Sterilization of the female dog is commonly performed surgically via the "spay," in which both ovaries and the uterus are removed. It is a major surgery, though a commonly performed one. Why all female dogs should be spayed Mammary Cancer A female dog spayed before her first heat will have a near zero chance of developing mammary cancer. After the first heat, this incidence climbs to 7% and after the second heat the risk is 25% (one in four!). It is easy to see that an early spay can completely prevent what is frequently a very difficult and potentially fatal form of cancer. But is it too late if a dog is already past her second heat? No, in fact spaying is important even in female dogs who already have obvious tumors. This is because many mammary tumors are stimulated by estrogens; removing the ovaries, the source of estrogens, will help retard tumor spread. Spaying removes both the uterus and both ovaries and is crucial in the prevention as well as the treatment of mammary cancer. Simple Convenience The female dog comes into heat every 8 months or so. There is a bloody vaginal discharge and attraction of local male dogs. Often there is an offensive odor. All of this disappears with spaying. What is pyometra "Pyometra" is the life-threatening infection of the uterus which generally occurs in middle-aged to older female dogs in the six weeks following heat. The hormone "progesterone," which primes the uterus for potential pregnancy, does so by causing proliferation of the blood-filled uterine lining and suppression of uterine immune function. It is thus easy during heat  for bacteria in the vagina to ascend to the uterus to cause infection. The uterus with pyometra swells dramatically and is filled with pus, bacteria, dying tissue, and toxins. Without treatment, the pet is expected to die.  Despite her serious medical state, she must be spayed quickly if her life is to be saved. This is an extremely common disease of older unspayed female dogs! Pyometra is not something which might happen: it probably will happen The older unspayed female dog has an irregular heat cycle. There is no end of cycling comparable to human menopause. If you still decide against spaying, be very familiar with the signs of pyometra. (These include loss of appetite, lethargy, vomiting, excessive thirst, marked vaginal discharge). For more information on pyometra, click here. Now that we know it is a good idea to spay, what happens next? It is very important that the patient has not been fed in at least 8 hours. Anesthetic medications commonly induce nausea and vomiting can be very dangerous in a sedated patient (vomit can be inhaled/aspirated leading to pneumonia). A preoperative evaluation is performed; pre anesthetic blood work completed and results examined. An intravenous catheter is placed to facilitate the administration of anesthetic drugs, intravenous fluids administration, and for use in case of emergency. This necessitates shaving a small patch of skin on one of the legs. A tranquilizer or other pre-anesthetic medication is administered to ease the induction of anesthesia. A special medication is given intravenously to induce sleep. This medication is called an "induction agent" and lasts only long enough to establish the maintenance of anesthesia by the inhalant anesthetic (gas). Once the pet is asleep, an tube is placed in the throat to insure that a clear airway is maintained through out the procedure. A pre-surgical injection of an anti-inflamatory is given to lessen post operative pain in your pet. Sometimes a cough is noted for a couple of days after surgery. This may have been caused by the tube in the throat. Such coughs only last a couple of days; anything that persists longer should be re-evaluated. The tube is hooked up to a special machine to deliver a specific concentration of inhalant gas mixed in 100% oxygen. A special technician is assigned to the monitoring of this pet so that the concentration of inhalant gas can be changed, color, heart rate, respiration and other parameters are followed. In the surgical prep area, the abdomen is shaved and scrubbed. The bladder is emptied and the patient is moved to a surgical suite, where she is draped with special clothes or papers to isolate the area where surgery will take place. An incision is made on the midline of the abdomen, and the three points where the ovaries and uterus attaches are tied off and cut. The abdomen is checked for bleeding and two or three layers of stitches are placed to close the incision. It is helpful to know that should the skin stitches come out, there are two layers below holding everything closed. Most commonly skin stitches are not placed but if they are present, you will need to return in 10-14 days to have them removed. The anesthesia technician continues monitoring until the pet dog wakes up and coughs out the throat tube. The patient is kept in an observation room until she is able to walk. What to expect at home Most spay patients go home the next day as if nothing had happened though some will need pain medication for a few days. Some nausea may occur in the first couple of days after surgery and it would not be unusual for the pet to refuse food for a day or two after surgery. As noted above, a cough may persist for a couple of days as a result of the throat tube. This should not persist longer than a couple of days. Dogs who show a propensity to lick their stitches will need an Elizabethan or "E" collar to restrict access to the stitches. This is not very comfortable for the dog but must be used strictly until the stitches are out and the incision is healed. Activity should be restricted during the week following surgery. Excessive activity can lead to swelling or fluid accumulation under the incision. If a fluid pocket does form, it should resolve on its own after a few weeks. If a fluid pocket forms and drains liquid from the incision, the dog should be re-checked with the veterinarian. Spaying is one of the most important health measures that can be provided for a female dog of any age. What about behavioral changes? The female dog's reproductive tract is dormant for most of the year. It only activates for the three week period of heat. This means that from a behavioral stand point, the female dog acts spayed most of the time. It is unlikely that any change will be evident.