I have written extensively about the subject of neutering (spaying and castrating male and female dogs and cats). The bulk of the discussion and debate about this procedure centers on the health effects. It is generally recognized to be a pretty safe procedure, though of course no surgery is entirely without risk. The scientific literature has limited information on the specific risks of the neutering surgery procedure itself and how often they occur.
Total complication rates for routine castration or spaying have been reported from 2.6%-33% of cases.The majority of these complications are minor and require no treatment. Complication rates vary considerably from practice to practice and are generally reported to be higher in studies of surgeries performed by students in training. Reported death rates are less than 0.1%.1-5
A new source of data on this subject has recently become available which represents the type of “Big Data” so popular these days. The Royal College of Veterinary Surgeons (RCVS) charity arm RCVS Knowledge, has a program in place that collects information from practices around the country in a central database. The goal is to encourage clinical audit, a quality improvement process in which veterinary practices can investigate the outcomes for their patients and compare these with those of other practices or with an established “gold standard.” This facilitates recognizing processes that aren’t working as well as they could and improvement in patient care.
The RCVS has recently released the results of data collection on complications of neutering. Though not the result of a controlled, prospective research process, this audit report is based on over 30,000 individual surgeries, so it at least represents a potentially powerful source of data. The specific variables that affect outcome of neutering surgery in individual animals can’t be identified, and there is the problem of patients who can’t be followed and whose outcome is unknown. However, this type of data complements the research evidence already available and gives us a general sense of the complication rates in the UK for these common procedures.
The outcomes measured were cases with no complications, those with minor complications not needing treatment, problems needing medical treatment, problems needing surgical treatment, and fatalities. About 8% of the cases in the database were not available for followup, and these were not included in the calculation of complication rates.
Total Overall Complications
|Abnormal but no treatment necessary||2795||9.3%||9.3%|
|Abnormal requiring medical treatment||2254||7.5%||16.8%|
|Abnormal requiring surgical intervention||341||1.1%||17.9%|
|Fatality of animal||29||0.1%||18.0%|
|No abnormality present||24627||82.0%||100.0%|
Complications for Male Cats
|Abnormal but no treatment necessary||56||1.4%||1.4%|
|Abnormal requiring medical treatment||53||1.3%||2.7%|
|Abnormal requiring surgical intervention||23||0.6%||3.3%|
|Fatality of animal||3||0.1%||3.4%|
|No abnormality present||3885||96.6%||100.0%|
Complications for Male Dogs
|Abnormal but no treatment necessary||977||11.4%||11.4%|
|Abnormal requiring medical treatment||796||9.3%||20.6%|
|Abnormal requiring surgical intervention||61||0.7%||21.3%|
|Fatality of animal||6||0.1%||21.4%|
|No abnormality present||6763||78.6%||100.0%|
Complications for Female Cats
|Abnormal but no treatment necessary||616||7.0%||7.0%|
|Abnormal requiring medical treatment||385||4.4%||11.4%|
|Abnormal requiring surgical intervention||163||1.9%||13.3%|
|Fatality of animal||5||0.1%||13.3%|
|No abnormality present||7596||86.7%||100.0%|
Complications for Female Dogs
|Abnormal but no treatment necessary||1146||13.2%||13.2%|
|Abnormal requiring medical treatment||1020||11.8%||25.0%|
|Abnormal requiring surgical intervention||94||1.1%||26.1%|
|Fatality of animal||15||0.2%||26.3%|
|No abnormality present||6383||73.7%||100.0%|
These results are broadly similar to previously reported numbers, though lower than sometimes seen in studies in which inexperienced veterinary students are performing the procedures. They confirm that the procedure is very safe, that most complications are minor and do not require much, if any, treatment, and that mortality rates are very low. Females experience more complications because the surgery is necessarily more invasive. These data don’t tell us anything about the differences between specific neutering procedures, breeds, ages of patients, and many other factors, so they don’t let us predict the precise risk for individual patients. But they provide a general background that help us in making decisions about neutering.
- Pollari FL, Bonnett BN, Bamsey SC, Meek AH, Allen DG.Postoperative complications of elective surgeries in dogs and cats determined by examining electronic and paper medical records. Journal of the American Veterinary Medical Association 1996;208(11):1882-6.
- Howe LM. Short-term results and complications of prepubertal gonadectomy in cats and dogs. Journal of the American Veterinary Medical Association 1997;211(1):57-62.
- Pollari FL, Bonnettt B.N. Evaluation of postoperative complications following elective surgeries of dogs and cats at private practices using computer records. Canadian Veterinary Journal 1996;37:672-8.
- Burrow R, Batchelor D, Cripps P. Complications observed during and after ovariohysterectomy of 142 bitches at a veterinary teaching hospital. Veterinary Record 2005;157(26):829-33.
- Root Kustritz MV. Effects of surgical sterilization on canine and feline health and on society. Reprod Domest Anim. 2012 Aug;47 Suppl 4:214-22.