History
A 4-year-old 636.4-kg (1,400-lb) Brangus bull was admitted in the middle of May to the J. T. Vaughan Large Animal Teaching Hospital for evaluation of lameness. Physical examination revealed that the source of the lameness was a subsolar abscess of the lateral claw of the left hind limb. The bull was hospitalized for further treatment.
During a routine physical examination, scrotal asymmetry was noticed as an incidental finding unrelated to the lameness. The left hemiscrotum was larger than the right, and asymmetry of the scrotal contents was attributed to a palpable 4-cm firm mass on the dorsolateral pole of the left testis. Ultrasonography of the affected area revealed that the mass (43 × 28 mm) was well circumscribed with a heterogeneous hypoechoic echotexture (Figure 1). The mass was in close proximity to the head of the epididymis, but no direct association with the epididymis was evident (Figure 2). No additional abnormalities were detected during ultrasonographic examination.
Ultrasonographic image of the left testis and a palpably firm mass in a 4-year-old Brangus bull. The mass is well circumscribed with a heterogeneous hypoechoic echotexture; size of the mass is 43 × 28 mm.
Citation: Journal of the American Veterinary Medical Association 252, 10; 10.2460/javma.252.10.1217
Ultrasonographic image of the left epididymis and the palpably firm mass of the bull of Figure 1.
Citation: Journal of the American Veterinary Medical Association 252, 10; 10.2460/javma.252.10.1217
A complete breeding soundness examination was performed. Scrotal circumference was 43 cm. No abnormalities of the accessory sex glands were detected during transrectal palpation. Electroejaculation was used to obtain a semen sample. Microscopic examination of the sample at 200× and 400× magnification revealed no gross or individual motility of spermatozoa. The ejaculate contained multiple round cells (Figure 3). Semen morphology was evaluated by use of eosin-nigrosin stain and light microscopy at 1,000× magnification. Only 1% of spermatozoa were classified as normal; there were 40% primary abnormalities and 59% secondary abnormalities. The predominant abnormality was detached normally shaped heads, and the most common primary abnormality was vacuoles within the head of spermatozoa. A sample of semen was placed on a microscope slide, allowed to air dry, and stained with modified Giemsastain for further characterization of the round cells. Numerous neutrophils were present in each hpf.
Photomicrograph of a semen sample collected from the bull of Figure 1. No stain; bar = 5 μm.
Citation: Journal of the American Veterinary Medical Association 252, 10; 10.2460/javma.252.10.1217
A second ejaculate was collected and evaluated in the same manner to eliminate concerns that abnormal spermatozoa in the initial semen sample might have been a result of long-term storage within the tail of the epididymides. Results were similar to those for the first ejaculate.
Question
What are the differential diagnoses for the well-circumscribed hypoechoic lesion found on the dorsolateral surface of the left testis? Please turn the page.
Answer
Inflammatory lesions including sperm granuloma, epididymitis, or testicular abscess; neoplasia (eg, interstitial cell [Leydig cell] tumor, sustentacular cell [Sertoli cell] tumor, seminoma, testicular germ-cell tumor of the nonseminoma type, teratoma, and lymphoma); and developmental anomalies including the appendix of the epididymis, segmental aplasia of the epididymis, and paramesonephric cysts.
Results
Combined results of the physical, ultrasonographic, and spermatozoal examinations indicated that pathological changes in the affected testis were adversely affecting spermatogenesis in both testes. Surgical removal of the left testis was considered necessary to restore function of the contralateral testis.
The bull was anesthetized and positioned in right lateral recumbency on a hydraulic tilt table. The scrotal area was clipped of hair and aseptically prepared for unilateral castration. A vertical skin incision approximately the length of the left testis was made over the left lateral aspect of the scrotum; the surgeon was careful to preserve integrity of the parietal vaginal tunic. The affected testis within the parietal vaginal tunic was carefully dissected free from the surrounding scrotal fascia. Fibrous tissue and adhesions between the parietal vaginal tunic and scrotal fascia were encountered, which indicated the condition likely was chronic. After the parietal vaginal tunic containing the affected testis was dissected free, a 25-cm incision was made through the parietal vaginal tunic along the long axis of the testis to allow exteriorization of the affected testis and spermatic cord. The spermatic artery, spermatic vein, and ductus deferens were isolated and double-ligated by use of size-0 chromic gut at a location 8 cm proximal to the pampiniform plexus; the spermatic cord was transected between the 2 ligatures. The external cremaster muscle was ligated separately and transected distal to the stump of the spermatic cord. The parietal vaginal tunic was transected at the level of the remnants of the spermatic cord, and the vaginal cavity was closed with size-0 chromic gut in an inverting Connell pattern. After the parietal vaginal tunic was closed, an ellipse of excessive scrotal skin was excised to allow for skin closure while minimizing dead space within the surgical site. The tunica dartos was closed with size-0 chromic gut in a simple continuous pattern. The scrotal skin was closed with size-3 nylon in a Ford interlocking pattern.
Penicillin G procaine (22,000 U/kg [10,000 U/lb], IM, q 24 h for 7 days) was administered after surgery. The bull was observed daily for swelling or drainage from the surgical site. Two days after surgery, there was swelling of the surgery site. An aerosol bandagea was applied to the suture line. Hydrotherapy (cold water applied to the area with a hose) combined with administration of flunixin meglumineb (2.2 mg/kg [1.0 mg/lb], IV, q 24 h for 3 days) were initiated. Swelling resolved after the initiation of hydrotherapy and administration of the anti-inflammatory medication, and there were no additional complications during the remainder of the recovery period. Sutures were removed 10 days after surgery.
The excised testis, epididymis, and mass were examined. The palpable mass was a fluid-filled structure, and there was a visible connection between the mass and head of the epididymis. Tissue samples from the mass were submitted for aerobic and anaerobic bacterial culture; culture results were negative for bacterial growth.
The testis and epididymis were sectioned and placed in neutral-buffered 10% formalin for histologic examination. Histologic examination revealed architectural disruption by abundant organizing collagen and well-demarcated circumscribed regions of intense inflammation, which separated individual widely dilated epididymal ducts. Inflammatory cells consisted of central accumulations of degenerate to pyknotic eosinophils and a few neutrophils admixed with spermatids, which were surrounded by multiple layers of epithelioid macrophages and a few multinucleated macrophages. Peripheral infiltrates of inflammatory cells were plasma cells with a few macrophages, lymphocytes, an occasional neutrophil, and eosinophils; there was a perivascular distribution (Figure 4). A few mitotic figures were found within areas of inflammation. The serosal aspect of the epididymis was thickened by a discrete raised area that contained edematous granulation tissue and mild perivascular infiltrates of lymphocytes and plasma cells. The testis had a histologically normal architecture. Seminiferous tubule lumens contained sloughed epithelial cells but no inflammatory cells. The histologic findings combined with the negative results for bacterial culture supported a diagnosis of a sperm granuloma.
Photomicrographs of tissue samples of the affected epididymis of the bull of Figure 1. A—Within areas of the epididymis with markedly dilated ducts separated by abundant organizing collagen and inflammation, there are well-demarcated, inflammatory foci composed of central accumulations of neutrophils, eosinophils, and eosinophilic coagulum surrounded by a palisading, circumferential layer of epithelioid macrophages and a few multinucleated macrophages. The surrounding stroma contains numerous dense perivascular infiltrates of plasma cells, lymphocytes, and a few neutrophils and eosinophils. B—Within the center of inflammatory foci, there are a few spermatids intermixed within clumps to sheets of pyknotic cells that consist of degenerate eosinophils and neutrophils. H&E stain; bar = 100 and 20 μm for panels A and B, respectively.
Citation: Journal of the American Veterinary Medical Association 252, 10; 10.2460/javma.252.10.1217
Discussion
The testes of bulls are contained within a pendulous scrotum and are dorsoventrally elongated; the head of the epididymis is located at the dorsal pole, the body of the epididymis is located along the axial face, and the tail of the epididymis is located at the ventral pole. Parenchyma of the testes consists of tubular and interstitial compartments; the core of the parenchyma contains a mediastinum, which contains the rete testis.1 The tubular compartment of the testes consists of highly convoluted seminiferous tubules, whereas the interstitial compartment comprises the blood vessels, connective tissue, and Leydig cells, which surround the seminiferous tubules.1 Seminiferous tubules, which are the site of spermatogenesis, include Sertoli cells and germ cells. Sertoli cells extend from the basement membrane to the lumen; they surround the germ cells and are often referred to as nurse or governor cells because they provide structural and functional support to the developing spermatocytes. Adjacent Sertoli cells are connected by tight junctions that contain occludins, claudins, and junctional adhesion molecules. These tight junctions are located in the basal third of the seminiferous epithelium and separate the tubules into adluminal and basal compartments. The tight junctions separate the germ cells located in the adluminal compartment from the blood supply, thus creating the blood-testis barrier.1 Spermatogenesis primarily occurs in the tubulus contortus section of the seminiferous tubules.
These tubules are surrounded by contractile peritubular cells, which promote flow out of the tubulus contortus into the rectus or straight portion of the seminiferous tubule, which in turn intersects the rete tubule. Spermatozoa travel from the rete tubule to the efferent ductules.
The efferent ductules, which are embryologically derived from the mesonephric tubules, are located in the head of the epididymis.2 These ductules provide communication between the rete testes and head of the epididymis. The efferent ductules consist of 3 segments: a nearly straight portion that exits the rete testis, a highly convoluted central portion, and a moderately coiled terminal portion that enters the epididymis.2 The ductules are lined with absorptive epithelium that promotes spermatozoa transport via resorption of water and encourages movement of spermatozoa into the ducts. Cilia line the epithelium and further support movement of the spermatozoa toward the epididymis.2 The number of efferent ductules in each epididymis of bulls ranges from 10 to 20.3
The portion of the epididymides that contains the efferent ductules is easily distinguishable during gross examination of tissue from mature animals. There is accumulation of a pale gray to green to brown pigment in the epithelium of the efferent ductules and connective tissue surrounding the ductules that results from phagocytosis of spermatozoa.4
The epididymides are also derived from the embryologic mesonephros and are grossly divided into 3 segments: the head, body, and tail.2 Spermatozoa travel from the efferent ducts into the head of the epididymis and progressively move through the body and tail. All 3 segments can be examined by palpation, with the head of the epididymis located craniodorsally on the testis.2 The body of the epididymis can be palpated by first moving the contralateral testis toward the base of the scrotum and then palpating the medial aspect of the testis; the body of the epididymis reportedly feels like a guitar string. The tail of the epididymis is turgid and is prominently located at the caudal pole of the testis. Similar to the seminiferous tubules of testes, the epididymal lumen is maintained as an immune-privileged site isolated by the blood-epididymis barrier composed of the basolateral membrane, apical membrane, and tight junctional complexes between epithelial cells; these tight junctional complexes contain multiple proteins including claudins, connexins, and catenins.1 The sequestration of spermatozoal antigens within the lumen of the seminiferous tubules and epididymides combined with the restriction of entry of immunoglobulins and immune cells into the lumen prevents spermatozoal antigens from contacting immune cells.1
Typically, monocytes, macrophages, CD4+ cells, and T cells are present in the epididymal epithelium and interstitium but are not found within the epididymal lumen. If spermatozoa or testicular germ cells enter the epididymal interstitium after disruption of the epididymal epithelium, the marked immunogenic response to antigens contained on the spermatozoa will culminate in a sperm granuloma.1
A sperm granuloma of an epididymis may result as a sequela to multiple inciting causes. The most common inciting factors include congenital anomalies (eg, aberrant or blind efferent ductules), infectious agents that lead to epididymitis, traumatic injuries, autoimmune reactions, vascular lesions, and adenomyosis of the epididymis secondary to estrogen.4
Congenitally malformed efferent ductules are characterized as blind efferent ductules or aberrant ductules. Aberrant efferent ductules can be defined as ductules that terminate at a site located distant from the expected site of fusion within the head of an epididymis, whereas blind efferent ductules are located within the head of an epididymis but fail to anastomose with the epididymal duct, which results in ductules from which spermatozoa and fluid cannot escape.3
Blind efferent ductules were found in 12% of specimens from bulls, and aberrant ductules were found in 20% of bull specimens.3 Accumulations of spermatozoa in these dead-end ductules eventually lead to spermatozoal stasis and localized accumulation of spermatozoa within a dilated epididymal duct (sometimes described as a spermatocele). As the lumen of the efferent ductules becomes increasingly occluded with spermatozoa, the lining epithelium becomes stretched, is flattened, and undergoes degenerative changes. These degenerative changes ultimately lead to severe epithelial damage and loss of the epithelial lining, which results in focal denuded areas. After the blood-epididymis barrier is lost, tissue fluid, macrophages, fibroblasts, lymphocytes, and neutrophils migrate from the interstitium through these denuded areas into the tubular lumen and mix with inspissated spermatozoa.5
Spermatoceles can be microscopically differentiated from sperm granulomas by the presence of the granulomatous reaction that follows extravasation of spermatozoa into the interstitium.3 Large spermatoceles and sperm granulomas of the epididymal head may be palpable during physical examination; however, in many bulls, these abnormalities are not detected during routine examinations and may be suspected only when semen quality deteriorates and the ejaculate contains an increasing number of detached spermatozoa heads and germinal epithelial cells.3 Ultrasonography provides an additional diagnostic option when poor spermatozoal motility and morphology are detected in the absence of palpable abnormalities of the testes or epididymides. Sperm granulomas are visible as anechoic to hyperechoic areas with distinct margins with or without a hyperechoic capsule and may be associated with various degrees of testicular degeneration and enlargement of the mediastinum testis secondary to granuloma formation.6 Normal testicular parenchyma should be homogeneous and moderately echogenic throughout, and width of the mediastinum testis should be 2 to 4 mm.6 The head of the epididymis can be identified on the proximocranial aspect of a testis; it should be less echogenic than the testicular parenchyma but homogenous in texture, with thin echogenic lines that demarcate it from the testis.6
Infectious causes of epididymitis are usually bacteria and most commonly involve the epididymal tail.4 Bacterial infections of an epididymis sometimes extend into the epididymal body and then the epididymal head, where a sperm granuloma may ensue. Recognized bacterial pathogens associated with epididymitis in cattle include Brucella abortus, Mycobacterium bovis, and Trueperella pyogenes.4 In the present report, formation of a sperm granuloma secondary to bacterial infection of the affected epididymis was thought unlikely because of negative results for aerobic and anaerobic culture of the tissue and because no bacterial organisms were evident during histologic examination of tissues.
Traumatic injury of the epididymides or testes followed by fibrosis may lead to spermatozoa stasis and subsequent granuloma formation. This sequence of events (ie, injury followed by fibrosis that leads to a sperm granuloma) seemed unlikely in the bull of the present report owing to a lack of grossly visible or ultrasonographically detectable evidence of traumatic injury to the testes or epididymides. Because of the lack of evidence for an infectious or traumatic inciting cause for the bull described here, we speculated that a congenital anomaly (eg, aberrant or blind efferent ductules) was the inciting factor.
Outcome
The bull was discharged to the owner 10 days after surgery. Bulls with unilateral scrotal pathological changes and transient testicular degeneration of the remaining testis would be expected to return to normal spermatozoa production approximately 60 days after removal of the diseased or injured testis.7 However, when unilateral castration is performed during summer months, physiologic testicular function may not resume until ambient temperatures moderate. It was recommended that the bull be returned in late fall (October or November) for semen collection and evaluation of the spermiogram.
References
1. Mital P, Hinton BT, Dufour JM. The blood-testis and blood-epididymis barriers are more than just their tight junctions. Biol Reprod 2011;84:851–858.
2. Turner TT. On the epididymis and its function. Invest Urol 1979;16:311–321.
3. Hemeida NA, Sack WO, McEntee K. Ductuli efferentes in the epididymis of boar, goat, ram, bull, and stallion. Am J Vet Res 1978;39:1892–1900.
4. McEntee K. Pathology of the epididymis of the bull and stallions, in Proceedings. Annu Meet Soc Theriogenol 1979;103–109.
5. Wu F. Sperm stasis and related lesions of the ductuli efferentes in the epididymis of the bull—a study of 953 cases. J Chin Soc Vet Sci 1981;7:95–102.
6. Pechman RD, Eilts BE. B-mode ultrasonography of the bull testicle. Theriogenology 1987;27:431–441.
7. Heath A, Baird A, Wolfe D. Unilateral orchiectomy in bulls: a review of eight cases. Vet Med 1996;9:786–792.
