Abstract
A 4-year-old castrated male domestic shorthair presented for 1 week of constipation and tenesmus. A rectal stricture had been diagnosed 8 months prior at the time of adoption and the cat had been successfully managed with stool softeners until presentation. A complete diagnostic work-up failed to reveal an underlying etiology for the stricture and colonoscopy was performed. Endoscopic biopsies of the stricture revealed benign non-specific inflammatory changes. Balloon dilation of the rectal stricture was performed during the initial colonoscopy and 3 and 9 days later. Triamcinolone acetonide was injected into the stricture site with endoscopic guidance during the third dilation procedure. The patient has been monitored for over 27 months; follow-up indicates no signs of tenesmus and repeated rectal examinations reveal no stricture recurrence. This case report demonstrates that endoscopic balloon dilation with intralesional steroid injection represented a minimally invasive and effective option for the treatment of a benign rectal stricture in this cat, and deserves further prospective investigation.
Although uncommon in veterinary practice, rectal strictures present a therapeutic challenge. Historically, treatment of rectal strictures has been limited to surgery and complications are common; therefore, a less invasive therapeutic approach for benign rectal strictures is desirable.
Endoscopic balloon dilation with or without intralesional steroid injection is the most common method of treating humans with benign rectal strictures. 1–5 A recent report described successful use of this technique in dogs. 6 To date, only one published report of a feline rectal stricture exists in the veterinary literature and was a complication from surgery to resect a rectal adenocarcinoma.7
A 4-year-old castrated male domestic shorthair was evaluated for a 1-week history of constipation and vocalizing while trying to defecate. The cat had been adopted 8 months prior and a rectal stricture was diagnosed at that time. The cat had been successfully managed with lactulose (Ani Pharmaceuticals, 2 ml q24 h PO) until presentation.
On physical examination the cat was mildly dehydrated. His abdomen was distended with fluid-filled intestinal loops. A circumferential stricture was palpated 1.5 cm into the rectum, obstructing further digital examination. Physical examination was otherwise unremarkable.
Complete blood count revealed mild mature neutrophilia (9680×103/μl; reference interval 2500–8500×103/μl). Serum biochemical profile revealed mild hyperglycemia (174 mg/dl; reference interval 70–150 mg/dl). Fecal flotation and giardia enzyme-linked immunosorbent assay were negative. Abdominal radiographs revealed moderate diffuse colonic distention with radiopaque debris, without evidence of complete obstruction. Abdominal ultrasound was unremarkable except for colonic distention. As no underlying etiology was suspected, endoscopic balloon dilation of the stricture was recommended.
The cat was held nil by mouth for 36 h before the procedure during which time he received a balanced electrolyte solution (Normasol-R; Hospira) intravenously to maintain hydration. Lactulose (2 ml PO q8 h) was administered to facilitate stool softening. Warm water enemas were given 24 h, 12 h, and immediately prior to the procedure to evacuate the colon. Ampicillin (Abraxis Pharmaceutical Products, 22 mg/kg IV q8 h) was given prophylactically for the risk of bacterial translocation both pre colonoscopy as well as post-procedure.
Proctoscopy and colonoscopy were performed under general anesthesia. The stricture was identified 1.5 cm from the anus, reducing the rectal lumen to 8 mm in diameter. Multiple endoscopic biopsies were obtained from the stricture and surrounding mucosa and were submitted for histopathology. A deflated 10-mm dilating balloon (CRE Balloon Dilatation Catheter, Boston Scientific) was passed alongside the endoscope and advanced through the stricture under direct endoscopic guidance. Following the manufacturer's recommendations, the balloon was inflated to maximum pressure for 1 min intervals three times. This procedure was repeated with sequentially larger balloons (12 mm, 15 mm, and 18 mm diameter). Mild bleeding with no evidence of perforation was noted following removal of the 18 mm balloon. After the last dilation, the endoscope could be advanced through the stricture, which measured approximately 1 cm in length. The rectal and colonic mucosa proximal to the stricture appeared normal. The cat was discharged that evening with fenbendazole (Panacur; Intervet, 50 mg/kg PO q24 h for 5 days) as empiric treatment for parasitic infection despite negative fecal examination, lactulose (3 ml PO q8 h) as a stool softener, butorphanol (Torbutrol; Fort Dodge Animal Health, 0.25 mg/kg PO q8–12 h) as needed for pain, a low-residue diet (Iams Veterinary Formulas Intestinal Low-Residue; Iams), and metronidazole (Pliva, 14.8 mg/kg PO q12 h for 7 days) with instructions to return 3 days later for re-evaluation.
Histopathology revealed moderate erosive and fibrosing proctitis with focal linear necrosis and mild infiltrates of mixed macrophages, lymphocytes, and plasma cells; changes that were thought to be due to prior trauma to the site. Proctoscopy was repeated 3 days later and the stricture had contracted the lumen to 15 mm. Balloon dilation was repeated as previously described to a maximal balloon diameter of 20 mm. Mild to moderate mucosal bleeding was noted at the stricture site with no evidence of perforation. The cat was discharged that evening with 10 days of amoxicillin clavulanate (Clavamox; Pfizer Animal Health, 15.6 mg/kg PO q12 h) in addition to the metronidazole to broaden antibacterial coverage for bacterial translocation due to a perceived increase in mucosal trauma from the second dilation procedure.
The cat returned again after another 6 days for further proctoscopy. The stricture had contracted the lumen to 15 mm. Prior to balloon dilation, 0.8 mg of triamcinolone acetonide (Vetalog; Fort Dodge Animal Health) was injected submucosally with endoscopic guidance in four evenly-spaced locations around the stricture using an endoscopic injection catheter (Disposable Injector NM-201L-0425 [25 g, 4 mm]; Olympus). Balloon dilation was repeated as previously described. Mild mucosal bleeding and tearing were noted at the stricture site, with no evidence of perforation. The cat was discharged with instructions to complete the course of Clavamox and to continue administering lactulose and feeding a low-residue diet long term.
An owner phone interview 2 weeks after the third dilation procedure revealed that the cat was defecating normally and without tenesmus. Repeated rectal examinations performed by the referring veterinarian indicated no recurrence of the stricture; the cat has remained asymptomatic for over 27 months as of the time of writing.
Rectal strictures are chronic narrowings of the intestinal lumen by abnormal tissue, resulting in complete or partial bowel obstruction. 8 This tissue may be scar tissue resulting from chronic rectal or anal inflammation, trauma from foreign bodies or prior surgery, perianal fistulas, or pelvic irradiation. 6,9,10 Infiltrative or proliferative neoplastic lesions may also create strictures. 6,9 Affected animals display tenesmus, often producing narrow ribbons of feces or no feces at all. If concurrent neoplastic or inflammatory disease is present, hematochezia, mucoid feces, diarrhea, anorexia, weight loss, or vomiting may also be seen. 6,9
The most important aspect of diagnosis is determining whether the stricture is malignant or benign. In this cat, histopathology revealed changes consistent with prior trauma to the site. Parasitic infection can also cause proctitis; this cat was empirically treated for parasitic infection despite negative fecal examinations. In retrospect, biopsies should have been taken along the entire colon in order to assess for underlying colonic disease that could predispose to stricture formation. This was not performed as the cat had no history of chronic gastrointestinal signs and was otherwise healthy.
Historically, surgical techniques like rectal pull-through or myotomy have been performed to manage rectal strictures. 11 These procedures are frequently associated with severe complications, such as fecal incontinence, infection or abscess formation, dehiscence, or restricture. 11 Endoscopic balloon dilation has been used to treat benign rectal strictures in humans with Crohn's disease for years, 2–4,6 and was recently reported as safe and effective for dogs.7
Balloon dilation exerts radial force on tissue, thereby elongating and rupturing the fibrous, collagen-rich tissue comprising the stricture. 2,3,12 The diameter of the balloon and the number of procedures required to achieve sustained opening of the lumen are variable. In humans and dogs, clinical signs may improve significantly or be eliminated after one or two dilations, although some patients require up to four dilations to resolve clinical signs. 2–6 The procedure is rarely ineffective necessitating surgical intervention. 3 The purpose of performing multiple procedures several days apart is to gradually increase stricture diameter without excessive tearing or inflammation, thereby reducing likelihood of restricture. 11 Although proctoscopy was not performed following the third procedure, the cat has not experienced further constipation or tenesmus in 27 months.
Intralesional steroid injections have been used with balloon dilation to treat esophageal strictures in dogs and cats for a number of years and are currently used to treat humans with colonic strictures secondary to Crohn's disease. 2,4,5,13 When combined with balloon dilation, intralesional triamcinolone injections resulted in better success rates than balloon dilation alone. 2 This protocol has proven successful in management of postoperative colonic strictures and esophageal strictures in humans that were refractory to serial dilations alone. 13,14 Additionally, a prospective, randomized, double-blind, placebo-controlled trial demonstrated that triamcinolone injection into recalcitrant esophageal strictures significantly diminished need for repeat dilation and average time to repeat dilation compared to sham injection.15
The mechanism of action by which triamcinolone prevents re-formation of strictures is unknown. Its efficacy in treatment of dermatologic scars, such as keloids in humans is well established. 16 It is postulated that triamcinolone inhibits collagen formation, enhances collagen breakdown, and prevents cross-linking of collagen that results in scar contracture.17
Complications associated with endoscopic balloon dilation of rectal strictures include perforation, abscess formation, and hemorrhage. These complications are rare, reportedly occurring in fewer than 11% of human cases, 1,2,18 with most studies reporting no complications. 3,6,13,19 Intralesional steroid injection could theoretically predispose to complications such as abscess formation, perforation, and septic peritonitis, although studies in humans have shown no additional risk compared to balloon dilation alone. 2,4,20,21
This report demonstrates that endoscopic balloon dilation with intralesional steroid injection was a minimally invasive and effective option to treat a benign rectal stricture in this cat. However, no double-blind, placebo-controlled studies have been conducted in cats to determine whether dilation alone or dilation with intralesional steroid injection provides the best outcome, and it is possible that this patient could have been cured by three ballooning procedures without intralesional steroids. Further investigation into this subject is, therefore, warranted.