Neuter

Orchiectomy

Orchidectomy

Synonymous

• Fix
• Castration

Definition

The removal of both testes to render the male rat sterile.

Clinical Signs

Intact male, the presence of testicles (testes).

Preventative

• To prevent unwanted mating if combining with female cage-mates.
• To eliminate testicular tumors.
• To reduce unwanted aggression.

Disease/Disorder/Emergency
May observe the following:

• Retained testicles in the abdomen.
• Unusual mass felt in addition to testes in the scrotum.
• Absence of one teste.

Etiology

The purpose for doing an orchiectomy (neuter) in the male rat is to prevent impregnating a female rat in the event of being housed together, to prevent/reduce/treat testicular tumors, and to reduce aggression influenced by the release of hormones; although ameliorating aggression is believed to be less successful if neutering is performed once puberty has been reached and hormone related behavior already established. Note: castration of elderly males is not recommended, unless there is a specific clinical condition like testicular tumor or other medically related issue. It should never be done in an elderly rat to reduce aggression because a significant part of aggression is learned behavior, and this may not disappear even if the rat is neutered. Recommendations for aggression against other rats are behavior modification or separation from other intact males if that is the issue. In the event aggression against humans is the issue, then neutering should be done, along with behavior modification.

In addition, intact (not neutered) adult male rats normally secrete fluids from the accessory sex glands that act as an energy source for sperm, contribute to the mobility and viability of sperm, help to lubricate the urethra and clear it of urine prior to ejaculation, and serves as a means of transporting the sperm in the female tract and creating a copulatory plug to help ensure fertilization. Secretions called smegma, composed of oils, moisture, and shed epithelial cells help to keep the glans moisturized. Under normal circumstances the healthy male rat is able to adequately clean the penis and sheath and prevent the buildup of secretions. However, in the aging or ill male rat, or those males with paresis, the ability or flexibility to groom may decline causing these secretions to become firm and large blocking or plugging the urethra. These urethral proteinaceous plugs can interfere with urination and/or lead to infection if not removed. In male rats where an orchiectomy (neuter) has been performed the development of urethral plugs is significantly decreased or eliminated.

The procedure for neutering a male rat is considered, by veterinary surgeons experienced with rats, to be easier, less traumatic, and associated with less morbidity and mortality than performing an ovariohysterectomy on a female rat. (Bennett, Rodents: soft tissue surgery, 2009; Bennett, Soft Tissue Surgery, 2012)

The following description in each section is presented to provide the rat owner with how to prepare their male rat for day of surgery and the type of care, prep, procedure(s), and recovery the veterinarian may follow. There are sections, also, for home care recommendations and additional comments which may be helpful.

Assessment and Checkup Prior to Surgery

The rat should be thoroughly evaluated for any signs of respiratory disease (as well as heart disease in older rats). This is particularly important since rats are obligate (i.e., preferred; allowing them to scent while eating) nasal breathers, having their soft palates permanently engaged around the epiglottis. Therefore, any respiratory secretions that are already present and thick or increased due to infection may become thicker and more sticky while the rat is under anesthesia, as a result of decreased respiratory rate and movement of secretions. This could potentially make them more susceptible to respiratory arrest if these secretions or other causes block the airways. (Girling, 2013)
*Note: although rats are identified as obligate nasal breathers, they do have a patent pathway from mouth to lungs for endotracheal intubation.

For rats with a history of respiratory illness, or for those rats that are elderly and where the pain and stress of a procedure can further suppress the immune system, it is advisable for the veterinarian to place the rat on an antibiotic with coverage for mycoplasma as a prevention to relapse. The antibiotic should be started a few days prior to surgery and continued until the surgical incision site has healed.

Ideally, a baseline minimal screening (hematocrit, total protein, blood glucose, blood urea nitrogen, urine specific gravity) may be advised preop. However, there is a wide range of normal lab values reported in rats and depending upon the procedure and age of the rat — unless the rat has a previous health history – it may not always be necessary. (Bruce & Olsen, Ovariectomy, ovariohysterectomy and orchidectomy, 1986)

Preparation Day of Surgery

It is not necessary to “fast” rats prior to surgery. Rats do not vomit. Providing food and water up to the time of preop prepping (just prior to anesthesia being given) helps to prevent the rat from becoming dehydrated or suffering ketoacidosis/hypoglycemia during surgery and recovery. *Note: some surgeries such as gastrointestinal surgery may require withholding food for 2 to 3 hours prior to the procedure, but water should be made available until just prior to anesthesia.

The pet rat should be brought in a small one level cage or carrier where the rat can be easily observed from all sides of the carrier by the veterinarian and staff. It is helpful to attach a small tag to the carrier with your rat’s name, sex, age, color/markings, type of surgery, as well as your name and a phone number where you can be reached. Also note whether or not the rat can be handled safely. Some rats may become frightened around unfamiliar humans, such as: semi-wild rats, or rats that may have been abused and rescued.

Provide non-ravel cloth (e.g., fleece or t-shirt type material) for bedding, preferably white or light-colored, so that signs of urination or bleeding are easily visible. In addition, provide an extra clean set of bedding if the rat is expected to wait awhile before the surgery (the bedding may become soiled).

A filled water bottle and the rat’s food, including fresh fruit and small treats, should accompany and be accessible to the rat. Note that the water bottle may need to be lowered during the recovery period, if the rat cannot sit up comfortably. In addition, it is advisable to include high caloric foods (e.g., pasta, porridge, oatmeal, farina, etc.) in the diet during a few days leading up to the day of surgery. Doing so can aid metabolic function, reduce hypoglycemia, and may improve healing time.

Preop

It is imperative to obtain an accurate bodyweight for correct dosing of anesthetics and analgesics.

Making sure the rat is well hydrated helps to prevent dehydration throughout the perioperative period. Note that the maintenance fluid volume for rats is approximately 100 mL/kg/day. Warmed, IV or SQ, crystalloid fluids (e.g., lactated Ringers or Hartmann’s solutions or Normal Saline-0.9% Sodium Chloride) may be required to maintain hydration perioperatively.

Since rats possess serum atropine esterase, which rapidly hydrolyzes atropine, administering atropine for secretion reduction or for its vagolytic effects may not be that effective. In cases where secretion reduction is necessary, and depending upon the procedure, the veterinarian may elect to use glycopyrrolate. (Bruce & Olson, 2008; Harkness, et al, 2010)

Preemptive analgesia should be used cautiously in rats. Although it may be desirable to reduce effects of pain upon arousing in recovery and provide the ability to reduce the percentage of gas anesthetic when giving an opioid such as buprenorphine prior to the anesthetic, both opioids and particularly NSAIDs (such as Metacam or carprofen) are best used postoperatively when blood pressure is more stable and the side effects less. *Note, that the use of NSAIDs alone does not require reduction of gas anesthetic. (Flecknell & Richardson, 2009; Bennett, 2012)

Providing oxygenation to the rat prior to intraop (along with providing oxygen intraop and postop) will significantly help prevent hypoxemia and hypocapnia.

Minimizing the area of fur shaved at the site for incision, prepping with warmed surgical scrub such as chlorhexidine and avoiding use of alcohol prep, and providing absorptive towels to prevent the rat from becoming wet will help to decrease development of hypothermia.

Intraop

Oxygen should be continued through to recovery to prevent hypoxia from developing.

It is important for the veterinarian to be prepared for emergencies prior to anesthetizing the rat. Any emergency drugs should be prepared and ready, at the correct dosage.

While some anesthetic agents are not appropriate for use in rats due to an increased risk of anesthetic death, the following are those with the widest margin for safety:

Inhalation Anesthetics

Isoflurane or Sevoflurane are considered the safest and most effective anesthetics for use in rats. The advantage is that each of these inhalation agents permits a quicker induction and recovery, being only minimally metabolized in the liver with the majority being eliminated through exhalation. This is particularly helpful in older rats or those rats with subclinical hepatic issues. While these inhalant anesthetics do have the effect of hypothermia and drying of respiratory mucous membranes, these effects can be countered by the use of a recirculating warm water pad or warm air blanket and monitoring the rat’s temperature, and keeping the rat hydrated, respectively. (Flecknell & Richardson, 2009; Girling, 2013)

Injectable Anesthetics

When administering injectable anesthetic agents those that allow for a specific antagonist to be used when the agents must be reversed quickly provide a better margin of safety. Agents such as xylazine and medetomidine can be reversed with atipamezole. Using either xylazine or medetomidine in combination with Ketamine allows for lower dosage of the drugs to be given, decreasing unwanted side effects. IV or IP administration is preferred over IM or SQ. IV administration allows the effects of the drugs to be seen quickly and for the dosing to be adjusted. Since these substances are irritating to tissue, giving them SQ or IM can result in nerve irritation and/or muscle necrosis at the injection site, as well as self-mutilation, if care is not taken when injecting. Injecting into thigh muscle should be avoided for this reason. A disadvantage of injectable anesthetics is that reversal and recovery take longer because they are required to be metabolized before being eliminated by the body, and the fact that they can cause severe hypotension. (Flecknell & Richardson, 2009)

The eyelids of rats do not always close completely under sedation. Placing ophthalmic lubricant on the eyes will prevent corneal desiccation (i.e., severe drying out of the cornea).

It is important to prevent hypothermia from developing. Anesthetic agents suppress the body’s ability to regulate temperature. Rats physically have a large body surface area to volume ratio and when inactive due to being sedated or anesthetized they can rapidly become hypothermic. When performing surgery on the rat it is therefore important that it be performed on a recirculating warm water pad, or warm air blanket. In addition, draping the rat as soon as possible while in surgery can decrease heat loss. (Mayer, 2013)

While warm water bags and heated pads regulated to 30-35 degrees centigrade (85-95 degrees Fahrenheit) and covered by a towel before placing the rat on it may also be used, this should be done carefully so as not to cause burns to the sedated rat. The temperature should also be carefully monitored throughout the surgery and recovery to ensure that the rat does not become overheated. Hyperthermia in the rat can be just as deadly as hypothermia.

Procedures

The primary functions of the male reproductive system are the production of sperm, the transportation of sperm from the testes out of the male body, the placement of sperm into the female’s vagina, and the production of glandular secretions and hormones.

Sperm are produced in the testes and then are transported by a series of ducts until they exit the penis via the urethra.

In male rats, the testes normally descend from the abdomen into the scrotum approximately 15 days following birth, although it is not uncommon for them to descend, in a young male rat, between 4 to 6 weeks of age. Testes that have not or do not descend may be retained in the abdominal cavity or the inguinal canal. It is important to note that throughout life male rats normally have open inguinal canals with a functional cremaster muscle that allows the testes (testicles) to migrate easily in and out of the abdominal cavity for both protection and temperature control.

The testicles, in male rats, are large in comparison to the size of their body and are oval and smooth in shape. They are contained in two muscular sacs within the scrotum. In addition, they have a large pad of epidydimal fat as well as a pad of fat on each side of the lower abdomen which aids in preventing herniation into the intestine. Noted, also, are the large seminal vesicles that aide in partially occluding the internal inguinal ring and helps to prevent visceral herniation. (Flecknell & Richardson, 2009) (Bennett, Rodents: soft tissue surgery, 2009; Bennett, Soft Tissue Surgery, 2012)

Castration (neuter, orchidectomy) involves the removal of the testicle, epididymis, and part of the vas deferens.

Various techniques and approaches are described, but it must be remembered that in this species the inguinal ring remains open, making it imperative that the vaginal tunic is closed following removal of the testicle. Following proper procedure with each approach can prevent catastrophic intestinal or visceral herniation, tearing of the vaginal tunic or testicular vessels, or damage to the prepuce. In addition, it is also important to prevent pulling the testicles to far from the body, in the male rat, when performing surgery so as not to tear the vessels. Inadequate control of subcutaneous vessels and those within the tunics can be cause for incisional and scrotal hemorrhage. (Bennett, Rodents:soft tissue surgery, 2009)

The types of techniques used to perform a castration (neuter, orchiectomy) are the following:

Open technique (applicable to scrotal and prescrotal approaches) —

The rat is placed in a dorsal recumbency (lying on its back) position. The fur is clipped around the scrotum and the penis, and the area is prepped aseptically. The vaginal tunic is incised, and the testicle exposed. The ligament of the head of the testis is broken down manually and the spermatic cord is directly clamped and ligated using either the 2- or 3-clamp technique. Absorbable suture material (e.g., polyglactin 3/0 or 4/0 ) should be used for the ligature. The stump is checked for bleeding before being replaced into the tunic, which must then be closed with a single encircling, transfixing or cruciate ligature, depending on the preference of the surgeon. Again, this should be an absorbable ligature. The subcutis and skin are then closed, with preference by veterinarian, using fine intradermal sutures for the skin to reduce the likelihood of interference by the rat.

Closed technique (applicable to scrotal and prescrotal approaches) —

The rat is also placed in a dorsal recumbency (lying on its back) position. The fur is clipped around the scrotum and penis, and the area is prepped aseptically. In closed technique the vaginal tunic is not incised. The testicle is exteriorized while still within the tunic, which is clamped and ligated along with the spermatic cord and vessels as described above in the open technique. The closed technique has the advantage that the tunic is not entered, therefore there is no communication with the inguinal ring or abdomen, and less risk of contamination (although if proper aseptic technique is employed this should not be a concern with either open or closed castration).

*Note: that using the closed technique may provide a slight advantage in terms of anesthetic time as there is no need to ligate the tunic separately, though this largely comes down to preference of the veterinary surgeon.

The types of approaches used to perform a castration (neuter, orchiectomy) are the following:

Scrotal approach —

A small area of the cranial scrotum is surgically prepared. Minimal clipping is needed. The incision is placed directly over the scrotum. This technique can be performed with either a single central incision through which both testicles are removed or one incision over each testicle. Again, this comes down to the veterinary surgeon’s preference. A single incision is theoretically less traumatic; however, a larger incision can be required in order to manipulate both testicles through it. The preference can also be for 2 incisions, which are tiny, right at the cranial end of each scrotal sac. Performing 2 incisions rather than through a single incision can make the approach quicker with less manipulation to both testicles, therefore reducing anesthetic time.

Precrotal approach —

The caudal abdomen is clipped and surgically prepared, and a single incision is placed slightly to one side of the midline (to avoid trauma to the penis), just cranial to the scrotum. Both testicles are manipulated through this single incision.

Abdominal approach —

The rat is placed in a dorsal recumbency (lying on its back) position. The abdomen is clipped (of fur), prepped and prepared aseptically, and as the inguinal ring remains open in this species, the testicles can be accessed via a caudal laparotomy incision and traction on the spermatic cord.

Abdominal castrations may be favored by some veterinarians, in the same way as ovariectomies. The theory is that it causes less soft tissue trauma. However, this may just be preference based since abdominal incision in and of itself does not appear less traumatic than 2 tiny incisions to the scrotum.

Abdominal castration is used primarily in congenital conditions of cryptorchidism, where the teste or testes fail to migrate freely into the scrotum but remain in the abdomen.

The disadvantage to abdominal castration is that there are greater risks if the rat chews the wound, more heat loss due to having the abdomen open and a larger surgical field, as well as a 3-layer abdominal closure that would be needed, all adding to the anesthetic time”….

For any of the above techniques the following closure material may be utilized based on veterinary preference:

Absorbable suture used to close muscle (as in abdominal technique), and the closing of the skin may be done with non-absorbable sutures, surgical adhesive. (Bennett, Rodents: soft tissue surgery, 2009; Bennett, Soft Tissue Surgery, 2012; Flecknell & Waynforth, 1992; Harkness, et al, 2010; Mayer, 2008)

Example of a veterinary technique for scrotal castration

A preferred technique for a 2 incision open scrotal castration is to use a 2 clamp technique, making procedure quicker with a much smaller clipped and prepped field, than other techniques. Making 2 tiny incisions, as opposed to a much longer single incision, and leaving the fat pad in unless it’s closely associated with the testis, in which case it can be removed along with the testes and finally closing with the use of polyglactin 3/0 or 4/0, depending on the size of the rat.

A mention, infrequent, drawback to the scrotal technique, which might be alleviated by an abdominal approach, is that due to the rat being low to the ground, the incision site does tend to get urine on it, which can lead to the potential of scrotal abscesses. For this reason, a course of an antibiotic, postoperatively, may be considered whether there is any prior respiratory disease or not.

Postop Recovery

To reduce any added concern with regard to hypothermia, the rat should be dried with a soft towel of any remaining wet drainage from surgery and be placed in a quiet, warm enclosure (e.g., incubator), on non-ravel, non-loop, white or light-colored cloth to monitor for any signs of hemorrhage (bleeding).

Continue oxygen and supplemental heat and monitor for and correct any signs of hypoxia, hypothermia and/or hyperthermia.

Turning and repositioning the rat approximately every 10 minutes, until crawl reflex returns, will help to stimulate respirations during recovery and reduce the chance of pulmonary congestion developing.(Bruce & Olson, 1986; Girling, 2013)

Warmed, IV or SQ, crystalloid fluids (e.g., lactated Ringers, Hartmann’s solution, Normal Saline-0.9% Sodium Chloride) should be continued or instituted if recovery is prolonged, to prevent dehydration, until animal is drinking and eating on its own.

Once the righting reflex returns the rat can be placed in a small cage or carrier, again on non-ravel light colored cloth or light-colored paper towels with provision for continued warmth and monitoring.

Encourage oral food and water intake upon being recovered from anesthesia. Small treats, fresh fruit or baby foods may be more welcome to the rat before moving to pelleted or block food.

Monitor rat to ensure the ability to urinate and defecate has returned.

Managing pain in the rat with analgesics such as with the use of opioids, buprenorphine or butorphanol and/or with NSAIDs such as meloxicam or carprofen can help aid in recovery and reduce the chance that the rat will bother the incision site.

Antibiotics should be continued or initiated if the rat has underlying illness, or in the event aseptic technique has not been maintained, or in the case of developing infection.

Discharge Instructions

Provide postop medication such as Metacam (an NSAID), or buprenorphine (an opioid) by buccal or sublingual administration for 3 to 5 days, and inform owner of the time the rat last received pain medication. Note, pica has been known to occur, in the rat, with the use of opioids like buprenorphine and is primarily dose related. Following discharge in the event the rat is observed chewing and ingesting bedding materials remove all bedding until the drug has cleared the rat’s system.

Provide and continue antibiotic if necessary.
Remove litter and substrate. Use paper towels or non-ravel cloth (e.g., felt or t-shirt type material) for bedding in cage.

Monitor incision site closely for infection or wound disruption for at least 72 hours.

In the event the rat has poor appetite and/or has not defecated or urinated by the morning following the day of surgery notify veterinarian!

Return to veterinarian for wound recheck in the event of any untoward, or unusual signs noticed with healing, or for suture removal when instructed to do so.

An Elizabethan collar should only be applied as a last resort since this can prevent the rat from holding its food when trying to eat or drink from a water bottle.

No diet restriction. Free access to food and water should be provided.

It can take up to a few weeks for testosterone level to decrease appreciably and therefore may take from 1 to 2 weeks for sexual activity to cease. Mounting may still persist in those male rats that previously mated with female rats. Pet owners are advised not to place the male back in with a female cage-mate immediately after surgery due to the presence of viable sperm that can still be present where the epididymis remains. References citing the timeline for post operative viable sperm being present in the remaining epididymis post neuter, in rats, vary greatly from 8 days to 8 weeks post-op. Anecdotally, waiting 2 to 4 weeks post-op before placing a neutered male with an intact female has not resulted in any known pregnancies. However, as noted in Bennett, Rodents: soft tissue surgery, 2009 and Bennett, Soft Tissue Surgery, 2012, viable sperm has been found to be present in the remaining epididymis in n rodents for up to 6 to 8 weeks following castration. A time frame of 6 weeks post neuter prior to placing a male rat with an intact female rat is most commonly practiced by pet rat owners.

Figures

Case histories

Orchiectomy
• Fig. 1a: Procedure description of scrotal neuter performed on two rats (Turing and Angelus). *Warning graphic.*
• Fig 2: Castration/neuter in 5-month-old male to reduce unwanted aggression and prevent mating (Joshua).

Surgical pictorials

Orchiectomy (Neuter)
• Fig. 1 Scrotal approach in the male rat performed by Dr. Peter Field B.V.S.C. (Hons.) M.A.C.V.Sc., of Australia.

Diagrams

Male Rat Reproductive Anatomy
• Fig.3a: Male rat reproductive anatomy and description.

Nursing Care at Home

• Contact the veterinarian if any of the following are observed:
  • Swelling, redness, bleeding, disruption (reopening) of the surgical site.
  • If there are signs of pain unrelieved by pain medication noted by: reduction of appetite, decreased drinking, hunched posture, rapid breathing, repeated tremors or abdominal stretching, aggression in an otherwise non-aggressive rat, or signs of pica (see below).
  • If there is absence of passing feces or urine, or if the rat is not eating or drinking by the morning following the day of surgery, or if there are signs of increased weight loss, unusual rapid weight gain, or lethargy.
  • It is important to be aware that pica (i.e., chewing and ingestion of non-food substances) may occur where pain has not been adequately addressed in the rat, or as a dosage related side effect of having been given an opioid such as buprenorphine. In this case, remove the rat from any bedding source that might be chewed and ingested, and provide additional fluids in the diet until the medication has passed through the rat’s system. Contact the veterinarian if the behavior becomes pronounced.
• Provide a hospital cage during recovery, or if there are concerns that the cage-mates may groom the sutures or surgical site.
• Provide clean bedding daily, such as fleece or soft t-shirt type material or ink-free paper towels. Avoid using material such as terry cloth type towels that can ravel. Also avoid litter-type bedding until the incision has healed, to prevent the chance of wound contamination or infection.
• Provide additional warmth to maintain body temperature within normal limits. It is essential that the rat does not become overheated or dehydrated. The rat should also be able to move away from the heat source if it becomes uncomfortable. If the rat is moving minimally, extreme care must be taken to keep the heat low and stable. The following are examples of warming products that may be used:
  • Isothermic products that are heated in the microwave, such as a SnuggleSafe®, may be used. Make sure to follow the product directions carefully and wrap it in a towel before placing it in the cage. The SnuggleSafe® will provide heat for 12 hours before needing to be reheated. Other similar types of products may vary in reheat time. Check the directions for the individual product.
  • If using a heating pad (good for long term use) use only the low heat setting, put a thick towel in between the pad and the cage bottom, and place it beneath a corner of the cage. Avoid use of heating pads with Aquarium-type glass tanks where over heating can occur rapidly. Care must be taken that the rat does not overheat!
  • If none of these options are available you can fill a sock with rice and heat it until it is warm in the microwave. An alternative is to fill 2 or 3 one-gallon plastic jugs with hot water, place around the outside perimeter of the cage, and drape cage and jugs with towels to contain and direct the heat into the cage.
• Medicate for post-op pain as directed by the veterinarian.
• Give or resume antibiotic(s) as directed by the veterinarian.
• Encourage the intake of oral fluids, such as water, Jell-O water, or electrolyte replacement drinks such as Pedialyte or Gatorade (which can be found in local grocery stores).
  • Please note that Pedialyte is only good refrigerated for 24 hours after opened, but can be frozen as ice cubes and thawed as needed.
  • Note: a juicy type of fruit also provides an additional fluid source in the diet.
• For 24-48 hours postop, where abdominal surgical approach is used, feed iron-rich foods to prevent anemia (e.g., cooked beef/chicken liver, cooked beef/turkey/oysters, scrambled or hard-boiled eggs) and additional high caloric foods, along with continuing the rat’s usual diet.

Outcome

• Post-op pain is relieved.
• Incision site remains free from infection.
• Appetite and fluid intake are normal.
• Abnormal weight loss is prevented.
• Feces and urine output are normal.
• Incision heals normally.
• Quality of life is improved.
• Comfort and quality of life increased where neuter has been performed in cases of disease/disorder or emergency.

Prevention of complications

• Assess the rat’s health and stability prior to the procedure. Use caution with rats that have signs of respiratory disease, are obese or elderly.
• Refrain from withholding food and water prior to or following the surgery, to prevent hypoglycemia or dehydration in the rat.
• To prevent hypothermia, monitor the body temperature throughout the procedure and postop, by using warm water circulating mats or heated pads at a controlled temperature. Note: monitor the body temperature closely as hyperthermia can be just as deadly to the rat as hypothermia.
• Determine the appropriate anesthetic agent for use in the rat, based on age, health and type of procedure. Note: reversal agents should be at the ready when using injectable anesthetic agents.
• Avoid giving injectable anesthetics IM or SQ to prevent the potential for skin and muscle necrosis and sloughing and self-mutilation by the rat due to irritating agents.
• Administer oxygen perioperatively to avoid hypoxemia and hypocapnia.
• Ensure proper procedure is followed for each technique to prevent visceral herniation, tearing of vaginal tunic or testicular vessels, or damage to prepuce. Prevent pulling testicle to far from body, in rats, when performing surgery so as not to tear the vessels. Inadequate control of subcutaneous vessels and those within the tunics can be cause for incisional and scrotal hemorrhage. (Bennett, Rodents: soft tissue surgery, 2009)
• Monitor for and correct signs of bleeding and/or fluid loss with warmed crystalloid fluids by parenteral (e.g., IV, SQ) routes as necessary.
• Prevent wound dehiscence or disruption by managing pain control. An Elizabethan collar should be avoided unless absolutely necessary, as rats utilize their hands to eat, and need to be able to reach their mouth.
• Provide a quiet environment to reduce stress and fear.

Comments

Pros and cons for the types of procedures:

Scrotal Approach:

• Pro: Least invasive, prevents reproduction, prevents testicular tumors, and may reduce aggressive behavior if done early in the rat’s life.
• Con: Due to the rat being low to the ground, the incision site does tend to get urine on it, which can lead to the potential of scrotal abscesses. For this reason, a course of an antibiotic, postoperatively, may be considered per veterinarian whether there is any prior respiratory disease or not.

Abdominal Approach:

• Pro: Prevents reproduction, prevents reduces/testicular tumors, correct cryptorchidism, and may reduce aggressive behavior if done early in the rat’s life.
• Con: More invasive, greater risks if the rat chews the wound, more heat loss due to having the abdomen open and a larger surgical field, as well as a 3-layer abdominal closure that would be needed, all adding to the anesthetic time”….

Consultants

• Adele Wharton BVSc, MRCVS, CertGP (F&L) Locum Veterinary Surgeon
• Lindsay Pulman, LVT, LATg

References

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2. Bennett, R. A. (2012). Soft Tissue Surgery. In K.E. Quesenberry & J.W. Carpenter (Eds.), Ferrets, Rabbits, and Rodents, Clinical Medicine and Surgery (Third Edition ed.) (pp. 378-380). St. Louis: Saunders.
3. Flecknell, P., & Waynforth, H. (1992). Experimental and Surgical Technique in the Rat, Second Edition. New York: Academic Press.
4. Girling, S. (2013). Part 1 Small mammals. Veterinary nursing of exotic pets (Second ed., pp. 36-47 and 91-97). Chichester, West Sussex: Wiley-Blackwell.
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6. Harkness, J. & Wagner, J. (1995). Biology and medicine of rabbits and rodents Fourth Edition. Baltimore: Williams & Wilkins.
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9. Martin, L., Thompson, A., Martin, T.,Kristal, M. (2001). Analgesic Efficacy of Orally Administered Buprenorphine in Rats. Comparative Medicine, copyright February 2001, American Association of Laboratory Animal Science, Vol. 51, No. 1, Pages 43-48
10. Mayer, J. & Donnelly, TM. (2013). Clinical Veterinary Advisor: Birds and Exotic Pets. St. Louis: Saunders
11. Murray, M. (2006). Spays and neuters in small mammals. Proc of the North Am Vet Conf, pp. 1757-9. Retrieved May 13, 2014, from http://www.ivis.org/proceedings/navc/2006/SAE/635.pdf?LA=1
12. Olson ME, Bruce J. Ovariectomy, ovariohysterectomy and orchidectomy in rodents and rabbits. Can Vet J. 1986;27:523–7. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1680421/?page=1
13. Richardson, C., & Flecknell, P. (2009). Rodents: anaesthesia and analgesia. In E. Keeble, & A. Meredith(Eds.), BSAVA manual of rodents and ferrets (pp. 63-72). Quedgeley: British Small Animal Veterinary Association.