Diagnostic Ultrasound - Abdomen and Pelvis

Abdominal Lymph Nodes
Anatomy: Abdomen
GROSS ANATOMY
Overview
• Major lymphatic vessels and nodal chains lie along major
blood vessels (aorta, IVC, iliac)
• Lymph nodes carry the same name as the vessel they
accompany
• Lymph from alimentary tract, liver, spleen, and pancreas
passes along celiac, superior mesenteric chains to nodes
○ Efferent vessels from alimentary nodes form intestinal
lymphatic trunks
○ Cisterna chyli (chyle cistern)
– Formed by confluence of intestinal lymphatic trunks
and right and left lumbar lymphatic trunks, which
receive lymph from nonalimentary viscera, abdominal
wall and lower extremities
– May be discrete sac or plexiform convergence
• Thoracic duct: Inferior extent is chyle cistern at the L1-2
level
○ Formed by convergence of main lymphatic ducts of
abdomen
○ Ascends through aortic hiatus in diaphragm to enter
posterior mediastinum
○ Ends by entering junction of left subclavian and internal
jugular veins
• Lymphatic system drains surplus fluid from extracellular
spaces and returns it to bloodstream
○ Important function in defense against infection,
inflammation, and tumor via lymphoid tissue present in
lymph nodes, gut wall, spleen and thymus
○ Absorbs and transports dietary lipids from intestine to
thoracic duct and bloodstream
• Lymph nodes
○ Composed of cortex and medulla
○ Invested in fibrous capsule, which extends into the nodal
parenchyma to form trabeculae
○ Internal honeycomb structure filled with lymphocytes
that collect and destroy pathogens
○ Hilum: In concave side, with artery and vein, surrounded
by fat
Abdominopelvic Nodes
• Preaortic nodes
○ Celiac nodes: Drainage from gastric nodes, hepatic
nodes, and pancreaticosplenic nodes
○ Superior and inferior mesenteric nodes: Drainage from
mesenteric nodes
• Lateral aortic nodes
○ Drainage from kidneys, adrenal glands, ureter, posterior
abdominal wall, testes and ovary, uterus and fallopian
tubes
• Retroaortic nodes
○ Drainage from posterior abdominal wall
• External iliac nodes
○ Primary drainage from inguinal nodes
○ Flow into common iliac nodes
• Internal iliac nodes
○ Drainage from inferior pelvic viscera, deep perineum,
and gluteal region
○ Flow into common iliac nodes
• Common iliac nodes
○ Drainage from external iliac, internal iliac, and sacral
nodes
○ Flow into lumbar (lateral aortic) chain of nodes
• Superficial inguinal nodes
○ In superficial fascia parallel to inguinal ligament, along
cephalad portion of greater saphenous vein
○ Receive lymphatic drainage from superficial lower
extremity, superficial abdominal wall, and perineum
○ Flow into deep inguinal and external iliac nodes
• Deep inguinal nodes
○ Along medial side of femoral vein, deep to fascia lata and
inguinal ligament
○ Receive lymphatic drainage from superficial inguinal and
popliteal nodes
○ Flow into external iliac nodes
IMAGING ANATOMY
Overview
• CT is test of choice for cancer staging
• May be supplemented by PET/CT in select cancers
• Ultrasound may be useful in children or thin adults
○ Normal nodes are elliptical with echogenic fatty hilum
and uniform hypoechoic cortex
○ Normal lymph nodes rarely detected on abdominal
ultrasound
• Normal diameter of lymph node varies depending on
location
○ Short axis diameter
– Abdominopelvic < 10 mm
– Hepatogastric ligament < 8 mm
– Retrocrural < 6 mm
ANATOMY IMAGING ISSUES
Imaging Recommendations
• Transducer: 2-5 MHz or 5-9 MHz for thinner patients
• Patient examined in supine position with < 4 hours of
fasting to decrease bowel gas
• Graded compression technique to clear overlying bowel
loops
CLINICAL IMPLICATIONS
Clinical Importance
• Nodal enlargement is nonspecific, may be neoplastic,
inflammatory, or reactive
• Normal-sized lymph nodes may harbor metastatic
malignancy
• Node morphology is more specific for pathology
○ Abnormal nodes have replacement or loss of fatty hilum
○ Look for central necrosis, cystic change, or calcification
• Lymphoma
○ Multiple enlarged hypoechoic or anechoic nodes
• Metastatic lymphadenopathy
○ More echogenic and heterogeneous nodes compared to
lymphomatous nodes
• Infectious/reactive lymphadenopathy
○ Nonspecific sonographic features
○ May contain necrotic centers in mycobacterial infection
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