A Novel Surgical Stapling Technique for Rectal Mass Removal: A Retrospective Analysis
Both benign and malignant rectal masses occur in dogs. The mainstay of treatment is surgical excision with adjuvant therapy based on histopathological diagnosis and completeness of removal. Location of the mass within the rectum helps dictate the approach used. This paper describes the use of a novel technique for removal of rectal masses involving the distal third of the rectum in seven dogs. To perform this technique, the rectum is prolapsed and stay sutures are placed to maintain prolapse. A thoracoabdominal stapling device is placed at the base of the mass with a minimum of 0.5- to 1-cm margins, and the mass is amputated. Mean time to veterinarian follow-up was 564 days, and no dog had recurrence of disease during this time.
Introduction
Intestinal tumors comprise approximately 3% to 10% of all tumors detected in dogs, with malignant masses being more common than benign.1,2 Rectal tumors represent a small, clinically relevant subset of these intestinal tumors.3 Benign rectal masses consist of polyps, leiomyomas, and adenomas. Malignant rectal masses consist of adenocarcinomas, lymphomas, leiomyosarcomas, hemangiosarcomas, plasmacytomas, and fibrosarcomas. The most common of all rectal masses is benign rectal polyp.4 Malignant transformation has been documented in 18% of dogs presented with adenomatous polyp or carcinoma in situ.5
The most common historical findings and chief complaints with rectal masses include tenesmus, hematochezia, dyschezia, intermittent rectal bleeding, and rectal prolapse. A thorough physical examination with digital rectal palpation is essential for diagnosis of rectal masses. Additional diagnostics include complete blood count (CBC), a biochemical profile, urinalysis, abdominal and thoracic radiographs, and abdominal ultrasound. Dogs may have single masses, diffuse disease, or multiple masses —not all of which are palpable on rectal examination. Therefore, most dogs also undergo proctoscopy and colonoscopy to determine the extent of disease. For dogs with diffuse disease or multiple masses, endoscopically obtained biopsies are important to determine the most appropriate treatment protocol. For dogs with only a single rectal mass, surgery may be both diagnostic and therapeutic.
Dogs diagnosed with rectal polyps and complete removal have a good prognosis; survival is reported to be 1 to 5 years.6 Local surgical resection of rectal carcinoma resulted in a mean survival time of 22 months.7
Various surgical techniques are utilized for rectal mass removal depending on the location of the mass. Abdominal approaches are typically used for masses involving the proximal third of the rectum. Perineal or transanal approaches are most commonly used for masses involving the middle third of the rectum. For masses involving the distal two-thirds of the rectum, several techniques may be utilized, including endoscopic removal with electrocautery or rectal pull-through with mass excision. Benign masses of the distal third of the rectum are classically removed with dissection to the deep margin of the mucosal layer.4 Danova et al recently reported removal of malignant masses involving the distal rectum using a technique of rectal prolapse, blade dissection, and suture repair of the defect created.3
The purpose of this report is to describe a novel technique for single rectal mass removal involving the distal third of the rectum.
Materials and Methods
Records from Colorado State University Veterinary Medical Center (CSU-VMC) were reviewed to identify dogs with rectal masses treated surgically with the staple technique (described in this paper) between January 2001 and June 2005. Dogs were included if their records were complete and they had a histopathological diagnosis. Medical records for each dog were reviewed, and data was extracted that included age, gender, breed, preoperative diagnostics, total surgery time, histopathology results, and postoperative medications and care.
Surgical Technique
Dogs were prepared for surgery by having food withheld for 24 hours preoperatively. No further bowel preparation was performed. Once the colon was free of obvious feces, surgery was performed. Dogs were placed under general anesthesia and maintained with inhaled anesthetics. Perioperative antibiotics were administered intravenously approximately 30 minutes prior to surgical manipulation of the mass. Cefazolin (22 mg/kg) or cefoxitin (22 mg/kg) were the antibiotics used depending on surgeon preference.
Each dog was placed in sternal recumbency, and the rectum was prepared in standard fashion (i.e., hair around the anus was clipped; chlorhexidine was used to prepare the skin, and the dog was draped in sterile fashion). The rectum was digitally prolapsed, and 3-0 nylon stay sutures were placed to maintain the prolapse and visualization of the rectal mass [Figure 1]. Two to four stay sutures were utilized and evenly spaced approximately 2 cm from the mass.
A 30-mm, vascular, thoracoabdominal (TA) stapling devicea was placed at the base of the mass in a manner (transverse or longitudinal) that allowed a minimum of 0.5- cm margins [Figure 2]. Two additional stay sutures may be placed at the base of the mass to facilitate proper positioning of the stapling device. The margins were evaluated, and if they did not appear to be adequate on gross examination, the stapler was repositioned more proximally. Once margins appeared adequate, the staples were deployed. The mass was then removed distal to the staples, using a scalpel blade just distal to the TA stapler. Lastly, the TA stapler was removed, leaving three rows of staggered staples, and the staple line was visually inspected for any hemorrhage. The mass was submitted for histopathological evaluation and margin assessment.
Follow-up was performed by phone interview with the owner and/or referring veterinarian. The date of the last veterinary examination that included a digital rectal examination was recorded and used to assess follow-up time. Information obtained from owners included a quality-of-life assessment (using a 10-point scale, where 1 is poor and 10 is excellent); a list of current medications; and whether or not the dog had any tenesmus or signs of recurrence. Referring veterinarians were questioned regarding any recurrence of disease as noted on digital rectal examination, survival status, and the cause of death when documented in the medical record.
Results
Seven cases of rectal masses were treated at CSU-VMC between January 2001 and June 2005 using the surgical stapling technique reported here. Dogs ranged in age from 6 to 14 years, with a mean age of 9.6 years. Five dogs were castrated males; one dog was an intact male; and one was a spayed female. Breeds represented included Australian shepherd, shih tzu, Airedale terrier, Shetland sheepdog, golden retriever, Great Dane, and keeshond [see Table].
Chief complaints included rectal bleeding, rectal prolapse, and rectal mass [see Table]. Rectal mass was diagnosed by digital rectal examination. All dogs had preoperative hematological evaluations (i.e., CBC and serum biochemical analysis). No consistent hematological abnormalities were noted preoperatively. Various other diagnostics were employed based on clinician preference, including abdominal radiography, thoracic radiography, abdominal ultrasonography, and colonoscopy. Only one dog had abdominal radiography performed; no abnormalities were identified. Of the five dogs that had thoracic radiographs, no metastases were noted. Abdominal ultrasonography was performed in four dogs. Of these four, one was found to have a urinary bladder mass as well as an enlarged prostate. A second dog was found to have large (i.e., reactive on cytological analysis) iliac lymph nodes. A third dog was found to have a splenic mass, cystic calculi, hepatomegaly, and adrenomegaly. Colonoscopy was performed in three dogs; all dogs had a single rectal mass and no other abnormalities.
Surgery was performed as described within this paper. Average surgical time was 14.8 minutes, with a range of 9 to 30 minutes. Mean size of the masses was 2.36 cm (range 0.5 to 4 cm; see Table). Although masses larger than the length of the TA stapler (3 cm) were removed, these masses had narrower bases of attachment to the rectal wall, which were <3 cm and therefore accommodating of the stapler. Distance of the mass from the anal sphincter could not be determined from medical records.
Dogs were discharged from the hospital the day of surgery on various nonsteroidal antiinflammatory drugs (NSAIDs) including piroxicam,b deracoxib,c and carprofend for short-term pain management. Two dogs were still receiving piroxicam at standard antiinflammatory doses when this report was written.
Histopathological diagnoses included adenocarcinoma (n=3), papillary carcinoma (n=1), carcinoma (n=1), plasma cell tumor (n=1), and chronic inflammation (n=1). Surgical margins were difficult to assess because of curling and shrinking of tissues within formalin. Only two masses were identified with clean margins; of the remaining five masses, one did not have margin assessment, one had 0.1-mm clean margins, one had a possible second lymphatic foci, and two had tumor cells present at the surgical margins on histopathological analysis. The two cleanly excised masses measured 0.5 and 2 cm [see Table].
Five dogs were alive at the time of this reporting; one died of an unknown cause according to the referral veterinarian 441 days postoperatively, and another was lost to follow-up after surgery. No tenesmus was noted postoperatively, and gentle digital rectal examination revealed no discomfort or apparent narrowing of the rectal lumen at the staple line. Of the six dogs with follow-up beyond the immediate postoperative period, owners and/or referral veterinarians considered all to be free of clinical signs at a mean follow-up time of 498±211 days. Four of these six dogs had a digital rectal examination performed by the referring veterinarian at a mean of 564±174 days; no recurrence of rectal masses was noted.
Discussion
In this report, a novel technique of rectal mass removal using a TA 3 V 30 stapler was described. This technique is an acceptable alternative to routine blade excision and suture closure.
Two potential advantages of this method are ease of stapler use and short surgical time (mean 14.8 minutes). No comparisons of surgical times could be made between this method of mass removal and blade excision with suture closure, as surgical times were not reported by Danova et al.3
Additionally, deeper surgical margins may be achieved with the stapling device. Traditionally, benign masses of the distal third of the rectum are removed with dissection to the deep margin of the mucosal layer.4 More recently, a similar technique has been used for malignant masses in this region, with 1-cm margins and dissection to the muscularis layer.3 To prevent bacterial contamination in the perirectal tissues or peritoneum and subsequent abscessation or peritonitis, care is taken to not exit the serosal surface. With the staple technique described here, the mucosa, submucosa, and muscularis layers are inverted into the lumen of the rectum (in the peritoneal rectum, the serosa is also present and inverted into the lumen of the rectum), and the stapler is placed in a manner that incorporates all layers [Figure 3]. Because of the inversion of tissues prior to resection of the mass, gross contamination of the surrounding tissues is eliminated unless dehiscence occurs. Dehiscence was not seen in the authors’ population of dogs and is unlikely due to the precision of the three rows of staples placed by the TA stapling device.
Histopathological margin assessment revealed only two dogs with clean surgical margins. This may be attributed to the difficulty in visually assessing margins with the large TA stapling device in place at the time of surgery. Despite the fact that both benign and malignant tumors were marginally excised, local recurrence was not observed in any of these five dogs during the follow-up period. Margin assessment may be inhibited by shrinkage of tissues when put in formalin. Histopathological analysis of the tissue remaining in the dog at the staple line would be necessary to determine if tumor cells survive within the staple line. However, because this procedure was performed on client-owned animals, resecting the incision line for further histopathological examination was not possible.
The authors’ surgical technique resulted in a smaller percentage of dogs with clean surgical margins than the percentage in the Danova et al study. This is likely due to the difference in planned margin resection (1 to 1.5 cm in Danova’s study as compared to 0.5 to 1 cm in this study). Further studies are needed to compare these methods for the rate of local recurrence for malignant rectal tumors. The dogs of this study had no tenesmus or rectal bleeding noted postoperatively; in contrast, six out of 23 dogs had rectal bleeding and/or tenesmus noted postoperatively in the Danova study. One possible explanation for this is that the stapling device provides superior hemostasis and less inflammation.
One potentially beneficial adjunctive treatment is the use of NSAIDs. These drugs have been shown to decrease the prevalence of, and mortality from, colon cancer by decreasing cell proliferation and inducing apoptosis of adenocarcinoma cells.8 Piroxicam has been previously reported to decrease the risk of rectal masses in humans, and it has caused regression of villous adenomas in humans.9,10 Additionally, piroxicam is reported to decrease the occurrence of colonic neoplasia in rats after pelvic irradiation.11 Piroxicam has been used to treat rectal polyps in dogs; clinical signs have been alleviated, and mass size has been decreased.12 In the authors’ study, four of the dogs with incomplete margins were placed on piroxicam postoperatively. Two of these dogs remained on piroxicam beyond the postoperative period (>14 days). The addition of piroxicam possibly inhibited recurrence in these dogs.
Conclusion
This report describes a novel technique for removal of rectal masses involving the distal third of the rectum with a base of attachment to the rectal wall <3 cm. Due to the small number of cases, statistical analysis of long-term outcome could not be performed. Further studies are needed to evaluate a larger number of animals using this technique compared to other techniques with regard to disease-free intervals and survival times. Rectal prolapse and rectal mass removal using a 3 V 30 TA stapler is a viable treatment modality that is rapid and effective.
Thoracoabdominal stapling device; United States Surgical Corporation/Tyco Healthcare, Norwalk, CT 06855
Piroxicam (Feldene); Pfizer Animal Health, Exton, PA 19341
Deramaxx (deracoxib); Novartis Animal Health, Greensboro, NC 27408
Rimadyl (carprofen); Pfizer Animal Health, Exton, PA 19341
Citation: Journal of the American Animal Hospital Association 45, 2; 10.5326/0450067
Citation: Journal of the American Animal Hospital Association 45, 2; 10.5326/0450067
Citation: Journal of the American Animal Hospital Association 45, 2; 10.5326/0450067
Stay sutures are placed to maintain the prolapse and gain access to the mass for removal.
A 30 V thoracoabdominal stapling device is placed at the base of the mass.
Illustration demonstrating the authors’ theory of how the stapler resects the mass and peritumoral tissues in full-thickness fashion. Drawing: Courtesy of Dave Carlson.
