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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Protracted extension of the penis in a flaccid state
  • Penile paralysis may result from a compromise of sacral nerves or a direct insult to the retractor penis muscle, leading to the inability to retract the penis into the prepuce

Signalment!!navigator!!

Stallions (predominantly) or geldings of any age.

Signs!!navigator!!

N/A

Causes and Risk Factors!!navigator!!

  • Trauma—direct penile trauma, spinal cord injury, or disease
  • Infectious disease—EHV-1, rabies, EIA, purpura haemorrhagica, dourine (Trypanosoma equiperdum)
  • Drug-induced—propiopromazine, acepromazine maleate, reserpine
  • Chronic paraphimosis or priapism
  • Exhaustion or starvation
  • Spinal cord lesion

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Differentiating Similar Signs

  • Paraphimosis results in prolapse of the penis and prepuce; dependent edema develops. The inability to retract the penis is generally due to the accumulated edema rather than true penile paralysis
  • Penile paralysis can be a sequela to chronic, severe paraphimosis. Longstanding penile paralysis can present as paraphimosis due to the formation of extensive dependent edema
  • Priapism, a persistent erection with engorgement of the corpus cavernosum penis, should not be confused with penile paralysis in which the penis is flaccid

Differentiating Causes

  • The presence of neurologic deficits other than the penile paralysis may link the penile problem with infectious causes and/or spinal cord injury as the primary problem
  • A recent history of respiratory disease (affected horse or on its farm) may implicate EHV-1 as a possible cause

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

EHV-1

  • Rising antibody titers from paired sera, collected at a 14–21 day intervals
  • PCR testing or virus isolation from nasopharyngeal swabs and blood in the acute stage of the disease

EIA

Agar gel immunodiffusion (Coggins) test.

Dourine

  • Identification of the causative agent in preputial or urethral exudates; serologic testing by complement fixation test
  • Note that dourine has been eradicated from North America and some areas of Europe

Imaging!!navigator!!

N/A

Other Diagnostic Procedures!!navigator!!

N/A

Pathologic Findings!!navigator!!

N/A

Treatment ⬆ ⬇

TREATMENT

  • Replace the penis in the prepuce as soon as possible to prevent accumulation of dependent edema, drying of exposed surfaces, and traumatic injury. If replacement is impossible due to swelling, slings can be used to support the penis against the ventral abdominal wall
  • Lubricate the exposed mucosal surfaces with an emollient or antimicrobial ointment
  • In cases of chronic, nonresponsive penile paralysis, surgical intervention, including penile amputation or penile retraction (Bolz technique), should be considered. Castration generally precedes these surgical techniques

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Anti-inflammatory medication (phenylbutazone 2–4 g/450 kg body weight/day PO) may be useful for patient comfort and to decrease inflammation.

Contraindications/Possible Interactions!!navigator!!

Phenothiazine tranquilizers should be avoided.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Initial management is intensive
  • Frequent evaluation is of paramount importance
  • Return of the ability to maintain the penis in the prepuce is a good prognostic indicator

Prevention/Avoidance!!navigator!!

N/A

Possible Complications!!navigator!!

  • Libido is often maintained, but if erection is impossible live cover will not be possible without human intervention and assistance
  • Some affected stallions can be trained to ejaculate into an artificial vagina
  • Ejaculation can be obtained by manual stimulation (i.e. application of hot compresses to the gland and base of the penis) and/or administration of tricyclic antidepressant
  • Possible secondary complications of paralysis:
    • Paraphimosis due to the accumulation of dependent edema
    • Frostbite due to exposure
    • Surface excoriations—ulcers, secondary bacterial contamination, necrosis

Expected Course and Prognosis!!navigator!!

N/A

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

  • Paraphimosis
  • Balanoposthitis

Age-Related Factors!!navigator!!

N/A

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Synonyms!!navigator!!

N/A

Abbreviations!!navigator!!

  • EHV = equine herpesvirus
  • EIA = equine infectious anemia
  • PCR = polymerase chain reaction

Suggested Reading ⬆ ⬇

McDonnell SM, Turner RM, Love CC, LeBlanc MM. How to manage the stallion with a paralyzed penis for return to natural service or artificial insemination. Proc Am Assoc Equine Pract 2003;49:291–292.

Memon MA, Usenik EA, Varner DD, Meyers PJ. Penile paralysis and paraphimosis associated with reserpine administration in a stallion. Theriogenology1988;30:411–419.

Vaughan JT. Surgery of the penis and prepuce. In: Walker DF, Vaughan JT, eds. Bovine and Equine Urogenital Surgery. Philadelphia, PA: Lea & Febiger, 1980:125–144.

Author(s) ⬆

Author: Ahmed Tibary

Consulting Editor: Carla L. Carleton

Acknowledgment: The author and editor acknowledge the prior contribution of Carole C. Miller.