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Basics ⬇

Outline

BASICS

Definition!!navigator!!

Inability to retract the penis into the preputial cavity, often due to extensive penile and preputial edema.

Pathophysiology!!navigator!!

  • Paraphimosis is often a complication of a primary traumatic injury, penile paralysis, or priapism
  • Penile prolapse occurs initially and is complicated by excessive swelling and edema
  • Vascular and lymphatic drainage are impeded, leading to further edema accumulation
  • Drainage is further restricted by the swelling of the internal preputial lamina and stricture at the level of the preputial ring
  • The exposed tissue may become excoriated and slough because of pressure necrosis
  • Chronic prolapse may lead to penile/preputial trauma, balanoposthitis, or penile paralysis (damage to the internal pudendal nerves)

Systems Affected!!navigator!!

  • Reproductive—prolapse of the penis and prepuce exposes them to trauma. Chronic paraphimosis may result in penile paralysis, fibrosis of the CCP, and an inability to achieve an erection
  • Urologic—urethral obstruction may be the inciting cause of paraphimosis, or it may occur secondary to edema

Signalment!!navigator!!

  • Predominantly stallions, but geldings can also be affected
  • No breed predilection
  • Unlikely to occur in the first month of life, when normal adhesions exist between the free penis and inner lamina of the preputial fold

Signs!!navigator!!

Historical Findings

  • Acute cases often present as traumatic injury to the penile or preputial area
  • Chronic cases—delay in presentation for veterinary care may occur if owners believed an injury was minor and attempted care themselves or the injury may only recently have become obvious because of its slow increase in size, e.g. a slow developing enlargement of the penis or preputial area such as is seen with Habronema spp. infections or neoplastic growths

Physical Examination Findings

  • Prolapse of the penis and prepuce with severe penile enlargement is readily apparent. Caudoventral displacement of the glans penis is common. A careful visual and digital examination is necessary to properly define the nature of the injury
  • Balanitis, posthitis, or balanoposthitis may be present. Serous or hemorrhagic discharges on the surface of the penis and prepuce are common. Lacerations, excoriations, ulcerative lesions, or neoplastic masses may be evident
  • Hematomas, when present, are generally located on the dorsal surface of the penis and usually arise from blood vessels superficial to the tunica albuginea
  • Transrectal palpation may reveal an enlarged urinary bladder indicative of urethral blockage
  • Chronic prolapse may result in penile paralysis

Causes!!navigator!!

Noninfectious Causes

  • Trauma—breeding injuries, fighting or kicks, improperly fitting stallion rings, falls, movement through brush or heavy ground cover, whips, or abuse
  • Priapism, penile paralysis, posthitis, or balanoposthitis
  • Postsurgical complication—castration or cryptorchid surgery
  • Neoplasia of the penis or prepuce—sarcoids, squamous cell carcinoma, melanoma, mastocytoma, hemangioma, or papillomas
  • Debilitation or starvation
  • Spinal injury or myelitis
  • Urolithiasis/urinary tract obstruction

Infectious Causes

  • Bacterial—Staphylococcus, Streptococcus
  • Viral—EHV-1, EHV-3, EIA, EVA
  • Purpura haemorrhagica—vasculitis as a sequela to infection or vaccine administration
  • Parasitic—Habronema muscae, Habronema microstoma, Draschia megastoma, Onchocerca spp., Cochliomyia hominivorax (screw worm)
  • Fungal—phycomycosis due to Hyphomyces destruens
  • Protozoal—Trypanosoma equiperdum (dourine)

Risk Factors!!navigator!!

  • Use of phenothiazine tranquilizers in stallions
  • Increased risk during transport
  • Open-range/pasture breeding, not in-hand, stud management
  • More aggressive stallions
  • Poor management, unsanitary conditions, or malnutrition

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • History, clinical signs, and examination of the lesions may help identify the underlying cause
  • Trauma—the presence of visible lacerations or hematomas, or a history of trauma, or surgical intervention
  • The presence of ulcerative or proliferative lesions warrants investigation to determine if the origin of the lesion is neoplastic, parasitic, or infectious
  • Systemic signs indicative of neurologic or systemic disease include ataxia, depression, lymph node enlargement, or increased rectal temperature

CBC/Biochemistry/Urinalysis!!navigator!!

  • Generally, there are no abnormal findings unless the causative factor is an infectious agent, neoplastic disease, or severe debilitation/starvation
  • Urinalysis may indicate urolithiasis/cystitis

Other Laboratory Tests!!navigator!!

  • Bacterial causes—culture (swab) of affected tissues
  • EHV-1—rising antibody titers (paired sera, collected at a 14–21 day interval); virus isolation from nasopharyngeal swabs and blood (buffy coat) during the acute stage
  • EHV-3—rising antibody titer (paired sera, collected at a 14–21 day interval); eosinophilic intranuclear inclusion bodies in cytologic smears; virus isolation from lesions during the acute stage
  • EIA—agar gel immunodiffusion (Coggins) test
  • EVA—rising antibody titer (paired sera collected at a 14–21 day interval); virus isolation from nasopharyngeal swabs
  • Protozoal—identification of the causative agent in urethral exudates; serology—complement fixation

Imaging!!navigator!!

Ultrasonography findings are generally unrewarding. In other species, fibrosis of the CCP has been visualized in chronic cases.

Other Diagnostic Procedures!!navigator!!

Cytology or biopsy of masses or lesions may provide a diagnosis in the case of parasitic, neoplastic, or fungal disease.

Treatment ⬆ ⬇

TREATMENT

  • The primary goals—reduce the inflammation and edema and return the penis to the prepuce to improve venous and lymphatic drainage. The initial management of the patient is intensive and may require hospitalization to allow adequate physical restraint and patient access
  • Ensure urethral patency—catheterize or perform a perineal urethrostomy, if necessary
  • Methods of manual reduction of the prolapse:
    • Elastic or pneumatic bandaging may reduce edema prior to attempting reduction
    • Preputiotomy if the preputial ring is preventing successful reduction
    • Purse-string suture of umbilical tape around the preputial orifice, tightened to a 1-finger opening, to hold the penis within the prepuce; has the additional benefit of maintaining pressure on the penis for sustained reduction of edema
    • Additional support can be gained by putting on a net sling, which covers the cranial aspect of the prepuce but allows urine to drain
  • In cases that are resistant to manual reduction, support remains of primary importance. Wrap the exposed penis and prepuce to reduce edema. Support in the form of a sling is essential. Nylon slings raise and maintain the penis close to the ventral belly wall. Using netting with small perforations allows urine to drain
  • Hydrotherapy—cold hydrotherapy for the first 4–7 days until edema and hemorrhage subside, then warm hydrotherapy. Generally applied for 15–30 min BID–QID
  • Massage the penis and prepuce BID–QID to reduce edema
  • Topical emollient ointment application—vitamin A and D ointment, lanolin, petroleum jelly, nitrofurazone
  • Exercise—confinement and limited activity until after active hemorrhage and edema subside, then slowly increase; aids in resolution of dependent edema
  • No sexual stimulation in the early stages of therapy. It may be necessary to prevent exposure to mares for up to 4–8 weeks
  • Local surgical resection, cryosurgery, or radiation therapy of neoplastic or granulomatous lesions, once the edema is resolved
  • Chronic refractory paraphimosis may require surgical intervention, including circumcision (reefing or posthioplasty), penile retraction (Bolz technique), or penile amputation (phallectomy)

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • NSAIDs, including phenylbutazone (2–4 g/450 kg/day PO) or flunixin meglumine (1 mg/kg/day IV, IM, or PO), for symptomatic relief and to reduce inflammation
  • Systemic or local antibiotics as indicated to treat local infection and prevent septicemia
  • Diuretics—furosemide (1 mg/kg IV daily or BID) if indicated in the acute phase for reduction of edema
  • Specific topical or systemic treatments for parasitic, fungal, or neoplastic conditions as indicated by results of diagnostic testing

Contraindications!!navigator!!

  • Tranquilizers, particularly the phenothiazine tranquilizers, should be avoided in males to avoid drug-induced priapism
  • Nitrofurazone should not be used on horses intended for food
  • Avoid sexual stimulation in the early stages and usually for 4–8 weeks after treatment for paraphimosis has begun

Precautions!!navigator!!

Diuretics are contraindicated if urinary obstruction is present. Their effectiveness in treating localized edema is in doubt.

Possible Interactions!!navigator!!

N/A

Alternative Drugs!!navigator!!

DMSO has been used topically (50:50 mixture by volume with nitrofurazone ointment) or systemically (1 g/kg IV as a 10% solution in saline BID–TID for 3–5 days) to reduce inflammation and edema. Note that the parenteral administration of DMSO is not approved and is considered extra-label use.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Initial management is intensive. Frequent evaluation is essential
  • Good prognostic indicators—reduction of edema, coupled with the horse's ability to retain penis in the prepuce

Possible Complications!!navigator!!

  • Excoriations/ulcerations or further trauma of exposed skin surfaces
  • Fibrosis of tissues, leading to the inability to achieve erection or to a urethral obstruction
  • Chronic paraphimosis
  • Continued hematoma enlargement indicates that a rent may be present in the tunica albuginea. The hematoma should be surgically explored
  • Penile paralysis
  • Frostbite due to exposure
  • Myiasis
  • Infertility

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

N/A

Age-Related Factors!!navigator!!

N/A

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Abbreviations!!navigator!!

  • CCP = corpus cavernosum penis
  • DMSO = dimethylsulfoxide
  • EHV-1 = equine herpesvirus 1, equine rhinopneumonitis
  • EHV-3 = equine herpesvirus 3, equine coital exanthema
  • EIA = equine infectious anemia, swamp fever
  • EVA = equine viral arteritis
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Arnold CE, Brinsko SP, Love CC, Varner DD. Use of a modified Vinsot technique for partial phallectomy in 11 standing horses. J Am Vet Med Assoc 2010;237:82–86.

Brinsko SP, Blanchard TL, Varner DD. How to treat paraphimosis. Proc Am Assoc Equine Pract 2007;53:580–582.

Clem MF, DeBowes RM. Paraphimosis in horses. Part I. Compend Contin Educ 1989;11:72–75.

Clem MF, DeBowes RM. Paraphimosis in horses. Part II. Compend Contin Educ 1989;11:184–187.

Gunn AJ, Brookes VJ, Hodder ADJ, et al. Balanoposthitis and paraphimosis in the stallion. A novel support for an inflamed penis and prepuce. Clin Theriogenol 2013;5:45–55.

Author(s) ⬆

Author: Ahmed Tibary

Consulting Editor: Carla L. Carleton

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