Introduction
Ovariectomy is a surgical procedure that is commonly performed in mammalian species; however, because of certain anatomic features, the procedure is more technically challenging in avian species. Most female birds, with few exceptions, have only the left side of the reproductive tract (ovary, oviduct, and uterus or shell gland) as a result of atrophy of the right side during embryonic development.1 The ovary is located along the ventral aspect of the left kidney and is tightly adhered to the CdVC, left CIV, and left kidney; thus, dissection and complete surgical removal of the ovary is difficult. The ovary is triangular, with the base of the triangle directed cranially and the apex directed caudally along the left CIV. The mesovarium is broad and short, with little distance between the wide-based ovary and the CdVC, left CIV, and left kidney. The blood vessels that supply the ovary are within the mesovarium, and hemorrhage from these vessels must be controlled during ovariectomy.1–5 Efforts to lift the ovary and occlude the ovarian vessels typically result in iatrogenic damage to the left CIV caudally, CdVC cranially, or renal veins and severe, often uncontrollable hemorrhage. Compared with mature birds, it has been suggested that juvenile birds have a more lax mesovarium and less well-developed blood vessels, which potentially facilitates ovariectomy. Both the left kidney and ovary are located under the ribs, which limits observation of and access to the ovary in birds.
Indications for partial or complete ovariectomy in birds include neoplasia, chronic or recurring ovarian cysts, oophoritis, and conditions refractory to medical management, such as bacterial yolk coelomitis.1–6 Undesirable behaviors of female birds have been linked to changes in circulating reproductive hormone concentrations during the natural breeding cycle. Sexual bonding of birds with their owners often leads to negative or unwanted behaviors, such as feather picking, courtship regurgitation, increased territorial and aggressive behaviors, tachypnea, and shaking.7,8 These behaviors can result in a bird being surrendered by the owner. Management of these behaviors includes husbandry changes, environment modification, and sex hormone manipulation with chorionic gonadotropin agonists.7–9 Theoretically, these behaviors would be ameliorated by complete ovariectomy. Such behavioral disorders have also been linked to chronic cloacal prolapse.8,10 Cloacal prolapse has a high postoperative recurrence rate because treatments are focused on maintaining reduction and not elimination of the hormonal influence on behavior. In one of the authors’ experience (RAB) with male cockatoos, bilateral orchidectomy has resulted in long-term success following cloacal surgery for prolapse. It has been theorized that complete ovariectomy would also improve the long-term success of surgical management of cloacal prolapse in female birds.
Ovariectomy for sterilization of birds is not recommended owing to the risk of fatal hemorrhage. In general, salpingohysterectomy is typically performed, after which birds are unable to lay eggs but still exhibit reproductive behaviors.3 Follicles develop yolks that are expected to be resorbed and not ovulated because they lack the hormonal feedback from the uterus necessary for ovulation.4 If partial salpingohysterectomy is performed, yolks might be ovulated into the coelom, predisposing the bird to development of yolk coelomitis.11
No standardized method for ovariectomy has yet been developed for birds. Limited success with use of monopolar radiofrequency electrosurgery wire loop and hemostatic clips, microsurgical techniques, carbon dioxide laser ablation, and minimally invasive techniques has been reported.1,2,4,12 None of these procedures has been able to mitigate the risk of iatrogenic damage to the CdVC and left CIV, which typically results in fatal hemorrhage. Once hemorrhage occurs, it is very difficult to control because the source cannot be readily identified, given that it is obscured by the ovary. Because of the risk of fatal hemorrhage, avian ovariectomies are often partial, involving removal of only the grossly evident ovarian tissue and not the ovary's attachments to the left kidney, CdVC, and left CIV. If the ovary is not completely excised, the ovarian remnant will likely undergo hypertrophy, produce follicles, and secrete hormones.
Vessel and tissue–sealing devices are commonly used to minimize hemorrhage, allow for rapid sealing and dissection of blood vessels and tissues, and decrease durations of surgery and anesthesia. One VTSDa has been approved by the US FDA to seal vessels ≤ 7 mm in diameter in humans. This VTSD rapidly senses the impedance of the tissue within its jaws and delivers energy output to create a permanent seal by denaturing collagen and elastin and reforming them to create a seal zone.13 It has been shown to create a 1-mm-wide zone of lateral heat damage. A blade within the handpiece incises through the middle of the seal zone when deployed so that both sides are sealed. The objective of the study presented here was to assess the feasibility of a novel technique involving a VTSD for ovariectomy in chickens to evaluate the potential application of the procedure to other avian species.
Materials and Methods
Chickens
Ten juvenile (< 4 months old) and 10 mature (> 18 months old) domestic chickens (Gallus domesticus) were used in the study. In the juvenile group, there were 3 Barred Rock chickens and 7 Rhode Island Red chickens. All of the birds in the mature group were Leghorn chickens. The birds were obtained from the Louisiana State University Poultry Unit. Each bird underwent a physical examination and was deemed healthy. All birds were allowed a 1-week acclimation period prior to the start of the study, during which time they were housed in food animal stalls in their respective age group and fed a 16% layer pellet dietb ad libitum. Fresh water was also provided ad libitum. On the day of surgery, each bird had food withheld for a minimum of 2 hours before intubation. The study protocol was approved by the Louisiana State University Institutional Animal Care and Use Committee (protocol No. 18-093).
Anesthesia and analgesia
The day of surgery was designated as day 0. Each bird was premedicated with butorphanol tartratec (2.0 mg/kg, IM) approximately 30 minutes prior to induction of anesthesia. Anesthesia was induced with isoflurane in oxygen delivered with a mask. Once unconscious, each bird was intubated with an uninflated, cuffed, endotracheal tube (internal diameter, 3.5 mm); an end-tidal carbon dioxide concentration sensor was attached to the endotracheal tube. Three ECG leads were attached to each bird's thorax to monitor heart rate and rhythm, and the bird was positioned on a circulating warm water pad. A surgical anesthetic plane was maintained throughout the procedure with isoflurane (1% to 2% in oxygen) delivered at a rate of 1.5 L/min through a nonrebreathing system. Each bird maintained spontaneous ventilation throughout the procedure; however, ventilation was assisted at a rate of 5 breaths/min.
A 22-gauge IV catheter was placed in the right medial metatarsal vein. The catheter was used to infuse crystalloid fluidsd (5 mL/kg/h), 2% lidocaine hydrochloride (2.0-mg/kg bolus followed by a constant rate infusion at 50 μg/kg/min), and cefazolin (30-mg/kg bolus administered slowly).
Patient position and preparation
Each bird was placed in right lateral recumbency with both wings positioned dorsally and secured to the table with adhesive tape. The right leg was positioned perpendicular to the vertebral column and secured to the table with adhesive tape. An adhesive tape stirrup was placed around the leg band on the left leg; the leg was extended and externally rotated as far as possible and then secured to the table. Feathers were removed from the left lateral and ventral aspects of the body wall and cranial aspect of the left leg to the level of the nonfeathered skin. The skin was scrubbed with gauzes soaked with 4% chlorhexidine solution,e alternating with gauzes soaked with isopropyl alcohol for 3 cycles.
Surgical procedure
All procedures were performed by a board-certified veterinary surgeon who was experienced in avian surgery (RAB). The surgeon used 3.5× surgical loupes.f Intraoperative and postoperative complications were recorded.
For each bird, a left lateral celiotomy was performed as previously described.1–4 In all mature birds, salpingohysterectomy was first performed with the VTSD to gain exposure to the ovary. Salpingohysterectomy was initiated with the VTSD applied to the ventral ligament to allow visualization of the dorsal ligament. Starting at the infundibulum, the VTSD was applied to the dorsal ligament and moved caudally to the level of the cloaca. The VTSD was used to seal the uterus and transect it to allow removal of the oviduct and uterus. No effort was made to ensure the entire uterus was removed because the goal was only to achieve visualization. Salpingohysterectomy was not necessary in immature birds; however, the intestines were packed caudoventrally with moist gauzes to provide exposure to the ovary. Large active ovaries with variably sized yolks in mature birds required debulking with the VTSD to allow identification of the ovary and deeper structures. Ovariectomy was performed with the VTSD in a caudal to cranial direction.
The caudal pole of the ovary was elevated from the left CIV, and the jaws of the VTSD were positioned between the ovary and the CIV. The current was activated; once the unit signaled the seal was complete, the blade within the jaws was deployed to cut through the seal zone. It was not possible to remove the entire ovary with 1 application of the VTSD. After the first application, the caudal portion of the ovary was elevated, and the process was repeated in a more cranial location. This repeated effort was continued until all grossly visible ovarian tissue was removed or hemorrhage prevented additional dissection.
Intraoperative hemorrhage was subjectively graded on a scale from 0 to 4 (0 = no hemorrhage, 1 = minimal hemorrhage, 2 = mild hemorrhage, 3 = moderate hemorrhage, and 4 = life-threatening hemorrhage). If hemorrhage was encountered during ovariectomy, it was controlled with placement of a gelatin spongeg and digital pressure. Dissection was continued after hemorrhage was controlled. In some birds, a gelatin sponge was held on the site of hemorrhage with forceps while ovariectomy was continued. If it appeared that continuing dissection would result in fatal hemorrhage, the procedure was abandoned and the celiotomy was closed. When ovarian tissue could not be excised without risk of life-threatening hemorrhage, it was left in place; subsequently, hemorrhage was controlled, the celiotomy was closed, and the bird was allowed to recover from anesthesia. In such cases, a second comparable surgery was performed a week later to remove the remaining ovarian tissue.
Once the ovary was removed, the site was inspected for residual ovarian tissue. If there was suspicion that some ovarian tissue remained, it was fulgurated with the VTSD. The suspected ovarian tissue was grasped within the jaws of the VTSD, and the current was activated because it was not possible to fit the jaws between the small pieces of ovary and the vessels. Following ovariectomy, a gelatin sponge was placed over the ovariectomy site for hemostasis and to allow identification of the site at necropsy. A gauze sponge count was not performed.
The duration of surgery (the interval between skin incision and incision closure) was recorded.
Recovery of birds from anesthesia
After closure of the skin incision, delivery of isoflurane was discontinued and delivery of oxygen was continued until each bird had recovered to a point when maintenance of endotracheal intubation was no longer possible. The duration of anesthesia (interval from endotracheal intubation to extubation) was recorded. Following extubation and regaining the ability to swallow, each bird was given meloxicam (1.0 mg/kg, PO). This dose of meloxicam was given once daily for 3 days. Additional rescue analgesia (butorphanol [2.0 mg/kg, IM, q 4 h]) was available as required. For the duration of the recovery period, birds were monitored multiple times daily by caregivers and the authors for increases in respiration rate and changes in behavior and general appearance to determine the need for rescue analgesia. A pain scale was not used because there was no standardized scale available for avian species.
Postmortem evaluation
Each bird was allowed a 14-day recovery period following surgery. Any bird that died prior to day 14 was submitted for necropsy. Fourteen days after surgery, the birds were administered isoflurane by a mask to induce unconsciousness and euthanized by IV injection of pentobarbital sodium (1 mL/4.54 kg of body weight). Once cardiac activity had ceased, a complete necropsy was performed by a board-certified veterinary pathologist, who is also a board-certified poultry veterinarian (NW). During necropsy, the site of the gelatin sponge placed during surgery was carefully examined for any remaining ovarian tissue, and tissue samples from the site were collected for histologic evaluation. Tissue samples were also collected from any other areas of gross abnormality.
Results
The mean ± SD body weights for the juvenile and mature birds were 1.12 ± 0.14 kg (range, 0.77 to 1.3 kg) and 1.31 ± 0.07 kg (range, 1.03 to 1.49 kg), respectively. The mean body weight for the combined population was 1.22 kg (range, 0.77 to 1.49). All mature birds had large active ovaries with variably sized yolks that underwent debulking with the VTSD to allow better observation of the ovary and deeper structures (Figure 1). All of the birds survived the surgical procedure and recovered from anesthesia without complications. No bird required rescue analgesia. One juvenile bird was found dead 12 days after surgery, and the cause of death was determined to be sepsis resulting from severe air sacculitis. Data regarding this bird's ovariectomy were included in the analyses.
Representative photographs of 2 domestic laying hens (Gallus domesticus) during ovariectomy performed with a VTSD through a left lateral celiotomy. A—In a mature (> 18 months old) bird, notice the ovary with multiple follicles and yolks of various sizes (arrows). B—In a juvenile (< 4 months old) bird, the ovarian tissue (asterisk) lacks yolks and follicles.
Citation: American Journal of Veterinary Research 82, 4; 10.2460/ajvr.82.4.310
The mean ± SD durations of anesthesia for juvenile and mature birds were 50.5 ± 5.1 minutes (range, 40 to 58 minutes) and 67.2 ± 7.6 minutes (range, 57 to 80 minutes), respectively. The mean durations of surgery for juvenile and mature birds were 31.6 ± 5.1 minutes (range, 20 to 39 minutes) and 45.3 ± 8.5 minutes (range, 33 to 62 minutes), respectively.
The VTSD functioned well to seal the vessels of the mesometrium and the vagina at the cloaca with no hemorrhage or other complications. The most common intraoperative complication was hemorrhage (Table 1). One mature and 2 juvenile birds developed life-threatening hemorrhage. Initially, an attempt was made to identify the source of hemorrhage. In some birds, holes were observed in the veins dorsal to the ovary, but the severity of hemorrhage precluded further investigations. The first attempt to perform ovariectomy was abandoned in 1 mature and 1 immature bird because of hemorrhage. Hemorrhage in the mature bird was categorized as moderate originally, but bleeding continued during additional dissection. The juvenile bird's hemorrhage was categorized as life-threatening. At necropsy, both of these birds had histologic evidence of remaining ovarian tissue. These 2 birds recovered from the first surgery uneventfully, and a second attempt to perform ovariectomy was made 1 week later. The remaining juvenile bird that developed life-threatening hemorrhage did not undergo a second surgery because the surgeon believed that all ovarian tissue had been removed. At necropsy, no gross ovarian tissue was present in this juvenile bird, but ovarian tissue was identified histologically.
Intraoperative hemorrhage score determined during ovariectomy performed with a VTSD in 20 chickens.
| Intraoperative hemorrhage score | No. of mature birds | No. of juvenile birds | Total No. of birds |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 1 | 0 | 4 | 4 |
| 2 | 4 | 3 | 7 |
| 3 | 5 | 1 | 6 |
| 4 | 1 | 2 | 3 |
Twenty domestic laying hens (Gallus domesticus), of which 10 were immature (< 4 months old) and 10 were adults (> 18 months old), underwent ovariectomy performed with a VTSD. Intraoperative hemorrhage was subjectively graded by the surgeon on a scale of 0 to 4 (0 = no hemorrhage, 1 = minimal hemorrhage, 2 = mild hemorrhage, 3 = moderate hemorrhage, and 4 = life-threatening hemorrhage).
Among the 20 birds, postoperative complications included incisional bruising (1 juvenile bird [5%]), minor surgical site dehiscence (1 [5%] adult bird), presence of a gossypiboma (1 [5%] juvenile bird), and sudden death at 12 days after surgery (1 [5%] juvenile bird). The bird that died suddenly 12 days after surgery was not one of the birds that developed life-threatening hemorrhage.
At necropsy, ovarian tissue was observed grossly in 2 mature birds (Figure 2) and identified histologically in 6 birds (2 mature and 4 juvenile birds; Figure 3). In the 2 mature birds, the volume of the remaining ovarian tissue detected grossly was 2 × 1 × 1 cm and 1.3 × 0.7 × 0.7 cm; in the other 2 mature birds, the histologically detected area of the remaining ovarian tissue was 0.7 × 0.3 cm and 0.2 × 0.2 cm. One mature bird had histologically detectable, nonviable, degenerated ovarian tissue. In the 4 juvenile birds, the histologically detected area of the remaining ovarian tissue was 0.7 × 0.5 cm, 0.1 × 0.1 cm, 1.2 × 0.4 cm, and 0.2 × 0.1 cm. The overall complete excision rate for ovariectomy was 60% (12/20 birds). Additional necropsy findings among the 20 birds included surgical site lymphohistiocytic inflammation and fibrosis with granulation tissue (20 [100%]), intralesional gelatin material (17 [85%]), intestinal adhesions to the site (13 [65%]), and a gossypiboma (1 [5%]).
Photographs of the ovariectomy site of a mature chicken that had residual gross ovarian tissue. This bird did not experience life-threatening hemorrhage during ovariectomy. A—View of the open coelom (the chicken is in right lateral recumbency with cranial orientation to the left). The ovary (arrow), lung (L), gel material (G), and left kidney (K) are visible. B—A close-up view of residual gross ovarian tissue (arrow) in proximity to the kidney (K). C—In this formalin-fixed specimen, residual gross ovarian tissue (arrow) with the gelatin sponge (G) is present. The left adrenal gland (A) and fibrosis (asterisk) are also visible.
Citation: American Journal of Veterinary Research 82, 4; 10.2460/ajvr.82.4.310
Photomicrographs of tissue sections obtained from the ovariectomy site of 2 separate mature birds following euthanasia 14 days after ovariectomy. A—Viable ovarian tissue. H&E stain; bar = 2.0 mm. B—In this section, notice the marked fibrosis (asterisk) and inflammatory infiltrates surrounding the gel material (G) and adhering to the left kidney (K). H&E stain; bar = 1.0 mm. C—In this section, marked fibrosis (asterisk) and inflammatory infiltrates have surrounded the gel material (G) as well as infiltrated the adrenal gland (A) and degenerated ovary (arrows). H&E stain; bar = 2.0 mm. D—Notice the degenerated ovary is infiltrated by granulomatous and lymphocytic infiltrates and fibrosis. H&E stain; bar = 500 μm.
Citation: American Journal of Veterinary Research 82, 4; 10.2460/ajvr.82.4.310
Discussion
The present study was undertaken to assess the feasibility of a novel technique involving a VTSD for ovariectomy in 20 chickens to evaluate the potential application of the procedure to other avian species. The surgical survival rate was 100% (20/20 birds), and the complete ovariectomy rate was 60% (12/20 birds). Only 10% (2/20) of the birds had gross ovarian tissue at necropsy.
The most common intraoperative complication of ovariectomy was hemorrhage, which developed in all birds. Hemorrhage was considered a serious complication (ie, moderate or life-threatening hemorrhage) in 9 of the 20 (45%) birds; however, the hemorrhage was controlled in all birds. In 2 birds, hemorrhage was so severe that the procedure was abandoned after control of bleeding was established. Hemorrhage always occurred dorsal to the ovary after the jaws of the VTSD were opened. Hemorrhage was controlled with rapid application of gelatin sponges and digital pressure. In some birds, a gelatin sponge was held on the hemorrhage site with forceps while ovariectomy was continued. Hemorrhage appeared to originate from the low-pressure venous system (CdVC and left CIV) and not the ovarian artery because the release of blood was not pulsatile. In some birds, a defect in the wall of the left CIV or CdVC created by the VTSD was observed.
Theoretically, the inherent properties of the VTSD would seal the vessels and tissue within the jaws, resulting in complete ovariectomy; moreover, that single instrument would seal any defect in the CdVC, renal veins, or CIVs, thereby providing a comparatively safer option for ovariectomy in avian species. However, in the present study, there was still a risk of serious hemorrhage.
In birds, the left ovary is located under the last 3 to 4 ribs. During left lateral celiotomy, the seventh and eighth ribs are transected; any additional dissection cranial to that site would damage the lungs. In the birds of the present study, the narrow operating space within the coelomic cavity as well as the anatomic restrictions provided by the ribs prevented dissection in a cranial to caudal manner. The limited access impeded application of the VTSD's jaws dorsal to the ovary and parallel to the veins, thereby resulting in a tendency for the tips of the jaws to angle slightly into the underlying veins. A conscious effort was made to keep the VTSD's jaws parallel to the veins dorsal to the ovary. It is possible the tips of the jaws damaged vessel walls but did not seal the defects, resulting in hemorrhage. This scenario may have accounted for the holes observed in the veins of some birds.
After each application, charred tissue was observed on both jaws of the VTSD. Often, the charred tissue within the jaws was adhered to the surrounding tissue, making it difficult to disengage the jaws. There was concern that when the jaws were pulled from the underlying blood vessels, it may have torn a hole. To combat this, both frequent cleaning of the jaws and stabilization of blood vessels during gentle opening of the jaws were employed; however, these strategies did not seem to resolve the problem or reduce the risk of hemorrhage.
In the present study, it was not possible to remove the entire ovary in any bird with 1 application of the VTSD. In some birds, small (< 1 mm3) portions of ovarian tissue remained, but because they were so small, it was not possible to apply the jaws between them and the veins. The VTSD was applied directly onto these pieces of ovary, and the current was activated in an attempt to fulgurate these ovarian remnants. Microscopic ovarian tissue could have remained and been detected at necropsy. In live birds, it is possible that this tissue would hypertrophy and produce hormones.
In 1 mature bird, nonviable, degenerated ovarian tissue was detected histologically. This may have represented destruction of the ovarian tissue by fulguration. On the basis of this finding, one may conclude that fulguration could successfully destroy small pieces of remnant ovary in birds undergoing ovariectomy.
The VTSD evaluated in the present study was chosen because of its commercial availability, short working length, small jaw size, and ability to incise tissues after the sealing cycle has been completed. All of these properties were considered important with regard to application of the device in a confined space, such as the coelom of a chicken, and for delicate dissection of an avian ovary. During the interval since the collection of data in the present study, there have been several advances in handpiece technology of the evaluated VTSD. There are 2 more precise handpieces now available,13,h,i which could provide solutions to the challenges of the mesovarium bunching during application and firing of the VTSD, causing a seal of the tissues to form incompletely, and difficulty in proper device placement faced during ovariectomy in birds. Another improvement in the VTSD technology is the addition of nonstick nanocoated jaws that are reported to reduce eschar buildup and decrease tissue adherence on the jaws, resulting in fewer and easier jaw cleanings.13 Had these options been available for the present study, complete ovariectomy in the chickens may have been easier and more successful.
In the study of the present report, birds were assigned to 1 of 2 groups on the basis of their reproductive stage. It has been suggested that ovariectomy is easier in juvenile birds than it is in mature birds because the mesovarium is more lax and the vessels supplying the ovary are not as well developed. Juvenile avian ovaries are small, allowing for easier identification of the CdVC and left CIV. These factors could increase the ease of performing a complete ovariectomy and potentially minimize the associated risk of fatal hemorrhage in avian species.
Most birds that require ovariectomy for medical reasons are adults. When a mature bird is reproductively active, the ovary is large with numerous follicles of variable size. To support follicle development, the blood supply hypertrophies, which increases the risk of hemorrhage during ovariectomy. Ideally, ovariectomy in a bird would be performed only when the ovary has cycled into a quiescent state or medications have been administered to achieve that state. One of the more common indications for ovariectomy in birds is ovarian neoplasia, which also typically results in a large, well-vascularized ovary.
The oviduct and shell gland of the mature chickens in the present study were large and well developed and occupied a considerable portion of the coelom. Salpingohysterectomy was performed prior to ovariectomy to allow observation of the ovary. The VTSD functioned well to seal the vessels of the mesometrium and the vagina at the cloaca with no hemorrhage or other complications. The end of the vagina was sealed, and there was no evidence of cloacal contents in the coelom of any mature bird at necropsy. Following salpingohysterectomy, the intestines were retracted with moist sterile gauzes. Complete retraction of the intestinal tissue proved to be difficult in the mature birds, even when an assistant focused on maintaining retraction. A similar strategy used in the juvenile birds proved to be more effective. Even after salpingohysterectomy and with retraction of the intestines in the mature birds, full and clear access to the base of the ovary was often difficult.
All mature chickens had yolks of variable size, indicative of an active reproductive state. Most of the ovarian tissue was debulked with the VTSD prior to attempting complete ovariectomy to identify the blood vessels during dissection. Among the mature birds, the durations of anesthesia and surgery were increased (mean increases of 16.7 and 13.7 minutes, respectively), compared with findings for the juvenile birds. Unfortunately, the time required for salpingohysterectomy and debulking of the follicles was not recorded for the mature birds. However, these additional procedures were believed to be the cause of the differences in durations of anesthesia and surgery between the 2 groups of birds rather than the conclusion of the procedure being easier to perform in the juvenile birds.
Birds of 2 reproductive stages were evaluated in the present study to assess whether complete ovariectomy would be more or less difficult at a particular stage. In this study, an equal number of mature and juvenile chickens (4 birds/group) had grossly or histologically detectable ovarian tissue at necropsy. Two mature birds had grossly detectable ovarian tissue, whereas no immature birds had gross ovarian remnants. The large size of the ovary in mature birds and limited working space within the coelom prevented complete exploration for remaining ovarian tissue during surgery. In birds of either reproductive stage, hemorrhage likely contributed to incomplete removal of the ovary and the presence of histologically detectable remnant ovarian tissue. It is likely that such remnant tissue would hypertrophy and become hormonally active.
In the present study, all 20 birds had some amount of hemorrhage during ovariectomy. Mature birds most commonly had a moderate amount of hemorrhage (5/10 birds); 4 birds had a mild amount of hemorrhage, and 1 had a severe amount. Most juvenile birds had a minimal amount of hemorrhage (4/10 birds); 3, 2, and 1 bird had a mild, severe, or moderate amount of hemorrhage, respectively. In 1 mature and 1 juvenile bird, hemorrhage was sufficiently serious that had the procedure been continued, each chicken likely would have died. However, for those 2 birds, hemorrhage was controlled; a week later, a second attempt to remove the remaining ovary from each bird was performed. The mature bird that underwent a second surgery had histologic evidence of residual ovarian tissue, whereas the immature bird that underwent a second surgery did not. Despite these results, ovariectomy proved to be faster and subjectively less difficult when performed in juvenile birds.
Twelve days after surgery, 1 juvenile bird died unexpectedly as a result of sepsis secondary to bacterial air sacculitis. Air sacculitis is a known potential risk for any bird undergoing celiotomy and is not related specifically to ovariectomy. In another juvenile chicken, an intracoelomic gossypiboma (gauze used for intestinal retraction) was identified. During the surgeries undertaken in the present study, gauze sponge counts were not performed but would be recommended for clinical cases.
The information obtained in the present study appeared promising, given that there were no available data regarding survival rates among birds undergoing partial or complete ovariectomy. Results of the present study included a surgical survival rate of 100% (20/20 birds), along with rates for complete and incomplete ovariectomy of 60% (12/20 birds) and 40% (8/20 birds), respectively. Although the number of birds in the present study was somewhat small, these rates could help owners of female birds assess the risks of having their pet undergo this procedure and make a more informed decision. However, because of the lack of previously published data on techniques and outcomes for ovariectomy in avian species, use of the VTSD for ovariectomy could not be compared with other techniques. In the birds that underwent ovariectomy in the present study, use of the evaluated VTSD did not prevent hemorrhage as well as expected; furthermore, the procedure was quite technically demanding. Most surgical procedures do not have a success rate of 100%, and each surgeon will likely encounter complications in some birds undergoing ovariectomy. It is important to note that the use of the VTSD does not eliminate the problems associated with neutering female birds and that all reported methods have equally serious complications. The data acquired in the present study may provide a first step in the generation of a large database regarding ovariectomy in avian species.
Limitations of the present study included a small sample size. The study population included only birds free of ovarian disease. Pathological changes could increase the risk of hemorrhage by making it more difficult to observe important anatomic features. For the study birds, long-term follow-up information was not collected. Grossly and histologically detectable ovarian tissue was present after surgery in 8 of the 20 (40%) birds, although it appeared nonviable in 1 bird; however, it remained unclear whether remnant ovarian tissue would produce hormones or follicles. Additional studies of birds undergoing ovariectomy with the VTSD should have longer follow-up periods and include assessment of postoperative circulating reproductive hormone concentrations to ascertain whether residual ovarian tissue becomes functional.
Results of the present study indicated that ovariectomy (partial or complete) with a VTSD was successfully performed in all chickens, both mature and juvenile birds, with a 100% surgical survival rate. The entire ovary was successfully removed in 12 of the 20 (60%) birds. However, the procedure proved to be technically challenging even for a surgeon with > 35 years of experience in avian surgery. Use of the evaluated VTSD could perhaps provide a safe method for ovariectomy in both juvenile and mature birds; however, there is still a risk of major hemorrhage. Application of the VTSD for ovariectomy in other avian species warrants investigation, especially as refinements to the equipment continue to be made.
Acknowledgments
The authors declare that there were no conflicts of interest.
The authors thank Meredith Anderson from Medtronic, Minneapolis, for the donation of the VTSD hand pieces used in this study.
Abbreviations
| CdVC | Caudal vena cava |
| CIV | Common iliac vein |
| VTSD | Vessel and tissue–sealing device |
Footnotes
LigaSure small jaw open sealer/divider, Medtronic, Minneapolis, Minn.
Layena pellets, Nestlé Purina, St Louis, Mo.
Zoetis Inc, Kalamazoo, Mich.
Vetivex, Dechra, Overland Park, Kan.
Mclnlycke, Norcross, Ga.
SurgiTel, General Scientific Corp Inc, Ann Arbor, Mich.
GelFoam, Pharmacia and Upjohn Co, Kalamazoo, Mich.
LigaSure Maryland jaw sealer/divider, Medtronic, Minneapolis, Minn.
LigaSure exact dissector, Medtronic, Minneapolis, Minn.
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