Cryptorchidism in horses refers to the condition where one or both testicles fail to descend into the scrotum. This condition is a developmental anomaly that can affect a horse's reproductive capabilities and behavior. Cryptorchidism can be unilateral, involving one undescended testicle, or bilateral, involving both. The undescended testicle(s) may be located in the abdominal cavity or the inguinal canal. Diagnosis typically involves physical examination, ultrasound imaging, and hormonal testing. Treatment often requires surgical intervention, commonly known as cryptorchidectomy, to remove the retained testicle(s). This page compiles peer-reviewed research studies and scholarly articles that explore the etiology, diagnosis, management, and implications of cryptorchidism in equine health and reproduction.
David JS, McCullagh KG.A large anastomosis of the spermatic artery and vein is described. This was found while surgically removing an abdominal testis. Before surgery the animal wanted to rear after exercise and could not stand on 3 legs for any length of time while being shod. This unusual behaviour disappeared after removal of the mass. The performance and conformation of the horse has also greatly improved.
Stickle RL, Fessler JF.Equine cryptorchidism was examined by a review of the literature and a retrospective study of 350 horses over a 14-year period. The incidence of left vs right testis retention was nearly equal. On the left side, 75.2% of the retained testes were retained abdominally and 24.8% inguinally; on the right side, 41.8% of the retained testes were retained abdominally and 58.2% inguinally. Preoperative diagnosis by rectal palpation of the vaginal rings was considered a valuable technique, with 87.9% accuracy in 190 horses. Invasive and nonivasive surgical techniques for abdominal cryptorchidectomy and...
Foote RH.Several inherited conditions associated with testicular defects, abnormal spermatogenesis and morphologically abnormal sperm have been found. These usually are controlled by single gene pairs. A notable exception is testicular size, with heritability in young bulls ranging from .42 to .88. Testicular size directly affects sperm output potential. The major contributor to variation in semen quality is the environment. Environmental effects may be temporary or permanent. Permanent effects occurring during prenatal and prepubertal periods and temporary or permanent factors acting after spermatogen...
Dawson FL.Mares rarely ovulate in winter; ovulation is induced by increase in daylight length. Ova accumulate in the oviducts of unserved mares. During pregnancy, corpora lutea accumulate; all regress together at mid pregnancy. Plasma progesterone levels rise and oestrogen levels fall towards the end of pregnancy. Methods are available for early termination of pregnancy and for induction of parturition. Pregnancy can be diagnosed efficiently by rectal examination, and by immunological assay of pregnant mare serum gonadotrophin. Service at the foal heat is associated with an increased prevalence of early...
McIlwraith CW, Owen RA, Basrur PK.Cytogenetic and histological studies were carried out on an intersex horse which was diagnosed clinically as a cryptorchid. Surgery confirmed the horse to be a bilateral abdominal cryptorchid and histological examination revealed ovarian tissue associated with the left epididymis. Chromosome analysis of cultured cells from testicular tissue, ovarian tissue and skin revealed 64-XX and 64-XY make-up, the left gonad containing a greater preponderance of XX cells over XY cells. The external characteristics and behaviour of the horse were indistinguishable from that of a "routine" cryptorchid. Othe...
Ganjam VK, Kenney RM.Total androgens, testosterone and total oestrogens were measured in twenty-one intact, nine unilaterally cryptorchid, three bilaterally cryptorchid stallions and four geldings. Total oestrogens were significantly higher (P less than 0-005) and total androgens significantly lower (P less than 0-05) in the bilateral cryptorchid compared to other groups. There was a significant (P less than 0-025) day and night variation in total androgen levels. Thyroidectomized and intact animals showed a marked decrease in total androgen as well as testosterone levels during the winter period thus showing an e...
Basrur PK, Kanagawa H, Gilman JP.Cytogenetic and histological studies have been carried out on an intersex horse which was clinically diagnosed as a cryptorchid. The horse had the general conformation of a stallion but the external genitalia included a well developed vulva and a penis. The right testis which was descended was devoid of germ cells and the left "gonad" located in the cavum vaginale contained neither testicular nor ovarian tissue. The male duct system on both sides were relatively well developed despite the absence of a testis on the left side. Chromosome analysis on cultured cells from the descended testis reve...
Serum anti-Müllerian hormone (AMH), a marker of equine cryptorchidism, is detectable in intact and cryptorchid stallions but not in geldings because it is secreted from Sertoli cells. A 4-year-old uncastrated Thoroughbred racehorse had no visible testes; therefore, the horse was considered a bilateral cryptorchidism. However, the serum AMH was undetectable (<0.08 ng/ml). Human chorionic gonadotrophin (hCG) stimulating test result indicated that the horse was a gelding. The results of sex chromosomal analysis and sequence analysis of SRY gene suggested that the horse was a genetically-intac...
Sassot LN, Ragle CA, Farnsworth KD, Lund CM.The major objective of this study was to describe the use of morcellation for standing laparoscopic cryptorchidectomy in 30 client-owned horses. A second objective was to describe a laparoscopic-assisted standing scrotal technique for removal of a descended testis in unilateral cryptorchids. Morcellation for extraction of abdominal testes is effective, efficient, and well-tolerated. Morcellation enabled safe and straightforward extraction of testes from the abdomen through an approximately 13- to 20-mm incision using a 2-portal technique. No incisional or morcellator-related complications occu...
Dunay MP, Németh T, Makra Z, Izing S, Bodó G.In the present series of cases, 8 laparoscopic cryptorchidectomies and 4 laparoscopic ovariectomies were carried out in sedated standing horses. Sedation involved a lesser anaesthesiological risk than does general anaesthesia. As compared to laparotomic exposure, the minimally invasive laparoscopic intervention provided better visualisation, shorter operative time and faster recovery. The blood vessels supplying the testes and ovaries and the suspensory ligaments of the organs were sealed and cut with EnSeal®, an adaptive bipolar electrosurgical blood vessel- and tissue-sealing device. The cl...
Brinsko SP.Genital neoplasms in the male horse are relatively uncommon. Squamous cell carcinomas and squamous papillomas are the most commonly diagnosed neoplasms of the penis and prepuce. Geldings appear to be overrepresented for these types of neoplasms, and accumulation of smegma may be a contributing factor. Early diagnosis and treatment are essential for salvaging these organs before lesions become excessively large and invasive or are allowed to metastasize. Newer treatment modalities such as 5-fluorouracil appear to be promising alternatives to surgical excision. Although generally considered to b...
al-Bagdadi F, Hoyt P, Karns P, Martin G, Memon M, McClure R, McCoy D, Shoemaker S.Eleven unilateral cryptorchid stallions, two to three years old, were castrated at Louisiana State University Veterinary Teaching Hospital. Five of these cryptorchid cases were abdominal and the rest were inguinal. This study was initiated to document the differences between the abdominal and inguinal equine cryptorchid testes. Specimens were obtained from the abepididymal side of each cryptorchid testes and processed for light and electron microscopic study. The cryptorchid testes were smaller than the scrotal testes, with the abdominal testes being one-fourth the size of the scrotal testes. ...
Fischer AT, Vachon AM.Laparoscopic intra-abdominal ligation and removal of cryptorchid testes in horses was evaluated retrospectively in 50 horses that underwent the procedure between 1991 and 1996. Sixty-one cryptorchid testes were removed by one of the following methods; the use of 1) an endoscoping stapling and transection device, 2) an endoscopic clipping device, 3) an endoscopic ligating loop. Monopolar electrosurgery was combined with these methods to facilitate coagulation and cutting of tissue. In 8 horses, 9 testes were retained between the internal and external inguinal rings. The inguinal testes were rem...
Pozor M, Freeman D, Troedsson M, Brown M, Morton A, Smith A, McNaughten J.Fusion anomalies of the epididymis with the testis may be clinically relevant in horses. However, anatomical variations in epididymal-testicular fusion have not been classified, and their clinical significance is unknown. Objective: To describe anatomical variations and clinical significance of epididymal-testicular fusion in stallions. Methods: Anatomical study of testes from castrations, and description of 2 clinical cases with atypical epididymal-testicular fusion. Methods: A total of 104 testes were obtained from equine castrations. Eight patterns of epididymal-testicular fusion were ident...
Claes AN, Ball BA.Anti-Müllerian hormone (AMH) plays a major role in sexual differentiation, Leydig cell differentiation, and folliculogenesis. In addition, AMH has clinical value in equine practice. In stallions, AMH can serve as an endocrine marker for equine cryptorchidism and as an immunohistochemical marker for Sertoli cell tumors. Considering that AMH is also an ovarian specific product, intact mares can be differentiated from ovariectomized mares. Peripheral AMH concentrations reflect the follicular population in mares, and therefore, are useful in the assessment of ovarian reserve and reproductive life...
Schambourg MA, Farley JA, Marcoux M, Laverty S.Transrectal ultrasonography is a reliable technique to identify intra-abdominal testes, but can be hazardous or impractical in fractious, juvenile or small equids. The transabdominal approach therefore requires validation. Objective: To evaluate the sensitivity and specificity of transabdominal ultrasonography to localise cryptorchid testes. Methods: Thirty-eight horses admitted for cryptorchidism underwent transabdominal ultrasonography to locate errant testes. Location of the testes was confirmed during surgery (n = 37) or necropsy (n = 1). Results: Horses weighed 175-760 kg. Twenty-two test...
Rode K, Sieme H, Richterich P, Brehm R.The formation of the blood-testis barrier (BTB) is defined as occurring with the first appearance of spermatocytes at around puberty and is vital for normal spermatogenesis. This barrier between two adjacent Sertoli cells (SCs) consists of a cell junctional protein complex, which includes tight junctions (TJs), adherens junctions, and gap junctions. In many mammalian species, BTB composition has already been investigated, whereas little is known about the equine BTB. In the present study, immunohistochemistry and qualitative Western Blot analysis were used to assess the expression and distribu...
Lerche E, Laverty S, Blais D, Sauvageau R, Cuvelliez S.An 18-month-old male Belgian horse was anesthetized and placed in dorsal recumbency for cryptorchidectomy. Xylazine was used for sedation and guaifenesin with thiamylal for induction of anesthesia. A surgical plane of anesthesia was maintained with halothane. During anesthesia, second-degree atrio-ventricular blocks, hypoventilation and a 1-minute duration rise of mean arterial pressure (80 to 130 mm Hg) occurred. Total anesthesia time was 1 hour. On recovery from anesthesia, the horse exhibited flaccid paralysis of the hind limbs and was only able to elevate himself to a dog sitting position....
Bergeron JA, Hendrickson DA, McCue PM.A 25-month-old castrated horse was admitted for evaluation of stallion-like behavior. Twelve months earlier, bilateral cryptorchidism had been diagnosed, and the horse underwent a laparoscopic castration. At that time, the left testis was removed from the abdominal cavity, but the right testis, which was located in the inguinal ring, was left in place to undergo avascular necrosis after laparoscopic cauterization and transection of the testicular vasculature. On physical examination, an apparently clinically normal right testis was palpated within the scrotum. Administration of human chorionic...
Hunt RJ, Hay W, Collatos C, Welles E.Two adult horses had colic attributable to spermatic cord torsion and strangulation of abdominally retained neoplastic testes. Both horses had caudal abdominal soft tissue masses palpable per rectum. One horse was treated successfully by surgical removal of the testis, and the other was euthanatized without treatment. Histopathologic diagnosis of the involved testes was testicular seminoma. Spermatic cord torsion of an abdominally retained testis should be considered in the differential diagnosis of signs of abdominal pain in cryptorchid stallions, especially those with a palpable caudal abdom...
Raś A, Rapacz A, Raś-Noryńska M, Janowski TE.Cryptorchidism is a partial or total failure of testicular descent. For a proper diagnosis different methods are required. The main aim of this study was to compare different diagnostic methods. Sixty two horses (15 stallions, 32 cryptorchids and 15 geldings) were used in the experiment. They were clinically examined and ultrasonography was used to locate the testes. Blood samples were taken from the animals to measure the plasma level of testosterone and total estrogen (RIA method). In 22 horses suspected of cryptorchidism, the hCG stimulation test was performed. Blood samples were taken ever...
Serum anti-Müllerian hormone (AMH), a marker of equine cryptorchidism, is detectable in intact and cryptorchid stallions but not in geldings because it is secreted from Sertoli cells. A 4-year-old uncastrated Thoroughbred racehorse had no visible testes; therefore, the horse was considered a bilateral cryptorchidism. However, the serum AMH was undetectable (<0.08 ng/ml). Human chorionic gonadotrophin (hCG) stimulating test result indicated that the horse was a gelding. The results of sex chromosomal analysis and sequence analysis of SRY gene suggested that the horse was a genetically-intac...
Searle D, Dart AJ, Dart CM, Hodgson DR.Complications associated with equine castration are the most common cause of malpractice claims against equine practitioners in North America. An understanding of the embryological development and surgical anatomy is essential to differentiate abnormal from normal structures and to minimise complications. Castration of the normal horse can be performed using sedation and regional anaesthesia while the horse is standing, or under general anaesthesia when it is recumbent. Castration of cryptorchid horses is best performed under general anaesthesia at a surgical facility. Techniques for castratio...
Stumpf G, Fietz D, Ezer J, Litzke LF, Bergmann M.Surgically removed testicular tissue in cryptorchid stallions is sometimes difficult to identify because of morphological and histological malformation. Therefore, a sure method to characterise the removed tissue is required. A 2-year-old Haflinger stallion was castrated after diagnosis of cryptorchidism to remove the left intra-abdomnial testis. Intra-operative exploration of the abdominal cavity revealed a firm, dysmorphic structure, which could not be identified as testis based on macroscopic anatomy. The removed tissue was Bouin-fixed and paraffin-embedded for histological examination. We ...
Hejmej A, Wiszniewska B, Kosiniak-Kamysz K, Sadowska J, Bilińska B.Distribution of androgen receptors (ARs) in the epididymal duct and prostate of three entire stallions and one bilaterally cryptorchid horse was studied immunohistochemically using a polyclonal rabbit antiserum against the ARs. In both the healthy stallions and the cryptorchid, the epithelial cells of the epididymides showed nuclear staining for ARs. The intensity of AR-staining in the principal cells of the epididymis was stronger than that of the basal cells. In the prostate, the glandular secretory cells were moderately stained whereas the basal cells expressed weak AR-staining. Immunostain...
Davis EW.The purpose of this study was to determine the feasibility of using laparoscopy to remove cryptorchid testes from standing horses. Methods: Prospective clinical study. Methods: Eleven client-owned horses ranging in age from 4 months to 2 years. Methods: Abdominal insufflation was initiated and maintained using a 20 F insufflation tube, attached via a stopcock, to the low pressure regulator on a standard carbon dioxide pressure tank. After trocar and laparoscope placement in the ipsilateral flank the testes were identified. Local anesthesia of the structures to be manipulated was administered t...
Han H, Chen Q, Gao Y, Li J, Li W, Dang R, Lei C.In the biological process of testicular spermatogenesis, the expression and interaction of many genes are regulated by microRNAs (miRNAs). However, comparisons of miRNA expression between descended testes (DTs) and undescended testes (UDTs) are rarely done in horses. In this study, we selected two UDTs (CKY2b and GU4b) from Chakouyi (CKY) and Guanzhong (GU) horses and eight DTs (GU1-3, CKY1, CKY3, CKY2a, GU4a, and GU5). Three groups were compared to evaluate expression patterns of testicular miRNA in stallion testes. Group 1 compared normal CKY horses and GU horses (CKY1 and CKY3 vs. GU1-3). G...
Han H, Dong H, Chen Q, Gao Y, Li J, Li W, Dang R, Lei C.Testes produce sperm, and investigations into gene expression in the testes will enhance the understanding of the roles of testicular genes in male reproduction. Cryptorchidism, the failure of one or both testes to descend into the scrotal sac, is a common congenital malformation in horses. The major clinical consequence of this abnormality is impaired fertility. The aim of this study was to analyze the expression patterns of testicular genes and to identify the differentially expressed genes (DEGs) in testes between cryptorchid and normal horses. In this study, the gene expression patterns in...
Cinone M, Albrizio M, Guaricci AC, Lacitignola L, Desantis S.Heat shock proteins are the most evolutionarily conserved protein families induced by stressors including hyperthermia. In the context of pathologies of the male reproductive tract, cryptorchidism is the most common genital defect that compromises the reproductive potential of the male because it induces an increase in intratesticular temperature. In equine species, cryptorchidism affects almost 9 % of newborns and few studies have been carried out on the molecular aspects of the retained testis. In this study, the expression pattern of HSP60, 70, and 90 in abdominal and inguinal testes, in t...
Shakeel M, Choi Y, Yoon M.Cryptorchidism affects spermatogenesis and testis development, often resulting in stallion subfertility/infertility. This study aims to identify the specific germ cells impacted by cryptorchism in stallions. In a previous study, we found that PGP9.5 and VASA are molecular markers expressed in different germ cells within stallions. Herein, we assessed the heat stress-induced response of spermatogonial stem cells (SSCs) in the seminiferous tubules (ST) of cryptorchid stallion testes (CST) and normal stallion testes (NST). This goal was accomplished by comparing PGP9.5 and VASA expression pattern...
