Page 1024 - Small Animal Internal Medicine, 6th Edition

996 PART VIII Reproductive System Disorders

True priapism (ischemic or nonischemic) can be associ-
ated with vascular disorders (efferent or afferent) or neu-
VetBooks.ir ropathy, or it can be idiopathic. A dysregulatory hypothesis
for the pathophysiology of priapism has been postulated.
Dysnergic neurostimulations of inflow and outflow penile
blood vessels cause prolonged vascular or smooth muscle
spasms. This dysregulation may occur at the level of the
penis or at other regulatory levels of penile erection, includ-
ing the central (spinal cord L1-4, S1-3) or peripheral nervous
system (Lavely, 2009).
Distinguishing ischemic (proceeds to gangrene) versus
nonischemic priapism and identifying and treating the
underlying cause is important. If determined to be ischemic,
prompt aspiration of the corpora cavernosa under sedation
or anesthesia with or without irrigation should be done.
Intracavernosal injections of phenylephrine should be con-
sidered. However, this may carry some risk as appropriate
dosages in dogs and cats have not been determined. Starting
with low dosages (1-3 mcg/kg) and cardiovascular monitor-
ing, therefore, is important. Providing lubrication is impor- FIG 56.16
tant to limit tissue damage secondary to exposure and Feline priapism in a tom cat overdosed with ace promazine.
excoriation. An Elizabethan collar may be indicated. If intra-
cavernosal drainage and injections are not successful or sig-
nificant tissue damage has occurred, then penile amputation
and perineal urethrostomy may become necessary.
Nonischemic priapism can resolve spontaneously. Thus
conservative therapy, protecting penile integrity with lubri-
cation, and an Elizabethan collar are recommended. Several
systemic medications are of potential benefit, although very
little controlled data exists regarding efficacy of systemic
drug therapy. Gabapentin, terbutaline, or pseudoephedrine
should be tried. If detumescence is not achieved after several
days of treatment with one drug, switching to another may
be successful.
Ischemic priapism has been reported in cats; penile
amputation and perineal urethrostomy may be indicated. A
traumatic cause should be considered in cats if they have a
recent history of mating; it has also been reported after FIG 56.17
Ultrasound image of normal canine testes, sagittal view.
orchiectomy. Surgical treatment making several small inci-
sions bilaterally in the tunica albuginea of the corpora cav-
ernosa penis and in some parts of the corpora cavernosa clinical signs similar to phimosis, and is treated by clipping
followed by irrigation with heparinized saline has been the preputial hairs.
reported to have some success. Skin sutures were then placed
closing the approach, but the tunica albuginea was not TESTICULAR NEOPLASIA IN STUD DOGS
closed. Nonischemic feline priapism can respond to medical
management as in the dog (Fig. 56.16). Unless the dog is a valuable and still fertile stud, the discov-
Phimosis is a condition in which the penis is trapped ery of a testicular mass warrants castration. If the dog is still
within the preputial cavity. It usually occurs as a congenital breeding and the tumor is limited to one testis, unilateral
defect in which the preputial opening is abnormally small castration can be performed. Testicular neoplasia is rare in
and the penis cannot protrude. Phimosis is uncommon in the tom cat. Risk factors for testicular neoplasia in the dog
cats and dogs. It may be recognized in young animals as a are age (>10 years) and cryptorchidism. The early diagnosis
cause of a urinary outflow tract obstruction or of the drib- of testicular neoplasia is often incidental and based on careful
bling of urine that has accumulated in the preputial cavity. palpation of the scrotal testes. Ultrasound can detect testicu-
Phimosis may be recognized in an affected postpubertal lar masses too small for manual detection and is therefore
male unable to copulate. It is treated by conservatively surgi- indicated annually in valuable breeding dogs. The normal
cally enlarging the preputial orifice. The preputial hairs of testis is uniform in texture with echogenicity similar to the
longhaired cats may entangle the preputial orifice, causing spleen (Fig. 56.17). The mediastinum testis is a thin, centrally