Morphometric and Histopathologic Evaluation of a Cryptorchid Testis in Cat

The position of the testes in prenatal life is in the abdominal cavity, somewhat caudal to the corresponding kidneys. The right testicle is a little cranial in location in comparison to left one (Spangenberg, 2021). The testes normally descend into the scrotum just immediately prior to birth and they can also freely traverse up and down in the inguinal canal before puberty (Karasu et al., 2024). The testicles descend into the scrotum in three stages: (a) translocation of the testicles within the inguinal canal; (b) trans-inguinal testicular migration; and (c) inguino-scrotal testicular migration, which is the process of moving the testicles from the outer ring of the inguinal canal into the scrotum (Amann and Veeramachaneni, 2018; Spangenberg, 2021; Romagnoli, 1991). The inability of one or both testes to descend from the abdomen into the scrotum within the proper time frame for an individual species after birth is known as cryptorchidism. Another term for cryptorchidism is maldescensus testis (Goericke-Pesch and Wehrend, 2013). Many factors, including genetic, epigenetic, and environmental, are now recognized as contributing to cryptorchidism. Environmental factors significance hasn’t been established yet (Amann and Veeramachaneni, 2018). It’s widely acknowledged that a genetic abnormality is typically the cause of cryptorchidism (Gubbels et al., 2009). Cryptorchidism in cat is thought to be inherited as actual etiology is unknown and a polygenic route of inheritance has been proposed to be suggested (Karasu et al., 2024; Gradil and McCarthy, 2023). It’s arguably the most prevalent congenital reproductive abnormalities in animals (Gradil and McCarthy, 2023; Khan et al., 2018). Normally, the condition is detected at birth or within a very short time after birth. The undescended testicle may be retained in the inguinal canal, in the abdominal cavity, or alongside the penis and prepuce at the base of the scrotum, and sometimes it may be located in subcutaneous tissues in the groin region, in between the inguinal canal and the scrotum (Romagnoli, 1991). The percentages of the cryptorchid testis in the pre-scrotal, intra-abdominal, and inguinal canal areas were 49%, 33%, and 14%, respectively (Richardson and Mullen, 1993). Multiple research investigations demonstrate that the occurrence of cryptorchidism in dogs is between 1–10%, whereas in cats it is around 2%. Smaller breeds such as Chihuahuas, Poodles, Yorkshire Terriers, and Pomeranians are approximately 2.7 times more probable to be affected than larger breeds (Mattos et al., 2000; Villalobos-Gomez et al., 2023; Millis et al., 1992). Within the feline population, Persians are more likely to be affected than any other breed, with a 1.3-6.2% incidence in purebred or pedigreed cats (Little, 2011).There are two types of cryptorchidism: unilateral and bilateral. The former is thought to be more commonly seen (78–90%) and affects both the right and left testicles equally, while other studies indicate that the right testis is more likely to be affected. It is stated that the cryptorchid testis produces testosterone, but the thermal suppression has prevented spermatogenesis from taking place. Because of this, although they may exhibit reproductive behavior because they have reproductive hormones, animals with bilateral cryptorchidism are often sterile. In contrast, animals with unilateral cryptorchidism, in which only one testis is still functional, may exhibit fertility (Mattos et al., 2000). Furthermore, according to some other findings, the cryptorchid testis is 13.6 times more susceptible than the normal testicle to developing neoplastic tissue. The reduced size of the retained testicle makes it challenging to diagnose internal cryptorchidism just by palpation; thus, an X-ray or ultrasonographic examination is typically thought to be useful in this situation (Felumlee et al., 2012). Because there is a chance of testicular torsion and the development of testicular neoplasia, as well as because the testicles of cats with cryptorchidism generate testosterone, the treatment option for cats with this condition is cryptorchidectomy (Brückner 2015). Laparotomy using a caudal midline approach is advised for the surgical management of intra-abdominal cryptorchidism, according to the literature (Richardson and Mullen, 1993). Laparoscopy and laparoscopy-assisted cryptorchidectomy were noted but least research have been found which focused the morphometric, histopathologic alterations of retained testis and hormonal alterations of a cat affected with unilateral cryptochidism. Therefore, understanding the tomcat’s gross morphometrical and histological characteristics as well as the variations between normal and cryptorchid testicles were the goal of this investigation. The hormonal action in cryptorchid animals was also demonstrated. The study may help with more in-depth investigation into animal cryptorchidism as well as its impact on reproduction.

The study animal was a Persian tomcat of around one year of age, which was brought to Veterinary clinics for treatment.

The study was conducted from February 2023 to October 2023. Tissue processing, microscopic study, photography and recording were accomplished at the post graduate laboratory, Department of Anatomy and Histology and Department of Pathology and Parasitology in Chittagong Veterinary and Animal Sciences University, Chittagong.

The clinical examination was conducted by expert’s veterinarian and recorded. For confirmation of cryptorchidism, abdominal palpation and X-rays were performed.

The study cat with unilateral abdominal cryptorchidism underwent a laparotomy procedure following standard protocol to remove both cryptorchid and normal testis, afterwards collected and shifted to the laboratory for tissue processing.

In order to evaluate any significant gross morhological changes, the obtained testes (normal and cryptorchid) were examined with naked eyes.

The length, width, and diameter of the normal and cryptorchid testes were measured by measuring scale manually for comparative study.

Tissue processing was completed following standard protocol of Slaoui and Fiette (2010).

After processing of tissue, a microscopic study was performed by using a Biological Digital Microscope with 10X, 20X, and 40X magnification for assessing histological changes in cryptorchid testis compared to normal testis. The recorded photomicrographs were analyzed with the help of ImageJ.exe software for measuring average tubular length and diameter of both normal and cryptorchid testis. 

The studied cat was showing reproductive behavior after being neutered (only one testicle removed) as another testicle was retained intra-abdominally and secreting testosterone. Abdominal palpation and X-rays were performed by the attending veterinarian to confirm cryptorchidism.

The external appearance of cryptorchid testicles differs markedly from normal in naked eye observation in terms of shape, size, weight and color. The cryptorchid testis was atrophied, congested and considerably smaller in size than the normal testis (Figure 1).

The cryptorchid testis was smaller in size than the normal testis. In terms of length, width, and diameter the percentages of disparities were found 10.43%, 40.98%, and 36% respectively. In addition, the study showed that, the head, body, and tail of the epididymis of a cryptorchid testis were found smaller than normal testis (Table 1).

To assess the histoarchiectural alterations, processed tissue sections of both normal and cryptorchid testes were studied under microscope using different magnification, compared, photographed and recorded Figures 2 and 3. Well organized tubules and spermatogenic lineage were observed in normal testis whereas seminiferous tubules in cryptorchid testis were found atrophied (reduced length and diameter), compacted and highly irregular in shape with disorganised spermatogenic lineage, as more spermatogonia were closer to the basement membrane, and other germ cells were also found somewhat disorganized in relation to their normal position, indicating irregular and abnormal spermatogenesis. The average length and diameter of the seminiferous tubules in the cryptorchid testis were found to be 46.52% and 31.49%

Table 1: Morphometrical findings of normal and cryptorchid testis.

Table 2: Histomorphometrical findings of normal and cryptorchid testis.

smaller than in the normal testis, respectively (Table 2). Multilayered and comparatively thicker basement membrane was found in cryptorchid testis due to leydig cell hyperplasia, vacuolated leydig cells and deformed sertoli cells. Moreover, peri-tubular fibrosis and interstitial mastocytosis were present in the cryptorchid testis but absent in the normal one.

Blood testosterone hormone level in the tomcat’s blood was measured and found 0.33 ng/mL of testosterone.

Persian cats are the most likely breed to be affected by cryptorchidism, which is also coherent with this study. A number of studies have shown that unilateral cryptorchidism is more common, with a greater frequency of 84.2% affecting the right testicle compared to the left (Villalobos-Gomez et al., 2023; Yates, 2003) which is inconsistent with the findings as the study animal was infected with left abdominal cryptorchidism. On the other hand, several other researchers reported that the prevalence of left and right cryptorchidism is identical (Felumlee et al., 2012). The exact cause of these variations is yet unknown in the incidence of unilateral (right or left) and/or bilateral cryptorchidism; however, heredity may be responsible for these variations. Young animals that have suffered typically do not exhibit symptoms of the illness until a related pathology, such as neoplasia or torsion, manifests in the affected testicle. As a result of their lack of clinical symptoms, owners frequently are unaware of the illness which also supported by the investigation of previous research (Karasu et al., 2024). The diagnosis made on the examined cat was made using X-ray imaging technology and thorough palpation, both of which are supported by earlier research (Spangenberg, 2021; Miller et al., 2004; Felumlee et al., 2012). The cat under study had a morphologicallydistinct features in cryptorchid testis from a normal testis, with decreased dimensions in terms of length, width, and diameter. Though the precise reason for the reduction in the size (length, width and diameter) of the cryptorchid testis is yet unknown, it could be brought on by hormonal imbalances, inadequate blood flow, and malnutrition. The study’s results will aid in more sophisticated morphometrical analysis in the future, even though there isn’t a published report on the comparison of normal and cryptorchid testis morphometrics. Histological structures have shown reduced spermatogenesis, fewer or no sertoli cells, leydig cell hyperplasia and disorganized germ cells that shed into the lumen, which are consistent with the findings of previously published report (Millis et al., 1992; Ali et al., 2022). Histological observations also reveal atrophied germinal epithelia, reduced and/ or disorganized germ cells, thickening of the basement membrane, and interstitial mastocytosis which were also in the findings of (Moon et al., 2014; Babaei et al., 2010; Christensen, 2012). The average diameter and length of seminiferous tubules in cryptorchid testis were found to be 35.37 µm and 146.26 µm smaller than those of normal testis, respectively, according to the histomorphometrical study. The results of this study will be useful for future, more complex histomorphometrical investigations, even though there isn’t a published report that compares the histomorphometrics of the normal and cryptorchid testis. The results of earlier studies (Hill et al., 2024; Diagone et al., 2012) supported the reduced tubular length, diameter, and abnormal architecture in semeiniferous tubules of cryptorchid testis compared to normal testis, although they were inconsistent with the findings of Fell (1923); which reported the diameter and shape of cryptorchid testis were similar to normal testis. However, no exact histomorphometrical study was present. These alterations of the testis may cause problem in productive and reproductive performance of the cat (Ali et al., 2022). The results of earlier investigations (Chaudhary et al., 2024; Millis et al., 1992) also validate the findings of this study such as altered anatomical and histological structures of the cryptorchid testis. The results of earlier research (Mosallanejad et al., 2019) showed that the average blood testosterone level in normal cat was 3.42±0.49 ng/ml, whereas the blood testosterone level of the study was 0.33 ng/mL, supporting the lower-than-normal blood testosterone level in the studied tom cat. It may be inferred that although the testis of cryptorchid animals can release testosterone hormone, even in small amounts, and exhibit reproductive behavior, it is unable to carry out the regular process of spermatogenesis. As a result, cryptorchid animals may exhibit sterility (Ali et al., 2022). It is concluded that, retained testis was found structurally and functionally impaired and imperfect in regard to reproduction.

This study was limited to a single case of unilateral cryptorchidism in a Persian cat, excluding statistical analysis and limiting the generalizability of the findings to the broader feline poplulation. Gross and histopathological evaluations were restricted to descriptive measurements and routine HandE staining without quantitative lesion scoring or advanced techniques such as special staining, immunohistochemistry, and ultrastructural analysis etc. due to time and resources constriction. Further studies with larger sample sizes and comprehensive morphological and molecular approaches are needed to validate these findings.

Based on the findings of the study such as reduced gross morphometrical testicular development and histomorphological testicular tissue alterations along with lower testosterone hormone production; It is concluded that, retained testis was found structurally and functionally impaired and imperfect in regard to reproduction.

Our gratitude goes out to the vets who contributed their skills in surgery and biopsies for the study. We also appreciate the sample preparation done by the personnels of Department of Anatomy and Histology and Department of Pathology and Parasitology, CVASU, for photomicrograph of histological slides.

This study provides a detailed comparative assessment of a unilateral abdominal cryptorchid testis and the contralateral normal testis in a Persian cat, integrating gross morphometry, histomorphometry, histopathological evaluation, and serum testosterone assessment. To the best of our knowledge, quantitative comparison of testicular and seminiferous tubular dimensions between normal and cryptorchid testes in the cat has been insufficiently documented. The study demonstrates marked reductions in testicular dimensions and seminiferous tubular length and diameter, together with distinctive histopathological alterations and reduced serum testosterone concentration in the retained testis. These findings provide useful baseline morphometric and histomorphometric information for understanding the structural and functional consequences of feline cryptorchidism and may support further investigations into its reproductive implications.

Kazi Asma Akther: Writing-original draft, Methodology, Formal analysis, Data curation, Conceptualization. Subrata Kumar Shil: Writing-original draft, Supervision, Methodology, Conceptualization. Saroj Kumar Yadav: Resources, Methodology. MD. Saiful Islam Siddiqui: Supervision, Writing- review & editing, Conceptualization. Rakibul Hasan: Writing- review & editing, Formal analysis, Data curation, Conceptualization. Saiful Islam: Formal analysis, Data curation.

The authors received no financial assistance for the research, authorship, and/or publication of this article.

The owner of the animal used in this study provided verbal and written informed consent for all procedure(s) that were carried out. In order to publish this work, no extra informed consent was needed because neither persons nor animals are identifiable.

The authors declare that no generative AI and AI assisted technology was used in the creation of this manuscript.

The authors have declared no conflict of interest.