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A C Zacuto 1, P A Pesavento 2, S Hill 3, A McAlister 4, K Rosenthal 5, O Cherbinsky 6, S L Marks 7
Background
Intestinal leiomyositis is a suspected autoimmune disorder affecting the muscularis propria of the gastrointestinal tract, leading to chronic intestinal pseudo-obstruction (CIPO). CIPO is characterized by severe hypomotility and functional ileus without mechanical obstruction. This study aimed to characterize the clinical presentation, diagnostic imaging, histopathologic findings, and outcomes of dogs diagnosed with intestinal leiomyositis.
Methods
A retrospective case series was conducted on six client-owned dogs diagnosed with intestinal leiomyositis between 2006 and 2014. Data were collected on:
-Clinical presentation (history, physical examination, lab results).
-Diagnostic imaging (radiographs, ultrasound, computed tomography).
-Histopathologic findings from full-thickness gastrointestinal biopsies.
-Treatment strategies and outcome.
-Immunohistochemistry (IHC) to assess inflammatory cell types.
Results
Signalment & Clinical Signs:
-Breeds represented: Labrador Retrievers (2), Portuguese Water Dogs (2), Bernese Mountain Dog (1), German Shorthaired Pointer (1).
-Median age: 5.4 years (range: 15 months–9 years).
Clinical signs:
-Vomiting (6/6 dogs)
-Small bowel diarrhea (3/6 dogs)
-Regurgitation (2/6 dogs)
-Anorexia (2/6 dogs)
-Median duration of signs before diagnosis: 13 days (range: 5–150 days).
Imaging Findings:
Abdominal radiographs (4/6 dogs):
-Gastric and small intestinal dilation (3/4 dogs).
-Diffuse loss of intestinal wall layering (2/4 dogs).
Abdominal ultrasound (5/6 dogs):
-Poor to absent peristalsis.
-Segmental small intestinal dilation without mechanical obstruction.
CT scan (1 dog): Confirmed functional ileus with no foreign body.
Histopathology & Immunohistochemistry:
Full-thickness intestinal biopsies showed:
-T-lymphocyte infiltration of the muscularis propria.
-Degeneration and necrosis of myofibers.
-Fibrosis replacing smooth muscle in chronic cases.
Immunohistochemistry:
-CD3+ T cells predominated (suggesting immune-mediated disease).
-B cells (CD20+, CD79+) and histiocytes (CD18+) were less abundant.
Treatment & Outcomes:
-All dogs received immunosuppressive therapy (prednisone, cyclosporine), prokinetics (cisapride, metoclopramide, erythromycin), antibiotics (metronidazole, amoxicillin, azithromycin), and supportive care (fluids, antiemetics, nutritional therapy).
-Median survival after diagnosis: 19 days (range: 3–270 days).
-All dogs were euthanized due to progressive disease.
-Main causes of euthanasia: refractory intestinal dysmotility and aspiration pneumonia.
Limitations
The small sample size (6 dogs) limits generalizability. The study was retrospective, meaning selection bias may be present. Histologic confirmation was required for inclusion, so cases diagnosed without full-thickness biopsy were not considered.
Conclusions
Intestinal leiomyositis is a rare but severe cause of chronic intestinal pseudo-obstruction in dogs, leading to poor outcomes despite aggressive treatment. Diagnosis requires full-thickness intestinal biopsy, as mucosal biopsies alone are inadequate. Early recognition and intervention may improve prognosis, though disease progression remains rapid and fatal in most cases.
Right lateral survey radiograph obtained from a 2-year MC Bernese mountain dog (dog 3). There is severe dilatation of the stomach with fluid and a small volume of gas. There are multiple irregular, variably sized mineral opacities present within the lumen of the stomach. The small bowel and colon is diffusely and severely fluid and gas dilated. Apparent gravel sign in the stomach is most consistent with chronic gastric outflow obstruction; however, given the diffuse changes, an underlying functional ileus should be considered.
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