Heywood R. (1979) Age-related variations in the testes and prostate of beagle dogs. Toxicology. 12(3):273-279.

Olson PN, Schultheiss P, Seim HB. (1992) Clinical and laboratory findings associated with actual or suspected azoospermia in dogs: 18 cases (1979). J Amer Vet Med Assoc 201: 478-482.

Protozoal epididymitis

Protozoal epididymitis, in particular caused by Leishmania, occurs where the disease is endemic. The lesions were microscopic only, and consisted of lymphocytic and histiocytic infiltrates in the peritubular interstitium.

Diniz SA, Melo MS, Borges AM, Bueno R, Reis BP, Tafuri WL, Nascimento EF, Santos RL. (2005)

Genital Lesions Associated with Visceral Leishmaniasis and Shedding of Leishmania sp. in the Semen of Naturally Infected Dogs Vet Pathol 42: 650-658.

Mycotic epididymitis

Inflammation of the epididymis induced by fungal agents is very rare.

Kadota et al (1995) reported on a case of granulomatous epididymitis from which Rhodotorula glutinis, a yeast, was isolated.

There is one case of blastomycosis diagnosed because epididymitis was found in the Yager-Best Histovet database (YB94471). The yeast Blastomyces dermatitis is a systemic infection which in one case affected the epididymis. The lesion was one of multiple coalescing granulomas within the interstitium of the tail of the epididymis of a dog.

Figure :Granulomatous epididymitis in a dog.

Figure : Granuloma containing Blastomyces dermatitis in the epididymis of a dog.

 

Kadota K, Uchida, K, Nagatomo T, Goto Y, Shinjo T, Hasegawa T, Ogawa H, Yamaguchi R, Tateyama S. (1995). Granulomatous wpididymitis related to Rhodotorula glutinis infection in a dog. Vet Pathol 32: 716-718.

Olson PN, Schultheiss P, Seim HB. (1992) Clinical and laboratory findings associated with actual or suspected azoospermia in dogs: 18 cases (1979). J Amer Vet Med Assoc 201: 478-482.

Viral infection

Viral infection of the epididymis would be expected to occur in canine distemper virus (paramyxoviral) infection.

Inclusion bodies may be found in the luminal epithelial cells but inflammation is absent. McEntee (1990) says that epididymitis is often associated with canine distemper.

Many dogs have clear, eosinophilic or crystaline inclusions in their epididymal head or other parts of the epididymis as an incidental finding.

 

Gouranton J, Folliot R, Thomas D.Fine structure and nature of the crystalloid intranuclear and intracytoplasmic inclusions in dog cauda epididymidis. J Ultrastruct Res. 1979 Nov;69(2):273-8.

McEntee (1990) Reproductive Pathology of Domestic Mammals. Academic Press. p320.

Spermatic granuloma of the epididymal head (SGEH)

Spermatic granuloma of the epididymal head is a condition seldom recognized in dogs. It is a congenital condition that usually is only recognised at puberty when spermatozoa are produced. It is the end result of efferent ductules failing to join to the epididymal duct at the region of the head of the epididymis. At puberty, spermatozoa are forced into the blind ended tubule, form a spermatocele and eventually a spermatic granuloma. This condition is well recognised in cattle, goats and rams, but is infrequently reported in dogs. Althouse et al (1993) reported one dog with bilateral sperm granulomas, and these were in the epididymal head. Foley et al (1995) reported on 3 dogs that had 'intratubular spermatic granulomas of the canine efferent ductules'.

There are 4 cases in the Yager-Best Histovet database and 3 others from the University of Guelph. The breeds affected include the Beagle, Golden retriever, Great Dane, and Rottweiler. They have varied from 0.5 cm to 2.5 cm in diameter. In each the tail of the epididymis was smaller than expected indicating lack of passage of spermatozoa.

Figure : Surgical specimen of spermatic granuloma of the epididymal head (Photo complements of Dr C Gartley, University of Guelph)

Althouse GC, Evans LE, Hopkins SM. (1993) Episodic scrotal mutilation with concurrent bilateral sperm granuloma in a dog. J Am Vet Med Assoc 202(5):776-778.

Foley GL, Bassily N, Hess RA. (1995) Intratubular spermatic granulomas of the canine efferent ductules. Toxicol Pathol. 23(6):731-734

Noninflammatory disease

Segmental aplasia of the mesonephric duct (SAMD)

Segmental aplasia or lack of development of any part of the mesonephric duct, from which is derived the epididymis, deferent duct and vesicular gland, is a heritable condition in bulls, and is assumed to be so in other species. Only animals with unilateral disease are fertile, and most cases reported are unilateral in distribution. Most cases involve the epididymis, but some also have a lack of the deferent duct.

Bloom (1954) reports seeing this. Majeed (1974) reported one case of segmental aplasia of the epididymis in a poodle dog. Copeland and Maclachlan (1976) reported a case of a dog with a lack of the left tail of the epididymis and deferent duct. Olson et al (1992) mentions one dog with a lack of both epididymides. McEntee (1990) reports on case in a Boston Terrier.

McEntee (1990) reports on 3 dogs with segmental aplasia of the deferent duct. Two were unilateral and one was bilateral.

There are 6cases in the Yager-Best Histovet database, and I have heard anicdotally of other cases. The breeds with a lack of the epididymis include the Basenji, Boston terrier, Bichon, Golden Retriever, and Pit Bull terrier. A Yorkshire terrier (see photo) had a small segment of the deferent duct missing. Macroscopic lesions include a lack of the tissue involved, and often dilation of the efferent tubules. Spermatic granulomas was present in one dog. The testis was atrophic and the rete and or mediastinum testis wasdistended.The dog with a segment of the deferent duct missing had distention of the duct and the tail of the epididymis. While the duct appeared to be present, sequential sections of the sit revealed a lack of luminal epithelium for several millimeters. The smooth muscle was intact.

Figure : Obstruction of the deferent duct. No lumen was found for a short segment of the duct.

One case (YB213669) had segmental no deferent duct or epididymal tail on one side. It had ia large cyst in the location of the tail of the epididymis. This cyst was surrounded by smooth muscle so was assumed to be a cystic remnant of the mesonephric duct.

Figure : Segmental aplasia of mesonephric duct and cystic remant of mesonephric duct (YB213669)

Bloom F (1954) Pathology of the dog and cat - The genitourinary system, with clinical considerations. American Veterinary Publications, Inc, Evanston Illinois. p215.

Copland MD, MacLachlan NJ (1976) Aplasia of the epididymis and vas deferens in the dog. J Small Anim Pract 17: 443-449.

Majeed ZZ. (1974) Segmental aplasia of the Wolffian duct; report of a case in a Poodle. J Small Anim Pract. 15(4):263-266.

McEntee (1990) Reproductive Pathology of Domestic Mammals. Academic Press p 313 - 314.

Olson PN, Schultheiss P, Seim HB. (1992) Clinical and laboratory findings associated with actual or suspected azoospermia in dogs: 18 cases (1979). J Amer Vet Med Assoc 201: 478-4

Epididymal hypoplasia

Development of the epididymis parallels that of the testis, and in particular, the passage of spermatozoa. A small and hypoplastic epididymis occurs with concurrent testicular hypoplasia, or with obstruction to the flow of fluid (and spermatozoa) from the testis such as with segmental aplasia of the epididymis (upstream of the hypoplastic segment) or with spermatic granuloma of the epididymal head

Epididymal atrophy

Atrophy of the epithelium of dogs is expected with testicular atrophy (Bloom 1954), or with any condition resulting in obstruction of testicular fluid..

Bloom (1954) as quoted by McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic Press p321

Epididymal hyperplasia (intraepithelial cysts or luminae)

One of the first recorded occurrences of epididymal epithelial hyperplasia was by Mawdesley-Thomas and Urwin (1967). James and Heywood (1979) also reports on cases in beagle dogs. They examined 198 dogs and found that 7% of dogs older than 2 years and 76% of those older than 7 years had this. McEntee (1990) reports seeing this change in dogs.

Mawdesley-Thomas LE, Urwin C (1967) Epithelial hyperplasia of the epididymis in the beagle. Vet Rec 81: 356-357.

James RW, Heywood R. (1979) Age-related variations in the testes and prostate of beagle dogs. Toxicology. 12(3):273-279.

McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic Press. p 322.

Adenomyosis of the epididymis

Adenomyosis is when there is an outpouching of the epitheliium of the epididymis into the smooth muscle layer. This cavity can be a site of spermiostasis and subsequent spermatic granuloma formation. It can be induced by exposure to estrogens.

Bloom (1954) was one of the first to report this condition in dogs. McEntee (1974) found this change in 13 of 27 dogs with Sertoli cell tumours. No spermatic granulomas were assoceated with this. Nascimento et al (1979) found 6 cases in 158 dogs, and one had a spermatic granuloma.

 

Bloom F (1954). "Pathology of the Dog and Cat: The genitourinary system, with clinical considerations" Am. Vet. Publ Evanston, Illinois as quoted by McEntee 1990 Reproductive Pathology of Domestic Mammals, Academic Press p 322.

McEntee K (1974) Adenomiosi dell'epididimo bovino e canino. Nuova Vet 50: 194. as cited by McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic Press p 322.

McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic Press p 322.

Nascimento EF, Silva JML and Nogueira RHG and Chquiloff MAG (1979) Testicular and epididymal alterations in dogs V. Tumors, hyperplasia of interstitial cells and adenomyosis. Arq Esc Vet Univ Fed Minas Gerais 31: 113-118. as cited by McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic Press p 322.

Cysts of epididymis

Cysts of or in the epididymis are not reported in dogs. One case submitted to YagerBest had a large cyst in the location of the tail of the epididymis, which was missing.. This cyst was surrounded by smooth muscle so was assumed to be a cystic remnant of the mesonephric duct.

Figure : Segmental aplasia of mesonephric duct and cystic remant of mesonephric duct. Cyst (right) and testis (left)is transected ((YB213669)

Neoplasia of the epididymis

Neoplasms of the epididymis is extremely rare!

Epithelial neoplasms

Salm (1969) reports a case of carcinoma of the epididymis in a dog. It was bilateral, so it may have been a manifestation of metastatic carcinoma. As with all things reproductive, McEntee (1990) is a wonderful resource. He has seen 1 carcinoma of the epididymis.

 

Salm R. (1969) Papillary carcinoma of the epididymis. J Pathol. 97(2):253-259.

McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic Press p 322.

Mesenchymal neoplasms

Bloom (1954) reports seeing 2 cases of neoplasia of the epididymis. Both were fibromas.

Ramírez et al (2020) reported a case of leiomyosarcoma in the epididymis of an old Rottweiler dog. The mass was in the right side and on the "posterodorsal aspect of the testis" but the exact part of the epididymis was not indicated. Posteriodorsal is likely to be the tail or distal body of the epididymis. It was well circumscribed, noninvasive and well differentiated. The mitotic count was "one per high power field". It was said to have Veracay bodies. It was smooth muscle actin, desmin and vimentin positive. I do not wish to be too picky, but none of these features indicate a sarcoma to me. Justification was based on the human scheme of calling a paratesticular smooth muscle tumor with mitoses a sarcoma. My preference is to call it a smooth muscle tumor. I was not convinced the Veracay body was a true Veracay body but rather dramatic pallisading.

 

Bloom F (1954). "Pathology of the Dog and Cat: The genitourinary system, with clinical considerations" Am. Vet. Publ Evanston, Illinois as quoted by McEntee 1990 Reproductive Pathology of Domestic Mammals, Academic Press p 322.

Ramírez GA, Suárez-Bonnet A, Sánchez-Salguero X, Molín J. Primary Verocay Body-rich Epididymal Leiomyosarcoma in a Dog. J Comp Pathol 2020; 178: 27-31

Round cell neoplasms

Lymphoma of the epididymis is reported

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Disease of the deferent duct (ductus deferens)

Vasectomy

Vasectomy is not a common operation so complications should be very rare. One of the complicatoins of vasectomy is the formation of a spermatic granuloma, both at the site of surgery or due to obstruction with spermatocele formation (Perez-Marin et al 2006).

Perez-Marin CC, Lopez R, Dominguez JM, Zafra R. (2006) Clinical and pathological findings in testis, epididymis, deferens duct and prostate following vasectomy in a dog. Reprod Dom Anim 41: 169-174.

Aplasia of a segment of the deferent duct is discussed inder segmental aplasia of the mesonephric duct above.

Bloom (1954) reports seeing a cystadenofibromyoma of the deferent duct. It was 4 cm from the prostate, and measured 2 x 3 cm. It was composed of epithelial structures embedded in fibrous tissue and smooth muscle.

Bloom F (1954) Pathology of the dog and cat - The genitourinary system, with clinical considerations. American Veterinary Publications, Inc, Evanston Illinois. p256.