1. health and fitness
2. disease

EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2005) 17 (6) 299-304
299
Case Report
Chemical ejaculation and cryopreservation of semen from a
breeding stallion with paraphimosis secondary to priapism
and haemorrhagic colitis
D. J. FEARY*, P. D. MOFFETT, J. E. BRUEMMER, L. SOUTHWOOD, P. MCCUE,
K. D. NISWENDER, C. DICKINSON AND J. TRAUB-DARGATZ
Veterinary Teaching Hospital, Colorado State University, 300 W Drake Road, Fort Collins, Colorado 80523, USA.
Keywords: horse; stallion; priapism; paraphimosis; chemical ejaculation; colitis
Introduction
Erectile dysfunction can occur in association with anaesthesia,
castration, administration of phenothiazine-derivative drugs,
traumatic injury, debilitation and priapism. This phenomenon
has been documented in dogs (Guilford et al. 1990; RootKustritz 1999), cats (Gunn-Moore et al. 1995), man and
horses (Pearson and Weaver 1978; Lucke and Sansom 1979;
Gerring 1981; Schumacher and Hardin 1987; Schumacher
and Varner 1988; Blanchard et al. 1991; Van Harreveld and
Gaughan 1999; Rochat 2001) and can have devastating
economic repercussions in sexually active individuals. The
20-year-old breeding stallion in this report developed
priapism in the acute stages of treatment for severe systemic
illness due to haemorrhagic colitis. Treatment with surgical
lavage of the corpus cavernosum penis (CCP) resulted in
resolution of priapism. However, paraphimosis developed
secondarily with subsequent loss of erectile function and
sensitivity of the glans and shaft of the penis. Following
recovery from systemic disease, successful collection and
cryopreservation of semen from the stallion was achieved by
chemical ejaculation. Four of 7 inseminated mares were
confirmed to be pregnant. To our knowledge, this is the
first report of successful pregnancies using frozen
semen obtained by chemical ejaculation.
Case details
History
A 20-year-old 500 kg Quarter Horse stallion was admitted to the
Colorado State University Veterinary Teaching Hospital (CSUVTH) with a history of an acute episode of severe colic and
*Author to whom correspondence should be addressed. Present
address: Veterinary Medical Teaching Hospital, University of California,
One Shields Avenue, Davis, California 95616-8747, USA.
profuse haemorrhagic diarrhoea. The horse was examined for
2 episodes of mild colic within 3 days prior to hospitalisation,
both of which were responsive to medical treatment.
Prior to referral, the horse was reportedly recumbent with
signs of severe abdominal pain, heart rate 120 beats/min,
rectal temperature 40ºC (104ºF), respiratory rate
30 breaths/min, injected dark purple mucous membranes,
capillary refill time 4 secs, complete absence of gastrointestinal
sounds and dark reddish/black watery faeces. The stallion was
given i.v. flunixin meglumine (1.1 mg/kg bwt), ampicillin
(0.01 g/kg bwt), gentamicin (6.6 mg/kg bwt), dexamethasone
(1.0 mg/kg bwt) and 3 litres 7% hypertonic saline followed by
15 l isotonic saline.
Clinical examination
On initial examination, the stallion exhibited obtunded
mentation and weakness. Physical examination findings
included heart rate 76 beats/min, rectal temperature 37ºC
(98.6ºF), respiratory rate 24 beats/min, purple mucous
membranes, capillary refill time 3 secs and complete absence of
gastrointestinal sounds upon abdominal auscultation.
Extremities were cold and digital pulses were not palpable.
Examination per rectum revealed a fluid-filled large colon and
a diffuse oedematous large intestinal wall. Faecal contents in
the rectum were dark red, malodorous and of liquid
consistency. Percutaneous abdominal ultrasonography revealed
a thickened large intestinal wall and a moderately increased
volume of anechoic peritoneal fluid. Abdominocentesis yielded
75 ml clear serosanguineous peritoneal fluid. The stallion was
exhibiting pollakuria during the examination. The penis and
prepuce appeared normal.
Laboratory findings
Pertinent findings on haematology included an elevated packed
cell volume of 67%, hypoproteinaemia (46 g/l), neutropenia
300
Fig 1: Persistent erection of the penis unassociated with sexual
arousal (priapism) was evident in the stallion 16 h after initiation
of intensive medical management for haemorrhagic colitis.
(2.7 x 109/l mature neutrophils) with a degenerative left shift
(3.8 x 109/l band neutrophils), 0.1 x 109/l nucleated red blood
cells and thrombocytopenia (80 x 109/l). Slightly toxic neutrophils
were noted on a blood smear. Serum biochemical abnormalities
included azotaemia (creatinine 0.058 g/l, blood urea nitrogen
0.36 g/l), hypoalbuminaemia (17 g/l), hypoglobulinaemia (22 g/l)
and marked elevations in creatine kinase (108,780 iu/l) and AST
(4374 iu/l). Serum electrolyte abnormalities included
hypernatraemia (141 mmol/l), hyperchloraemia (108 mmol/l),
hyperkalaemia (5.9 mmol/l), hypocalcaemia (0.084 g/l) and
hypocarbia (14.3 mmol/l) with an anion gap of 24. Results of a
faecal sample submitted on the day of admission for aerobic and
anaerobic culture yielded a moderate growth of haemolytic
E. coli. No Salmonella sp. or Clostridia sp. were isolated from
sequential daily faecal samples. Analysis of initial voided urine
revealed gross pigmenturia and isosthenuria, pH 5.0, glucosuria,
2+ proteinuria and 4+ blood. Urine sediment cytopathology
revealed increased numbers of squamous and transitional
epithelial cells, hyaline casts and granular casts. Peritoneal fluid
analysis was consistent with a transudate with protein level 52 g/l
and nucleated cell count <0.5 x 106 cells/l.
Chemical ejaculation and cryopreservation of semen
Fig 2: The engorged penis was supported against the ventral
body wall with a stocking sling.
of vitamin E was administered. The horse was housed in a
large animal isolation facility with optimal hygiene to prevent
spread of potential enteropathogens to other patients.
Ongoing treatment included i.v. isotonic polyionic fluids
supplemented with calcium gluconate at a rate of 4 l/h,
bolus administration of 1.5 x 106 u polymixin B and 500 g
DMSO at 12 h intervals, continued antibiotic and analgesic
treatment, daily antidiarrhoeal agent administration via
nasogastric intubation as above and oral omeprazole
(4 mg/kg bwt). Two litres of equine plasma were
administered on the second day of hospitalisation. Daily
vitamin E treatment was continued with 10,000 u
administered per os throughout the treatment period.
During the first 12 h of hospitalisation, the stallion
continued to produce voluminous, malodorous, dark red liquid
faeces and exhibited persistent signs of mild to moderate
abdominal pain, diffuse muscle fasciculations and anorexia.
Small amounts of isosthenuric urine were passed frequently.
Sixteen hours following hospitalisation, the stallion developed
priapism (Fig 1).
Priapism: medical treatment
Treatment
Initial treatment included nasal oxygen insufflation, i.v.
administration of a polyionic, isotonic fluid as a 50 litre bolus,
1.5 x 106 u polymixin B in 1 litre isotonic fluid, 500 g
dimethylsulphoxide as a 10% solution and 4 litre equine
plasma. Antimicrobial treatment was instituted and included
i.v. potassium penicillin (44.000 iu/kg bwt), enrofloxacin
(7.5 mg/kg bwt) and oral metronidazole (15 mg/kg bwt).
Analgesia was provided with a combination of i.v. flunixin
meglumine (0.5 mg/kg bwt) and butorphanol (0.02 mg/kg
bwt) at 6 h intervals. Laminitis prophylaxis included topical
nitroglycerine patches, removal of shoes and thick foam pads
applied to the soles of the front feet. Oral antidiarrhoeal
agents included 0.5 kg biosponge, 120 g brewer’s yeast,
2 litres bismuth subsalycilate, 120 g psyllium powder and 30 g
probiotic (Probios)1 via nasogastric tube. A single i.m. injection
Penile massage and lubrication were performed initially 4 h
after development of priapism in conjunction with regular ice
water baths and application of a sling to provide penile
support and prevent dependent oedema (Fig 2). These
conservative methods were unsuccessful. At 8 h following
development of priapism, a single i.v. infusion of 8 mg
benztropine mesylate (Cogentin)2 diluted in 1 litre 0.9% sterile
saline was administered. Heart rate, respiratory rate and
mental state were monitored and no abnormalities detected.
There was no change in the penis and prepuce observed over
the following 4 h.
The stallion exhibited pollakuria and inability to void the
bladder completely. Catheterisation of the bladder yielded 7 litres
grossly normal urine. The penis remained engorged; therefore,
surgical treatment was initiated in an attempt to achieve
detumescence and preserve breeding ability of the stallion.
D. J. Feary et al.
Fig 3: Irrigation of coagulated blood from the corpus
cavernosum penis via surgical lavage.
301
Fig 4: Post operative care following surgical lavage; application
of a support sling.
Priapism: surgical treatment
Sixteen hours following development of priapism,
detumescence was achieved by irrigation of the CCP under
general anaesthesia. Briefly, the stallion was sedated with
xylazine HCl (200 mg i.v.) followed by anaesthetic induction
with ketamine HCl (1000 mg i.v. bolus) and diazepam
(700 mg i.v. bolus). Anaesthesia was maintained for 30 mins
with an i.v. infusion of 10% glyceryl guaiacolate (500 ml) and
intermittent, as needed, doses of i.v. ketamine (200, 500 and
300 mg, respectively). The horse was placed in left lateral
recumbency with the right hindlimb held in abduction to
facilitate access to the scrotum and penis. The penis, prepuce
and scrotum were prepared routinely and draped. One litre
heparinised 0.9% NaCl solution (10,000 u heparin/l) was
infused through a 14 gauge needle inserted into the engorged
CCP approximately 6 cm proximal to the glans penis. A second
14 gauge needle was inserted simultaneously into the CCP
approximately 16 cm caudal to the scrotum (Fig 3). Irrigation
of coagulated blood from distal to proximal CCP resulted in
immediate detumescence and the flaccid penis was able to be
placed within the external preputial lamina and retained with
umbilical tape in a purse-string pattern. The horse recovered
from anaesthesia and an indwelling urinary catheter was
placed and secured to the ventral body wall.
Post operative care included regular application of DMSO
ointment and hot packing to reduce inflammation and
oedema (Fig 4). The urinary bladder was lavaged with 1 litre
10% DMSO solution made up in warm sterile isotonic fluid
every 12 h for 2 days and the indwelling urinary catheter was
removed. The horse was placed on bethanecol (0.05 µg/kg
bwt) per os q. 6 h for 3 days. Urination returned to normal
following resolution of priapism.
At 72 h post surgery, the penis was examined and found
to be erythematous, chaffed and flaccid throughout its length.
Initially, only the proximal third of the penis was able to be
retracted into the prepuce and the distal two-thirds remained
flaccid (Fig 5). Application of focal stimuli with haemostats at
the skin of the glans penis did not elicit a response from the
Fig 5: Examination of the penis 72 h post surgery revealed
paraphimosis and lack of skin sensation to the distal penis.
horse. A diagnosis of paraphimosis was made. The penis was
cleaned and dried and a combination of Desitin3 and DMSO
ointment was applied at regular intervals. The penis was
replaced back into the preputial orifice for decreasing periods
over 3 days. The penis developed moderate oedema localised
to the preputial reflection. The purse-string suture was
removed due to evidence of suture site infection, pain and
swelling of the prepuce. The penis was supported against the
ventral body wall with a sling and topical treatment continued.
Response to treatment was minimal.
Over the 11 days of treatment, regular hydrotherapy and
topical anti-inflammatory medications were applied to the
penis and prepuce. Paraphimosis persisted in this stallion
despite gradual resolution of diarrhoea and other medical
issues and ongoing conservative treatment of the penis and
prepuce. While the stallion regained the ability to retract all
but the distal 7.5 cm (3 inches) of the penis into the prepuce,
there was concern that paraphimosis and lack of sensation of
the distal tip of the penis would prevent complete erection.
Additional problems that the stallion developed included
laminitis, persistent hypoproteinaemia and right forelimb
302
Fig 6: Collection of semen from the stallion following
administration of oral imipramine and i.v. xylazine 2 months
after recovery from systemic illness.
swelling and oedema. Bilateral distal phalangeal radiographs
revealed mild palmar rotation of the third phalanx in relation
to the hoof capsule of both the left and right forelimbs. Bone
resorption and production of the third phalanx indicated
chronic laminitis of both forelimbs. Treatment involved
continued application of foam foot pads and parenteral
phenylbutazone treatment (1 g i.v. b.i.d.).
Marked improvements in sequential haematology and
biochemistry, urine analysis and abdominocentesis reflected
the stallion’s gradual improvement in systemic state and
parallelled improvement in mental attitude, faecal consistency,
appetite and overall response to medical management. Faecal
culture results yielded a moderate growth of haemolytic
E. coli. No Salmonella sp. or Clostridia sp. were isolated in
several sequential faecal samples.
Reproductive management
Sixty days after discharge from the hospital, the stallion was
presented to the Equine Reproduction Laboratory at Colorado
State University for reproductive evaluation. The horse
exhibited excellent libido but never achieved a full erection and
had no sensation on the glands and distal body of the penis.
Consequently, it was determined that collection could not be
effected using conventional techniques. The owners elected to
pursue chemical ejaculation (or ex copula ejaculation) as a
technique to obtain semen. A protocol using oral imipramine
hydrochloride4 followed by i.v. administration of xylazine was
used as a guide (McDonnell 2001). Imipramine HCl is a tricyclic
antidepressant used for the relief of depression in human
adults and as a temporary adjunctive treatment in reducing
enuresis in children. It has been reported to lower the
ejaculation threshold in stallions (McDonnell 1999).
Three mg/kg bwt of imipramine HCl tablets were crushed,
mixed with molasses and given per os. One hour later,
250 mg xylazine was given i.v. Xylazine is an α2 agonist
shown to have a side effect of emission of semen in horses
Chemical ejaculation and cryopreservation of semen
(England and Clarke 1996). The stallion ejaculated a small
volume of semen (10 ml) 1.5 mins after xylazine
administration. All attempts at chemical ejaculation and
semen collection occurred in a stall, without sexual
stimulation (Fig 6). Low-volume high-concentration semen
samples are common with chemical ejaculation, presumably
as a result of the effect of imipramine in reducing accessory
sex gland contraction and enhancing ampulla contraction
(McDonnell 2001). The next 2 attempts at ex copula
ejaculation were unsuccessful; therefore, the time between
imipramine and xylazine administration was extended to
1.5 h and the xylazine dose was reduced to 150 mg. The
stallion subsequently ejaculated 13 mins after xylazine
administration. The volume collected was 24 ml and the
concentration was 84 x 106 spermatozoa/ml. The total and
progressively motile sperm were determined to be 60 and
40%, respectively. The semen was extended with a
commercial skim-milk glucose extender (E-Z Mixin-OF)5 and
2 x 109 progressively motile sperm were inseminated into a mare
in oestrus that had recently ovulated. The mare was confirmed
to be pregnant by ultrasonography 14 days after insemination.
The chemical ejaculation protocol was subsequently
modified to 125 mg xylazine and extending the time between
drug administration to 2 h. The dose of imipramine remained
constant at 3 mg/kg bwt. A total of 5 ejaculates were
collected from 15 attempts (33% success rate) over a period
of 39 days. Each ejaculate was frozen at a concentration of
400 x 106 sperm/ml in 0.5 ml straws using lactose-EDTA
freezing extender (Squires et al. 1999). Six additional mares
were bred using frozen-thawed semen and 3 became
pregnant. A total of 4 of the 7 mares (57.1%) bred using
semen collected by chemical ejaculation became pregnant.
Discussion
Priapism is defined as a persistent erection of the penis
unassociated with sexual arousal (Root-Kustritz 1999). The
penis affected by priapism cannot be retracted into the
prepuce (Rochat 2001) and causes discomfort and difficulty in
urination (Root-Krustritz 1999). Priapism occurs uncommonly
in the horse, has a higher incidence of occurrence in stallions
than in geldings, and may result in impotence in breeding
animals (Pearson and Weaver 1978; Schumacher and Hardin
1987; Blanchard et al. 1991; Rochat 2001).
Priapism is a failure of detumescence. Penile erection
results when parasympathetic stimulation from the sacral
spinal cord actively increases arterial blood flow to the corpus
cavernosum and corpus spongiosum and reduces penile
venous drainage (Schumacher and Varner 1988; Root-Kustritz
1999; Rochat 2001). Detumescence typically occurs when
sympathetic stimulation results in diminished arteriolar blood
flow and relaxation of penile smooth muscle (Schumacher and
Varner 1988; Root-Kustritz 1999; Rochat 2001). Priapism
results when sympathetic stimulation necessary for
detumescence fails (Schumacher and Varner 1988); in contrast
to normal erection, it results from a selective engorgement of
the CCP (Rochat 2001).
D. J. Feary et al.
Regardless of the primary cause, vascular stasis and
increased carbon dioxide tension of the stagnant blood within
the corpus cavernosum increase blood viscosity resulting in
venous occlusion of draining veins. Oedema of corporeal
trabecular tissue may contribute to venous occlusion with
eventual irreversible fibrosis and disruption of arteriovenous
flow. Impotence and ischaemic necrosis of the penis may
ensue (Schumacher and Hardin 1987; Schumacher and Varner
1988; Root-Kustritz 1999; Rochat 2001).
Numerous causes for the development of priapism
reported in the veterinary literature include administration of
phenothiazine derivatives such as acepromazine (Pearson and
Weaver 1978; Lucke and Sansom 1979; Gerring 1981;
Schumacher and Hardin 1987), general anaesthesia (Pearson
and Weaver 1978), inflammatory spinal cord lesions, traumatic
injury (e.g. castration), purpura haemorrhagica, debilitation
and severe constitutional distress. In horses, priapism is most
often associated with administration of phenothiazine
tranquillisers (Pearson and Weaver 1978; Lucke and Sansom
1979; Gerring 1981; Schumacher and Hardin 1987;
Schumacher and Varner 1988), although no such drug was
given to the horse in this report.
Priapism other than that associated with administration of
phenothiazine tranquillisers is reported to be uncommon in
horses (Blanchard et al. 1991). A definitive cause for the
development of priapism of the stallion in this report was not
determined. A possible explanation may be an association
with the severe systemic illness. Severe constitutional distress,
exhaustion and debility have all been associated with penile
abnormalities in horses (Simmons et al. 1985; Love et al.
1992). The effects of endotoxaemia on vasodilation, vascular
permeability and coagulation may have contributed to failure
of detumescence, as could the effect of inflammatory
mediators and other aspects of endotoxaemia that were an
integral part of the stallion’s disease process.
Recognition and diagnosis of priapism in a timely manner is
imperative, because treatment options become limited with
ischaemic necrosis of the penis. The importance of close
observation of the penis should be considered in the care of
male horses with systemic disease and those undergoing
routine sedation and/or general anaesthesia. Treatment options
include conservative treatment consisting of hydrotherapy,
massage, emollient dressings and slinging; and pharmacological
treatment such as systemic diuretics, corticosteroids and i.v.
administration of diphenhydramine, terbutaline and the
anticholinergic agent benztropine mesylate (Sharrock 1982;
Wilson et al. 1991). Conservative measures were not effective in
the treatment of priapism in the stallion in this report. Diuretics
were not administered due to the stallion’s apparent inability to
void the bladder and systemic status (haemoconcentration and
azotaemia). Corticosteroids were avoided because they had
been administered previously and because the stallion was
profoundly neutropenic and at risk of development of laminitis.
Benztropine mesylate is an anticholinergic/antihistaminic
drug used for the symptomatic treatment of Parkinson’s
disease in man (Wilson et al. 1991). The drug is believed to
have central acetylcholine antagonising effects and has been
303
reported to be successful in the immediate resolution of
priapism in 3 horses following anaesthesia (Sharrock 1982;
Wilson et al. 1991) when given within 6 h of development,
but was unsuccessful in the treatment of a stallion when
administered 4 days after the onset of priapism (Schumacher
and Hardin 1987). A single i.v. dose of benztropine mesylate
administered to the stallion in this report 8 h after onset of
priapism was ineffective. The lack of response to the drug
may have been due to the prolonged period before
administration with subsequent clotting of blood within the
cavernous spaces preventing venous drainage. Alternatively, a
cholinergic antagonist may not have been beneficial in this
stallion, as the cause of priapism was not secondary to
administration of phenothiazine derivatives or general
anaesthesia as in previously successful reports (Sharrock
1982; Wilson et al. 1991).
If detumescence cannot be achieved by medical treatment
within 12 h, surgical intervention should actively be pursued
(Blanchard et al. 1991; Rochat 2001) because histological
changes consistent with fibrosis probably develop early in the
disease process (Rochat 2001). A precise time from onset of
priapism to the beginning of irreversible pathological changes
in the penile erectile tissue has not been determined in horses
(Schumacher and Varner 1988). The procedure of choice for
initial management of priapism is lavage of the CCP (Rochat
2001). Flushing of coagulated blood and evidence of efflux of
fresh haemorrhage from the cavernous spaces suggests a
positive prognosis (Schumacher and Varner 1988; Rochat
2001). If arteriolar damage or persistent venous occlusion is
evident by failure to achieve detumescence after 3 irrigations,
a surgically created shunt between the CCP and the corpus
spongiosum penis has been reported to be successful
(Schumacher and Hardin 1987; Schumacher and Varner 1988;
Schumacher et al. 1999).
Detumescence was achieved rapidly in the stallion in the
present report with surgical lavage of the CCP. However,
paraphimosis progressing to paralysis and loss of sensation of
the distal third of the penis followed resolution of the
priapism, preventing erection and ejaculation as assessed
during breeding soundness evaluation 2 months later. A
suggested explanation for this may be excess gravitational pull
associated with prolonged priapism causing stretching and
damage to the dorsal pudendal nerves or compression of the
nerves against the ischium affecting motor and sensory
function of the penis as reported by Blanchard et al. (1991).
The prognosis for successful breeding of stallions with
penile dysfunction secondary to priapism or paraphimosis has
been poor in the past (Love et al. 1992). Successful return to
natural breeding was achieved in a Thoroughbred stallion with
severe loss of erectile function and penile sensitivity by
manually assisted ejaculation (Love et al. 1992). The stallion in
this report exhibited similar penile dysfunction and was
collected successfully by chemical ejaculation.
Chemical ejaculation has been used previously to collect
semen from healthy stallions (McDonnell and Love 1991;
McDonnell and Odian 1994; Johnston and DeLuca 1998), as
well as from a stallion with a fractured radius (Turner et al.
304
1995) and an old debilitated stallion (Card et al. 1997). Semen
collection success rate using the chemical ejaculation protocol
in this report was identical to the 33% reported by McDonnell
and Odian (1994) and slightly less than the 57% reported by
Johnston and DeLuca (1998). Pregnancy rate in our case
(57.1%) was between those reported by Card et al. (1997)
and Johnston and DeLuca (1998), who reported pregnancy
rates of 80 and 40%, respectively, after insemination of mares
with semen collected by chemical ejaculation. To our
knowledge, this is the first report of acceptable pregnancy
rates from the use of frozen semen following chemical
ejaculation of a stallion with an acquired penile abnormality.
In conclusion, semen was collected successfully by
chemical ejaculation from a stallion with paraphimosis
secondary to priapism. Pregnancies were subsequently
obtained in 4 of 7 mares following insemination with
both fresh and frozen semen from the affected stallion.
Although it is unlikely that this stallion will regain normal
reproductive function, chemical ejaculation and subsequent
cryopreservation of semen offers the possibility of maintaining
fertility and achieving future pregnancies.
Manufacturers’ addresses
1CHR
Hansen, Milwaukee, Wisconsin, USA.
Co. Inc., West Port, Pennsylvania, USA.
New York, New York, USA.
4Par Pharmaceutical Inc., Spring Valley, New York, USA.
5Animal Reproduction Systems, Chino, California, USA.
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3Pfizer,
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