112 EQUINE VETERINARY EDUCATION / AE / APRIL 2006

Case Report Laparoscopic-assisted diagnosis of monorchidism in a horse G. KELMER*, J. KRAMER AND M. A. MILLER† Departments of Veterinary Medicine and Surgery and †Veterinary Medical Diagnostic Laboratory College of Veterinary Medicine, University of Missouri, Columbia, Missouri 65211, USA. Keywords: horse; monorchidism; ; laparoscopy

Introduction (Pfizerpen)1 (22,000 iu/kg bwt i.v. q. 6 h), gentamicin sulphate (GentaMax)2 (6.6 mg/kg bwt i.v. q. 24 h) and phenylbutazone Monorchidism is defined as the complete absence of one (Phenylbute)2 (4.4 mg/kg bwt i.v. q. 12 h). testis, whereas cryptorchidism is the failure of either one or The horse was anaesthetised and placed in dorsal both testes to descend into the . Monorchidism is rare recumbency; following aseptic preparation and draping, in the horse (Parks et al. 1989), while cryptorchidism is a 12 mm incision was made just cranial to the umbilicus. A relatively common (Hayes 1986). Preoperative differentiation teat cannula was introduced into the abdomen and connected between monorchidism and cryptorchidism is difficult. to an electronic carbon dioxide insufflator providing intra- The purpose of this report is to describe an equine abdominal pressure of 15 mmHg. The teat cannula was then case of monorchidism and introduce the diagnosis of removed and an 11 mm trocar and cannula inserted into the monorchidism as another advantage of laparoscopic abdomen. A rigid 30°, 10 mm diameter, 33 cm long cryptorchidectomy in the horse. laparoscope was inserted via the cannula and connected to a Case details xenon light source, a videocamera and the insufflation unit. The horse was then tilted into Trendelenburg position (head History and clinical findings down 30°) and the right inguinal region was explored. Instrument portals were created 10 cm left lateral and A 2-year-old 400 kg Arabian was admitted to the 15 cm caudal to the laparoscope portal and 5 cm caudal and veterinary teaching hospital for cryptorchid . The right lateral to the laparoscope portal. Exploration of the right referring veterinarian had placed the horse under general inguinal region revealed a small vaginal ring with several thin anaesthesia, but surgery was not performed because only the strands of connective tissue (Fig 1). The origins of the tissue left testis was palpable. The horse had not changed ownership attaching to the vaginal ring were traced in expectation of since birth and had no history of previous castration. On finding epididymal or testicular tissue. Babcock forceps were admission, the horse’s physical parameters were within normal used to retract intestine and follow the tissue’s attachments. A limits. Palpation under sedation revealed a normally descended left testis. No testis was palpable in the right scrotal or inguinal region. Diagnosis and treatment

Laparoscopy

Laparoscopic-assisted cryptorchidectomy under general anaesthesia was recommended and opted for by the owners. Food was withheld overnight and surgery performed the next morning. Prior to anaesthesia, haematology showed packed cell volume and total protein to be within normal limits. Perioperatively, the horse received potassium penicillin G

*Author to whom correspondence should be addressed. †Present address: Animal Disease Diagnostic Laboratory at the University of Fig 1: Laparoscopic view of the origin of the tissue strand Purdue, Lafayette, Indiana, USA. originating near the internal inguinal ring. EQUINE VETERINARY EDUCATION / AE / APRIL 2006 113

Fig 2: Laparoscopic view of the same tissue strand (as in Figure 1) at its attachment to the ventral body wall. Fig 4: Histology of the removed tissue, showing fibrous tissue with heavy accumulation of haemosiderin-laden macrophages.

Outcome

The horse recovered uneventfully from anaesthesia. Post operative management consisted of continued i.v. antibiotic and nonsteroidal anti-inflammatory therapy. The horse recovered well initially but developed colitis on the fifth post operative day, having been discharged earlier the same day. Antibiotic therapy had been changed to oral trimethoprim-sulphadiazine (Tucoprim)3 (15 mg/kg bwt per. os. q. 12 h) on the previous day. Clinical signs consisted of depression, mild abdominal pain and diarrhoea. Haematology and serum biochemistry findings were within normal limits. The horse was readmitted and treatment included i.v. isotonic fluids and flunixin meglumine Fig 3: Direct inguinal approach showing the vaginal process 4 (arrow). (Flunixamine) (1.1 mg/kg bwt i.v. q. 12 h). Faecal culture results were positive for Salmonella type B. The horse responded well tubular ductus deferens-like tissue was identified and traced to to treatment and was discharged after 10 days without further the dorsal aspect of the bladder. A narrow strand of complications. At follow-up conversation 6 months after mesorchium-like tissue was traced to the dorsal body wall. The surgery, the owner reported that the horse was no longer cranial aspect of the vaginal ring had a tubular strand of tissue showing masculine behaviour and was very easy to handle. that was traced to the ventral body wall near the laparoscope Histopathology of the tissue removed during surgery portal (Fig 2). A 2–3 cm area of irregular nodular tissue was identified degenerated tissue with heavy infiltration by present near the tissue strand attachment on the ventral body pigment-laden macrophages and no evidence of epididymal wall. Further exploration did not reveal a testis or . or testicular tissue (Fig 4). Histopathology of the left testis showed normal testicular tissue. Direct surgical approaches Hormonal assay A direct inguinal approach was then made over the right external inguinal ring to explore the . No testicular Four days after surgery, basal serum level was or epididymal tissue was found, but the vaginal process was measured and a human chorionic present (Fig 3); this was incised and the epididymal ligament (hCG) stimulation test performed as described previously (Cox was absent. The abdomen was then entered through a 10 cm et al. 1986); briefly, 10,000 iu hCG were given i.v. and blood caudal paramedian incision to remove the tissue attached to the samples for serum testosterone level collected 60 and ventral body wall and explore the abdomen by hand. The tissue 120 mins following injection. Results of the hCG stimulation attached to the ventral body wall and the vaginal ring was test indicated a lack of testosterone-producing tissue. Both removed. Exploration of the inguinal region and dorsal caudal baseline and post stimulation testosterone levels were abdomen by hand did not yield additional information. Incisions below 40 pg/ml, levels found only in . Based on the were closed routinely and the left testis removed by a routine history, surgical findings, histopathology and hormonal assays, open castration technique. it was concluded that the horse was a monorchid. 114 EQUINE VETERINARY EDUCATION / AE / APRIL 2006

Discussion canal and is invaded by an extension of peritoneal lining forming the vaginal process. During the process of testicular As reported in our case, equine monorchids originally descent, the gubernaculum differentiates into the proper presented for cryptorchid castration due to the presence of ligament, ligament of the tail of the epidydimis, and scrotal only one descended testis have been described previously ligament (Dyce et al. 2002). Cryptorchid surgery is based on (Parks et al. 1989; Santschi et al. 1989; Strong et al. 1997). the presence of one or more of these structures, using it In man, 12–45% of patients with only one descended testis to locate the retained . The presence of a vaginal are found to be monorchids during surgery (Merry et al. process implies that, at some point, gubernacular and 1997; Cohen et al. 1999; Lee and Coughlin 2002; Barqawi probably also testicular tissue had been present in this horse et al. 2003). Cryptorchidism in horses is common, but (Parks et al. 1989; Dyce 2002). monorchidism does not represent a significant percentage In man, testicular degeneration is usually secondary to of equine cryptorchid presentations. An epidemiological ischaemia, which is often the result of (Harris study that included 5009 cryptorchids concluded that et al. 1982; Lamesch 1994). Testicular torsion predominantly cryptorchidism affected about 15% of 2–30-year-old affects descended testes of adolescents, but can occur in presented to a referral centre (Hayes 1986). Equine adults (Daehlin and Servoll 1997) and neonates (Al-Salem monorchidism is rare and, to the best of our knowledge, there 1999). Neonatal testicular torsion is thought to occur in utero have been only 17 reported cases (Adams 1964; Stickle and and has been diagnosed by fetal ultrasonography (Herman et Fessler 1978; Parks et al. 1989; Santschi et al. 1989; Strong et al. 2002). In man, there is considerable evidence to suggest al. 1997). In previous reports, diagnosis of monorchidism has that monorchidism results from testicular regression following been based upon history, physical examination, surgical in utero torsion (Lamesch 1992,1994). In dogs, testicular exploration and hormonal testing after removal of the torsion usually occurs in mature cryptorchids with an descended testis. Typical historical findings include suspected abdominal testis (Burke and Reynolds 1993). In the horse cryptorchidism and masculine behaviour in a young male testicular torsion is uncommon, but it has been reported in horse that had been castrated. Physical examination findings mature stallions with a descended testis (Horney and Barker include only one palpable descended testis. Surgical 1975; Threlfall et al. 1990) as well as in mature cryptorchids exploration reveals the absence of one testis. Hormonal (Hunt et al. 1990). A recent report described testicular torsion testing following removal of the single testis verifies lack of in a horse diagnosed upon routine cryptorchidectomy. The functional testicular tissue. authors allude to the possibility that, had the castration been delayed, the horse would have been diagnosed as monorchid Hormonal assays upon surgical exploration (Parker and Rakestraw 1997). According to Parks et al. (1989), most cases of equine Hormonal testing to rule out the presence of functional monorchidism can be attributed to testicular degeneration testicular tissue includes hCG stimulation testing in horses rather than agenesis. The identification of degenerated tissue above 18 months of age (Cox 1975) and oestrone sulphate with heavy infiltrates of pigment-laden macrophages is concentration assay in horses above 3 years of age (Cox et al. consistent with the description by Lamesch (1994) of 1986; Arighi and Bosu 1989). The horse in our report was testicular regression after torsion in man. Based on the 26 months old and therefore the hCG stimulation test was identification of a vaginal process and the histopathological chosen. The laboratory reference range for the hCG findings, we believe that this case of monorchidism was also stimulation test was similar to that in other reports ( due to testicular degeneration. The tissue strand that <50 pg/ml; stallion >800 pg/ml; cryptorchid 100–500 pg/ml) extended to the bladder was probably a remnant of the (Cox 1975; Cox et al. 1986). Following surgery, all 3 samples ductus deferens and the tissue that extended cranioventrally before and after stimulation were below 40 pg/ml. from the inguinal region and attached to the ventral body Testosterone levels can be low in the winter, even in response wall may have been atrophied testicular vessels. Parks et al. to stimulation, especially when the testis is abdominal (Cox (1989) described very similar remnant orientation in an 1975; Ganjam and Kenney 1975). Our test was performed in equine monorchid. early summer and should not have been influenced by these seasonal limitations. Laparoscopic surgery

Aetiology Reported indications for diagnostic laparoscopy include chronic colic, weight loss, suspected urogenital tract lesions, While cryptorchidism is related to failure of normal testicular mesocolon tears, peritonitis and rectal tears. Reported surgical descent, monorchidism can be due to either agenesis or indications include ovariectomy, cryptorchidectomy, colopexy, testicular degeneration. Normal testicular descent involves adhesiolysis, nephrosplenic space obliteration, umbilical enlargement and then regression of the gubernaculum, a resection, cystorrhaphy, inguinal herniorrhaphy, embryo mesenchymal condensation within the genital fold connected transfer and potential rectal tear repair (Fischer 1999; to the developing testes. This enlargement of the Walmsley 1999; Brugmans and Deegen 2001; Marien et al. gubernaculum extends through the vaginal ring and inguinal 2001; Boure et al. 2002; Lansdowne et al. 2004). EQUINE VETERINARY EDUCATION / AE / APRIL 2006 115

Advantages from the use of laparoscopy for cryptorchid Barqawi, A.Z., Blyth, B., Jordan, G.H., Ehrlich, R.M. and Koyle, M.A. castration include visual evaluation of the inguinal region, (2003) Role of laparoscopy in patients with previous negative 61 smaller body wall incisions, no disruption of the external and exploration for impalpable testis. Urol. , 1234-1237. internal inguinal rings and a shorter recovery period. The Boure L.P., Pearce, S.G., Kerr, C.L., Lansdowne, J.L., Martin, C.A., Hathway, A.L. and Caswell, J.L. (2002) Evaluation of laparoscopic primary disadvantage is the expense of the instrumentation. adhesiolysis for the treatment of experimentally induced adhesions Laparoscopic cryptorchid castration can be performed in pony foals. Am. J. vet. Res. 63, 289-294. standing through a flank approach or under general Brugmans, F. and Deegen, E. (2001) Laparoscopic surgical technique anaesthesia in dorsal recumbency through a caudal ventral for repair of rectal and colonic tears in horses: an experimental approach. Advantages of the standing procedure include study. Vet. Surg. 30, 409-416. avoidance of complications and the expense associated with Burke, T.J. and Reynolds, H.A. (1993) The testis. In: Disease general anaesthesia, and improved visualisation of the Mechanisms in Small Animal Surgery, 2nd edn., Ed: M.J. Bojrab, inguinal region (Fischer and Vachon 1992; Rodgerson and Lippincot Williams & Wilkins, Philadelphia. pp 545-551. Hanson 1997). Advantages of the ventral approach include Cohen, Z., Newman, N., Kurzbart, E., Kapuller, V. and Mares, A.J. (1999) Diagnostic and therapeutic laparoscopy for non-palpable the ability to evaluate both inguinal regions through one testis. Harefuah 36, 111-113. approach, the use of general anaesthesia for fractious horses Cox, J.E. (1975) Experiences with a diagnostic test for equine and the ability to remove inguinal testes (Fischer and Vachon cryptorchidism. Equine vet. J. 7, 179-183. 1992). We chose general anaesthesia and the ventral Cox, J.E., Redhead, P.H. and Dawson, F.E. (1986) Comparison of the approach for the horse in this report, because of the higher measurement of plasma testosterone and plasma oestrogens for the incidence of inguinal retention in right-sided cryptorchids diagnosis of cryptorchidism in the horse. Equine vet. J. 18, 179-182. (Stickle and Fessler 1978; Coryn et al. 1981) and our Coryn, M., De Moor, A., Bouters, R. and Vandeplassche, M. (1981) preference for removal of the descended testis under general Clinical, morphorogical and endocrinological aspects of anaesthesia. Standing laparoscopy in this case would have cryptorchidism in the horse. Theriogenol. 16, 489-496. allowed easier evaluation of the internal inguinal region. Daehlin, L. and Servoll, E. (1997) Torsion of the spermatic cord. A clinical However, evaluation and removal of the tissue attached to the material on 109 patients. Tidsskr. Nor. Laegeforen 117, 1769-1771. ventral body wall would have been difficult and exploration of Dyce, K.M., Sack, W.O. and Wensing, C.J.G. (2002) The urogenital apparatus. In: Textbook of Veterinary Anatomy, 3rd edn., W.B. the inguinal canal would not have been possible. Saunders Co., Philadelphia. pp 173-174. We did not gain any additional information from manual Fischer, A.T. Jr. (1999) Laparoscopically assisted resection of umbilical exploration of the abdomen. Manual exploration of the structures in foals. J. Am. vet. med. Ass. 214, 1813-1816. abdomen increased the invasiveness of the surgery and the Fischer, A.T. and Vachon, A.M. (1992) Laparoscopic cryptorchidectomy anaesthesia time. Multiple recent reports stress the in horses. J. Am. vet. med. Ass. 201, 1705-1708. importance of laparoscopic intervention in human patients Ganjam, V.K. and Kenney, R.M. (1975) and oestrogens in with impalpable testes (Cohen et al. 1999; Barqawi et al. normal and cryptorchid stallions. J. Reprod. Fert., Suppl. 23, 67-73. 2003; Zerhouni et al. 2003) and have found laparoscopy to be Harris, B.H., Webb, H.W., Wilkinson, A.H. and Stevens, P.S. (1982) more accurate than open exploration in the diagnosis of Protection of the solitary testis. J. Pediatr. Surg. 17, 950-952. monorchidism (Barqawi et al. 2003). In this horse, direct Hayes, H.M. (1986) Epidemiological features of 5009 cases of equine visualisation using abdominal laparoscopy simplified and cryptorchism. Equine vet. J. 18, 467-471. substantiated the diagnosis of monorchidism. Herman, A., Schvimer, M., Tovbin, J., Sandbank, J., Bukovski, I. and Strauss, S. (2002) Antenatal sonographic diagnosis of testicular Acknowledgement torsion. Ultrasound Obstet. Gynecol. 20, 522-524. Horney, F.D. and Baker, C.A.V. (1975) Torsion of the testicle in a The authors would like to thank Dr Vance Grossenburg for standardbred. Can. vet. J. 16, 272-273. referring this case. Hunt, R.J., Hay, W., Collatos, C. and Welles, E. (1990) Testicular associated with torsion of the spermatic cord in two cryptorchid stallions. J. Am. vet. med. Ass. 197, 1484-1486. Manufacturers’ addresses Lamesch, A.J. (1992) Unilateral anorchidism or monorchidism. Chirurg. 118, 328-333. 1Roerig, Division of Pfizer Inc., New York, New York, USA. 2Phoenix Scientific Inc., St. Joseph, Missouri, USA. Lamesch, A.J. (1994) Monorchidism or unilateral anorchidism. 3Pharmacia & Upjohn Animal Health Ltd, Corby, Northamptonshire, UK. Langenbecks Arch. Chir. 379, 105-108. 4 Fort Dodge Animal Health, Fort Dodge, Iowa, USA. Lansdowne, J.L., Boure, L.P., Pearce, S.G., Kerr, C.L. and Caswell, J.L. (2004) Comparison of two laparoscopic treatments for References experimentally induced abdominal adhesions in pony foals. Am. J. vet. Res. 65, 681-686. Adams, O.R. (1964) An improved method of diagnosis and castration Lee, P.A. and Coughlin, M.T. (2002) The single testis: paternity after of cryptorchid horses. J. Am. vet. med. Ass. 145, 439-446. presentation as unilateral cryptorchidism. J. Urol. 168, 1680-1683. Al-Salem, A.H. (1999) Intra-uterine testicular torsion: early diagnosis Marien, T., Adriaenssen, A., Hoeck, F.V. and Segers, L. (2001) and treatment. BJU Int. 83, 1023-1025. Laparoscopic closure of the renosplenic space in standing horses. Arighi, M. and Bosu, W.T.K. (1989) Comparison of hormonal Vet. Surg. 30, 559-563. methods for diagnosis of cryptorchidism in horses. J. equine vet. Merry, C., Sweeney, B. and Puri, P. (1997) The vanishing testis: Sci. 9, 20-26. anatomical and histological findings. Eur. Urol. 31, 65-67. 116 EQUINE VETERINARY EDUCATION / AE / APRIL 2006

Parker, J.E. and Rakestraw, P.C. (1997) Intra-abdominal testicular torsion Strong, M., Dart, A.J., Malikides, N. and Hodgson, D.R. (1997) in a horse without signs of colic. J. Am. vet. med. Ass. 210, 375-377. Monorchidism in two horses. Aust. vet. J. 75, 33-35. Parks, A.H., Scott, E.A., Cox, J.E. and Stick, J.A. (1989) Monorchidism Threlfall, W.R., Carleton, C.L., Robertson, J., Rosol, T. and Gabel, A. in the horse. Equine vet. J. 21, 215-217. (1990) Recurrent torsion of the spermatic cord and scrotal testis in a stallion. J. Am. vet. med. Ass. 196, 1641-1643. Rodgerson, D.H. and Hanson, R.R. (1997) Cryptorchidism in horses. Part 2. treatment. Comp. cont. Educ. pract. Vet. 19, 1372-1379. Walmsley, J.P. (1999) Review of equine laparoscopy and an analysis of 158 laparoscopies in the horse. Equine vet. J. 31, 456-464. Santschi, E.M., Juzwiak, J.S. and Slone, D.E. (1989) Monorchidism in Zerhouni, H., Lachhab, M., Amrani, A., Ettayebi, F. and Benhammou, three colts. J. Am. vet. med. Ass. 194, 265-266. M. (2003) The importance of laparoscopy in therapeutic Stickle, R.L. and Fessler, J.F. (1978) Retrospective study of 350 cases of approach of intra-abdominal testes in child. About 35 cases. equine cryptorchidism. J. Am. vet. med. Ass. 172, 343-346. Ann. Urol. 37, 140-142.

Clinical Commentary The value of laparoscopy in equine cryptorchidism and monorchidism P. R AKESTRAW Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Texas A&M University, College Station, Texas, USA.

The horse in the report above (Kelmer et al. 2006) was performed with no attempt to remove the retained testis, with diagnosed with the very rare condition of monorchidism. As the horse subsequently being sold as a castrated animal. the authors state, preoperative differentiation between In either case, when stallion-like behaviour is displayed in monorchidism and cryptorchidism is difficult. Consequently, at ‘castrated’ horses, the first step is to confirm that the horse is the time of surgery most surgeons operate under the a cryptorchid. The diagnosis is made by performing an hCG assumption that the horse is a cryptochid until proven stimulation test or measuring oestrone sulphate concentration otherwise. This demonstrates how laparoscopy can be (the indications for both are well described in the report by advantageous in making this diagnosis. It also illustrates the Kelmer et al. 2006). In that report, the authors chose to use importance of making the appropriate diagnostic and the hCG stimulation test to confirm their diagnosis that the treatment decisions when presented with a horse that has a horse was a monorchid after surgical exploration of the presumptive diagnosis of a retained testis. abdomen and inguinal canal failed to reveal a second testis. A The first treatment decision was made by the referring more frequent scenario that this author has seen is a history veterinarian, who very appropriately elected not to remove the where a referred horse had a previous cryptorchid surgery by descended right testis after being unable to palpate the left manual exploration, no testis was found, and the hCG test testis in the scrotum or inguinal region with the horse under was positive for testicular tissue. As Kelmer et al. (2006) general anaesthesia. There is no advantage in removing one suggest, the use of laparoscopy for cryptorchid surgery should descended testis, since further surgical intervention is needed significantly improve the chances of expeditiously finding a to remove the retained testis, at which time the descended retained testis with no need for the trauma involved in testis can also easily be removed. Monorchidism occurs so introduction of a hand and arm into the abdomen and manual infrequently that the veterinarian castrating a horse should exploration of the abdominal cavity for the retained testis. never assume that the horse has only the one descended testis. If the presence of testicular tissue is confirmed, a decision has It is not uncommon for our referral centre to evaluate horses to be made on which surgical approach to select. In our hospital, with a history of being castrated but continuing to we often first perform rectal palpation under sedation and demonstrate stallion-like behaviour. In other cases, horses epidural anaesthesia to determine on which side the retained ‘presumed’ to be castrated but with unknown castration testis(es) is/are located. If the horse is small or intractable, histories have presented to our hospital with stallion-like increasing the risk of a rectal tear, rectal examination may not be behaviour. Although some of these horses have had bilateral indicated. Determining on which side a single retained testicle is surgical approaches to the inguinal canal with removal of what located is beneficial primarily when using a surgical approach to was thought to be 2 testes, it is possible that in some cases a explore the inguinal canal or when performing standing unilateral castration of the descended testis had been laparoscopy. Laparoscopic surgery with the horse in dorsal 118 EQUINE VETERINARY EDUCATION / AE / APRIL 2006

recumbency allows good visualisation of both internal inguinal ductus deferens will cause bulging at the ring as the testis puts rings with the laparoscope inserted in midline by the umbilicus. pressure against the extra-abdominal side of the ring. The In the report by Kelmer et al. (2006), the authors performed internal ring can be enlarged slightly by cutting it with laparoscopy under general anaesthesia. They selected dorsal laparoscopic scissors to allow the testis to be brought back recumbency instead of standing laparoscopy because of their into the abdomen (Hendrickson 2001). preference to remove the descended testis under anaesthesia. In conclusion, laparoscopic retraction of an inguinal testis They also referred to several reports (Stickle and Fessler 1978; is not restricted to horses under general anaesthesia and can Coryn et al. 1981) which found a higher incidence of inguinal also be performed in the standing horse, which eliminates the retention in right-sided cryptorchids. Their assumption was, need to explore the inguinal canal. since this horse was thought to be a right-sided cryptorchid, that the testis had a good chance of being in the inguinal References canal. In this case, the testis could be removed by either making an incision over the inguinal canal or retraction into the Coryn, M., De Moor, A., Bouters, R. and Vandeplassche, M. (1981) abdomen while the horse was under anaesthesia, and these Clinical, morphological and endocrinological aspects of procedures could not be performed during standing cryptorchidism in the horse. Theriogenol.16, 489-496. laparoscopy. After not finding the testis in the abdominal cavity, Fisher, A.T. (2001) Laparoscopic cryptochidectomy in dorsally the authors explored the inguinal canal and incised the vaginal recumbent horses. In: Equine Diagnostic and Surgical Laparoscopy, tunic, searching for testicular or epididymal tissue. Ed: A.T. Fischer, W.B. Saunders Co. Philadelphia. pp 149-154. Determining the structures that enter the internal inguinal Hendrickson, D.A. (2001) Standing laparoscopic cryptorchidectomy. ring can be difficult. If the testis is in the inguinal canal, both In: Equine Diagnostic and Surgical Laparoscopy, Ed: A.T. Fischer, the mesorchium and the ductus deferens should be observed W.B. Saunders Co. Philadelphia. pp 155-161. to enter the internal inguinal ring. Abdominal cryptorchids Kelmer, G., Kramer, J. and Miller, M.A. (2006) Laparoscopic-assisted often have a ‘bulls eye’ appearance to the internal inguinal diagnosis of monorchidism in a horse. Equine vet. Educ. 18, 84-88. ring, with only a gubernaculum attaching to it (Fischer 2001). Stickle, R.L. and Fessler, J.F. (1978) Retrospective study of 350 cases of With inguinal testes, traction placed on the mesorchium or equine cryptorchidism. J. Am. vet. med. Ass. 172, 343-346.