Clinical Case Challenge: Horse with Paraphimosis and Anemia

Thoroughbred gelding has rare reaction to sedative
A brown horse standing in the snow.
Justin, a 20 year-old Thoroughbred gelding stands outside. Photo: Chris Axten

Justin, a 20-year-old Thoroughbred gelding, presented to Cummings School of Veterinary Medicine’s Hospital for Large Animals (HLA) with an uncommon medical condition known as paraphimosis, the inability to retract and retain the penis within the prepuce. Complicating his care even further, Justin also suffered from severe anemia.


Before coming to HLA, Justin had undergone a procedure to treat secondary sinusitis associated with dental disease of several maxillary cheek teeth on the left side. Several teeth had been extracted, and one had fragmented, with an opening created between the sinus and the mouth (or sinus fistula). As can occur with some procedures addressing disease in the paranasal sinuses, Justin experienced a significant amount of bleeding.

While being treated with supportive care after this procedure and the postoperative bleeding, Justin was administered a dose of a commonly used injectable calming medication called acepromazine. While this medication is tolerated well in most patients, Justin began to exhibit a rare side effect that occurs in approximately 1 in 10,000 male horses administered this medication—paralysis of the penis, also known as paraphimosis.     

“Since he had no control of his penis and was persistently dropped due to gravity, it became swollen and painful,” says Dr. Thomas Jenei (he/his), HLA director and associate clinical professor in the Department of Clinical Sciences.

To support his paralyzed penis within the prepuce, Justin had been previously treated by placing a purse string to decrease the size of the preputial orifice after the paralyzed penis was manually replaced within it. As the skin through which the sutures were placed became irritated over time, a penile repulsion device (also known as a probang) was used and put in place at the time of referral. Although he had regained some ability to retract somewhat into the prepuce, he was unable to maintain his penis within the prepuce. 

Despite continued supportive care for several weeks, Justin’s paraphimosis and decreased red blood cell levels had not improved, and he was referred to Cummings School’s HLA for further evaluation and treatment. 

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Clinical examination:
On presentation to HLA, Justin appeared very lethargic, and he had an elevated heart rate of 60 beats per minute, well above the normal range of 28-40. His oral mucous membranes were pale, and his previous surgical sites overlying his left paranasal sinuses appeared to have some local inflammation and infection, with some nasal discharge also apparent from the left side.

Stall-side blood work revealed severe anemia. Justin’s red blood cell levels (packed cell volume, “PCV”) were markedly decreased at 15% (with normal being between 30-40%), and his blood protein levels (total solids, “TS”) were moderately decreased at 5.2 g/dL (normal being between 6.0 to 7.0 g/dL).

Justin’s lethargic demeanor and elevated heart rate indicated that his body was struggling due to his decreased red blood cell level. “Red blood cells carry oxygen to the rest of your tissues,” Dr. Jenei explains. “If your tissues aren’t getting enough oxygen, the body tries to compensate by making the heart work harder.”

Facing two issues, the HLA team—including Drs. Stephanie Arndt, Carl Kirker-Head, and Amanda Prisk—worked together to treat Justin. With these signs and his history, it was clear Justin would benefit from a blood transfusion.

Exploring options for blood transfusion:
Horses have eight major blood groups (A, C, D, K, P, Q, U, and T), and more than 30 type-specific blood factors (antigens) exist, with many possible red blood cell phenotypes. Some of the blood groups are more likely to cause a reaction, so before any transfusion, the donor and recipient blood should undergo a test called crossmatching—this is a way to see if there will be a reaction between the blood being donated and the recipient’s blood. Even in horses that are compatible on a crossmatch, vigilant monitoring occurs when horses are given a transfusion of any blood product (whole blood or plasma) to watch for a reaction to the blood, which can occur in up to 16% of whole blood transfusions. In an emergent situation, or when crossmatching is unavailable, a horse can receive a transfusion from an unrelated donor. 

HLA has a herd of healthy horses that help teach veterinary students and act as blood donors. Justin was crossmatched against all of these horses and, unfortunately, found incompatible with all of the available donors at Cummings School and additional healthy donors from a nearby farm, so he could not have a blood transfusion. 

“We were unable to address the anemia directly,” Dr. Jenei explains, “but it also meant that we were unable to safely undertake other potentially more advanced procedures for management of the sinusitis or paraphimosis because of his anemia.”

Supportive care:
HLA clinicians now faced the challenge of supporting Justin while his bone marrow began to create new red blood cells and bring his PCV to a more normal level. He was administered intravenous fluids, an oral iron supplement, an oral Vitamin E supplement, and, as Justin had evidence of inflammation and infection at his previous surgical sites, antibiotics based upon aerobic and anaerobic culture and sensitivity. Additionally, for several days after admission, his sinuses were flushed with a hypertonic solution with dilute betadine. A penile repulsion device was used to retain Justin’s paralyzed penis within the prepuce, with once-daily release to allow for cleaning and evaluation of his function.

Fortunately, this treatment path aligned well with supportive care and monitoring of his paraphimosis, as some horses can regain function over time. Nearly three weeks after being admitted to HLA, Justin’s body had regenerated enough red blood cells to allow him to be a candidate for more advanced interventions, both for treating his paraphimosis and evaluating his sinuses and teeth.

Justin was placed under general anesthesia and, using a combination of endoscopic examination of the sinuses (sinoscopy) and advanced diagnostic imaging (computed tomography, “CT”) of his skull were performed to evaluate in as much detail as possible. These examinations revealed that Justin’s sinuses and oral cavity were healing well and required no additional intervention.

Partial phallectomy:
Despite weeks of supportive care, Justin had not yet regained the function of the muscles that control positioning of his penis. The team decided the best option to help him was a partial phallectomy, in which a portion of the penis was removed.

“Through this procedure, the penis is shortened to a more appropriate position,” says Dr. Jenei. “And because it’s not completely hanging down, you then get less swelling, and it needs less management, which is more comfortable and functional for the horse and its owner.”

The surgery was successful, and Justin stayed at the hospital for another ten days to ensure the condition would heal properly. He was treated with broad-spectrum antibiotics, anti-inflammatory medications, and monitoring to ensure he was able to urinate normally and comfortably. Justin then transitioned home for continued care.

“I was impressed by their willingness to provide him with the supportive care he needed to recover, followed by the surgery and detailed post-surgical care,” says Justin’s owner, Chris Axten. “He was there for a month, and they didn’t miss a day calling me with an update on his condition.”

Home recovery:
The HLA team provided Axten with a weekly plan to build back Justin’s strength at home, which he carefully followed.

After some rest, Justin did “in-stall walking and some hand-grazing,” says Dr. Jenei. “He then spent a couple of weeks in a horse paddock on his own so other horses wouldn’t persuade him to run around.”

Gradually, Axten started to work him under tack (donning the equipment required to ride) again, as they needed to help him rebuild his fitness and conditioning. Over the next few months, Justin regained his strength and recovered well.

According to Axten, without the care and support of the HLA team, “Justin would not be here today.”  

Comments from Cummings School of Veterinary Medicine HLA Surgical Team

First aid for paraphimosis:
Paraphimosis most commonly occurs as a result of trauma to the external genitalia and associated edema or hematoma formation. Still, it can also result from the administration of acepromazine, local neurologic disorders, and severe debilitation with muscle loss. When the penis is unable to be retracted, even more swelling can occur and, with the weight of the swollen tissues, the muscles can fatigue and the nerves can stretch—this further exacerbates the paraphimosis and results in a vicious cycle. Continued prolapse of the penis can cause the skin to dry and crack, which can allow for bacterial infection to establish in the tissues and even further swelling.  

When paraphimosis occurs, rapid implementation of certain first-aid measures is critical to minimize the worsening of the condition and potentially improve the outcome. The first measure is to attempt to reduce swelling of the exposed penis and prepuce. This may entail administration of systemic anti-inflammatory medications (non-steroidal anti-inflammatory medications, corticosteroids), massaging, hydrotherapy, hand walking to enhance lymphatic and venous drainage, or temporary compression using bandages and/or pressure bags designed for intravenous fluids. Additionally, a hydrophilic agent such as glycerine may help reduce the swelling. If the edema is so severe that even despite such measures, the penis cannot be reduced, it will need to be supported against the abdominal wall using a support sling (“jock strap”) until the edema has reduced further.   

Once edema has reduced enough to allow the penis to be retained in the prepuce, it should be temporarily retained there to break the vicious cycle of edema formation from gravity and potential trauma from continued exposure. Traditionally, placing a purse string suture at the preputial orifice has been used and can be successful. However, the inflamed and swollen tissue may become reactive and not hold up to repeated use of the sutures. In such circumstances, a penile repulsion device (also commonly referred to as a “probang”) can be used. Regardless of the retention method used, the penis should be allowed to extrude once daily to evaluate the degree of swelling, skin excoriation, and function, as well as allow for cleaning and reapplication of any recommended ointments. With the gelding or stallion unable to extend the penis for urination, both methods require intensive care with frequent bathing and application of ointments to minimize the local effects of urine contacting the skin. Depending on the cause of the paraphimosis, this supportive care can be continued for a prolonged period of time. However, if the horse does not show any improvement in several weeks, the prognosis for resolution with conservative management is poor, and surgical intervention may be necessary.