Case Selection

The medical records of dogs who underwent SPL treatment for ORS between 2010 and 2018 at the University of Guelph (Ontario Veterinary College), University of California – Davis School of Veterinary Medicine, University of Florida College of Veterinary Medicine, Centre Veterinaire DMV, and University of Pennsylvania (Matthew J. Ryan Veterinary Hospital), were reviewed. Dogs were included if their medical records were complete and they received SPL surgical treatment for ORS using a commercially available single-port device^a. Data collected from the medical record included history, signalment, weight, clinical signs, operative details, time to presentation from initial sterilization surgery, preoperative vaginal cytology and hormonal assay testing, diagnostic imaging type, and results. Operative data recorded included surgical time (defined as time from first incision to final suture), size of the incision, location of port placement, need for additional port placement, surgical findings, complications, and histopathologic evaluation of resected tissue. Patient follow-up was performed via telephone interview with the owner and/or referring veterinarian.

Diagnostic Evaluation

ORS was diagnosed using serum progesterone^b, vaginal cytology, and/or abdominal ultrasonography prior to SPL surgery.

Patient Preparation

The dogs were routinely anesthetized with a nonstandardized protocol approved by the attending anesthesiologist and were placed in dorsal recumbency. The ventral abdomen was clipped from xiphoid to pubis and the skin aseptically prepared for surgery. The dog was draped as for an open ventral midline abdominal exploration.

Surgical Technique

All surgeries were performed or directly supervised by a board-certified veterinary surgeon with expertise in laparoscopic procedures. A 2–3 cm skin incision was made centered over or just caudal to the umbilicus. Using a combination of sharp and electrosurgical dissection, the incision was extended through the linea alba. Stay sutures with 2-0 polydioxanone^c, or rat tooth thumb forceps, were placed in the lateral aspects of the exposed rectus sheath for traction, and a commercially available single-port device^a was inserted into the incision as previously described.¹⁷ The peritoneal cavity was insufflated to 8–10 mm Hg with CO₂ using a mechanically regulated insufflator device^d. Visual exploration of the abdominal cavity was performed to assess for abnormalities. The patient was rotated 25–45° laterally either manually or using a motorized mechanical tilt table to allow for improved visualization of the right and left abdominal cavity to evaluate the previous surgical sites (ovarian pedicles). When abnormal tissue was identified, it was grasped using laparoscopic forceps. Once grasped, the abnormal tissue was dissected from its surrounding tissue using a bipolar vessel-sealing device or articulating J-hook monopolar cautery^e. After the tissue was dissected, the patient was rotated into dorsal recumbency, and the single-port device was removed while simultaneously holding the abnormal tissue. The single-port device was then reinserted into the abdomen, and the contralateral side of the abdomen was explored in the same manner as previously described. In cases in which uterine stump pathology was suspected based on abdominal ultrasonography, the region of the uterine stump was explored and hysterectomy performed using the vessel-sealing device if required. The single port was removed, pneumoperitoneum was purged, and a routine three-layer closure of the surgical wound was performed.

Operative data including anesthetic time, surgical time, location of ovarian remnant tissue, and complications were recorded. Intraoperative complications were classified as either minor or major. Minor complications were those that did not require conversion to open laparotomy and resolved with minor adjustments to surgical approach. Major complications were those that required conversion to open laparotomy or intervention that prevented successful completion of SPL treatment of ORS. Tissue samples were fixed in 10% formalin and stained using hematoxylin and eosin according to standard protocol of the diagnostic pathology service at each institution. Histopathology of the resected tissues was reviewed.

Postoperative Care

All dogs received an analgesic protocol as determined by the attending clinician. All dogs received hydromorphone (0.025–0.1 mg/kg [0.01–0.045 mg/lb] IV or subcutaneously), buprenorphine (0.01 mg/kg [0.045 mg/lb] subcutaneously or IV), or methadone (0.2 mg/kg [0.09 mg/lb] IV) at 4–6 hr intervals for 12–24 hr postoperatively. Hospitalization time, medications dispensed, time until follow-up, postoperative clinical status, and diagnostics were obtained from the patients’ medical records.

Statistical Analysis

Descriptive statistics such as mean, median, and range were calculated for continuous variables (e.g., age at initial procedure, time to presentation, and surgical time), and frequency percentages were calculated for categorical variables (e.g., dogs with neoplastic tissues).

Animals

Thirteen female dogs who had previously undergone open OVH (n = 11) or OVE (n = 2) were included in this study. Dog breeds included mixed-breed dog (n = 5), Labrador retriever (n = 2), dachshund (n = 1), greyhound (n = 1), Kerry blue terrier (n = 1), Pit bull terrier (n = 1), mastiff (n = 1), and Australian shepherd (n = 1). The median weight of the dogs was 28 kg (61.6 lbs; range, 5–48.7 kg [11–107 lbs]) with a median age of 28 mo (range, 12–100 mo).

Preoperative Diagnostic Evaluation

The median age at the time of initial surgery was 7 mo (range, 2–48 mo). All initial surgical procedures were performed through a ventral midline laparotomy. The median time interval between the initial surgical procedure and surgical treatment of ORS was 19 mo (range, 8–94 mo). The median time interval between initial sterilization surgery and clinical presentation was 14 mo (range, 1–72 mo). Dogs were presented for suspicion of ORS, and the clinical signs described by the owners included hemorrhagic vaginal discharge (n = 12), vulvar swelling (n = 12), behavior changes (n = 8), and mammary enlargement (n = 5). Vaginal cytology was performed on five dogs revealing stages of the estrus cycle (cornified epithelial cells in four dogs and polymononuclear cells with a mixture of parabasal and intermediate cells signifying diestrus in another dog). Serum progesterone levels were performed in three dogs demonstrating elevated progesterone levels (1.8 [0.57], 3.9 [1.23], and 16 [5.0] nmol/L [ng/mL]; <1.5 nmol/L [<0.5 ng/mL] normal reference range for a spayed bitch). Ultrasonography was performed in nine dogs to identify the presence of an ovarian remnant. In all nine dogs, a hypoechoic nodular mass was identified at the region of the ovarian pedicle and suspected to be ovarian remnant tissue. In five dogs, evidence of remnant tissue was discovered on the right side, two dogs had remnant tissue on the left side, and two dogs had remnant tissue bilaterally. Additional ultrasound findings included three dogs with evidence of hydrosalpinx, two with evidence of uterine stump enlargement, and two with remnant uterine horns without mucometra. In one of these dogs, the uterine horn remnant developed into an 8 × 4.5 × 3.5 cm cystic structure associated with a histologically normal left ovarian remnant.

Operative Data

The median anesthetic and surgical times for the 13 dogs undergoing SPL treatment of ORS was 122 min (range, 80–200 min) and 45 min (range, 30–90 min), respectively. In 8 dogs, ovarian remnant tissue was right sided, 3 dogs were left sided, and 2 dogs were bilateral. The predicted location of the ovarian remnant in all dogs who underwent ultrasonography was confirmed at the time of surgery. Major intraoperative complications were not encountered in any dog. In 2 dogs, minor complications occurred. In 1 dog, an additional 6 mm trocar/cannula assembly^d was placed between the single port and the xiphoid process to help facilitate visualization and dissection of a dilated uterine horn remnant. In this dog, the uterine horn remnant was found to be markedly dilated (>5 cm) during abdominal ultrasonography. Following dissection and sealing of the ovarian pedicle, a 22-gauge hypodermic needle was inserted transcutaneously to aspirate the fluid present in the uterine horn remnant. This allowed for removal of the tissue through the single-port access incision. In another dog, a rigid, conical, reusable single-port device^f was initially placed; however, as a result of persistent insufflation leakage, the surgeon removed this port and placed the single port used in the remainder of the dogs in the study^a.

Histopathology

All resected tissues were submitted for histopathological evaluation totaling 15 samples. Twelve samples were determined to be nonneoplastic ovarian remnant tissue and 3 were consistent with sex cord stromal cell tumors. In addition, three samples showed evidence of hydrosalpinx.

Outcome

The median hospitalization time postoperatively was 24 hr (range, 5–28 hr). All dogs were discharged from the hospital on either oral meloxicam (0.1 mg/kg [0.045 mg/lb] q 24 hr for 3–7 days) or carprofen (2.2 mg/kg [0.1 mg/lb] q 12 hr for 3–7 days), and 8 dogs were discharged with both meloxicam (0.1 mg/kg [0.045 mg/lb] q 24 hr for 3–7 days) and tramadol (4 mg/kg [1.8 mg/lb] q 8–12 hr for 3–7 days). Follow-up via telephone interview with the owner and/or referring veterinarian was available for all dogs included in the present study. The median follow-up time for dogs of this study was 17 mo (range, 3–48 mo). There was no report of postoperative complications following surgery in any dog, and all clinical signs relating to ORS had resolved. Two dogs were lost to follow-up 3 mo postoperatively. With these dogs removed from the analysis, the median follow-up time for the remaining 11 dogs was 18 mo (range, 7–48 mo). One dog who was diagnosed with a sex cord stromal tumor had repeat abdominal ultrasonography at 90 days postoperatively and had evidence of a 9.0 × 4.6 mm hypoechoic nodule in the region of the previous surgery site. A repeat abdominal ultrasound 8 mo postoperatively was performed and identified the hypoechoic nodule and had remained similar in size (8.6 × 2.2 mm) compared with the previous evaluation. This was suspected to be associated with the suture material (suture-related granuloma) from the initial open OVH at the ovarian pedicle, although recurrent neoplasia could not be excluded. A second dog diagnosed with a sex cord stromal tumor continued to have persistent urinary tract infections and vaginitis, although all signs of estrus had resolved. Abdominal ultrasonography performed 150 days after surgery revealed a thickened uterine stump with no evidence of ORS 23 mo following surgery.