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Hemolymphatic System
Judith Hudson

Department of Clinical Sciences, College of Veterinary Medicine, Auburn, AL, USA

29.1 Normal Thoracic Lymph Nodes but also the thoracic portions of the aorta, esophagus, tra-
chea, heart, mediastinum, and diaphragm.
There are 3–4 groups of lymph nodes in the thorax: the aor-
tic thoracic, sternal, tracheobronchial (TB), and cranial
mediastinal (CM) lymph nodes or lymph centers 29.2 Normal Abdominal
(Figure 29.1). The aortic thoracic lymph nodes are located Lymph Nodes
along the ventral aspect of the thoracic vertebrae but are
not present in all cats. There is usually one sternal lymph Abdominal lymphocenters can be divided into two catego-
node that drains the ribs, sternum, serous membranes, thy- ries: visceral and parietal lymph nodes. Most lymph nodes
mus, adjacent muscles, and mammary glands [1]. This are not visible radiographically but a small opacity may be
node may also enlarge with abdominal diseases such as present at the site of the medial iliac lymph nodes in the
pancreatitis and carcinomatosis. It is located ventrally at caudodorsal abdomen. The visceral lymphocenters include
the level of the second intercostal space but is small and is the cranial mesenteric lymphocenters, the caudal mesen-
not always visible radiographically. teric lymphocenter, and the celiac lymphocenter. The cra-
The CM lymph nodes are found in the cranial dorsal nial mesenteric lymphocenter can be further subdivided
mediastinum at the ventral aspect of the trachea. This into jejunal, right colic, and middle colic lymphocenters.
group of lymph nodes drains the muscles of the abdomen, The jejunal lymphocenter comprises the nodes that are
neck, and thorax, the scapula, caudal cervical vertebrae, most likely to be imaged sonographically in a normal cat.
ribs, trachea, esophagus, thyroid, thymus, mediastinum, The celiac lymphocenters can be subdivided into hepatic,
costal pleura, heart, aorta, and other thoracic nodes. The splenic, gastric, and pancreatico‐duodenal lymphocenters.
thymus is found in the cranioventral thorax. It is thin and Parietal lymph nodes include lumbar, sacral, hypogas-
not normally visualized in adult cats. On the ventrodorsal tric, and medial iliac lymph nodes [1]. Aortic lumbar
projection, the width of the mediastinum should not lymph nodes are found along the aorta and caudal vena
exceed the width of the spinal column. cava from the diaphragm to the deep circumflex iliac artery.
Radiographically, CM masses originating from the These are small and are not normally seen radiographically
CM lymph nodes appear similar to those arising from ster- but are visible sonographically. The renal lymph nodes are
nal lymph nodes or thymus (see below). The left and right TB also small and are located near the renal vessels. The
lymph nodes are immediately cranial to the TB bifurcation, medial iliac lymph nodes are larger and are the most com-
with the left being located dorsally compared to the right. monly visualized nodes. These nodes are located between
The middle TB lymph node is located caudal to the TB the deep circumflex iliac artery and the origin of the exter-
bifurcation. These nodes drain mainly the lungs and aorta nal iliac artery on each side. The hypogastric lymph nodes

Feline Diagnostic Imaging, First Edition. Edited by Merrilee Holland and Judith Hudson.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.