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Research Updates: Should biopsy samples be routinely collected from the duodenum and ileum in dogs with clinical signs suggestive of concurrent small and large bowel diarrhea?
Ileal biopsy in dogs with diarrhea may provide additional information that affects the final diagnosis.
The diagnosis and treatment of gastrointestinal diseases depend largely on histologic examination of biopsy samples. When biopsy samples are obtained endoscopically, operator experience, the anatomic site from which biopsies are obtained, the number of samples taken per site, and how samples are processed have all been shown to be critical in determining the final diagnosis and, thus, the treatments prescribed and prognosis.
Previous studies have evaluated the effects of sample quality and tissue processing and the value of surgical full-thickness vs. endoscopic mucosal or submucosal biopsy samples on the assessment of intestinal disease.1-3 However, no study has evaluated the diagnostic value of collecting samples from the ileum in addition to the duodenum in dogs with both small and large bowel diarrhea. The ileum is a technically more difficult region to sample endoscopically than the proximal gastrointestinal tract. Also, additional biopsy collection sites increase the procedure and anesthetic time with both surgery and endoscopy and may increase the risk of complications.
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The goal of this study was to compare histopathologic results of biopsy samples taken from duodenal, colonic, and ileal samples in dogs with diffuse gastrointestinal disease and determine whether ileal biopsy provides additional information that affects the final diagnosis that would not have been obtained with biopsy samples from alternative regions.
To determine the value of ileal biopsies in dogs with both small and large bowel diarrhea, the authors retrospectively identified dogs that had endoscopic (n=30) or surgical (n=10) biopsy samples collected from both the duodenum and ileum during routine diagnostic evaluation. These histologic samples were then blindly evaluated by two of the authors using the published World Small Animal Veterinary Association Gastrointestinal Standardization Group scoring system; a histopathologic diagnosis and severity score were determined independently for each site.
The most common histologic findings noted in the 40 dogs were absence of any abnormalities, eosinophilic inflammation, lymphocytic-plasmacytic inflammation, and granulomatous inflammation; intestinal lymphoma was not diagnosed in any of the dogs. Of the 30 cases that had inflammatory lesions noted in the duodenum and ileum, the diagnoses were the same in both regions in only about one-fourth (27%) of cases.
When agreement in the severity of inflammation was also required for the authors to consider that an identical diagnosis had been made in biopsy samples from both sites, then agreement was noted in only 10% of cases. When comparing histopathologic diagnoses made after examination of ileal and colonic biopsy samples, again, only about one-fourth of cases (24%) demonstrated agreement. Unfortunately, the small number of biopsy samples collected via laparotomy did not allow a comparison of the agreement in histopathologic results when biopsy samples were collected endoscopically vs. surgically.
Based on these results, the authors concluded that collecting biopsy samples from the ileum does, in fact, appear warranted in dogs with clinical signs of both large and small bowel diarrhea. Obtaining biopsy samples from the most distal small intestinal segment would indeed have altered the final diagnosis in most dogs. When severity was considered as well, only one in 10 dogs would have had an unchanged diagnosis after examination of the ileal biopsy sample.
Unfortunately, most colonic biopsy samples obtained from the study dogs did not reveal any histopathologic lesions, emphasizing that ileal samples are required when examining the distal gastrointestinal tract. The authors note that in some cases, lesions were in fact identified in the ileum whereas the duodenum was histologically unremarkable, which may be because the distal intestine's thinner mucosa allows easier collection of adequate samples by most endoscopists. Alternatively, in some dogs, the ileum may be the location of earliest disease changes, in which case ileal biopsies would be required if diffuse disease did not yet involve the entire intestine.
Unfortunately, the authors did not report folate or cobalamin concentrations in this report, which would have provided indirect evidence about the extent of small intestinal disease in these dogs. Correlating the presence and degree of hypocobalaminemia with ileal histopathologic changes could prove to be a useful indicator as to the need to obtain biopsy samples from the ileum.
The primary limitations of this study are the failure to include dogs with intestinal lymphoma and the relatively high percentage of dogs with eosinophilic gastroenteritis. Because most published studies on idiopathic gastroenteritis (i.e. inflammatory bowel disease) have demonstrated that lymphocytic-plasmacytic enteritis is the most common histologic subtype encountered, the population included here raises concern for unintentional study bias. Additionally, although this study suggests that type and severity of inflammation may differ depending on which anatomic site is sampled in dogs with diffuse bowel clinical signs, the utility of obtaining ileal biopsies in patients with only small bowel diarrhea is still unknown.
Casamian-Sorrosal D, Willard MD, Murray JK, et al. Comparison of histopathologic findings in biopsies from the duodenum and ileum of dogs with enteropathy. J Vet Intern Med 2010;24(1):80-83.
The information in "Research Updates" was provided by Erika Meler, DVM, MS, and Barrak Pressler, DVM, PhD, DACVIM, Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.
1. Willard MD, Mansell J, Fosgate GT, et al. Effect of sample quality on the sensitivity of endoscopic biopsy for detecting gastric and duodenal lesions in dogs and cats. J Vet Intern Med 2008;22(5):1084-1089.
2. Willard MD, Moore GE, Denton BD, et al. Effect of tissue processing on assessment of endoscopic intestinal biopsies in dogs and cats. J Vet Intern Med 2010;24(1):84-89.
3. Kleinschmidt S, Meneses F, Nolte I, et al. Retrospective study on the diagnostic value of full-thickness biopsies from the stomach and intestines in dogs with chronic gastrointestinal disease symptoms. Vet Pathol 2006;43(6):1000-1003.