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Equine Surgery Risks

Surgical procedures are frequently necessary in the treatment and management of disease and injury of horses.

Before providing consent for surgery to your horse, it is important that you understand that all surgical procedures involve some risk to the patient.

Horses are complex animals and while it is not possible to detail all the potential complications associated with surgery; the following is an outline of the recognised areas of risk.

The risks and complications associated with equine surgery are closely linked with the risks and complications involved in anaesthesia and sedation.

This information on "Equine Surgery" should be read in conjunction with the attached information on "Equine Sedation and Anaesthesia for Surgery".

Risks and Complications Related to Surgery

Surgical Risks are divided into General Risks, which accompany all surgery and Specific Risks which are related to a particular procedure or class of horse.

General Surgical Risks

All surgical procedures have the following potential complications: haemorrhage, infection, pain, neurological problems and iatrogenic or inadvertent injury. The consequences of a horse suffering one or more of these conditions can range from minor to fatal, depending on the degree to which the horse is affected and the organ system involved.

SEH Veterinarians are aware of the risks and potential consequences of surgery and act to manage these risks as far as is practically possible.

Occasionally and in spite of all precautions, horses suffer one or more of these general complications when they undergo surgery. This most commonly occurs when the horse is already suffering from disease or injury, is very young or is an older animal; however it can also happen to horses which appear fit and healthy and show no signs of compromise prior to surgery.

General surgical risks include:

  1. Haemorrhage

    Surgical procedures can result in bleeding or haemorrhage from the surgical site. This can range from minor bleeding of little consequence to severe haemorrhage that could potentially be life threatening. Circulatory blood volume is maintained during anaesthesia using intravenous fluid therapy and in some surgical cases where increased blood loss may be anticipated, blood transfusion may be peformed during surgery. However, in an emergency situation donor blood is usually not available in horses and severe haemorrhage can be fatal.

  2. Infection

    Bacterial tissue infection can occur following surgical procedures. Risk of infection is significantly increased with tissue trauma, compromised patients, prolonged surgery times, and surgical implants such as orthopaedic plates and screws. Antibiotics are commonly administered prior to and after a surgical procedure to reduce the risk of bacterial infection. Occasionally, and in-spite of all precautions infection can occur that can range from minor wound infection to systemic infection that could lead to other complications eg septic shock, endocarditis, that may require intensive treatment and could potentially be fatal.

  3. Pain

    All surgical procedures are invasive and will stimulate a pain response in the patient. In order to safely perform surgical procedures on horses a combination of sedation and local anaesthesia or general anaesthesia is necessary. Sedative and anaesthetic drugs provide an analgesic or "painkilling" effect which varies depending on the drugs used. Non steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone are also routinely administered prior to surgery to help reduce any pain response. Controlling pain is very important and significantly reduces the risk of complications during and in recovery from anaesthesia as well as minimizing stress for our equine patients and providing for their welfare.

  4. Neurological Problems

    Damage to nervous system is a rare complication associated with surgery. Very rarely damage to the brain or spinal cord (central nervous system CNS) may occur associated with spread of blood clots from a surgical site. Damage to the CNS may also occur if there is decreased blood supply ie severe haemorrhage or decreased oxygenation of the blood. Acute blood loss can occasionally cause blindness that may be permanent and irreversible. Additionally, myopathy or neuropathy may occur occasionally as a complication of general anaesthesia. This can rarely result in a horse that is unable to stand in recovery and may lead to death.

  5. Iatrogenic / inadvertent Injury

    Accidental injury may occur in any procedure and accidental tissue damage may occur during any surgical procedure. The consequences of this injury will depend on the tissue involved.

Specific Surgical Risks

While the general complications are a risk with all types of surgery, they can be more likely and potentially more serious when certain procedures are performed.

Orthopaedic Surgery (involving surgery of joints and bones)

  • Fracture repair

    Many fractures can be successfully repaired in the horse and enable return to full work. Surgery ("internal fixation") may be necessary to facilitate fracture repair and the prognosis will vary depending on the bone involved, the type of fracture and other factors such as the size and temperament of the horse.
    Complications associated with fracture repair include implant failure, infection, supporting limb laminitis and as surgery time is often prolonged there may be increased complications associated with anaesthesia.

    Surgical implants, i.e metal bone plates and bone screws, are necessary in many fracture repairs.
    "Implant failure", where the plates and screws bend or come loose, can occur in the recovery phase from anaesthesia or later following surgery. Implant failure is associated with excessive forces from weightbearing and incoordination and results in disruption of the fracture repair. In most cases, this is catastrophic and euthanasia of the horse is necessary.

    Risk of infection is also increased in fracture repair because of soft tissue trauma associated with the injury. Infection associated with plates and bone screws may be difficult to control and can lead to delayed or failure of fracture healing. Removal of implants may be necessary in some cases and this will require a second surgery usually under general anaesthesia.

    Fractures usually cause severe lameness in the affected leg. Successful surgical repair will usually improve the level of weight bearing on the affected leg however there is often overloading of the contralateral (opposite) leg which can lead to "supporting limb laminitis" or "founder" in the otherwise normal leg. This can be a major complication that can lead to euthanasia. It is most frequently seen in heavy adult horses and in front legs.

    Prolonged surgery time may be necessary to achieve satisfactory fixation of complex fractures in horses. Increased anaesthesia time is known to be associated with increased risk of complications in recovery

  • Joint Surgery "Arthroscopy"

    Arthroscopic surgery involves inserting a camera and instruments into a joint through small skin incisions. This technique allows good visual assessment of the internal structures of the joint with faster recoveries and lower risk because of the small incisions and sterile flushing of the joint.

    Arthroscopic surgery is performed under general anaesthesia.

    Complications associated with arthroscopic surgery are rare and this technique has become the standard method of joint surgery in horses.

    Joint infection following arthroscopic surgery is rare and the incidence has not been reported in horses. In humans, post operative infection rates following arthroscopic surgery of the knee have been reported to be between 0.08% and 0.42%. Treatment of a joint with corticosteroids prior to arthroscopic surgery is recognised as significantly increasing the risk of post operative infection.

    Other specific complications include tissue swelling and haemorrhage. However, these complications are generally minor and self resolving. Rarely, a synovial hernia may occur at the site of instrument or arthroscope insertion that can lead to a soft swelling on the skin surface over the joint.

    Inadvertent damage to cartilage or other tissues adjacent to the joint may occur rarely.

    Instrument breakage is rare but may require extended or subsequent surgery to remove the broken fragment.

    Post operative care of arthroscopic cases is important and careful attention should be paid to discharge instructions, maintaining a clean stable environment and bandage changes to avoid post operative complications.

    In some cases, arthroscopic surgery can involve multiple joints. Whilst this may reduce the costs associated with multiple surgeries, it will increase surgical and anaesthetic times which may increase the risks to the patient. The decision to perform arthroscopy on multiple joints will be considered and discussed prior to surgery.

  • Transphyseal Bridge / Periosteal Strip surgery

    Periosteal elevation surgery ("Strips") and transphyseal bridge surgery ("Bridges") are performed in foals to help correct angular limb deformities ("Bent legs").

    Periosteal "strips" and transphyseal "bridges" are performed under general anaesthesia.

    Periosteal strip surgery may be performed "on farm" if there are suitable facilities and staff or at Scone Equine Hospital at the discretion of the farm management and veterinary surgeon.

    Complications associated with periosteal strips are rare but can include infection of the surgical site. Failure to correct the deformity may occur or the deformity may continue to worsen as the foal matures.

    Overcorrection of angular limb deformity does not occur following periosteal strip surgery.

    Transphyseal bridge surgery may be recommended if the angular limb deformity is severe or if there has been insufficient correction following periosteal stripping. "Bridge" surgery involves the placement of orthopaedic implants across the "physis" or "growth plate" of the bone to limit bone growth on that side and allow straightening of the limb. Success of this surgery is dependent on bone growth and therefore the age of the foal when this surgery is performed is very important.

    Transphyseal bridge surgery is always performed at our surgical facility at Scone Equine Hospital.

    Occasionally the single screw bridge may "pull loose" from the bone resulting in failure of the bridge. This has usually been observed in young foals with severe deformities. As a result, the alternative "Two screw and wire" technique may be recommended for these cases.

    Local wound infection may occur, however; this is usually readily controlled by antibiotic therapy. Occasionally removal of the bridge may be required to control the infection.

    Persistent local wound infection may lead to scarring and permanent white hairs at the surgery site.

    Failure to remove the bridge at the appropriate time can result in "over-correction" of the angular deformity. It is therefore important that the foal is closely monitored for correction and is re-presented to the veterinary surgeon for bridge removal.

    Failure to remove the bridge will mean that it will be visible on yearling sale radiographs.
    It is the responsibility of the farm management to ensure that foals are re-presented for assessment and bridge removal.

    Bridge removal requires a second general anaesthetic and surgical procedure.

    Rarely, orthopaedic drill or screw breakage may occur. In most cases, the broken drill or screw can be removed but occasionally this is not possible. Whilst this is unlikely to be of clinical significance to the horse, the broken screw will remain visible on sales radiographs.

    Inadvertent damage to a joint or fracture of the physis associated with bridging is extremely rare.

    Post operative care is extremely important to reduce complications such as wound infection.

    In young foals with carpal valgus or "Knock knee" deformity, restriction of exercise can be very important to reduce the risk of serious complications such as "carpal bone fracture" of the knee.

Soft Tissue Surgery

  • Colic

    Abdominal pain in horses is commonly referred to as "Colic". Colic ranges in severity from mild abdominal discomfort, to severe life-threatening, uncontrollable pain that requires surgical intervention.

    Colic surgery is a life saving and most frequently emergency procedure which allows examination of the abdomen and intestine and permits correction of surgical problems.

    Colic surgery is performed by a midline incision through the abdominal wall under general anaesthesia.

    Colic can cause serious changes to the normal function of many body systems, which can lead to cardiovascular compromise or shock. These changes will generally be worse if the duration of colic is prolonged. There is an increased risk of anaesthesia associated with such patients.

    Complications are commonly encountered in colic patients because of the severity of the disease. Post operative complications can include persistent pain or colic, endotoxaemia that can lead to other complications including "endotoxic shock" and laminitis or "founder" (inflammation and destruction of the tissues of the feet), "peritonitis" (infection within the abdomen), "colitis" (inflammation of the large intestine), adhesion formation (internal scar tissue), incisional infection of the surgery site that can lead to hernia or evisceration (release of the intestine through the wound), and infection or thrombosis of the blood vessels such as the jugular vein.
    In some cases these complications may be life threatening despite intensive care treatment.

    Success of colic surgery will vary depending on the particular surgical problem identified, ease of surgical correction, the duration of colic and the occurrence and successful management of post operative complications.

    Overall colic surgery is associated with a success rate of approximately 70%. Prompt referral and surgical intervention can significantly reduce the risk of complications and improve the chances of success of colic surgery.

  • Castration

    Castration involves surgical removal of the horse's testicles.

    Castration can be performed in the standing horse under sedation and local anaesthesia or under general anaesthesia. The decision to perform castration standing or under general anaesthesia is made in consultation with the person who is physically in charge of the horse at the time of the surgery. Owners who require that the surgery is performed either standing or under general anaesthesia should make this requirement known to both the veterinary surgeon and the person in charge of the horse.

    Whilst castration is a "routine" procedure very commonly performed on colts for management reasons, there are potentially serious complications associated with castration in horses.

    Accurate identification and signed consent form is mandatory before castration will be performed on any horse.

    Castration may be performed by either an "open" or "closed" technique and may be performed "on farm" or in our surgical facility. Choice of technique is dependant on whether castration is performed on the standing or anaesthetized horse, facilities available, age and type of the horse and preference of the veterinary surgeon. Potential complications exist with both techniques and whether the procedure is performed on the standing or anaesthetized horse.

    "Open" castration can be performed in the standing horse or under general anaesthesia. Potential complications associated with "open" castration include swelling, bleeding or haemorrhage, infection and herniation or evisceration (release of internal tissue or bowel through the wound). Minor complications such as swelling of the scrotum and sheath or local infection are common and most often require little or no treatment. However, occasionally more serious complications can occur including severe haemorrhage or more rarely herniation of intestine. These complications can be life threatening and emergency treatment may be necessary to save the horse.

    "Closed" castration is performed under general anaesthesia and involves placement of a suture around the spermatic cord before emasculation (removal of the testicle). This technique reduces the risk of serious haemorrhage, herniation of the intestine and often reduces post operative swelling.

    "Closed" castration requires increased surgery time and the placement of sutures which can increase the risk of infection. Closed castration is generally recommended in cases where there may be an increased risk of complications associated with the "open" technique, such as castration of an older horse or where a scrotal hernia is suspected.

    If castration is requested at the time of another surgical procedure, such as arthroscopy, that requires a period of confinement post operatively, "closed" castration is generally performed because of the reduction in post operative swelling.

  • Cryptorchid "Rig" castration

    Cryptochidism is where one or both testes have failed to descend from the abdomen into the scrotum. Cryptochid castration involves surgical exploration to remove the retained testes.

    Cryptorchid castration surgery is performed in a surgical facility and may be done under general anaesthesia or via laparoscopy (inserting a camera and instruments into the abdomen) on the standing sedated horse.

    Complications can include bleeding, swelling of the surgical site, infection and breakdown of the tissue at the surgical site which could lead to peritonitis (infection within the abdomen) or herniation of intestine.

  • Laparoscopic Surgery

    Laparoscopic surgery involves the insertion of a camera and surgical instruments through the abdominal wall. Laparoscopic surgery may be recommended for reproductive surgery such as removal of an abnormal ovary ("ovariectomy") e.g. Granulosa cell tumour, "oviduct flushing" or "uteropexy" in subfertile mares or cryptorchid castration in colts. Laparoscopy also allows visualization of areas of the horse's abdomen that are inaccessible by other surgical methods, and may allow diagnosis and treatment without the need for more invasive abdominal surgery and general anaesthesia.

    Complications and post operative recovery times associated with laparoscopic surgery are significantly reduced because of the small incisions that are used. However, potential complications that are infrequently encountered include intra-abdominal bleeding or haemorrhage, peritonitis (infection of the abdominal cavity), inadvertent injury to intestine and instrument breakage or loss.

  • Caesarean

    Caesarean section surgery to manage "dystocia" (foaling difficulty) in the horse is an emergency procedure that is used to deliver a live foal or a foal that has died and cannot be safely delivered through the vagina.

    Caesarean section surgery to is performed through a large surgical incision in the mare's abdomen and uterus to remove the foal and is performed under general anaesthesia.

    Complications are commonly encountered due to the severity of the condition and its effects on the various tissues and organs of the mare. In addition to increased risk of anaesthesia in a foaling mare, surgical risks associated with caesarean section include bleeding/haemorrhage, peritonitis (infection within the abdomen), infection and tissue breakdown at the surgical site which can lead to hernia or evisceration( release of the intestine through the wound). Retained placenta and foetal membranes occur commonly following caesarean section and are normally managed post operatively with uterine lavage (flushing) and other medical treatments but are associated with risk of infection, endotoxaemia and laminitis.

    "Elective Caesarean section" may be performed on mares that have a previous history of foaling difficulty, cervix injury or narrowing of the pelvic canal. Elective Caesarean is performed to decrease the risk to the mare and increase the chances of the foal's survival. Birth of a viable foal via elective Caesarean is dependent on "readiness of the foal for birth" and how well the mare tolerates the anaesthesia and surgery. It is critical that elective Caesarean is performed at the optimal time. Intensive monitoring of the mare and foal are undertaken prior to elective Caesarean.

    The risks associated with an elective Caesarean are lower than for an emergency Caesarean however this remains a major surgical procedure and there is the potential for similar complications to occur.

    "Terminal Caesarean section" may be performed in the emergency situation to remove a live foal from a mare that is dying but is close to her expected foaling date. The procedure results in a dead mare and a foal which requires intensive care to survive.

  • Sinus surgery

    Sinus surgery may be necessary to treat problems such as "ethmoid haematomas" (benign growths of highly blood filled tissue within the nasal cavity and sinus) or infection of the sinuses "sinusitis".

    These conditions are more frequently encountered in older horses.

    Sinus surgery may be performed on the standing horse, under sedation and local anaesthesia, or under general anaesthesia.

    Potential risks associated with sinus surgery include blood loss, persistent infection, oromaxillary fistula (a permanent hole) formation and neurological problems. Removal of a "bone flap" to allow surgical access to the sinus, may also result in a poor cosmetic appearance.

    If the risk of blood loss is considered high, a transfusion of blood from a donor horse may be performed. Blood transfusion carries a risk of "transfusion reaction" which can be life-threatening.

  • Surgery of the eye

    Surgical treatment of the eye or adjacent structures is performed for a variety of conditions including injury and infection.

    Surgical treatment of eyes is most often performed under general anaesthesia but minor procedures such as the placement of eye treatment tubes (subpalpebral treatment tubes) may be performed on the standing horse using sedation and local anaesthesia.

    All surgical procedures of the eye or close to the eye, carry the risk of inadvertent injury to the structures and tissues of the eye and inflammation that could lead to loss of vision.

    An increased risk of "bradycardia" (slow heart beat) and occasionally "cardiac arrest" have been associated with eye surgery due to stimulation of the vagus nerve. Local nerve blocks, topical local anaesthesia, non steroidal anti-inflammatory treatments are utilized in addition to careful monitoring of general anaesthesia to minimize this risk associated with eye surgery.

    Conjunctival pedicle grafts ("Conj Grafts") are commonly used to help treat deep corneal ulcers. Risks associated with this procedure include breakdown or failure of the graft, ongoing infection that could lead to rupture of the globe (eyeball), and permanent scar formation leading to corneal opacity. Globe rupture can result in permanent blindness and removal of the eye may be necessary. Permanent corneal scarring may lead to a reduction in the field of vision; the significance of this will vary depending on the location on the cornea.

    Sub-palpebral lavage tubes ("eye treatment tubes") are frequently used to aid medical treatment of the eye. These tubes are well tolerated by most horses but occasionally cause irritation and rubbing that may result in self inflicted trauma to the eye.


Class of Horse

  • Foals

    Foals commonly undergo general anaesthesia and surgery to treat angular or flexural limb deformities ("bent legs").

    Foals may also undergo general anaesthesia and surgery to treat injuries, infections, colic or ruptured bladder.

    In general, the specific risks associated with anaesthesia and surgeries of newborn foals are related to the immaturity of their physiological systems.

    Any condition which causes stress to a foal may predispose the foal to gastric ulceration. This may lead to perforation of the stomach or intestine and subsequent death. To minimise stress, foals are kept with the mare as much as possible in the induction of and recovery from anaesthesia.

    Colic surgery in foals is a high risk procedure and foals are susceptible to all of the complications outlined under "Colic" above.
    In particular, colic surgery in foals is associated with an increased risk of "adhesion formation" (internal scarring within the abdomen), which can lead to subsequent episodes of colic and possibly death.

    Foals with ruptured bladders are high risk patients. They are unable to excrete potassium from the body. High blood potassium can cause serious heart problems and death if not corrected. These cases are treated medically before surgical repair is performed under general anaesthesia however the effects of electrolyte imbalances make the foal more susceptible to the adverse effects of anaesthetic drugs.

  • Pregnant mares

    Pregnant mares may undergo general anaesthesia and surgery for treatment of a variety of conditions including injury, infection, colic and foaling difficulties.

    General anaesthesia during pregnancy carries a risk of abortion. This risk is extremely low, especially in the first two thirds of pregnancy. When possible, elective surgery under general anaesthesia in heavily pregnant mares is avoided. There is no evidence that any of the anaesthetic drugs commonly used in horses cause foetal damage or loss.

    Anaesthesia in pregnant mares also carries increased risks associated with reduced heart function, blood flow and respiration. Pregnant mares have an increased risk of catastrophic limb fracture during recovery from anaesthesia. Limb fracture usually results in death of the mare.

  • Stallions

    Stallions may undergo general anaesthesia and surgery for treatment of a variety of conditions including injury, infection and colic.

    Specific risks associated with surgery on stallions are related to temperament and size. Stallions may be at increased risk of myositis (muscle injury) or neuropathy (nerve injury) because of their increased muscle mass and weight. Temperament may lead to poor anaesthetic induction or recovery which can lead to injury.
    Sperm production and fertility can be affected by any condition which causes a stress reaction in a stallion; these conditions can include pain, infection, high temperature, general anaesthesia and surgery

  • Older Horses

    Older horses may undergo general anaesthesia and surgery for treatment of a variety of conditions including injury, infection and colic.
    Ageing is associated with less effective organ function, diseases affecting metabolism, lameness, reduced joint flexion, osteoporosis ("weak bones") and muscle weakness. All of these factors are associated with increased risks for general anaesthesia and surgery.

  • Sick Horses

    Horses which are suffering from underlying illness may need to undergo general anaesthesia and surgery for treatment of a variety of conditions including injury, infection and colic.

    There is an increased risk associated with anaesthesia and surgery of sick horses.
    The underlying illness may be associated with less effective organ function, including a lower ability to cope with the adverse effects of anaesthetic drugs and an increased susceptibility to infection.
    The underlying illness can result in severe and potentially life threatening consequences.

    Medical treatment including fluid therapy may be recommended prior to performing surgery in some cases.

    The advantages and disadvantages of performing surgery on any sick horse are considered and discussed prior to a decision being made.

  • Fit Athletic Horses

    Fit athletic horses may undergo general anaesthesia and surgery for treatment of a variety of conditions including injury, infection and colic.

    There is an increased risk associated with anaesthesia of fit horses. Fit horses often have significantly lowered respiratory and heart rates during anaesthesia. Fitness, coupled with the effects of the anaesthetic drugs can lead to decreased heart and lung function and to low blood pressure which can result in severe and potentially life threatening consequences.

    It is common practice for fit horses to be rested or "let down" for a period of time before elective surgery.


In summary:

In consenting to surgery for your horse, you accept that:

  • All Surgery involves some risk.
  • SEH veterinarians act to manage the risks as well as possible.
  • Complications do occur and can be serious and life threatening.
  • If complications occur we will inform you and advise you on the best course of action.


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