Intestinal neoplasms are uncommon in dogs and adenocarcinoma is the predominant histological type (9). Rectal adenocarcinomas are classified as nodular (single or multiple), pedunculated, or annular constrictive according to the type of disease. The gross appearance can determine the outcome. The mean survival time for annular-obstructing masses is only 1.6 months, whereas pedunculated or polypoid lesions reportedly have a good prognosis after surgical resection (2,7,10). Most cases with clinical signs of dyschezia and hematochezia are euthanized due to poor prognosis and difficulties in postoperative management (6).

Limited information is available on the use of colostomy in veterinary surgery due to difficulties in postoperative management (4,11,12). Incontinent end-on colostomy was administered in one case of a dog with annular-obstructing adenocarcinoma (6), but other than one case of temporary end-on colostomy for anastomotic dehiscence, no additional reports have been published (3). Due to the lack of information on these types of cases, treatment of dogs with annular-obstructing perianal adenocarcinoma is difficult. Therefore, we report the results and progress of end-on colostomy in a dog with dyschezia secondary to advanced colorectal adenocarcinoma. Although the colostomy bags used in previous studies are not economical for use in veterinary cases, our experience in this case will help in the treatment of dogs with similar diseases.

A 12-year-old neutered male Shetland sheepdog, weighing 12.7 kg, was referred to the Western Referral Animal Medical Center with the main symptom of difficulty defecating. On physical examination, a 4 × 6 cm² perianal ulcerative tumor and a resulting rectal stricture were identified (Fig. 1A). Due to a calcified mass in the anus, dyschezia was aggravated, and the owner complained that it had become increasingly difficult to remove the stool with softeners or manually due to increased pressure on the rectal lumen. No major abnormalities were identified in blood analyses (Complete blood count (CBC), serum chemistry, and electrolytes). On chest and abdominal radiographs, distant metastases related to perianal tumors were not observed, but hepatomegaly and T12-13 spondylosis deformance were observed. Ultrasonography revealed gall bladder sludge and slight enlargement of the bilateral medial iliac lymph nodes. Computed tomography (CT) revealed an irregular marginal mass (6.2 × 4.7 × 5.6 cm³) surrounding the distal colon, rectum, and anus. Leftward displacement and compression of the rectal lumen due to the mass were also observed (Fig. 1B-D). As a result of fine-needle aspiration (FNA) cytology of the perianal mass, an aggressive type of adenocarcinoma was diagnosed, and a poor prognosis was predicted (Fig. 2A, B). Histological examination by punch biopsy was also adenocarcinoma (Fig. 2C).

Figure 1. CT and actual images of a perianal mass as a probable cause of dyschezia. (A) Perianal ulcerative tumors observed on physical examination. (B) Several calcified substances and heterogenous contrast enhancement are observed within the perianal mass after contrast agent injection. An irregular marginal perianal mass enclosing the distal colon, rectum, and the anus is identified. (C, D) Leftward displacement and compression of the rectal lumen are observed with this perianal mass.

Figure 2. FNA and histologic results of the perianal mass. Hematoxylin and Eosin staining. (A, B) Nuclei of various shapes are observed with anisocytosis. The mass is suspected to be a highly malignant adenocarcinoma, and a poor prognosis is expected. Scale bars, 20 μm. (C) Histologic images of the perianal mass. Board-certified pathologists also commented on adenocarcinoma. Scale bars, 20 μm.

Treatment and results

Surgical procedure

Based on the results above, normal defecation was considered impossible due to the perianal mass affecting the anus, rectum, and colon. After discussion with the owner, a decision was made to perform end-on colostomy as a surgical correction method to reduce difficulty in defecation and increase quality of life. The dog was premedicated with atropine (0.05 mg/kg subcutaneously; Daehan Atropine; Daehan Pharmaceutical, Seoul, Korea), cephazolin (20 mg/kg intravenously [IV]; cefazolin sodium; Chong Kun Dang Pharmaceutical Corporation, Seoul, Korea), and tramadol (2 mg/kg IV; Tridol inj; Yuhan, Seoul, Korea). Anesthesia was induced using propofol (6 mg/kg IV; Provive 1%^®; Myungmoon Pharm. Co., Ltd., Seoul, Korea) and maintained with isoflurane (Forane; JW Pharmaceutical, Seoul, Korea) after intubation. After anesthesia, the patient was positioned in dorsal recumbency, and a median incision was made to access the colon. After the colon was transected, the distal part of the colon was returned to its original position and the end was oversewn with a Parker-Kerr pattern using a 4-0 polyglyconate suture (Maxon^TM Monofilament Absorbable Sutures, Covidien, Mansfield, MA, USA). The proximal end was extended to the left flank paralumbar area where a circular incision was made (Fig. 3A-C). After passing the proximal end of the colon through the circular incision site, the seromuscular layer of the exteriorized colon was sutured to the abdominal muscles along the circumference with a simple interrupted pattern using a 4-0 monofilament nonabsorbable suture (Dermalon^TM Monofilament Nylon Sutures, Covidien, Mansfield, MA, USA) (Fig. 3D). After washing the abdominal cavity with warm saline, the operation was completed with closure sutures in a routine manner.

Figure 3. Images of end-on colostomy for improvement of dyschezia. (A, B) After dissection of the colon, the distal end of the colon is oversewn and returned to its original position. (C) The proximal end of the colon is brought to the left flank paralumbar area where a circular incision is made. (D) The seromuscular layer of the exteriorized colon is sutured along the circumference of the abdominal muscles.

Post-surgery care

After the surgery, a one-piece drainable pouch (ConvaTec, Princeton, NJ, USA) was used for fecal evacuation and collection. Antibiotics were prescribed in combination with cephalexin (Medicephal cap; Korus, Chuncheon, Korea), enrofloxacin (Baytril flavor^® tablets, Bayer Animal Health, Mexico city, Mexico), and metronidazole (Flasinyl tab; CJ Pharmaceutical Co, Seoul, Korea) for two weeks, and postoperative analgesia was managed with tramadol. For ostomy site management, gauze and Tegaderm^® (3M Medical, St. Paul, Minnesota, USA) were used to fit around the stoma opening, and a colostomy bag was attached. However, with this method, stool frequently leaked out of the colostomy bag, and it was necessary to replace gauze and Tegaderm 2-3 times per day. To overcome these drawbacks, stomahesive paste (ConvaTec, Princeton, NJ, USA) and ConvaTec colostomy bags were used after shaving and disinfecting the skin around the stoma (Fig. 4A, B). During hospitalization, dermatitis and inflammatory exudate developed around the stoma opening and were managed using topical mupirocin ointments (Bactroban, Hanall Biopharma, Seoul, Korea; Hanyoung Gentizone Cream, Hutecs Korea Pharmaceutical Co. Ltd, Hwaseoung, Korea) and flushing using an 8-Fr feeding tube (JMS Co. Ltd., Hiroshima, Japan). The patient was discharged 10 days after the surgery. For outpatient management, selection of an appropriate colostomy bag and owner education on how to appropriately manage it was necessary. However, the ConvaTec colostomy bag used during hospitalization was inconvenient for long-term use because of its high cost. When referring to cases in human medicine, ConvaTec colostomy bags can be supplied at a low cost through national medical insurance. However, the price we could obtain without national insurance was much higher than that paid by human patients. For this reason, we attempted to use a different product, which has been documented in veterinary and human medicine. The product, a disposable colostomy bag (Rootics, Seoul, Korea), could be easily purchased on the open market at a lower price than the ConvaTec colostomy bag (Fig. 4C, D). However, this disposable bag demonstrated poor adhesion to the dog’s skin, therefore the attachment was reinforced using Tegaderm and ConvaTec stomahesive productive powder. The owner was instructed to attach a colostomy bag after the skin had dried well, and periodically shave the area around the stroma. Disposable colostomy bags were replaced after defecation every other day by the owner, and the colostomy site was examined during follow-up every one to two weeks for outpatient management. The patient’s ability to defecate and his quality of life improved, but the tumor around the anus gradually increased 30 days after the operation. Adjunctive chemotherapy was not initiated immediately after surgery because the owner refused. However, on the 41st day after surgery, toceranib phosphate (Palladia^® 2.5 mg, Zoetis, FlorhamPark, NJ, USA) was administered three times per week to delay tumor progression (5,13). On the 63rd day after surgery, a CT scan revealed a perianal mass that was larger than that previously observed (6.2 × 4.7 × 5.6 cm³ and > 8.6 × 5.7 × 9.6 cm³, respectively), and significant increases in the bilateral medial iliac lymph nodes were also observed. Moreover, the enlarged perianal mass appeared to have adhered to or invaded the peripheral soft tissue (urethra and peripheral muscle). But there was no distant metastasis. On the 71st day after surgery, the dog was presented to the hospital with symptoms of dysuria. Retrograde urethrography confirmed partial urethral obstruction due to an increase in the tumor size, and flushing was performed. On the 94th day after surgery, the patient was euthanized at the request of the owner because of the development of acute renal failure and poor quality of life.

Figure 4. (A, B) Stomahesive paste and a one-piece drainable pouch (ConvaTec) are used for fecal evacuation and collection during hospitalization. (C, D) For outpatient management, an economical disposable colostomy bag is selected. The owner replaces the disposable colostomy bag on the dog after defecation every other day.

In this case, a dog was diagnosed with a rectal adenocarcinoma with a gross appearance of annular constriction. The owner complained that the patient’s quality of life had deteriorated significantly as a result of worsening symptoms of dyschezia. However, based on previous studies, if the perianal mass was removed and a rectal pull-through procedure was performed, sequelae of fecal incontinence and reduced quality of life would be expected (1,4,6). Incontinent end-on colostomy has been previously described in the management of a dog with annular rectal adenocarcinoma; however, in that case, stricture and dehiscence were confirmed within one week of the rectal pull-through procedure (6). Referring to that case report and previous studies showing that fecal incontinence and incisional dehiscence are common if > 4 cm rectum is resected with rectal pull-through surgery (6,8), we decided that in this case the rectal pull-through procedure would not help improve the dog’s quality of life.

After discussing the diagnosis results and surgical methods with the owner, we prioritized treatment to improve the patient’s quality of life.

Although there were expected difficulties (insufficient information about colostomy bags in dogs compared to that observable in human medicine and lack of experience in postoperative management due to the rarity of such cases in veterinary practice), we performed end-on colostomy to improve the dog’s quality of life by alleviating dyschezia symptoms.

The surgery was successful, and no complications other than dermatitis or inflammatory exudates occurred during hospitalization after surgery. Since the skin irritation and inflammatory exudates were adequately resolved during hospitalization, stoma and colostomy bag management were possible with outpatient treatment. The owner easily performed stoma management by reinforcing the attachment of the stoma bag with Tegaderm and stomahesive productive powder products, and by substituting an appropriate disposable colostomy bag. Ultimately, successful surgery and stoma management allowed the dog to survive for three months with a satisfactory quality of life.

A limitation of this study is that the perianal mass was not resected during the end-on colostomy surgery. Considering that the dog was euthanized on the 94th day after surgery because of dysuria and acute kidney failure, a longer life span might have been possible if the perianal mass had been partially resected without the anal sphincter muscle. Another limitation was that adjuvant chemotherapy was not initiated immediately because the owner refused. However, treatment with toceranib was initiated 41 days after surgery because the growing tumor prompted a change in the owner’s opinion. Based on previous studies showing the therapeutic effect of toceranib on rectal adenocarcinoma, the time to tumor-causing urinary tract obstruction might have been delayed if toceranib treatment was initiated immediately after surgery (5,13).

This report describes improvement in quality of life and extension of life span to 90 days enabled by end-on colostomy and adjunctive chemotherapy in a dog with dyschezia due to an anal adenocarcinoma-associated obstruction. Our experience in this case shows that economical treatment of dyschezia due to rectal adenocarcinoma with a gross appearance of annular constriction is possible if disposable colostomy bags typically used in human patients are actively used for dogs. Consequently, the methods described in this study will aid in the treatment of animals requiring artificial defecation.

The authors received no financial support for the research, authorship, and/or publication of this article.

The authors thank the owner of the dog included in this study.

The authors have no conflicting interests.