Testis torsion in a non-neoplastic cryptorchid testis of a cat

Abstract

Case summary

Cryptorchidism is a condition rarely encountered in cats, with a reported prevalence below 3.8%. In the canine species, it is known to predispose for both testicular torsion and neoplasia; therefore, cryptorchidectomy is recommended. Although neoplasia was previously described in feline cryptorchid testes, testicular torsion is a very rare condition in cats. This is the first description of testicular torsion in a non-neoplastic, abdominal testis of a tom cat. A 1-year-old male domestic longhair cat was admitted for elective orchidectomy. Physical examination revealed right unilateral cryptorchidism. The testis could be located within the abdomen upon ultrasonographic examination. Cryptorchidectomy and scrotal orchidectomy of the contralateral testis were performed. The abdominal testis appeared severely discoloured, exhibiting a dark blue coloration, and the spermatic cord was twisted. In contrast, the scrotal testis appeared normal. Surgery and postoperative recovery were uneventful. Histopathological examination of the abdominal testis revealed severe, diffuse congestion with marked interstitial haemorrhage and oedema affecting both the testis and epididymis. Spermatogenesis was arrested at the level of spermatogonia, and Sertoli-cell-only syndrome was observed, findings commonly associated with abdominal cryptorchid testes.

Relevance and novel information

The present case shows that testicular torsion is a potential complication of cryptorchidism in cats. Therefore, prevention of torsion may represent an additional indication for cryptorchidectomy, alongside the previously reported increased risk of neoplasia and the common reasons for neutering tomcats, such as population control and reduction of undesirable male behaviour.

Plain language summary

Testis torsion in a retained testis of a cat

Cryptorchidism is a rare hereditary condition in cats where one or both testes fail to descend into the scrotum and are retained within either the abdomen or the inguinal canal. In dogs, the condition is known to predispose the animals to neoplastic growth and testicular torsion, a painful condition with the spermatic cord twisting around itself. Testicular torsion is thought to be very rare in cats. This is the first description of torsion affecting a testis retained within the abdomen. A 1-year-old, male domestic longhair cat was presented for a routine neutering procedure. Clinical examination showed that the right testis had failed to descend into the scrotum. Further diagnostic tests using ultrasound confirmed that it was retained within the abdomen. Surgery was subsequently performed to remove both the retained and the normally descended testes. During surgery, the retained testis was found to be twisted upon itself and showed severe, dark discoloration, implying tissue damage. The surgery and postoperative recovery were uneventful. The testicular tissues were examined microscopically, revealing bleeding and oedema, as well as loss of normal testicular function. The presented case shows that testicular torsion can occur in cryptorchid cats and supports an additional indication for removal of both undescended and descended testes.

Introduction

Cryptorchidism, the failure of the testicles to undergo a normal descent, is a rare condition in cats,^{1 –5} occurring both unilaterally and bilaterally. The previously reported prevalence ranges from less than 0.5% ¹ to 3.8%, ⁶ with a recognised predisposition in Persian cats. ³ However, cryptorchidism remains the most common congenital defect of the urogenital system in cats.^1,7 Although the heritability of this condition has been extensively investigated in dogs, ⁸ it has not been studied to the same extent in cats. Nevertheless, the accumulation of cases within the Persian breed leaves little doubt to a heritable component in cats. ¹

The gonads develop from primordial germ cells that actively migrate to the genital ridge, mesonephric cells and invading mesonephric ducts medial to the mesonephros in the coelomic cavity. ⁹ In dogs, testicular descent is coordinated by gubernacular outgrowth and is divided into intra-abdominal, intra-inguinal and extra-inguinal phases. ¹ Little is known about testicular descent in cats. The mechanisms of gubernacular outgrowth and regression are thought to be similar to those described in dogs. ¹ Passage of the testes through the inguinal canal into the scrotum is usually completed before birth; however, the testes may move freely within the inguinal canal until puberty, when closure of the inguinal ring occurs.^1,4 Therefore, a definite diagnosis of cryptorchidism cannot be made before puberty. ¹ In cats, cryptorchidism is more commonly unilateral than bilateral.^2,4,5 Reports on the occurrence of abdominal testes among cryptorchid cats are in the range of 26.9–30%.^2,5 In contrast, one study found at least one intra-abdominal testis in 14/23 cats, corresponding to a prevalence of approximately 60%. ³

Gonadectomy, of either both gonads or only the affected gonad, is generally advised in cases of cryptorchidism because of the increased risk of testicular neoplasia and testicular torsion.^10,11 These recommendations are usually extrapolated from findings in dogs, as evidence regarding these conditions in cats is limited or lacking. Testicular neoplasia in undescended feline testes was described in two case reports.^12,13

Testicular torsion is a condition is rarely found in cats, with only a single case report published. ¹⁴ To the authors’ best knowledge, it has never been described in an undescended feline testis. The presented case describes testicular torsion in a cryptorchid cat.

Case summary

A 1-year-old, male domestic longhair cat with a body weight of 3.8 kg was presented to a small animal practice for elective orchidectomy. Physical examination revealed right unilateral cryptorchidism. Palpation of the inguinal region did not show signs of inguinal cryptorchidism. The contralateral testis was normal on palpation. Besides the cryptorchidism, clinical examination showed no abnormalities. The cat was in good general health and had a normal body condition (body condition score 5/9).

The owner was unaware of the cryptorchidism and ultrasonography was advised to localise the undescended testis. Blood analysis was rejected by the owner because of financial restrictions.

Ultrasonography

Ultrasonography of the inguinal region and the abdomen was performed using a 11 MHz linear probe (GE Logiq P5; GE Healthcare). A small, ovoid, hypoechoic structure was found in the right caudal quadrant of the abdomen adjacent to the ventral abdominal wall. The hyperechoic mediastinum testis was partially indistinct, and part of the spermatic cord could be identified. The parenchyma was slightly inhomogeneous. A round hypoechoic structure caudal to the testis was identified as the epididymis and a small anechoic rim surrounding the structure was considered to be a peritoneal effusion around the cryptorchid testis (Figure 1).

Figure 1

Ultrasonographic appearance of the right cryptorchid testis (T). The epididymis (E) is found adjacent to the testis on the right side. The spermatic cord (SC) can be seen on the left side. The arrows indicate the region of interest

Cryptorchidectomy

An intravenous catheter was placed in the cephalic vein for the induction of general anaesthesia and maintenance of perfusion during the perioperative period with a constant rate infusion of a balanced electrolyte solution (4 ml/kg/h IV, Sterofundin ISO; B Braun Vet Care). Anaesthetic premedication was administered with methadone (0.3 mg/kg IV, Comfortan; Dechra Veterinary Products Deutschland) and medetomidine (1 µg/kg IV, Domitor; Orion Corporation). General anaesthesia was induced with ketamine (0.3 mg/kg IV, Anesketin; Dechra Veterinary Products Germany) and alfaxalone (IV, Alfaxan multidose; Zoetis Deutschland) to effect. General anaesthesia was maintained with isoflurane (Iso-Vet; Dechra Veterinary Products Deutschland) after endotracheal intubation. Robenacoxib (Onsior 20 mg/ml; Elanco Deutschland) was administered for postoperative analgesia (2 mg/kg SC).

The patient was positioned in dorsal recumbency and the surgical field (abdomen and scrotum) was clipped and aseptically prepared. A midline caudal celiotomy was performed and the abdomen was inspected. A small ovoid structure, craniolateral to the bladder, was identified as the cryptorchid testis. It showed severe dark discoloration, with a dark red to blue appearance of the testicular parenchyma and vasculature. The spermatic cord was twisted and showed no signs of infarction in the proximal part (Figure 2). The abdominal testis was exteriorised, ligated with a 3-0 monofilament glyconate suture (Monosyn; B Braun VetCare) and removed. Routine closure of the abdomen was performed. The left scrotal testicle was then removed in a standard scrotal orchidectomy procedure. ¹⁵

Figure 2

Testicular torsion of the right cryptorchid testis was diagnosed during cryptorchidectomy. The spermatic cord was twisted and the testis showed marked dark discoloration

Post-anaesthetic and postoperative recovery was uneventful, and the patient was discharged on the same day. Analgesia with robenacoxib (Onsior 6 mg tablets; Elanco Deutschland) was continued orally for 5 days.

Histology

Handling of the testis for fixation, embedding and staining was as previously described. ¹⁶ Briefly, the testis was fixed in formalin, washed in phosphate-buffered saline, dehydrated in ethanol and xylene, and subsequently embedded in paraffin. The tissue was sectioned at approximately 2 µm thickness, stained with haematoxylin and eosin, and mounted using Histokitt (Assistent).

Histological examination revealed diffuse congestion with significant interstitial haemorrhage and oedema. Blood vessels were markedly dilated, and numerous erythrocytes were present not only in the interstitial tissue but also within the seminiferous tubules. Spermatogenesis was arrested at the spermatogonia stage, and some tubules showed Sertoli-cell-only syndrome, as typically observed in abdominal cryptorchid testes (Figure 3). Significant haemorrhage was also noted in the epididymis.

Figure 3

Histological appearance of the retained testis: (a) overview and (b) detailed view of a seminiferous tubule (ST). The testicular capsule, consisting of connective tissue (CT) surrounds the ST and the interstitial tissue. Significant interstitial haemorrhage (IH, red-brown colouration) and oedema (IE) are clearly visible. The detailed view shows numerous erythrocytes (E), mainly in the interstitial compartment, collocated with Leydig cells (LC). The main cell population within the seminiferous tubules is represented by Sertoli cells (SC), but a few spermatogonia (SG) can also be identified, representing the typical appearance of abdominal cryptorchid testes. Scale bar: (a) 200 µm, (b) 50 µm

Discussion

Testicular torsion is very rarely reported in cats, with only a single case report published in the modern literature. ¹⁴ It is more often encountered in dogs, where an association between cryptorchidism and testicular torsion is well known.^{17 –25} Affected animals often present with signs of an acute abdomen, such as acute abdominal pain, lethargy and anorexia.^{17 –20,22} The cat in this report was presented for routine castration and showed no signs of disease or pain, according to the owner. Pain in cats is often not recognised, especially by observers unfamiliar with pain assessment in this species; ²⁶ therefore, the absence of reported signs of pain should be interpreted with caution in cats.

Testicular neoplasia, mostly Sertoli cell tumours and seminomas, are well described in cryptorchid dogs.^27,28 Sertoli cell tumours were previously described in cats,^12,29,30 with two reports of the neoplasm in the feline undescended testes.^12,13 Histological examination showed no evidence of neoplasia in the patient’s testis. However, it revealed marked interstitial and intratubular haemorrhage, arrest of spermatogenesis at the spermatogonia stage and Sertoli-cell-only syndrome in a few tubules, the latter being a typical histological feature of cryptorchidism. ⁸

The aetiology of testicular torsions is unknown; ³¹ however, it is postulated that torsion of the spermatic cord might occur more commonly in undescended testes owing to greater mobility inside the abdomen compared with the scrotum. ¹⁹ Moreover, spermatic cord torsion is thought to be a sequela of neoplastic enlargement in canine testes. ²⁵ Both factors might also apply to the cat, although the presented case showed no testicular enlargement that possibly contributed to the torsion of the spermatic cord.

Surgical removal of cryptorchid testis is generally recommended.^4,10 Different surgical approaches for cryptorchidectomy have been described, including simple inguinal incision, caudal midline incision and caudal midline celiotomy for intra-abdominal testes.^4,10,32 Laparoscopic cryptorchidectomy for the removal of intra-abdominal testes is also described in cats, with lower complication rates and patient morbidity.^10,32 Common indications for surgical removal are the increased risk of testicular neoplasia and testicular torsion in cryptorchid abdominal testicles, which have been described in dogs.^{8,18 –22,24,27,28} Recommendation of cryptorchidectomy in cats is based on the same indications, despite the low evidence of these conditions in cats. Moreover, undesired male behaviour (eg, urine spraying) and population control are important indications for neutering tom cats. In unilateral abdominal cryptorchid cats, removal of only the scrotal testis will result in infertility while unwanted male behaviours persist, because unlike spermatogenesis, hormonal production is not impaired by the intra-abdominal location of the testis.^1,33 The persistence of male behaviours after scrotal testis removal warrants further diagnostics to assess for cryptorchidism.

Conclusions

This case presents the first reported instance of testicular torsion in a cryptorchid feline testis, indicating that this condition can occur in cryptorchid cats, as it does in dogs. However, data on the true incidence of this condition in cats are lacking.