*Francisco J. Llabrés-Díaz
1. The ability of ultrasound to identify and interrogate canine medial iliac lymph nodes, comparing these findings with what has already been published in the recent veterinary literature.
2. The ability of ultrasound to differentiate medial iliac lymph nodes affected by lymphoma or metastases from adenocarcinomas of the apocrine glands of the anal sac from medial iliac lymph nodes of dogs included in a control group.
Sixty-one medial iliac lymph nodes of 38 different dogs (8 affected by metastases of adenocarcinomas of the apocrine glands of the anal sac, 13 suffering from multicentric lymphoma, 6 suffering from multicentric lymphoma but out of clinical remission and 11 included in a control group) were evaluated ultrasonographically to assess the ability of ultrasound to identify and interrogate these nodes and to differentiate nodes from the four different groups using multiple sonographic parameters (ease of identification, size, shape, margination, presence of a complete peripheral hyperechoic rim, presence of vascular invasion, location, number of detected nodes and echo pattern).
Ultrasound proved to be a very useful tool to assess canine medial iliac lymph nodes, especially when scanning from a dorsal approach, with the transducer ventral to the epaxial muscles. Both longitudinal and transverse planes should be used in both sides of the patient and care must be taken not to collapse the caudal vena cava if excessive pressure is applied with the transducer.
An increase in size or number of detected medial iliac lymph nodes or finding rounder nodes could reliably differentiate unaffected lymph nodes from nodes affected by lymphoma or metastases from adenocarcinomas of the apocrine glands of the anal sacs. Ultrasound, however, was unable to separate these two malignancies. Nodes of dogs affected by lymphoma but out of remission at the time of the ultrasound examination showed intermediate characteristics between the control group and the remaining groups.
The area of the medial iliac lymph nodes should be routinely interrogated in every abdominal ultrasonographic examination.
The results of this study agree with the general opinion gained from the recent human literature that affirms that ultrasound is a very reliable and useful tool for the detection of abnormal lymph nodes, but it is generally unable to reach a specific diagnosis based only on sonographic criteria. Fine needle aspiration or biopsies of abnormal canine medial iliac lymph nodes will still be needed to reach a definitive diagnosis.