title: Utility of Computed Tomography versus Abdominal Ultrasound Examination to Identify Iliosacral Lymphadenomegaly in Dogs with Apocrine Gland Adenocarcinoma of the Anal Sac.
abstract: BACKGROUND
  Apocrine gland adenocarcinoma of the anal sac (AGAAS) is associated with high rates of iliosacral lymph node metastasis, which may influence treatment and prognosis. Magnetic resonance imaging (MRI) recently has been shown to be more sensitive than abdominal ultrasound examination (AUS) in affected patients.
  
  
  OBJECTIVE
  To compare the rate of detection of iliosacral lymphadenomegaly between AUS and computed tomography (CT) in dogs with AGAAS.
  
  
  METHODS
  Cohort A: A total of 30 presumed normal dogs. Cohort B: A total of 20 dogs with AGAAS that underwent AUS and CT.
  
  
  METHODS
  Using cohort A, mean normalized lymph node : aorta (LN : AO) ratios were established for medial iliac, internal iliac, and sacral lymph nodes. The CT images in cohort B then were reviewed retrospectively and considered enlarged if their LN : AO ratio measured 2 standard deviations above the mean normalized ratio for that particular node in cohort A. Classification and visibility of lymph nodes identified on AUS were compared to corresponding measurements obtained on CT.
  
  
  RESULTS
  Computed tomography identified lymphadenomegaly in 13 of 20 AGAAS dogs. Of these 13 dogs, AUS correctly identified and detected all enlarged nodes in only 30.8%, and either misidentified or failed to detect additional enlarged nodes in the remaining dogs. Despite limitations in identifying enlargement in all affected lymph nodes, AUS identified at least 1 enlarged node in 100% of affected dogs.
  
  
  CONCLUSIONS
  Abdominal ultrasound examination is an effective screening test for lymphadenomegaly in dogs with AGAAS, but CT should be considered in any patient in which an additional metastatic site would impact therapeutic planning.
authors: Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA.
authors: S
authors: S
authors: Palladino
authors: Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA.
authors: M A
authors: MA
authors: Keyerleber
authors: Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA.
authors: R G
authors: RG
authors: King
authors: Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA.
authors: K E
authors: KE
authors: Burgess
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000662:veterinary*; D000694:Anal Gland Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D000695:Anal Sacs / Q000000981:diagnostic imaging* / Q000473:pathology; D000818:Animals; D001050:Apocrine Glands / Q000000981:diagnostic imaging* / Q000473:pathology; D004283:Dog Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D004285:Dogs; D005260:Female; D008207:Lymphatic Metastasis; D008297:Male; D014057:Tomography, X-Ray Computed / Q000662:veterinary; D014463:Ultrasonography / Q000662:veterinary
keywords: Cancer staging; Dog; Lymph node; Metastasis