Rectal Strictures in 19 Dogs: 1997–2005
The etiologies for nonneoplastic rectal strictures in dogs included foreign bodies, postoperative formation, inflammatory disease, and congenital malformation. Sixteen of 19 dogs underwent balloon dilatation therapy, and 14 of these 16 dogs received intralesional triamcinolone injections. Following dilatation, clinical signs persisted in one dog, improved with continued medical therapy in five dogs, and resolved in nine dogs for the duration of their follow-up period (mean 18 months; median 12 months); one dog was lost to follow-up. Balloon dilatation and triamcinolone were parts of a treatment regimen that improved clinical signs in the majority of dogs diagnosed with nonneoplastic rectal strictures.
Introduction
Rectal strictures have rarely been reported in dogs. Published case reports of canine rectal strictures include one dog whose stricture was caused by a rectal adenocarcinoma and another dog whose rectal stricture formed secondary to Prototheca colitis.1,2 Both dogs had their rectal strictures surgically removed and were euthanized 4 months later. A report also documents a subset of dogs (six of 41) that developed rectal strictures following surgery for perianal fistula disease, but management of the strictures was not further described.3
Endoscopy-assisted balloon dilatation with concurrent intralesional injection of triamcinolone has been used to treat esophageal strictures in dogs and cats and is currently used to treat humans with colonic strictures secondary to Crohn’s disease.4–6 No published reports have described the use of either balloon dilatation or intralesional triamcinolone injection for the treatment of rectal strictures in dogs; however, both techniques are frequently employed at Colorado State University Veterinary Medical Center (CSU VMC).
The objectives of this study were to describe the clinical presentations and underlying etiologies for nonneoplastic rectal strictures in a larger number of dogs than had been previously reported; identify treatments used for dogs with nonneoplastic rectal strictures; and report the outcomes of such cases seen at CSU VMC where the endoscopy-guided balloon dilatation procedure was used.
Materials and Methods
Medical records of dogs diagnosed with a nonneoplastic rectal stricture between January 1997 and July 2005 were obtained from CSU VMC and reviewed. A nonneoplastic rectal stricture was defined as a segmental narrowing of the rectal luminal diameter that was not caused by a neoplastic process and was located anywhere from the pelvic inlet to the level of the external anal sphincter. Nineteen cases fit these criteria.
The complete medical record for each dog was reviewed, and the signalment, presenting complaint, duration of clinical signs prior to the diagnosis of a rectal stricture, rectal examination findings, laboratory data, imaging studies, colonoscopy reports, histopathology, etiology, treatment protocol, and outcome were recorded. An attempt was made to contact the owner of any dog for which follow-up information covered a <3- month period.
Descriptive statistical calculations were performed using a computer spreadsheet.a Median and mean values were calculated for age at presentation, body weight, duration of clinical signs prior to diagnosis, rectal stricture diameter, time until repeat balloon dilatation procedure, dose and duration of oral prednisone treatment, and follow-up duration.
Results
Clinical Data
Of the 19 dogs, 14 were purebred and five were mixed-breed dogs; of the purebred dogs, only the German shepherd dog was represented more than once [see Table]. The median and mean ages of dogs at the time of diagnosis were 7.0 and 6.5 years, respectively (range 2 weeks to 14 years). Eleven were castrated males, one was an intact male, five were spayed females, and two were intact females [see Table]. The median and mean body weights of the dogs were 16 and 20 kg, respectively (range 3 to 36 kg).
Fourteen of the 19 dogs were presented for tenesmus. Additional presenting complaints included hematochezia (n=3) and diarrhea (n=4), melena (n=1), and bleeding from the rectum (n=1). The three German shepherd dogs all had histories of chronic perianal fistula disease. For all dogs, the median and mean durations of clinical signs prior to diagnosis were 1.0 and 2.8 weeks, respectively (range 1 to 24 weeks). Rectal strictures that occurred postoperatively were identified a median and mean of 3.5 and 3.0 weeks, respectively (range 1 to 4 weeks), following surgery. Strictures caused by a foreign body were detected a median and mean of 2.0 and 2.3 weeks, respectively (range 1 to 4 weeks), after the foreign body had been digitally removed. Strictures were palpated during digital rectal examination in all 19 dogs.
The biochemical profile, complete blood count, and urinalysis were normal except for one dog (case no. 6) with inflammatory bowel disease that was hypoalbuminemic (1.7 gm/dL; reference range 2.5 to 4.0 gm/dL).
Abdominal radiographs were considered normal in six of 12 dogs. Five dogs (case nos. 3, 12, 13, 16, 19) showed evidence of colonic dilatation with fecal material proximal to the stricture, and in one dog (case no. 1) a barium enema demonstrated a narrowing in the distal rectum consistent with a congenital rectal stricture.
Abdominal ultrasound examination was considered normal in six of nine dogs. The thickness of the colonic wall was considered increased in two dogs (case nos. 3, 15), and enlarged sublumbar lymph nodes were reported in one dog (case no. 10) with chronic large bowel diarrhea.
In 15 dogs, colonoscopy was used to visualize the rectal strictures and guide balloon placement for the dilatation procedure. The median and mean diameters of the rectal strictures were estimated visually to be 10.0 and 10.2 mm, respectively (range 4 to 15 mm). Orad of the stricture, the colon appeared grossly normal in all but three dogs (case nos. 4, 6, 15); in these dogs, the colon was described as having a cobblestone or erythematous appearance. Colonoscopy was not performed in the three German shepherd dogs with perianal fistula disease and in one dog (case no. 3) whose rectal stricture was distal enough to be treated without endoscopic visualization.
Histopathology revealed evidence of inflammation, including chronic, fibrosing, ulcerative proctitis and/or colitis, in five dogs (case nos. 6, 10, 12, 15, 19). In one dog (case no. 4), histopathology revealed pyogranulomatous lesions consistent with fungal disease [see Table].
Etiologies were determined in 18 of the 19 dogs [see Table]. In the three German shepherd dogs, the rectal stricture was considered to be an extension of the chronic perianal fistula disease. In four dogs (case nos. 14, 16–18), a circumferential rectal stricture was identified subsequent to surgical resection and anastomosis of a neoplastic rectal mass. A foreign body was determined to be the cause of a rectal stricture in three dogs (case nos. 2, 3, 8). Five dogs (case nos. 6, 10, 12, 15, 19) were diagnosed with proctitis and/or colitis, and two of these dogs (case nos. 6, 10) were also diagnosed with small intestinal inflammatory bowel disease at the time of the initial dilatation procedure. In one dog (case no. 13), the rectal stricture appeared to form secondary to anal sacculitis. In one dog (case no. 4), histoplasmosis was diagnosed at the time of the first balloon dilatation. In the 2-week-old puppy (case no. 1), the stricture was a congenital malformation caused by an imperforate anus.7
Treatments
Sixteen of the 19 dogs were treated with balloon dilatation; the exceptions were the three German shepherd dogs with perianal fistula disease. The procedure employed for the balloon dilatation of rectal strictures was almost identical to the published procedure for balloon dilatation of esophageal strictures in dogs and cats.8–10 The diameters of the dilatation balloons ranged from 8 to 35 mm. In general, small dogs (<15 kg) were dilated with balloons of 18- and 20-mm diameter; medium dogs (between 15 and 30 kg) were dilated with balloons of 20- and 25-mm diameter; and large dogs (>30 kg) were dilated with balloons between 30 and 35 mm in diameter. One dog (case no. 6) showed visual evidence of significant mucosal tearing after balloon dilatation; no other complications associated with the balloon dilatation procedure were observed.
Repeat dilatation was based on the continuation of clinical signs and repeat rectal examination. Ten dogs (case nos. 1, 3, 6, 8, 10, 12, 13, 15–17) required one dilatation procedure; four (case nos. 4, 14, 18, 19) required two separate dilatation procedures; one dog (case no. 9) required three separate dilatation procedures; and one dog (case no. 2) required four separate dilatation procedures. The median and mean durations until repeat balloon dilatation procedures were 2.0 and 3.0 weeks, respectively (range 1 to 6 weeks), following the previous dilatation.
Fourteen of the 16 dogs in which balloon dilatation was performed also received an intralesional injection of triamcinoloneb (10 mg/mL) at the time of the first dilatation procedure. A total of 0.5 to 1.0 mL of triamcinolone was injected submucosally in four evenly spaced locations around the stricture just prior to the dilatation procedure. In most cases, placement of the needle for injection was endoscopically directed using an endoscopic injection catheter;c in one dog (case no. 13), the needle was directed into the stricture site digitally. In those dogs that required more than one balloon dilatation procedure, the triamcinolone injection was repeated during the second, but not the third or fourth, dilatation procedure. In seven dogs (case nos. 6, 8, 10, 13, 15–17), oral prednisoned was instituted following the initial dilatation procedure at median and mean doses of 1.0 and 1.2 mg/kg, respectively (range 0.5 to 2.0 mg/kg), for a median and mean duration of 28 days (range 14 to 60 days). Additional postprocedure medications that were used in one or more dogs included lactulose,e cisapride,f and antibiotics (i.e., amoxicillin,g tylosin,h or metronidazolei). Two of the dogs (case nos. 6, 10) with concurrent small intestinal inflammatory bowel disease continued treatment with either azathioprinej or cyclosporine,k and the one dog (case no. 4) with histoplasmosis was treated with itraconazole.l Five dogs (case nos. 1, 9, 15, 16, 18) were placed on a high-fiber diet,m and two dogs (case nos. 10, 19) were placed on a low-residue diet.n
Outcome
For the 16 dogs that underwent balloon dilatation of the rectal stricture, follow-up took place a median of 6.0 months and a mean of 14.3 months after the last dilatation procedure (range 1 month to 4 years). In 10 of the 16 dogs, clinical signs related to the rectal stricture were completely resolved for the duration of their follow-up (median 1 year; mean 2.4 years; range 3 months to 10 years) [see Table]. Clinical signs improved in two dogs (case nos. 17, 19), but treatment with lactulose was continued for the duration of their follow-up. In three dogs (case nos. 4, 6, 10), clinical signs improved, but continued treatment was required for ongoing disease (i.e., histoplasmosis or small intestinal inflammatory bowel disease). The owners of one dog (case no. 18) reported that clinical signs persisted following balloon dilatation. No follow-up information was available for one other dog (case no. 13).
None of the three German shepherd dogs included in this study underwent balloon dilatation. One of these dogs (case no. 7) was euthanized shortly after diagnosis of a rectal stricture; one dog (case no. 11) underwent surgical correction of the stricture and had no recurrence of clinical signs at a 3-month recheck appointment; and one dog (case no. 5) was lost to follow-up.
Discussion
The results of this study suggest that rectal strictures occur in a variety of breeds, across a wide range of body weights and ages. Three of the dogs were German shepherd dogs with perianal fistula disease. Although there is a prior report of rectal strictures developing as a complication of surgery for this disorder,3 an important difference between that study and the present one is that the rectal strictures identified in the German shepherd dogs described here occurred spontaneously and not as the result of surgery for their perianal disease. This finding suggests that any dog with perianal fistula disease showing persistent clinical signs in the face of appropriate therapy should be closely examined for the development of a rectal stricture.
Twelve of the 19 dogs were males. The obvious pertinent anatomical difference between the sexes is the presence of a prostate gland in the male. However, the majority of the male dogs in this study (11 of 12 dogs) were castrated, and the strictures developed distal to the level of the prostate gland. Other explanations for the difference in the prevalence of rectal strictures between male and female dogs were not apparent, and the difference may be simply a function of the small number of cases.
In this study of dogs with rectal strictures, tenesmus was the presenting complaint in the majority of cases (14 of 19 dogs). When stricture formation was secondary to mechanical disruption, clinical signs appeared to develop relatively quickly, and veterinary attention was sought within 1 to 3 weeks. In some dogs, the diagnosis was not made until clinical signs had been present for much longer; delay in diagnosis may result if the stricture forms secondary to a separate disease process, such as colitis, or if the clinician has a low index of suspicion for this rarely reported condition. For all of the dogs in this study, strictures were palpated on digital rectal examination, highlighting the importance of this portion of the physical examination in dogs that are presented with signs of gastrointestinal disease.
Although serum biochemical values, abdominal radiographs, and ultrasound were important for ruling out other differentials for gastrointestinal disease, none of these diagnostic test results were specific for a rectal stricture. A barium contrast study may identify an intestinal stricture proximal to the rectum, but it appears unnecessary in those dogs that are presented with tenesmus and in which digital rectal examination reveals a stricture.
Colonoscopy allowed for visualization of the stricture, accurate placement of the balloon in the stricture lumen, and guidance for distributing intralesional injections of triamcinolone. One dog in this study underwent these procedures without the aid of colonoscopy. Without colonoscopy, however, it is impossible to accurately assess aspects of the procedure that may help the clinician determine important parameters, such as the size of the balloon(s) employed.
Histopathology was available for only six dogs but revealed a previously undiagnosed condition in all six; in light of this finding, histopathology should be a routine part of the diagnostic workup of these cases. Histopathology can rule out potentially treatable intestinal disease that may result in stricture formation, or it can identify the presence of a neoplastic process that would require surgical removal.
The most common etiology for rectal stricture formation in this study was mechanical trauma from either foreign objects or surgery. Making the determination of rectal stricture formation is more difficult in dogs wherein the underlying etiology may be ongoing pathology, as in cases of inflammatory intestinal disease. Dogs with proctitis, colitis, and even small intestinal inflammatory bowel disease can be presented for clinical signs similar to those caused by a rectal stricture.
Endoscopic-guided balloon dilatation with intralesional triamcinolone injection was used to treat the majority of the dogs in this study. A similar procedure has been reported to be effective for dogs and cats with esophageal strictures.8–10 Twelve of the 16 dogs in this study that were treated with the balloon dilatation procedure had either significant or complete resolution of their clinical signs. Fourteen of these 16 dogs also received an injection of triamcinolone. Eleven of these 14 dogs had a resolution or improvement in clinical signs; two required continuing treatment; and one was lost to follow-up. Of the two dogs that underwent balloon dilatation but did not receive triamcinolone, one had a resolution of clinical signs and one continued to require treatment. No significant adverse events were recorded during the dilatation procedures, and no long-term complications were associated with the procedure. In one dog, however, the treatment did not appear to have any effect on clinical signs.
Conclusion
Rectal stricture is a differential diagnosis for tenesmus in dogs, especially in cases involving any form of mechanical trauma or inflammation in the area. Balloon dilatation is a safe treatment modality for rectal strictures, and in many dogs, clinical signs can improve significantly or be eliminated following one or two dilatation treatments. The effectiveness of intralesional triamcinolone injection or postprocedure oral prednisone therapy could not be determined, and a prospective placebo-controlled study is warranted. Rectal strictures were palpable by digital rectal examination in all of the dogs in this study; this highlights the importance of this part of the physical examination, even in those dogs with preexisting inflammatory intestinal disease.
Microsoft Office Excel 2003; Microsoft Corporation, Redmond, WA 98052
Triamcinolone; Bristol-Myers Squibb, Princeton, NJ 08543
Disposable Articulator Injection needle (25 ga); US Endoscopy Corporation, Mentor, OH 44060
Prednisone; Cardinal Health, Dublin, OH 43017
Lactulose; Apotex Corporation, Weston, FL 33326
Cisapride; Compounded by Colorado State University, Fort Collins, CO 80523
Amoxicillin; Pfizer Animal Health, Exton, PA 19341
Tylosin; Eli Lilly and Company, Indianapolis, IN 46285
Metronidazole; Pliva, Inc., East Hanover, NJ 07936
Azathioprine; Roxane Laboratories, Inc., Columbus, OH 43216
Cyclosporine; Ivax Pharmaceuticals, Inc., Miami, FL 33137
Itraconazole; Sancoz, Inc., Princeton, NJ 08540
Hill’s w/d; Hill’s Pet Nutrition, Inc., Topeka, KS 66601
Eukanuba Low-Residue Adult; The Iams Company, Dayton, OH 45414
