Surgical Updates

Elizabeth M. Hardie, DVM, PhD, Diplomate ACVS

College of Veterinary Medicine

North Carolina State University, Raleigh, NC

 

     Spaying: What, When and How?

 

            Spaying has been shown to reduce unwanted pregnancies, prevent pyometra and decrease the risk of mammary gland tumors in female dogs and cats.  However, increased tendency to develop obesity, bone cancer, aggressiveness, sedentary behavior, and urinary incontinence may develop after spaying.  The ideal spay would result in positive effects from spaying with the least risk of developing negative effects.  It would also result in minimal pain and immediate postoperative complications.  Controversy thus continues to surround the best time and method of spaying.  Veterinarians in the United States should be aware of differing practices and the rationale for their use. 

 

            A major controversy is whether ovariohysterectomy or ovariectomy is the preferable surgery.  The rationale for removing the uterus is that stump pyometra may develop if the uterus is not removed.  The rationale for ovariectomy is that the surgery is less invasive and the risk of pyometra is minimal once the animal is no longer cycling.  In several long term studies of dogs and cats under going ovariectomy, stump pyometra did not occur in any animal after surgery.  Studies have also shown that there is no difference in the incidence of urinary incontinence after ovariectomy or ovaraiohysterectomy in the dog.

 

            A second controversy surrounds whether or not a midline approach or a flank approach is preferable.  The midline approach is the standard method taught in veterinary schools in the United States.  The flank approach is routinely used to perform ovariectomy, with each ovary being approached through a small, muscle-separating approach.  The flank approach is also used to perform ovariohysterectomy in feral cat neutering programs.  One ovarian pedicle is ligated, the uterine horn is followed to the cervix, the uterus and uterine vessels are ligated and then the opposite uterine horn is is followed to the second ovary.  The advantages of the midline approach are that it is technically easier to perform an ovariohysterectomy from this approach, the incision can be quickly opened if needed, and both sides of the reproductive tract are easily accessible from one approach.  The advantage of the flank approach is that, in experienced hands, it allows ovariectomy or ovariohysterectomy to be performed through a very small lateral incision.  The flank approach can be closed with a few buried sutures and has a minimal risk of dehiscence.

 

            More recently, techniques for laprascopic ovariectomy and ovariohysterectomy have been described for the dog.  Although the surgery is technically challenging, the advantage of performing a spay using minimally invasive surgery is that the dog experiences less postoperative pain and distress. 

 

            A third controversy surrounds the best time to perform a spay.  This controversy has been widely discussed in the United States literature in regard to the issue of neutering at a very young age compared to the traditional age of 6-8 months.  Initial studies of 2-300 dogs and cats followed for up to 4 years did not indicate physical or behavioral differences between early age spaying or traditional age spaying.  A larger study of 983 dogs found that 12.9% of dogs spayed at < 3 months developed urinary incontinence, while only 5% dogs spayed at >3 months became incontinent.  Other differences documented in early age neutered dogs compared to traditional age neutered dogs were an increased incidence of cystitis, hip dysplasia, noise phobias and sexual behaviors, and a decreased incidence of obesity, separation anxiety, escaping behaviors, and inappropriate elimination when frightened.  In 859 cats, an increased incidence of shyness was found in early age neuters compared with traditional age neuters, whereas a decreased incidence of asthma, gingivitis and hyperactivity were found.

 

 

In Europe, the debate has centered on whether or not to spay before or after the first heat.  The mammary carcinoma data would suggest that performing a spay before the first heat would result in the lowest chance of mammary cancer.  The pyometra data would suggest that as long as a spay was performed in the first 4 years of life, pyometra is not likely.  One study of 809 bitches showed no difference in urinary incontinence in animals spayed before or after the first heat at the 5% significance level, but a difference at the 10% level.  Other studies have documented urinary incontinence in 9.7% of bitches spayed before the first heat compared to a 20% incidence in bitches spayed after the first heat.  Even though the incidence of incontinence was lower in bitches spayed before the first heat, severity of the incontinence in these dogs was much worse than in dogs spayed after the first heat.  The risk of obesity associated with spaying appears to be worse in sexually mature animals compared to immature animals. 

 

More recently, studies in Rottweilers have shown that the risk of osteosarcoma is increased in spayed and neutered animals compared to intact animals.  For each month that an animal remained intact, there was a 1.4% decrease in osteosarcoma risk.  The overall incidence of osteosarcoma in the study population of 683 Rottweilers was 12.6% during the study period.  Cruciate injury has also been shown to be more common in spayed and neutered dogs.

 

The question must be asked: is there a group of animals, particularly dogs, in which the risks of spaying may outweigh the benefits?  The most likely candidates would be large breed dogs at increased risk for cruciate rupture, osteosarcoma, urinary incontinence and/or dominance aggression.  Osteosarcoma may result in early death, while urinary incontinence and/or dominance aggression can result in a pet becoming unacceptable and at risk of euthanasia.  Weighing the risks of these conditions may shift the balance of “spay to prevent mammary cancer and pyometra” to “don’t spay or delay spay to prevent severe urinary incontinence or biting”. 

 

Okkens AC, Kooistra HS, Nickel RF.  Comparison of long term effects of ovariectomy versus ovariohystrectomy in bitches.  J Reprod Fertil Suppl 1997; 51:227-231.

Spain CV, Scarlett JM, Houpt KA.  Long term risks and benefits of early age gonadectomy in dogs.  JAVMA 2004; 224:80-387.

Spain CV, Scarlett JM, Houpt KA.  Long term risks and benefits of early age gonadectomy in cats.  JAVMA 2004; 224:372-379.

Cooley DM, Beranek BC, Schlittler DL, et al.  Endogenous gonadal hormone exposure and bone sarcoma risk.  Cancer Epidemiology, Biomarkers & Prevention 2002; 11:1434-1440.

 

Condition

Spayed

Intact

Reference

Pyometra

 

15% of dogs > 4 years in Beagle colony, avg age 9 years

Fukuda S, 2001

 

 

Pyometra

Mammary Carcinoma

Weight Gain > 150%

0% cats, dogs

1.6% dogs, 2% cats

10.9% dogs, 9.4% cats

 

Mikaye YI 1988

95 dogs, 162 cats

ovariectomy or ovariohysterectomy

Weight gain

Sedentary behavior

Aggressive behavior

Urinary Incontinence

Excessive Hair Shedding

Smooth to Fluffy Coat

Pyometra

60%

29%

22%

18%

 

26%

7%

0%

 

Janssens LAA 1991

 

72 dogs, ovariectomy

Daily food intake

Metabolic rate

Weight gain

Increased over intact

67.2 kcal/kg0.75/day

40%

 

83.7 kcal/kg0.75/day

16%

Fettman MJ 1997

 

cats

Urinary Incontinence

0.0174 per animal year

0.0022 per animal year

Thrusfield MV 1998

809 dogs

Odds of a dog > 1 year biting a member of household

2.13 (compared to intact female)

 

Guy NC, 2001

Risk of mammary cancer

0.5%, 8%, 26% of female dogs will develop if spayed prior to 1st, 2nd, 3rd estrus

 

 

Schneider R 1969

 

dogs

Survival after mammary cancer surgery

Median survival 755 days if spayed < 2 years before sx, 301 days if spayed > 2 years before sx

Median survival 286 days if intact

Sorenmo KU,  2000

 

dogs

Risk of Mammary Cancer

 

7 times higher than spayed

Dorn 1968

cats

Osteosarcoma

3X risk of intact

 

Cooley, 2002

Cruciate Rupture

increased

 

Slauterbeck, 2004

Histomorphometry of bone, bone mass

No difference spayed and intact

 

Shen V, 1992

dogs

 

 

 

 

 

Biliary Surgery

 

            Biliary surgery is increasingly being performed in the dog and cat.  The main diseases affecting the dog are biliary mucocele, necrotizing cholecystitis, gall bladder perforation, obstruction secondary to pancreatitis, neoplasia, and trauma.  In cats, extrahepatic biliary tract obstruction is mainly associated with neoplasia, pancreatitis, cholangiohepatitis, and cholecystitis.  Cholelithiasis can occur in either species, mainly associated with chronic infection.  Signs associated with biliary tract obstruction are vague: anorexia, vomiting, abdominal discomfort, weakness, +/- fever. The signs can be waxing and waning or peracute.  Icterus occurs when bilirubin is greater than 1.5-2 mg/dL.  In addition to a CBC and serum chemistry, abdominal ultrasound is the best method of examining the gall bladder and bile duct.  Ultrasound can identify biliary distention, choleliths, gall bladder wall thickness, the presence of abnormal bile, gas in the gall bladder, the presence of peritonitis, gall bladder rupture, and masses or inflammation obstructing the bile duct.  In general, animals with surgically correctable extrahepatic biliary tract disease should be treated as emergencies.  The presence of infected bile makes them absolute emergencies.  The surgical options available for treatment include removal of the gall bladder (cholecystectomy), biliary diversion (cholecystoduodenostomy or cholecystojeujunostomy), flushing of the bile duct to remove inspissated bile, and placement of a biliary stent or catheter to maintain patency.  A jejunal feeding tube is often placed to allow feeding while disease is resolving.  If bile peritonitis is present, the abdomen is thoroughly lavaged and drained.  The postoperative course of these patients can be difficult, and the clinician must be prepared to manage pancreatitis, sepsis and shock.  The prognosis for animals with extrahepatic biliary disease that undergo surgery depends on the condition and the presence of infection.  In a study of 22 dogs with biliary mucocele, 15/22 (68%) survived surgery.  In a study of 60 dogs undergoing extrahepatic biliary tract surgery, 43/60 (72%) survived, with the presence of septic bile peritonitis, increased serum creatinine, long PTT, and hypotension being associated with death.  Overall survival of dogs with bile peritonitis is 50%, but survival is 27% in animals with septic bile peritonitis and much higher if the bile is sterile.  In a study of 19 cats undergoing surgical treatment of extrahepatic biliary disease, 100% of cats with neoplasia and 40% of cats with non-neoplastic disease died or were euthanized.

 

Worley DR, Hottinger HA, Lawrence HJ. Surgical management of gallbladder mucoceles in dogs: 22 cases (1999-2003). JAVMA 2004225:1418-1422.

Mayhew PD, holt DE, McLear RC, et al. Pathogenesis and outcome of extrahepatic biliary obstruction in cats. J small Anim Prac 2002 43:247-253.

Mehler SJ, Mayhew PD, Drobatz KJ, et al. Variables associated with outcome in dogs undergoing extrahepatic biliary surgery: 60 cases (1988-2002)