Computed Tomography Characteristics of Canine Tracheobronchial Lymph Node Metastasis

Abstract

Tracheobronchial lymph node evaluation is critical for accurate staging of canine thoracic neoplasia and is more accurately achieved with computed tomography (CT) than radiography. Thoracic CT scans of 18 canine patients with known tracheobronchial lymph node histopathology and 10 clinically normal dogs were compared to establish if enlargement or contrast enhancement pattern correlated with metastatic status. Absolute lymph node size and three anatomically normalized lymph node ratios were significantly correlated with metastasis or severe granulomatous lymphadenitis (P < 0.0003). Transverse maximum lymph node diameter of 12 mm or lymph node to thoracic body ratio of 1.05 are proposed cutoffs, above which metastatic involvement is very likely; however, only minimal accuracy was gained with normalized ratios. Lymph node contrast enhancement pattern was also significantly correlated to disease. A heterogenous and/or ring pattern was related to metastatic disease (P = 0.03). Recommended protocol for CT examination of the tracheobronchial lymph nodes is 1-1.5 mm slices and intervals, intravenous contrast, and control of respiratory motion.

Computed tomographic appearance of abdominal lymph nodes in healthy cats

“…Five of the 10 lymph nodes with heterogenous or peripheral contrast enhancement also had intranodal fat, which may play a role in explaining this appearance. Other potential causes for lack of homogenous contrast enhancement include abscessation, necrosis, cystic change, areas of hemorrhage, mineralization, or circulatory disturbances as well as neoplasia . On ultrasonography, heterogeneity of abdominal lymph nodes in cats has been shown not to be associated with malignancy .…”

Ultrasound and computed tomography of the iliosacral lymphatic centre in dogs with anal sac gland carcinoma

“…The identified iliosacral LNs were counted and assessed for location (medial iliac, internal iliac, sacral), laterality and size (length = greatest cranial to caudal dimension measured on sagittally reformatted images, width = greatest right to left dimension on transverse images and height = greatest dorsal to ventral dimension on transverse images). LNs were subjectively deemed normal or abnormal based on the presence of 1 or more of the following factors: increased size, abnormal shape or heterogenous contrast enhancement as previously reported . Given the wide range of reported normal values for sacroiliac LN size, sacroiliac LNs were deemed increased in size if they were substantially larger than the same LN on the other side or if they seemed subjectively enlarged.…”

Pulmonary lymph node charting in normal dogs with blue dye and scintigraphic lymphatic mapping

“…A possible alternative to methylene blue dye or technetium is thoracic CT imaging; lymphadenopathy as detected with CT imaging has been strongly correlated with metastasis in dogs with primary lung tumors (Ballegeer et al, 2010;Marolf et al, 2011;Paoloni et al, 2006). Future intrathoracic lymph node biopsy recommendations should include description to penetrate the mediastinal pleural envelope and dissect overlying fat to remove any palpable or visual N2 lymph nodes in dogs presenting for resection of primary lung tumors.…”