Canis ISSN: 2398-2942

Large intestine: neoplasia

Contributor(s): Lori Ludwig, Isabelle Desmas-Bazelle


  • Most found in rectum or distal third of colon.
  • Cause: benign adenomatous polyps which can undergo malignant transformation.
  • Signs: tenesmus, blood in feces.
  • Diagnosis: rectal examination and proctoscopy if lower colorectal lesions.
  • Treatment: wide surgical excision because of their potential for malignant transformation for carcinoma and sarcoma. Chemotherapy for lymphoma.
  • Prognosis: good if rectal polyps, guarded if malignant.






  • Some forms of benign adenomatous polyps found in the colon of dogs have the potential to undergo malignant transformation in much the same way as human colonic familial polypoidosis, although the incidence of this phenomenon is unknown.


  • Tumor mass may cause physical obstruction or interference with peristalsis.
  • The proximal bowel becomes distended with feces/fluid resulting in tenesmus and dyschezia.
  • Hemorrhage is common due to mucosal damage caused by the passage of feces over an intraluminal mass.


  • Months to years.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Adamovich-Rippe K N, Mayhew P D, Marks S L, Selmic L E, Culp W T et al (2017) Colonoscopic and histologic features of rectal masses in dogs: 82 cases (1995-2012). JAVMA 250 (4), 424-430 PubMed.
  • Desmas I, Burton J H, Post G et al (2017) Clinical presentation, treatment and outcome in 31 dogs with presumed primary colorectal lymphoma (2001-2013). Vet Comp Oncol 15 (2), 504-517 PubMed.
  • Hayashi K, Okanishi H, Kagawa Y et al (2012) The role of endoscopic ultrasound in the evaluation of rectal polypoid lesions in 25 dogs. Jpn J Vet Res 60 (4), 185-189 PubMed.
  • Van den Steen N, Berlato D, Polton G et al (2012) Rectal lymphoma in 11 dogs: a retrospective study. JSAP 53 (10), 585-591 PubMed.
  • Rannou B, Helie P, Bedard C (2009) Rectal plasmacytoma with intracellular hemosiderin in a dog. Vet Pathol 46 (6), 1181-1184 PubMed.
  • Morello E, Martano M, Squassino C et al (2008) Transanal pull-through rectral amputation for treatment of colorectal carcinoma in 11 dogs. Vet Surg 37 (5), 420-426 PubMed.
  • Trevor P B, Saunders G K, Waldron D R, Leib M S (1993) Metastatic extramedullary plasmacytoma of the colon and rectum in a dog. JAVMA 203 (3), 406-409 PubMed.
  • McPhernon M A, Withow S J, Seim H B et al (1992) Colorectal leiomyomas in 7 dogs. JAAHA 28 (1), 43-46 VetMedResource.
  • Church E M, Melhalt C J & Patnalk A K (1987) Colorectal adenocarcinoma in dogs - 78 cases (1973-1984). JAVMA 191 (6), 727-30 PubMed.
  • White R A S, Gorman N T (1987) The clinical diagnosis and management of rectal and pararectal tumors in the dog. JSAP 28 (2), 87-107 VetMedResource.
  • Birchard S J (1986) Non-lymphoid intestinal neoplasia in 32 dogs and 14 cats. JAAHA 22, 533-7 CiNii.

Other sources of information

  • Vail D M, Withrow S J, Page R L (2013) Cancer of the gastrointestinal tract. In: Small Animal Clinical Oncology. Eds S J Withrow and E G MacEwen. 5th edition. Philadelphia: W B Saunders Co. pp 412-423.