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Castration is one of the mostcommon surgical pro c e d u re sperformed in equine practice.1,2

Although the pro c e d u re is considere droutine, surgical complications consti-tute the most common cause ofmalpractice claims against equine prac-titioners in North America.3 A completeunderstanding of male re p ro d u c t i veanatomy and physiology and goodsurgical technique will reduce the rateof surgical complications. Pre s u r g i c a le valuation and surgical approach tocryptorchid and monorchid horses are am o re complex diagnostic and surgicalchallenge. This article provides practi-tioners with a re v i ew of re l e vant infor-mation on the embryological deve l o p-

ment and anatomical features of themale equine re p ro d u c t i ve tract, theapproaches to castration of the normal,cryptorchid, and monorchid horse, andthe diagnosis and management ofsurgical complications.

Embryonic development andsurgical anatomy of the equinetestis

The embryonic gonad differe n t i a t e sinto a testis at approximately 51⁄2 we e k sof gestation, at which time it lies on theventral aspect of the mesonephrick i d n e y.4,5 A re t roperitoneal cord ofmesenchyme coursing across theabdominal cavity from the caudal poleof the testis to an extraperitoneal posi-tion at the site of the future scro t u mforms the gubernaculum.5 The guber-naculum is divided into two parts bythe mesonephric duct which ultimately

EDITOR

DAVID WATSON

ADVISORY COMMITTEE

AVIANLUCIO FILIPPICH

EQUINEDAVID HODGSON

OPHTHALMOLOGYJEFF SMITH

PRODUCTION ANIMALS JAKOB MALMO

SMALL ANIMALS JILL MADDISON

SURGERYGEOFF ROBINS

ZOO/EXOTIC ANIMALS LARRY VOGELNEST

EDITORIAL ADMINISTRATION AND DESKTOP PUBLISHING

ANNA GALLO

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C L I N I C A L S E C T I O N

Australian

V E T E R I N A RYJO U R N A L

Equine castration: review ofanatomy, approaches, techniquesand complications in normal,cryptorchid and monorchid horses

D SEARLE, AJ DART, CM DART and DR HODGSONUniversity Veterinary Centre, Department of Veterinary Clinical Sciences, The Uni-versity of Sydney, Werombi Road, Camden, New South Wales 2570

Complications associated with equine castration are the most common cause ofmalpractice claims against equine practitioners in North America. An understand-ing of the embryological development and surgical anatomy is essential to differen-tiate abnormal from normal structures and to minimise complications. Castration ofthe normal horse can be performed using sedation and regional anaesthesia whilethe horse is standing, or under general anaesthesia when it is recumbent.Castra-tion of cryptorchid horses is best performed under general anaesthesia at a surgi-cal facility. Techniques for castration include open, closed and half-closed tech-niques. Failure of left and right testicles to descend occurs with nearly equal fre-quency, however, the left testicle is found in the abdomen in 75% of cryptorchidhorses compared to 42% of right testicles. Bilateral cryptorchid and monorchidhorses are uncommon. Surgical approaches described for the castration of cryp-torchid horses include an inguinal approach with or without retrieval of the scrotalligament, a parainguinal approach, or less commonly a suprapubic paramedian orflank approach. Laparoscopic castration of cryptorchid horses has recently beendescribed but the technique has limited application in practice at this time. A defini-tive diagnosis of monorchidism can only be made after surgical exploration of theabdomen, removal of the normal testis and hormonal testing. Hormonal assaysreported to be useful include analysis of basal plasma or serum testosterone oroestrone sulphate concentrations, testosterone concentrations following hCG stim-ulation, and faecal oestrone sulphate concentrations. Reported complications ofcastration include postoperative swelling, excessive haemorrhage, eventration,f u n i c u l i t i s, peri t o n i t i s, hy d r o c e l e, penile damage and continued stallion-likebehaviour.Aust Vet J 1999;77:428-434Key words: Horse, equine, castration, cryptorchid, monorchid.

IM IntramuscularlyIV Intravenously

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d i f f e rentiates into the epididymis.4 Atday 45 a peritoneal outpouching at thesite of the future internal inguinal ringi n vades the extraperitoneal segment ofthe gubernaculum forming the va g i n a lp ro c e s s .5 Ul t i m a t e l y, when it iscompletely differentiated, the gubernac-ulum can be divided into the thre edifferent segments identified in the adulthorse: the proper ligament of the testislies between the caudal pole of them a t u re testis and the tail of theepididymis, the ligament of the tail ofthe epididymis lies between the tail ofthe epididymis and the parietal tunic ofthe vaginal process, and the scrotal liga-ment lies between the parietal tunic ofthe vaginal process and the scro t u m(Figure 1).5

At approximately 6 weeks gestation,the interstitial cells of the testis begin tom u l t i p l y. By 5 months the embryo n i ctesticle approaches the size of that of am a t u re stallion and lies in contact withthe kidney and the internal inguinalr i n g .4 , 5 Be t ween 7 and 10 months ofgestation the testicle atrophies toa p p roximately one tenth of its formers i ze as the gubernaculum short e n s .4 , 5

The epididymis and the ligament of thetail of the epididymis expand to dilatethe vaginal ring and inguinal canal.5

Ultimately, at 9 and 10 months of gesta-tion dilation of the inguinal ring,contraction of the gubernaculum andi n c rease in intra-abdominal pre s s u recombine to force the small, flaccidtesticle into the inguinal ring.5 T h evolume of extra-abdominal gubernac-ulum pre vents the testicle fro mdescending completely into the scrotum,so at birth the testicles usually lie withinthe inguinal rings.4,5 The mass of guber-naculum is quite large at birth and maybe mistaken for a testicle.5 During thefirst few weeks of life vaginal ringscontract to approximately 1 cm in diam-eter and gubernacular tissues reduce ins i ze, allowing the testicle to assume ascrotal position.4,5

The testicular tissue is encased in thetunica albuginea.2,5 In the horse the lefttesticle is usually larger than the rightand is suspended more ventrally andsituated more caudally.5 The head of theepididymis is found cranially continuingas the body and tail to become theductus deferens caudally.5 The testicleslie within an outpocket of abdominal

p e r i t o n e u mk n own as thetunica va g i-n a l i s .2 , 5 T h etunica va g i n a l i sconsists ofvisceral and pari-etal tunics. T h evisceral tunic istightly adhere dto the testicle,ducts and vessels,and the parietaltunic is contin-uous with theparietal perito-neum (Figure 1).5

The cre m a s t e rmuscle is ac a u d o l a t e r a lextension of theinternal abdom-inal obliquemuscle and iscontinuous withthe parietal laye rof the tunicav a g i n a l i si n s e rting at thecaudal pole of thetesticle (Fi g u re2 ) .5 The parietaltunic is inti-mately adhere n tto the scrotal skint h rough thes c rotal fascia andtunica dart o sm u s c l e .2 , 5 T h etunica dart o ssends a sagittalseptum into thes c rotal sacdividing it into left and right pouches.5

The spermatic cord courses fro mabdomen to scrotum through theinguinal canal which is bounded by deepand superficial inguinal rings. The deepinguinal ring is a dilatable openingb e t ween internal abdominal obliquemuscle, rectus abdominus muscle,prepubic tendon and inguinal ligament.The superficial inguinal ring is formedby a small opening in the externalabdominal oblique muscle.

Preoperative considerationsBe f o re castration all horses should

undergo physical examination including

external examination of the reproductivet r a c t .5 Sedation may be re q u i red topalpate the scrotum and the inguinalcanals for the presence of two testiclesand absence of an inguinal hernia.Tetanus prophylaxis should be curre n t .Some practitioners choose to givep rocaine penicillin (20 mg/kg IM)p rophylactically prior to surgery. T h eefficacy of this in reducing postoperativecomplications in castration of normalhorses is questionable. The use ofa n t i m i c robials for horses undergoingc ry p t o rchid or monorchid castrationshould be considered on a case-by - c a s ebasis but cannot be a substitute foraseptic technique. Preoperative adminis-

Figure 1.The testicular structures seen during castration of themature male horse using an open castration tech n i q u e. T h etesticle (t) is tightly enclosed in the tunica albuginea.The head ofthe epididymis (a) continues as the body (b) and the tail (c) thelatter continues as the vas deferens (d).The tail of the epididymisis attached to the caudal pole of the testis by the proper ligamentof the testis (e).This continues as the ligament of the tail of theepididymis (f) between the tail of the epididymis and the parietaltunic (pt).The visceral tunic cov e rs the visceral surface of thet e s t i cl e, e p i d i dy m i s , spermatic vessels (sv), and vas defe r e n s .The parietal tunic and cremaster muscle (cm) have been incisedand are partially retracted.

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tration of a nonsteroidal anti-inflamma-t o ry drug (phenylbutazone 2.2 to 4.4mg/kg or flunixin meglumine 1 mg/kg),and postoperative administration asrequired, may help control postoperativepain and swelling.

Castration can be performed in thestanding sedated horse using re g i o n a lanaesthesia or with the horse undergeneral anaesthesia. The choice is largelybased on the surgeon’s pre f e rence andexperience. Docile colts whose genitalscan be palpated readily without sedationa re usually the safest candidates forstanding castration.5

Sedation and anaesthesia for cas -trationStanding castration

A combination of physical and chem-ical restraint and regional anaesthesia isgenerally re c o m m e n d e d .2 Drugs usedc o m m o n l y, alone or in combination,include acepromazine, xylazineh yd rochloride, romifidine, detomidinehydrochloride and butorphanol tartrate.A combination of detomidineh yd rochloride (20 to 40 µg/kg) orxylazine hyd rochloride (0.3 to 0.5mg/kg) and butorphanol tartrate (0.01to 0.05 mg/kg) provides reliable seda-tion and analgesia.6

Various re g i o n a lanaesthetic tech-niques have beend e s cribed for castra-tion of the standingho r s e .2,5,6 L o c a la naes-thetic can beinjected into thespermatic cord ,t e s t i c u l a rp a renchyma, orboth. The testicularn e rves may beanaesthetised byd i rectly injecting15 to 30 mL oflocal anaestheticinto the sp e r m a t i cc o rd using a 21-gauge 1.5 inchneedle. This can beachieved by placinggentle traction onthe testicle allowingaccess to the sper-matic cord or bydepositing the localanaesthetic at the

l e vel of the superficial inguinal ring.2

Infiltration of the spermatic cord mayoccasionally cause a haematoma whichcan interf e re with application of thee m a s c u l a t o r.5 When injecting into thetesticular parenchyma, the testis istensed in the fundus of the scrotum and15 to 25 mL of local anaesthetic isinjected into the parenchyma of eachtestis using a 18-gauge 1.5 inch needle.Gi ven sufficient time the local anaes-thetic is proposed to diffuse from thepampiniform plexus to anaesthetise thec o rd .2 When combining both tech-niques, infiltration of the testicle firstcan facilitate access to the cord inanxious horses. In our hands this combi-nation provides reliable anaesthesia formost horses. Using either technique, 5to 10 mL of local anaesthetic should bedeposited under the scrotal skin eitherside of the median raphe along theproposed incision line.2

Recumbent castrationWe prefer to use general anaesthesia

because surgical exposure is improve dand it carries less risk for surgeon andpatient. Various drugs and drug combi-nations have been recommended for thisprocedure.2,5 The placement of a jugularcatheter is warranted for drug adminis-

tration. Thiobarbiturates (thiopentonesodium 4 to 8 mg/kg IV to effect)a d m i n i s t e red following sedation withxylazine hyd rochloride (0.3 to 0.5mg/kg IV) or acepromazine (0.03 to0.05 mg/kg IV), or given with or aftermuscle relaxants such as guaifenesin(100 mg/kg IV to effect) have beenrecommended for short anaestheticp ro c e d u re s .2 While these combinationsp rovide excellent muscle relaxation andanalgesia, anaesthetic re c ove ry may bec o n s i d e red less than satisfactory ifrepeated administration of the barbitu-rate is required.2,5

Xylazine hyd rochloride (1.1 mg/kgIV) followed by ketamine hydrochloride(2.2 mg/kg IV) combined withd i a zepam (0.05 to 0.1mg/kg IV) is ane f f e c t i ve combination.2 , 5 Di a ze p a mp rovides muscle relaxation and appearsto improve the quality of anaestheticinduction and recovery. The addition ofbutorphanol tartrate (0.02 to 0.03mg/kg IV) will provide additional anal-gesia and may improve anaestheticre c ove ry. This combination generallya l l ows at least 12 to 15 min of surgicaltime. Additional doses of xylazine (0.25mg/kg IV) and ketamine (0.5 mg/kg IV)can be used safely to extend surgicalanaesthesia.

Cryptorchid castration Unless the position of the non-

descended testicle can be accuratelydetermined and is easily accessible, thiss u r g e ry is best performed at a surgicalcentre under gaseous anaesthesia.3,5

Surgical techniques for castrationof normal horses

Surgical re m oval of the descendedtestis can be performed using an openor closed technique. T h e re is also a va r i-ation on the closed technique re f e r re dto as half-closed or semi-closed castra-t i o n .2,5 T h e re are several modificationsof each technique but, re g a rdless ofwhether the horse is sedated andstanding or recumbent and anaes-thetised, the surgical principles forcastration remain the same.. 2 , 5 Tr a d i-t i o n a l l y, castration techniques allow forsecond intention healing of scro t a lwounds, howe ver some have advo c a t e dp r i m a ry closure .7,8 Pr i m a ry closure isr a rely suited for castrations perf o r m e din the field but may be of benefit inselect cases where castration is

Figure 2.The testicular structures seen during castration of theadult male horse using a closed tech n i q u e.The testicle (t) andthe tail of the epididymis (c) are outlined within the parietal tunic(pt).The cremaster muscle (cm) can be seen fanning out to inserttowards the caudal pole of the testis (cp).The scrotal fascia (sf)remaining after the testicle and cord have been stripped can stillbe seen.

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p e rformed aseptically in a surgicalfacility. Reported advantages of primaryc l o s u re include early return to work ,minimal postoperative management anda more favourable and early cosmeticoutcome with no possibility of eve n t r a-tion.7

Open techniqueTwo incisions are made through the

s c rotal skin, tunica dartos, scrotal fasciaand parietal tunic parallel to the medianraphe, approximately 2 cm apart and 8to 10 cm long. The testis is pro l a p s e dout of the tunic but remains attached tothe parietal tunic by the ligament of theepididymis (Figure 1). This ligament canbe transected to release the parietal tunicand cremaster muscle and expose thevessels and ductus deferens which canthen be emasculated. To reduce theo c c u r rence of postoperative complica-tions such as scirrhous cord and hyd ro-cele, it is desirable to digitally strip thefascia around the parietal tunic as farp roximal as possible so it may be emas-culated and re m ove d .2 , 5 This is easilya c h i e ved if the parietal tunic alone (notthe parietal tunic and testicle together) ispulled distally with Carmalt forc e p swhile the fascia is stripped prox i m a l l yusing gauze swabs. Alternatively theparietal tunic, the cremaster muscle, thevessels and the ductus deferens can all beemasculated together.

Closed techniqueIncisions similar to those for the open

technique are made down to but nott h rough the parietal tunic (Fi g u re 2).The testicle, still encapsulated by thetunic, is grasped and the scrotal fascia isstripped from the parietal tunic using adry swab, until the cremaster muscle andthe parietal tunic are clearly exposed.The entire spermatic cord is then emas-culated.2,5

Half-closed techniqueThe approach is similar to the closed

technique, howe ver after the parietaltunic and the cremaster muscle areexposed a 2 to 3 cm ve rtical incision ismade through the parietal tunic justp roximal to the testicle. The inside ofthe parietal tunic is inspected to ensuret h e re is no evidence of herniated intes-tine and the entire spermatic cord isemasculated prox i m a l l y. Alternative l ythe vessels and ductus can be exteri-orised from the parietal tunic and emas-

culated before emasculating the parietaltunic and cremaster muscle. In anothermodification the surgeon’s thumb can beplaced through the incision made in theparietal tunic and the fingers used top rolapse the testicle, vessels and ductusd e f e rens through the incision. T h i sp rovides the surgeon with a secure gripon the parietal tunic. The vessels andductus deferens can then be emasculatedseparately prior to emasculation of theparietal tunic and cremaster muscle orthe cord can be emasculated in one.5

Cryptorchid castrationThe failure of the right and left testicle

to descend occurs with nearly equalfrequency.9,10 Of left testicles that fail todescend 75% are found within theabdomen compared to 42% of rightt e s t i c l e s .1 0 Fa i l u re of both testicles todescend is uncommon, affecting 9 to14% of cryptorchid horses.5,10

An accurate castration history ishelpful in determining the surgicala p p roach to the cry p t o rchid horse.5 , 1 1

Palpation of the scrotum and inguinalrings for presence of testicular structuresmay require sedation in younger or moreanxious colts.5 Tr a n s rectal examinationgenerally contributes little to differe n t i-ating the type of cryptorchid and carriesi n h e rent risks in younger or more frac-tious animals.5,11

Surgical options include inguinal,parainguinal, suprapubic paramedianand flank appro a c h e s.2 , 5 Mo re re c e n t l y,standing and recumbent cry p t o rc h i d e c-tomy using a laparoscopic techniquehave been described.12,13

Inguinal approach Two approaches are described for

inguinal exploration.5,11 A 10 cm inci-

sion is made through the scrotal skinw h e re the testicle should be and digitaldissection is continued tow a rds the

s u p e rficial inguinal ring.5 A l t e r n a t i ve l y,a 8 to 15 cm incision can be maded i rectly over the superficial inguinalr i n g .1 1 A scrotal incision results in lessskin haemorrhage and precludes theneed to displace inguinal fat to locatethe superficial inguinal ring.11 Re c o g n i-tion of anato-mical features is improvedif haemorrhage is controlled. Du r i n gdissection down to the inguinal ring thesmooth, white parietal tunic of thevaginal process is sought. If no structuresa re identified the inguinal extension ofthe gubernaculum testis (scrotal liga-ment) can often be identified exitingfrom the superficial inguinal ring. It is athin, flat, fibrous band that courses fromthe vaginal process to the scrotum. It canbe located by carefully inspecting thelateral or medial margins of the cranialt h i rd of the superficial inguinal ring.1 4

Gentle traction on this ligament usingsponge forceps will eve rt the va g i n a lp rocess from the superficial inguinalring and it can be opened longitudinallyusing scissors. Commonly the tail of theepididymis is the first stru c t u re identi-fied and gentle traction on theepididymis will expose the ductusd e f e rens, the proper ligament of thetestis, and finally the testis.

If the vaginal ring can accommodatem o re than the tips of the index andmiddle fingers then the inguinal canalshould be packed with sterile gauze for24 to 36 h or closed with sutures toreduce the risk of intestinal pro l a p s et h rough the canal. A sterile gauzebandage can be used as packing to oblit-erate the inguinal canal and the distalend is left hanging freely from thes c rotal wound. The pack is maintainedin the inguinal ring by loosely suturingskin edges. Alternatively the superf i c i a lring can be sutured closed using simplei n t e r rupted sutures of heavy absorbablesuture material.

Parainguinal approach W h e re the testis cannot be exteri-

orised from the inguinal canal usingn o n i n va s i ve inguinal appro a c h e s ,1 0

s e veral more inva s i ve techniques havebeen described to explore the inguinalc a n a l .5 , 1 1 These have been usedcommonly but it has been suggestedthat they increase the risk of eviscera-t i o n .10,11 The parainguinal appro a c hp rovides a convenient alternative wherethe noninva s i ve inguinal appro a c h e s

Surgical approaches for cryptorchidhorses

Inguinal

Parainguinal

Suprapubic paramedian

Flank

Laparoscopic

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h a ve been unsuccessful.15 A 4 cm inci-sion is made in the aponeurosis of theexternal abdominal oblique muscle 1 to2 cm medial and parallel to the superfi-cial inguinal ring. The incision isc e n t red over the cranial aspect of thering. The internal abdominal obliquemuscle underlying the aponeurosis isbluntly separated along its muscle fibresto expose the peritoneum which is thenpenetrated to enter the abdominalcavity. The internal inguinal ring can beidentified caudolaterally and, with asweeping action, the fingers should pickup any testicular stru c t u res. These canbe exteriorised and emasculated. If diffi-culty is encountered in locating theepididymis or associated stru c t u res theincision can be enlarged to allow thes u r g e o n’s hand to enter the abdominalcavity for exploration of the uro g e n i t a ltract. The incision in the aponeurosis isclosed using heavy absorbable suture sand the subcutaneous tissue and skincan be closed or left open to heal bysecond intention.15

Suprapubic paramedian approachAn incision of 8 to 15 cm is made

cranially from the level of the pre p u t i a lorifice approximately 5 to 10 cm lateralto the ventral midline.5 , 1 6 The abdom-inal tunic, which is closely adherent tothe ventral sheath of the rectus abdo-minis muscle, is incised longitudinallyand the underlying fibres of the re c t u sabdominis muscle are bluntly separatedin the same direction. Blunt dissection isused to penetrate through the dorsalrectus sheath, re t roperitoneal fat andperitoneum. The testicle is usuallyfound near the deep inguinal ring and iseasily exteriorised. After emasculation,the abdominal tunic, the subcutis andskin are each closed separately withi n t e r rupted or continuous sutures. T h i sp ro c e d u re has largely been supersededby the parainguinal approach, howe ve rit is proposed to allow access to bothtesticles in the case of a bilateral cry p-torchid.5

Flank approachA standard flank approach can be used

in standing or recumbent horses.17 T h etesticle is located and re m oved using asimilar technique to the paramediana p p roach. This technique is less accept-able cosmetically than the otherapproaches and is now generally reservedfor removal of large neoplastic testicles.5

LaparoscopyLaparoscopic techniques for castration

of cryptorchid horses have recently beend e s c r i b e d .1 2 , 1 3 L a p a roscopy re q u i re sspecial instruments not readily ava i l a b l ein general practice5 and further re f i n e-ments are needed in the method.13 Atpresent this technique has limited appli-cation in general practice but it may bemore feasible in the future.5

MonorchidismMo n o rchidism is the complete

absence of one testicle and is rare in theh o r s e .5 A definitive diagnosis can onlybe made after surgical exploration of theabdomen, re m oval of the other testisand hormonal testing.1 8 , 1 9 Us e f u lhormonal assays include basal plasma ors e rum testosterone and oestro n esulphate concentrations, testostero n econcentrations following hCG stimula-tion, and faecal oestrone sulphatec o n c e n t r a t i o n .5,18,19 The hCG stimula-tion test in horses older than 18 months,basal oestrone sulphate assay in horsesolder than 3 years or a combination of

both tests appear to be most re l i-a b l e .5 , 1 1 , 1 8 , 1 9 The hCG stimulation testm e a s u res plasma or serum testostero n econcentrations, before and 1 and 24 hafter intravenous administration of 6000to 10,000 IU of hCG.1 8 , 1 9 T h e re shouldbe no increase above basal testostero n econcentrations in horses with no testic-ular tissue. The response in horses withtesticular tissue may be poor duringwinter or if testicular tissue is abdominal.Both tests should be performed if eithertest is inconclusive. Samples should besubmitted to laboratories that ro u t i n e l yassay equine testosterone and oestro n esulphate concentrations so that re l i a b l ere f e rence values are ava i l a b l e .1 4 , 1 9

Complications of castrationPostoperative swelling

Some preputial and scrotal oedema isnormal, usually greatest 3 to 6 days after

s u r g e ry and subsiding by 9 days.2 0

Excessive swelling is a common compli-cation and typically occurs with inade-quate wound drainage, inadequate post-o p e r a t i ve exe rcise, poor lymphaticdrainage, exc e s s i ve surgical trauma orinfection.1,20

Postoperative swelling can be reducedby creating a large scrotal incision,a voiding exc e s s i ve tissue trauma,re m oving as much tunica vaginalis aspossible, manually stretching the surgicalincision and removing the median rapheduring surgery.5,20 Following castration,exercise, hosing the wound, and the useof nonsteroidal anti-inflammatory drugscan reduce swe l l i n g .1 , 5 , 2 0 The ow n e rmay start riding the horse 24 to 48 hafter surgery.20

Exc e s s i ve postoperative swelling ispainful and reduces willingness to exe r-cise, causing the wound to seal pre m a-t u rely and compounding the pro b l e m .Treatment invo l ves nonsteroidal anti-inflammatory drugs to decrease pain andinflammation and increase tolerance toe xe rc i s e .1 , 5 , 2 0 If scrotal wounds haveclosed, it may be beneficial to sedate thehorse and reopen the wounds manuallywearing a sterile glove .1,5,20 This mayneed to be repeated on consecutive daysuntil the swelling reduces. Antimicrobiald rug treatment may be indicated wherethe discharge is purulent. Se c o n d a ryproblems associated with severe swellinginclude phimosis, paraphimosis, cellulitis,wound infection and dysuria.20

Excessive haemorrhageHaemorrhage may occur during,

immediately after or several days afters u r g e ry.2 0 Some bleeding from scro t a lwounds after castration is normal but ifp rofuse bleeding continues unabated form o re than 15 min haemorrhage shouldbe considered exc e s s i ve .1 , 5 , 2 0 Exc e s s i vehaemorrhage generally occurs from thetesticular art e ry, but may originate fro mtraumatic ru p t u re or laceration ofbranches of the external pudendalve i n .1 , 2 0 A rterial haemorrhage is generallya result of inadequate crushing by theemasculators. The emasculators should b eapplied perpendicular to, and withouttension on, the spermatic cord with thecutting blade closest to the testes.1 , 5 , 2 0

Precise guidelines for when to inter-vene surgically are not established buttreatment of postoperative haemorrhageis best performed under general anaes-

Hormonal assays detecting testicular tissue

Hormone detected Sample

Basal testosterone Serum or plasma

Basal oestrone Serum, plasma or sulphate faeces

Testosterone following Serum or plasma hCG stimulation

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t h e s i a .1 , 5 , 2 0 Be f o re anaesthesia thepatient should be assessed care f u l l y,paying particular attention to cardiovas-cular status. The site of haemorrhageshould be identified. The spermatic cordmay be grasped with long forceps passedinto the inguinal canal and the testiculara rt e ry occluded. The cord can then beemasculated proximally or ligated. If thec o rd cannot be ligated or emasculated,the forceps can be left in place for 12 to24 h to allow thrombosis to occur.W h e re the end of the cord cannot begrasped, haemorrhage can usually bec o n t rolled by packing the scrotum withg a u ze. If the haemorrhage is occurringf rom a large superficial vein in thes c rotal or inguinal area, ligation of thevessel is the treatment of choice.

EventrationEventration through the vaginal ring

and open scrotal incision is uncommon,generally occurring within 4 h but mayoccur up to 6 days after surgery.21 Even-tration of the small intestine makes up67% of cases while omental pro l a p s ecomprises the re m a i n d e r.2 2 A surv i va lrate of 85 to 100% can be expectedw h e re appropriate treatment is insti-t u t e d .2 2 Suggested predisposing factorsinclude a pre-existing undetectedinguinal hernia, presence of viscerals t ru c t u res adjacent to the internalinguinal ring, and increased abdominalp re s s u re following surgery.2 2 Pa l p a t i o nof the scrotum and inguinal regions forhernias prior to castration is re c o m-mended in foals. St a n d a rd b red horsesa re believed to be predisposed tocongenital inguinal herniation.5

If evisceration occurs the main objec-tive is to clean and protect the intestineand return it to the abdomen before it ise xc e s s i vely traumatised or contami-n a t e d .2 1 The intestine should bep rotected by a moistened towel shaped

into a sling and the horse anaesthetisedand positioned in dorsal re c u m b e n c y.2 1

In the field the intestine should bel a vaged and where possible placed backwithin the scrotum which is suture d .2 1

Bro a d s p e c t rum antimicrobial therapyshould be initiated, an analgesic dose offlunixin meglumine administered andthe horse immediately re f e r red to asurgical facility. To replace the intestinesinto the abdomen, dilation of thevaginal ring and traction on theintestines through ventral midline orparainguinal celiotomy are usuallyn e c e s s a ry.5 , 2 1 The tunic should beligated and emasculated as far prox i-mally as possible and the superf i c i a linguinal ring closed with large-diameter,absorbable suture material.1,5,20 Alterna-t i ve l y, the inguinal canal can be packedwith gauze for 24 to 48 h, howe ve rintestine may still eventrate around thep a c k i n g .1,5,21 Prolapse of the omentumthrough the inguinal ring can usually bemanaged using sedation and transectingthe prolapsed omentum as far prox i-mally as possible. After re c ove ry fro manaesthesia the horse should be keptquiet in a stall for 24 to 48 h.5,21

Evisceration of omentum from thescrotal wound is much less serious and isbest treated with transection of theomentum which can be performed withthe horse standing.5

Funiculitis Funiculitis refers to inflammation of

the spermatic cord .1 , 5 , 2 1 It is usually aseptic process developing as an extensionof a scrotal infection or from a contami-nated emasculator or ligature.5 Failure toremove the tunica vaginalis and externalc remaster muscle during open castra-tions predisposes horses to septic funi-c u l i t i s .2 3 Signs va ry with pyrexia, lame-ness, inguinal and scrotal swelling andc h ronic discharge often noted.1 , 5 T h e s emay not develop for months or ye a r safter castration.5,21

In the early stages, funiculitis oftenre s o l ves with antimicrobial therapy andthe establishment of drainage, but occa-sionally surgical re m oval of the infectedstump is re q u i re d .5 , 2 1 A chronic infec-tion with pyogenic bacteria iscommonly referred to as scirrhous cord,h owe ver the term ‘c h a m p i g n o n’ and‘ b o t r i o m yc o s i s’ have been used histori-cally to describe infection with St re p t o -coccus spp and Staphylococcus spp, respec-

tively.5,21 Extension of the septic processt h rough the inguinal ring and into theperitoneal cavity is possible butu n c o m m o n .5 Treatment of scirrhousc o rd re q u i res surgical resection anda n t i m i c robial therapy.1 , 5 , 2 0 The horseshould be anaesthetised and positionedin dorsal re c u m b e n c y. The infectedstump is then isolated from healthytissue using blunt dissection. The cord isemasculated proximal to the infectedstump and the wound is left to heal bysecond intention.5

PeritonitisThe vaginal and peritoneal cavities

communicate and nonseptic peritonitisis common following castration.1 , 5 , 2 1

Haemoperitoneum and secondaryinflammation can increase peritonealtotal nucleated cell counts to more than10 x 109 cells/L for at least 5 days withcounts greater than 100 x 109 cells/L notuncommon.23 Septic peritonitis is rare,1

but should be considered where signsinclude abdominal pain, pyrexia, tachy-cardia, diarrhoea, weight loss and reluc-tance to move .1 , 5 , 2 1 Toxic or degeneraten e u t rophils and intracellular bacteriafound on abdominocentesis confirm thed i a g n o s i s .1 , 5 , 2 1 Cu l t u re of a peritonealfluid sample is suggested where possible.Treatment consists of appro p r i a t ea n t i m i c robial and nonsteroidal anti-i n f l a m m a t o ry therapy, and prov i d i n ganalgesia, peritoneal drainage andl a vage, and adequate drainage thro u g hthe scro t u m .5 Until culture re s u l t sbecome available, procaine penicillin(20 mg/kg IM twice daily) and gentam-icin sulphate (6.6 mg/kg, IV or IM oncedaily) should be considered.

HydroceleA hyd rocele is an accumulation of

sterile amber-coloured fluid within thevaginal tunic. It can appear months toyears following castration.1 , 5 , 2 1 It isb e l i e ved to result from failure to re s e c tthe vaginal tunic adequately duringcastration and is reported to occur mostcommonly in mules.1 , 5 It appears as afluid-filled enlargement of the scro t u mthat can often be reduced by squeez i n gthe fluid into the abdominal cavity.Treatment is only necessary where thes welling is unsightly or interf e res withfunction. The skin is incised over the sacand the vaginal tunic is isolated prox i-mally to the inguinal ring and emascu-lated.1,5

Complications of castration

Postoperative swelling

Excessive haemorrhage

Eventration

Funiculitis

Hydrocele

Penile damage

Continued masculine behaviour

Aust Vet J Vol 77, No 7, July 1999434

Clinical

Penile damageComplications involving the penis are

r a re and generally associated with iatro-genic trauma to the penile shaft. Pe n i l ep rolapse can occur secondary to exc e s-s i ve swelling, and priapism and penileparalysis has been re p o rted follow i n gadministration of phenothiazine-deriva-tive tranquillizers.1,5,21

Continued masculine behaviourCastration does not always result in

elimination of objectionable stallion-likeb e h a v i o u r. This has been attributed toincomplete re m oval of epididymaltissue, presence of heterotopic testiculartissue, production of high concentra-tions of androgens from the adre n a lgland, incomplete cryptorchid castrationand psychological re a s o n s .1 , 5 A n d ro g e n sare not produced by the epididymis andt h e re f o re the presence or absence ofepididymal tissue cannot influencemasculine behaviour. Amputating thespermatic cords was re p o rted to abolishobjectionable masculine behaviour in75% of castrated horses, but no satisfac-t o ry explanation was offered for thisre s p o n s e .24 He t e rotopic testicular tissueand production of adrenal andro g e n sh a ve never been established in horsesand are unlikely to be the cause ofcontinued stallion-like behaviour.1 , 5

About 20 to 30% of horses display somemasculine behaviour following castra-

tion.3,26 It is likely that this is psycholog-ical in origin and re p resents normalsocial interaction between horses. Wherethis behaviour is excessive or the castra-tion history is obscure, hormonal testing(see monorchidism) can be used toestablish whether testicular tissue ispresent.

References1. Schumacher J. Complications of castration.Equine Vet Educ 1996;8:254-259.2. Trotter GW. Castration. In: McKinnon AO, VossJL, editors. Equine reproduction. Lea and Febiger,Philadelphia, 1993:907-914.3. Wilson JF, Quist CF. Professional liability inequine surgery. In: Auer JA, editor. E q u i n e

surgery. Saunders, Philadelphia, 1992:13-35.4. Smith JA. The development and descent of thetestis in the horse. Vet Ann 1975;15:156-161.5. Schumacher J. Surgical disorders of the testicleand associated structures. In: Auer JA, editor.Equine surgery . Saunders, Philadelphia,1992:674-703.6. Geiser DR. Chemical restraint and analgesia inthe horse. Vet Clin North Am Equine Pract

1990;6:495-512.7. Palmer SE. Castration of the horse usingprimary closure technique. Proc Am Assoc Equine

Pract 1984;30:17-20.8. Barber SM. Castration of horses with primaryclosure and scrotal ablation. Vet Surg 1 9 8 5 ; 1 4 : 2 -6.9. Cox JE, Edwards GB, Neal PA. An analysis of500 cases of equine cryptorchidism. Equine Vet J

1979;11:113-116.10. Stickle RL, Fessler JF. Retrospective study of350 cases of equine cryptorchidism. J Am Vet Med

Assoc 1978;172:343-346.11. Cox JE. Cryptorchid castration. In: McKinnonAO, Voss JL, editors. Equine reproduction. L e aand Febiger, Philadelphia, 1993;915-920.

12. Davis E. Laparoscopic cryptorchidectomy instanding horses. Vet Surg 1997;26:326-331.13. Hendrickson DA, Wilson DG. Laparoscopiccryptorchid castration in standing horses. Vet Surg

1997;26:335-339.14. Valdez H, Taylor TS, McLaughlin SA, MartinMT. Abdominal cryptorchidectomy in the horseusing inguinal extension of the gubernaculumtestis. J Am Vet Med Assoc 1979;174:1110-1112.15. Wilson DG, Reinerston EL. A modified parain-guinal approach for cryptorchidectomy in horses:an evaluation in 107 horses. Vet Surg 1987;16:1-4.16. Cox JE, Edwards GB, Neal PA. Supra-pubicparamedian laparotomy for abdominal cryp-torchidism in the horse. Vet Rec 1975;97:428-432.17. Swift PN. Castration of a stallion with bilateralabdominal cryptorchidism by flank laparotomy.Aust Vet J 1972;48:472-473.18. Arighi M, Bosu WTK. Comparison of hormonalmethods for diagnosis of cryptorchidism in horses.J Equine Vet Sci 1989;9:20-26.19. Strong M, Dart AJ, Malikides N, Hodgson DR.Monorchidism in two horses. Aust Vet J

1997;75:33-35.20. Hunt RJ. Management of complications asso-ciated with equine castration. Compend Contin

Educ Pract Vet 1991;13:1835-1873.21. Hunt RJ, Boles Cl. Postcastration eventrationin horses: eight cases. Can Vet J 1 9 8 9 : 3 0 : 9 6 1 -963.22. van der Velden MA, Rutgers LJE. Visceralprolapse after castration in the horse: a review of18 cases. Equine Vet J 1990;22:9-12.23. Schumacher DJC, Schumacher J, Spano JS etal. Effects of castration on peritoneal fluidconstituents in the horse. J Vet Intern Med

1988;2:22-25.24. Smith JA. Masculine behaviour in geldings. Vet

Rec 1974:94:160-161.25. Line SW, Hart BL, Sanders L. Effect of prepu-bertal versus postpubertal castration on sexualand aggressive behaviour in male horses. J Am

Vet Med Assoc 1985;186:249-251. (Accepted for publication 21 December 1998)

Erysipelas in malleefowl

DJ BLYDE and R WOODSWestern Plains Zoo, PO Box 831 Dubbo, New South Wales 2830

The malleefowl (Leipoa ocellata) isa gro u n d - d welling Au s t r a l i a nn a t i ve bird originally found in a

range of habitats. It belongs to themound-building family of birds, theMegapodiidae, which are confinedalmost entirely to the Australian region.Members of this family va ry greatly incolour and form. However, they all havein common the fact that they do notbuild a nest and brood their eggs, butb u ry them in the ground, or in a

mound, or in heaps of fermentingvegetable material built up for thispurpose (Fi g u re 1). The incubationp rocess utilises external sources of heatsuch as decomposing vegetation or inci-dent solar radiation. The adults keep theeggs at a constant temperature byconstantly remodeling the mound,adding or removing dirt and leaves. Theeggs hatch in the mound and the chicksa re left to look after themselve s .1

Numbers of malleefowl have declined

a p p reciably since Eu ropean settlement.2

Factors influencing this decline includeland clearance for cropping andpastoralism, predation by the Eu ro p e a nf ox ( Vulpes vulpes), changes in firef re q u e n c y, grazing of malleefow lcommunities by domestic stock, and thep resence of introduced mammalianpests, particularly goats ( Ca p ra hirc u s )and rabbits ( Oryctolagus cuniculus).3 Nore p o rts of disease as a factor in thedecline of the malleefowl are ava i l a b l e