(O31) Usefulness of Computed Tomography in Combination with Iodized Oil (Lipiodol^®) in Detecting Sentinel Lymph Nodes

Abstract:

Background: Visualization of sentinel lymph nodes (SLN) with computed tomography (CT) using iodized oil has not been thoroughly investigated yet.

Hypothesis/

Objectives: To demonstrate methodological review and clinical recommendations of using CT in combination with lipiodol.

Animals: Five client-owned dogs with subcutaneous tumors diagnosed with mammary gland tumors (n =2) and mast cell tumors (n = 3) were included.

Methods: A pilot prospective study. Whole body radiography was taken before injection. Lipiodol of 0.5 or 1 mL depending on the size of patient was administered into four quadrants encircling the tumor using a 25G needle. After 24 hours, both radiographic and CT images were taken. Surgically accessible identified lymph nodes were resected with primary tumor, followed by histopathology or cytology.

Results: A total of sixteen draining lymph nodes were identified on CT (16/16, 100%), while only eight of them (8/16, 50%) were clearly identified on radiography. Cytology or histopathology was performed in 5/16 (31.3%: CT, 5; radiograph, 3). Malignancy was identified in 2/5 (40.0%, CT, 2; radiograph, 1). Adverse effects were identified in one dog as granuloma adjacent to injection site. 3 dogs were capable of follow-up radiography or CT scanning. Residence of lipiodol was identified at injection sites 42, 168, and 218 days after injection, respectively.

Conclusions and clinical significance: CT using iodized oil was able to better clarify SLN in dogs. Malignancy may be identified in draining nodes detected clearly only in CT, emphasizing clinical importance. Lipiodol should be used with caution regarding adverse effects and residual period.