Common Problems of the Penis and Sheath
Although not exactly every person’s favourite subject, a gelding or stallion’s penis and sheath are prone to a number of problems. As Dr Natasha Hovanessian from the Canberra Equine Hospital explains, being a very sensitive area of a male horse’s anatomy that allows the elimination of urine from the bladder, any problem can easily become a major complication. Early recognition by horse owners and veterinary intervention are the best way to ensure a successful outcome.
The normal anatomy
In order to be able to identify problems with the penis and sheath, it is important to first appreciate what is normal. The equine penis is composed of three parts: the base (inside the horse), the shaft (the main part) and the glans penis (the round part at the tip). The urethra (the tube that transports urine from the bladder) and urethral process are inside of the penis and allow the horse to urinate. The urethral process should be distinctly visible at the center of the glans penis as a small pink opening leading up into the urethra.
Surrounding the urethral process is the urethral fossa, a little cavity where accumulations of secretions called smegma, also known as ‘beans’, are a common occurrence. The prepuce is the covering surrounding the penis when it is retracted. It is composed of a double fold of hairless skin and is designed to protect the penis. The external, hair-covered part of the prepuce is also known as the sheath and is the outermost protective layer.
Examination of the penis and sheath is something which should be done on a regular basis. It is important to establish normal skin texture, penis size and sheath size of your horse, so you can easily identify when something changes. Regular visual examination of the sheath can easily become part of your routine when you are grooming, saddling, feeding or visiting your horse.
Proper examination of the penis itself can be difficult, as most horses will not appreciate you exteriorising their penis to get a look and may kick. Take the opportunity to visually examine the penis any time your horse is urinating or is very relaxed. Build-ups of secretions and sweat is a common problem in many geldings and stallions, hence cleaning of the penis and sheath is an important part of managing our mates.
Cleaning should be done approximately every six months and it is a good idea to do it at the same time as your regular dental check-up. Not only is your veterinarian there to help and answer any questions, but the horse is likely to be sedated, which makes for a much more cooperative patient!
Indications of a problem
Once you have identified what is normal for your horse, any changes from normal can be detected. Penile or sheath problems may present in a number of ways including:
- Bad odour,
- Penis remaining extended out,
- Growths (masses),
- Difficulty urinating, including repeated posturing to urinate or dribbling urine, and
- Kicking at the abdomen.
Inflammation of the penis and prepuce
Inflammation of the penis is one of the most common signs of disease involving the penis. Penile inflammation can be identified by redness, swelling (which can become extreme), heat, pain, odour and interference with function. It can be caused by a number of factors, including infection, trauma or neoplasia (cancerous growths).
Difficulty urinating can occur as a result of a smegma ‘bean’ as mentioned above. However, there are other, more sinister causes of difficulty to urinate. If you notice your horse is having trouble urinating, only urinating in small amounts or posturing to urinate but failing to do so, first check his urethral fossa for a build-up of secretions. If no bean is found, or he is still having difficulty, a more thorough examination by your veterinarian may be required. Other causes of obstruction to the urethra can include trauma to the urethra or surrounding tissue, bladder stones, which have travelled down to the urethra, or neoplasia.
Trauma to the penis and prepuce can encompass a large range of injuries, including kicks, abrasions, lacerations, chemical irritation, contusions (bruising), photosensitization (sun damage) and strangulation. Regardless of the cause, penile injuries are usually accompanied by heat, pain, severe swelling and can interfere with the function of the penis or prepuce.
This term refers to a condition where the penis is retained within the prepuce and is unable to be exteriorised. There are a number of potential causes of this condition. Therefore, careful examination is required to determine if the failure to exteriorise is due to stricture (narrowing) of the preputial ring internally, from a process such as inflammation, a large bean formation or neoplasia.
Treatment for an inability to drop the penis will depend on the cause, but may involve widening of the preputial ring by surgery. Inflammation of the penis can result in failure to either exteriorise or retract the penis, which can cause a host of other complications. If you notice any abnormal swelling, discharge or growths, it is important that you contact your veterinarian, so the cause of the problem can be identified and treated appropriately.
As well as priaprism (see below), paraphimosis is a condition that refers to a state where the penis is stuck outside of the prepuce and sheath. Paraphimosis refers to the condition where the penis is constantly exteriorised and the penile tissue is limp. Paraphimosis is generally a result of inflammation, swelling and fluid retention of the prepuce. The weight of the swollen prepuce pulls it downward along with the penis, which swells and can no longer be retracted.
Alternatively, trauma to the penis itself can result in swelling of the penis and the subsequent increase in weight pulls it down. A haematoma (blood clot) resulting from trauma is another potential cause of paraphimosis, where the weight of the increased blood in the tissues causes a downward pull.
Priapism refers to a condition where the penis is constantly exteriorised and erect, or engorged with blood. It has been reported that this condition is mainly associated with an overactive libido. However, spinal cord injuries and a complication of castration are other potential causes. Both paraphimosis and priaprism have also been reported in association with neoplasia (abnormal growths on the penis), parasitism, debilitation from ageing or illness, as well as the use of phenothiazine-derivative tranquilisers (such as acepromazine or ACP).
If caught early, gravitational oedema, (fluid collecting in the tissues) can be managed through the use of cold hosing, massage, exercise and application of an elastic bandage. Exercise should be carried out carefully as the exteriorised penis is at risk of further trauma if the horse moves around too much. Your veterinarian can direct early treatment for paraphimosis or priapism, but it is important to institute therapy early.
The basis of veterinary treatment is to reduce the oedema to the point where the prolapsed structures can be replaced into the retracted position. Replacing the prolapsed structures allows for more protection and better healing of the mechanism which holds the penis and prepuce in place. Slings made of a water permeable material, so that urine can still pass through, such as stockings, can be used to hold the penis/prepuce in the retracted position until the animal is able to do so themselves. Alternatively, a bottle fashioned into a sling also works well.
If complications, such as further inflammation occur, the resulting damage to the penis may mean that it can never be retracted again. In these cases, surgery to re-open the prepuce may be successful. However, complete penile amputation may be the only cure.
Parasitism and infection
There is a large and varied range of parasites and bacteria which can cause problems with the penis and/or prepuce. Below, are a few of the more common ones:
Habronemiasis, also known as ‘summer sores’, is a parasitic infection of the skin caused by the larvae of the Draschia spp. and Habronema spp. of flies. The larvae invade the skin causing inflammation, which is accompanied by intense itching. The irritation leads to self-trauma and large inflamed/reddened areas. If the infection is around the urethral opening, it may cause an obstruction, which will require surgical intervention and local treatment of the parasitic infection with topical anti-parasiticides.
Staphylococcus infection commonly occurs secondary to other problems which have caused a break in the skin. Treatment is much the same as for any other infection and involves exposure of the bacteria to the environment through thorough cleaning and debridement of wounds, as well as use of antiseptics and possibly antibiotics.
Equine Coital Exanthema is a disease caused by one of the Equine Herpes viruses (EHV-3) and is transmitted during breeding activity. The virus causes papules (small pimples or swelling on the skin), pustules (small blisters or pus-filled pimples) and ulcers on the penis of the affected male. The appropriate management is to treat the symptoms until all lesions have healed and to isolate the infected animal to prevent spread of the infection.
Squamous cell carcinoma
Neoplasia refers to abnormal growths or lumps of tissue. The most common neoplasm affecting the equine penis, prepuce and sheath is squamous cell carcinoma (SCC). SCC’s tend to be more common on light-coloured horses including Appaloosas, greys, palominos and any horse with pink tissue on the penis or sheath, which many solid-coloured horses can have. SCC’s can present in a number of ways, so it is important that if you notice any kind of lump on your gelding or stallion’s penis or prepuce that you get it checked out by your veterinarian before it enlarges.
It can be difficult to determine the extent of the SCC’s, as what looks like a small nodule on the penis can extend quite deeply into the rest of the tissue and be present in local lymph nodes. A deep invasion such as this can cause a host of other problems, including oedema, abscesses and multiple draining tracts, which can subsequently make the diagnosis difficult.
While SCC’s do tend to spread, they do so relatively slowly, which means that surgical management of the penile lesions is often very rewarding. Extensive lesions involving the glans penis (or tip) may require phallectomy, or removal of the penis, especially if urine flow is affected.
Sarcoids are the second most common neoplasm of the skin (and thus potentially affecting the penile/ preputial skin). A sarcoid tumour tends to invade quite deeply, making successful removal difficult and recurrence common. There are a variety of treatment options used, including chemical applications, cryotherapy (freezing areas of the skin), surgical excision, as well as local chemotherapy, radiation and laser surgery. Your veterinarian will best advise on an appropriate course of therapy for sarcoids on the penis or sheath.
Melanomas are a common skin cancer of horses and mainly occur in grey horses. Essentially, melanomas are benign tumours and grow slowly. However, 70 per cent of horses with external melanomas have them internally as well and, if the melanoma has the potential to obstruct the normal function of urination or retraction of the penis, it should be removed early.
The long and short of it…
Although the horse’s penis and sheath are prone to a number of problems, regular cleaning and observation, as well as check-ups from your veterinarian, will help alert you, as horse owner, to problems early on to allow for a successful outcome.