+ General Considerations

  • Mean age 8.5 years (range, 2-14 years)
  • Sex predilection: 60%-70% male
  • Sites: large intestine and mid-to-distal rectum
  • Gross appearance is variable:
  • Nodular (single or multiple)
  • Pedunculated (mid-to-distal rectum)
  • Annular constriction or obstruction (colon to mid-rectum)
  • Metastatic rate is highly variable depending on the study


+ Physical Examination

  • Cachexia is common
  • Abdominal mass is frequently palpable via either abdomen and rectal palpation
  • Other findings include dehydration and abdominal pain

+ Laboratory Tests

  • Anemia and leukocytosis reported but occur less commonly than small intestinal tumors
  • Paraneoplastic leukocytosis reported with adenomatous rectal polyp

+ Endoscopy

  • Endoscopy is recommended prior to definitive treatment
  • Biopsy samples should be interpreted histologically as cytologic misdiagnosis is common with intestinal ADC being misdiagnosed as either septic inflammation or LSA
  • Biopsy samples are often small and superficial resulting in false-negative diagnosis if lesion is either submucosal or associated with surface ulceration and necrosis


+ Surgery

  • Surgical approaches: rectal eversion, rectal pull-through, or resection and end-to-end anastomosis
  • Fecal incontinence is uncommon if rectal resection < 4 cm
  • However, fecal incontinence and incisional dehiscence is common if > 4 cm rectum is resected with rectal pull-through surgery
  • Transanal endoscopic resection of benign rectal tumors has been described in 6 dogs
  • Incontinent end-on colostomy has been described in the management of 1 dog with rectal ADC

+ Chemotherapy

  • No effective chemotherapy for ADC, but combination of 5-fluorouracil and cisplatin may be effective

+ Prognosis

  • Mean survival time 22 months following surgery
  • Radical surgery associated with high complication rate and poor survival (< 1 week)
  • Local appearance may be predictive of survival:
  • Mean survival time 32 months if pedunculated
  • Mean survival time 12 months if nodular or cobblestone
  • Mean survival time 1.6 months if annular
  • Mean survival time 24 months following cryosurgery
  • Survival times following electrocautery are reported between 18-29 months
  • MST 7 months following intraoperative orthovoltage radiation therapy with 12-month survival rate 67%, local tumor recurrence in 54%, and median DFI 6 months