Single incision laparoscopic-assisted ovariohysterectomy for an ovarian tumor in a dog

Abstract

This report describes a single-incision, laparoscopic-assisted ovariohysterectomy in a 6-year-old, intact female Keeshond dog for the staging and treatment of a left-sided ovarian tumor. Abdominal access was obtained using a modified-Hasson technique allowing for placement of a multi-channel, single incision laparoscopic surgery port. Following carbon dioxide insufflation, superficial laparoscopic exploration of the abdominal cavity was performed and then both ovarian pedicles were sealed and divided using a vessel-sealing device. Laparoscopic-assisted ovariohysterectomy was performed with the aid of a wound retractor for exteriorization of the mass. There were no perioperative complications and the patient was discharged 1 day after surgery. Histopathology of the mass revealed an ovarian teratoma. Telephone follow-up 608 days after surgery revealed a good clinical outcome. Single-incision, laparoscopic-assisted ovariohysterectomy is technically feasible for the treatment of selected ovarian tumors in the dog.

Canine ovarian tumors are rare, likely due to early ovariohysterectomy, and represent 0.5% to 1.2% of all canine neoplasms (1). Primary canine ovarian tumors are histopathologically classified as either epithelial, sex cord-stromal, germ cell, or mesenchymal in origin, with epithelial and sex-cord stromal tumors being the most commonly diagnosed (2). The degree of malignancy varies widely among histopathological types with epithelial and germ cell, specifically teratomas, classified as having the highest reported metastatic rates in the canine species mainly due to peritoneal dissemination (1–3).

Canine ovarian neoplasia is often not diagnosed until clinical signs warrant investigation, which include non-specific signs (anorexia, weight loss, lethargy), abdominal distension, palpable abdominal mass, ascites, vulvovaginal discharge, dyspnea, or abnormal estrus behavior (4,5). Ovariohysterectomy is the treatment of choice for ovarian tumors, and has been curative in some cases of benign disease (1). However, long-term prognosis is difficult to predict due to the lack of long-term outcome data (1,3).

Laparoscopic and laparoscopic-assisted procedures are becoming increasingly popular in veterinary medicine as a result of improved visualization, reduced postoperative pain, suspected reduction in incidence of surgical site infection, and shorter hospital stays (6–9). Specifically, dogs receiving multiport laparoscopic-assisted ovariohysterectomy (LAOVH) required less postoperative analgesia and had significantly shorter durations of blood glucose and cortisol elevations after surgery than dogs undergoing open ovariohysterectomy (OVH) (8). In human medicine, laparoscopic surgery has become the gold standard in the management of benign ovarian adnexal masses (10). Specifically, laparoscopic treatment of benign ovarian tumors, either by cystectomy or oophorectomy, results in reduced operative morbidity, reduced postoperative pain and analgesic requirement, decreased hospitalization duration, and shorter recovery period (10).

Compared to conventional multiport laparoscopy, single port laparoscopic surgery (SPLS) has become more popular for use in humans due to several benefits, including lower rates of port-site infections and higher patient satisfaction scores following laparoscopic hysterectomy (10–12). A recent comparison in dogs demonstrated decreased surgical time and decreased complications when SPLS was used instead of multiport laparoscopy (13). Single port laparoscopic surgery has been described for ovariectomy, ovariectomy + gastropexy, ovariohysterectomy, and cryptorchidectomy in dogs with good outcomes (13–17). In addition, a SPLS approach has recently been described for ovariohysterectomy in dogs with pyometra (18). A SPLS approach for planned staging and treatment of ovarian neoplasia has yet to be described in dogs, and is the purpose of this report.

Case description

A 6-year-old, 14.6 kg, intact female Keeshond dog was presented to the Ontario Veterinary College Health Sciences Centre (OVC-HSC) for further evaluation of an ovarian mass that was discovered at the time of surgery for OVH by the family veterinarian. Upon discovery of the ovarian mass, the procedure was abandoned and the dog was recovered from anesthesia. Upon presentation, physical examination of the patient revealed a 6-cm, ventral midline incision and vital parameters were within normal limits.

Preoperative staging included a complete blood (cell) count (CBC), a serum biochemistry profile, 3-view thoracic radiographs, and an abdominal ultrasound of the genitourinary tract. Blood analysis was unremarkable and 3-view thoracic radiographs did not reveal any abnormalities. Abdominal ultrasound of the genitourinary tract revealed a partially mineralized ovarian mass measuring 7 cm at the largest diameter within the left ovary and mild dilation of the uterine tubules with trace uterine fluid (Figure 1). Single port laparoscopic surgery OVH was recommended for treatment of presumptive left ovarian neoplasia. Ovariectomy was not considered based on the age of the dog as it is generally performed in young, healthy dogs (9).

Figure 1.

Preoperative ultrasound image of the neoplastic left ovary (arrows). The ovarian mass measured 7 cm at its largest diameter and was partially mineralized.

Surgical technique

The patient was premedicated with dexmedetomidine (0.5 mg/mL; Zoetis Canada, Kirkland, Quebec), 5 μg/kg body weight (BW), IM, and hydromorphone chloride (2 mg/mL, Sabex, Boucherville, Quebec), 0.1 mg/kg BW, IM, and general anesthesia was induced using a 1:1 ratio of 0.5 mL of ketamine hydrochloride (50 mg/mL; Sabex) and midazolam (1 mg/mL; Sabex) IV. The patient was maintained under general anesthesia using isoflurane (Abbott Laboratories, North Chicago, Illinois, USA) in 100% oxygen. Antimicrobial prophylaxis was administered 30 min before surgery and every 90 min during surgery. Following induction, the patient was positioned in dorsal recumbency and the ventral abdomen was clipped and aseptically prepared cranially from the xiphoid, caudally to the pubis, and laterally to the proximal third of the flank. Approximately 3 cm of the previous 6-cm ventral midline incision was opened using sharp dissection. The linea alba was incised to gain access to the abdominal cavity. Two stay sutures were placed into the rectus sheath at the incisional margins. Two adjacently placed, staggered, Carmalt forceps were attached to a SPLS port (SILS port: Covidien, Mansfield, Massachusetts, USA) to allow for its insertion into the abdomen, as previously described (15). The SPLS port was inserted and three, 5-mm cannulas were placed into the SPLS port. The abdomen was insufflated with CO₂ to a maximum pressure range between 10 to 12 mmHg using a pressure regulating mechanical insufflator (Endoflater; Karl Storz Veterinary Endoscopy, Goleta, California, USA). A 5-mm, 30°, 29-cm laparoscope (Hopkins II 0° and 30° 5-mm 29-cm Telescope, Karl Storz Veterinary Endoscopy) was placed within the caudal most cannula, and the abdomen was superficially explored in a clockwise fashion. Exploration revealed a slightly mottled appearance diffusely throughout the liver, and the left ovary contained a moderately sized mass that was heterogenous in appearance (Figure 2). No adhesions to the left ovary were noted. The visible gall bladder, diaphragm, peritoneum, spleen, kidneys, urinary bladder, gastrointestinal tract, omentum, and right ovary appeared within normal limits.

Figure 2.

Intraoperative photograph at time of laparoscopy. A Babcock forceps is grasping the distal aspect of the uterine horn to suspend the left ovarian tumor (arrow) that is abutting the left kidney (arrowhead).

Multiple laparoscopic liver biopsies of the right lateral and quadrate lobe were performed using laparoscopic cup biopsy forceps (Laparoscopic biopsy forceps; Karl Storz Veterinary Endoscopy). Hemorrhage was controlled utilizing direct pressure from a blunt laparoscopic probe (Palpation probe; Karl Storz Veterinary Endoscopy).

The patient was tilted 45° towards left lateral, and the normal right ovary was visualized and exposed using a laparoscopic blunt probe. The proper ligament of the right ovary was visualized, grasped and retracted with laparoscopic Babcock forceps (Clickline, 5 mm, Straight Babcock Forceps; Karl Storz Veterinary Endoscopy) to visualize the suspensory ligament and vascular pedicle. The suspensory ligament and vascular pedicle were transected using a vessel sealing device (5-mm Ligasure; Covidien). The broad ligament was sealed and transected using the vessel sealing device to a level just cranial to the uterine body. The Babcock forceps grasping the right proper ligament was released and instruments and laparoscope were removed from the abdomen. The patient was then tilted 45° towards right lateral recumbency, and the left ovary was visualized and exposed using a laparoscopic blunt probe. Retraction of the ovary via the proper ligament alone provided incomplete visualization of the suspensory ligament and vascular pedicle because of obstruction by the large ovarian mass. In order to improve visualization of the vascular pedicle the uterine horn was grasped with laparoscopic Babcock forceps for manipulation of the ovary. The suspensory ligament and vascular pedicle were sealed and transected using the vessel sealing device. The left broad ligament was ligated and transected using the vessel sealing device to a level just cranial to the uterine body.

The laparoscope and vessel-sealing device were removed, and the CO₂ was evacuated from the abdomen by removing the SILS port. The ventral midline incision was extended to 6 cm in length, along the previous laparotomy incision. A 5 to 9 cm wound retractor (Alexis Wound Retractor; Applied Medical Resources, Rancho Santa Margarita, California, USA) was placed into the abdominal incision as previously described (19). Briefly, the interior single ring was placed into the abdominal incision with care not to entrap any internal abdominal organs. Traction was placed on the ring intra-abdominally, and the exterior double ring was rolled down upon itself until contact was made with the external body wall. The right and left reproductive tract, including the ovarian tumor, were identified by hand and removed from the abdomen (Figure 3). The uterine body was crushed using a Carmalt forcep, and a single 2-0 PDS (Polydioxanone; Johnson and Johnson, Markham, Ontario) circumferential ligature was placed around the uterus. The uterus was transected and the uterine stump was returned to the abdomen while monitoring for hemorrhage.

Figure 3.

Intraoperative photograph following exteriorization of the reproductive tract through a wound retraction device. A large, left-sided ovarian mass is present.

The linea alba was closed using 2-0 polydioxanone in a simple continuous pattern. The subcutaneous tissues were lavaged and closed using 3-0 Monocryl (poliglecaprone 25; Johnson and Johnson) in a simple continuous pattern. The skin was closed with 3-0 Prolene (Polypropylene; Johnson and Johnson) in a simple continuous pattern. Surgical time was 75 min.

Histopathology results

The histopathology of the ovarian tumor revealed a well-differentiated mass with 3 germinal layers (ectoderm, mesoderm, neuroectoderm), which is consistent with the diagnosis of a teratoma. The histopathology from the liver and uterus was unremarkable.

Postoperative care

The dog recovered uneventfully following recovery from anesthesia. Analgesia was achieved using hydromorphone (Sabex), 0.025 mg/kg BW, SQ, q4-6h and Metacam (meloxicam; Boehringer Ingelheim, Burlington, Ontario), 0.1 mg/kg BW, PO, q24h. The patient was discharged 1 d after surgery with metacam for 5 d after surgery. The owner reported that the dog was clinically normal at follow-up by telephone 608 d after surgery.

Discussion

This report describes the successful application of SPLS OVH for the staging and treatment of canine ovarian neoplasia. Perioperative complications were not encountered, and the dog was without clinical signs at time of telephone follow-up 608 d after surgery. Minor challenges were encountered during vessel-sealing of the left ovarian pedicle as the tumor obstructed our view. Using retraction of the uterine horn to “sway” the mass lateral to the pedicle improved exposure of the vascular pedicle. Despite this technical challenge, surgical time of the SPLS technique was similar to the previously described reports for conventional LAOVH (7,8).

Preoperative staging of dogs with ovarian neoplasia is critical to assess for laparoscopic feasibility and to evaluate for metastatic disease. Preoperative screening should entail a CBC, serum biochemistry panel, 3-view thoracic radiographs, and abdominal ultrasound. An abdominal ultrasound is critical to localize the disease in the ovary (unilateral or bilateral) and to evaluate tumor size and ovarian internal architecture, to identify free abdominal fluid, and to assess for other abdominal organ involvement (4). The presence of free abdominal fluid and cytological evaluation may allow for a presurgical diagnosis of malignant ovarian neoplasia (20). The identification of preoperative ovarian size without evidence of metastatic disease may help decide if SPLS OVH is feasible.

Ovarian tumors vary widely in size, ranging from 2 to 15 000 cm³, with diameters up to 22 cm reported (2,4). The ovarian tumor in the dog herein measured 7.0 × 4.0 × 3.0 cm using ultrasonography. Large ovarian tumors are likely not ideal candidates for multiport or SPLS OVH. The access incision required to extract the ovarian tumor following sealing of the ovarian pedicles was approximately 6 cm. While further study is required, tumors that are > 7 cm at the largest dimension will require equivalently larger access incisions for tumor extraction. The upper limit of tumor size, in which the benefits of assisted laparoscopy are outweighed by increasing incision size and surgical trauma, remains unknown in veterinary medicine. Additionally, large ovarian tumors pose an intraoperative challenge for the surgeon as visualization of the ovarian pedicle will be difficult. Larger ovarian tumors may be reduced in size with a morcellator intracorporeally after being placed in a specimen retrieval bag to decrease access incision size (21). Morcellators, however, are not commonly used in small animal veterinary medicine. This strategy has been used in the horse for removal of unilateral benign granulosa cell tumors via a hand-assisted laparoscopic approach through the paralumbar fossa for tumors as large as 20 cm in diameter (21).

The benefits of SPLS compared with multiport laparoscopy have yet to be determined in veterinary medicine. A recent study demonstrated that SPLS had decreased surgical times and decreased intraoperative hemorrhage compared with multiport laparoscopy for elective laparoscopic procedures (13). Another study by Case et al (22) demonstrated prolonged surgical times with no differences in complications with SPLS compared with multi-port laparoscopy for laparoscopic ovariectomy in dogs. Surgical time likely relates to experience with SPLS and/or multiport laparoscopy. Access-related complications can be reduced with SPLS since a mini-laparotomy incision is created (~2 cm) with clear visualization of abdominal organs for SPLS port insertion (13). Veress needle insertion is blind and can result in splenic laceration and additional abdominal organ trauma (13). Regardless, SPLS requires proficiency in multiport laparoscopy and is associated with a steep learning curve. In laparoscopic cases in which careful dissection is required, multiport laparoscopy may be preferred to prevent instrument clashing and improve triangulation. In humans, multiport laparoscopy is typically performed for hysterectomy, however, SPLS is gaining popularity (10). A prospective study comparing single-port versus multiport laparoscopy for hysterectomy demonstrated longer surgical times, but lower rates of port site infection and higher patient satisfaction scores (10).

The ovarian tumor, the normal right ovary and uterine horns and body were extracted through a wound retraction device (Figure 3) which has previously been reported for use in veterinary laparoscopy (19,23,24). The wound retraction device exerts a radial force on the incisional edges, which not only provides increased wound opening and retraction for removal of abdominal viscera/pathology but also provides incisional protection from both infection (25) and potential contamination by neoplastic cells (26). Portal site metastasis has been reported in the veterinary literature (27) and measures to reduce its incidence, such as the use of a wound retraction device in this case, are of paramount importance. Variable sized wound retraction devices are available for various incision sizes and purposes.

In conclusion, SPLS OVH can be used for the treatment of ovarian tumors in dogs. Appropriate pre-operative staging should be completed before surgery to determine candidacy for laparoscopy. Should challenges be encountered using SPLS for visualization of the ovarian pedicle, an additional port can be placed on the ventral midline to aid in retraction of the ovarian mass. Further study in a large number of dogs is required to determine the benefits of laparoscopy for the treatment of ovarian neoplasia. CVJ