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(instead of fusiform dilatation)

Fig. 13.2a

Fig. 13.2b

Fig. 13.2c

Lymph nodes (55) are generally hypoechoic and must be differentiated from fluid-filled bowel loops (46) by absent peristalsis and from veins by lack of compressibility. Computerized tomography (CT) is superior in evaluating thrombosed veins (non-compressible) or markedly obese patients, but sonography is advantageous in very thin or cachectic patients. Enlarged lymph nodes can be found with inflammation, malignant lymphoma (Hodgkin disease or non-Hodg-kin lymphoma), and metastatic deposits.

ITie normal size of abdominal lymph nodes is given as 7-10 mm. Larger and still normal lymph nodes measuring up to 20 mm in longitudinal diameter can be found in the inguinal region and along the distal external iliac artery (21) (Fig. 14.3). Important for all enlarged lymph nodes are follow-up examinations to determine any possible progression or regression—for instance, for the evaluation of chemotherapy. Furthermore, any possible hepatomegaly or splenomegaly should be documented and quantified.

Lymph nodes with inflammatory changes maintain their ovoid shape, have a distinct border, and exhibit two layers with a centrally increased echogenicity at the hilum (hilar fat sign) and peripheral liver-like echogenicity. Inflammatory lymph nodes can often be encountered along the hepatoduodenal ligament (Fig. 24.3) accompanying viral hepatitis, cholangitis, or pancreatitis (Fig. 19.3).

In contrast, metastatic lymph nodes are more round than oval, frequently of heterogeneous echogenicity, and indistinct in outline. They also have the tendency to form aggregates. The site of the primary tumor can be deduced from the known lymphatic pathways; para-aortic lymphadenopathy in young men, for instance, suggests a testicular tumor.

Enlarged lymph nodes as manifestation of malignant lymphoma generally exhibit an ovoid form, smooth margins, and more pronounced hypoechogenicity than found in inflammatory or metastatic lymph nodes. In one third of cases, the spleen shows concomitant focal or diffuse involvement (Fig. 48.1). Predominant involvement of the mesenteric lymph nodes (55) (Figs. 14.1, 14.2) suggests a non-Hodgkin lymphoma and not Hodgkin disease, which has a predilection for thoracic and retroperitoneal lymph nodes. Malignant lymphomas indent or displace adjacent vessels (Fig. 14.2) but respect the vascular wall and do not invade adjacent organs (see also p. 21).

Inferior Mesenteric Lymph Nodes
Fig. 14.1 a
Fig. 14.2a
Fig. 14.3a

The systematic evaluation of the retroperitoneum should delineate and document all abnormalities of the major vessels. Atherosclerotic plaques (49) along the aorta can be seen directly by their echogenicity or indirectly by their acoustic shadowing (45) (Fig. 15.1).

The inferior vena cava (16) should be evaluated for a dilatation exceeding 2 cm (or 2.5 cm in young athletes), which would suggest a venous congestion as manifestation of a right cardiac insufficiency (Fig. 15.2). The measurements are obtained perpendicular to the longitudinal vascular axis (!) and should not accidentally encompass the hepatic veins (10), which enter the inferior vena cava subdiaphragmatically (Fig. 15.2). In questionable cases, the luminal diameter of the inferior vena cava is observed during forced maximal inspiration, which can be achieved by asking the patient to take a deep breath with the mouth open. The transmitted sudden increase in intrapleural negative pressure causes a brief collapse of the subdiaphragmatic portion of the normal inferior vena cava, with the lumen being reduced to a third or less of its diameter during quiet respiration. With fluid overload of the right cardiac atrium, the cava does not collapse during forced inspiration. During the thoracic movement of this maneuver, it can be difficult to stay with the same sonographic section of the inferior vena cava. For further clarification, the luminal diameter of the hepatic vein should be assessed in the right subcostal oblique section (see p. 25). Do you remember why in Figure 15.2 the hepatic parenchyma appears more echogenic dorsal to the distended inferior vena cava than anterior to it? If not, return to page 9 and name this phenomenon.

When visualizing the distal iliac vessels (Fig. 15.3) following an inguinal vascular puncture, a hematoma (50) can occasionally be encountered adjacent to the iliac artery (21) or vein (22). If blood flows into this perivascular space through a connection with the arterial lumen, a false aneurysm (aneurysma spurium) is present. This type of aneurysm differs from a true aneurysm (aneurysma verum), which represents luminal widening of all mural layers and is not caused by a complete mural tear (Fig. 15.3). Old inguinal hematomas must be differentiated from psoas abscesses and synovial cysts arising from the hip joint, and, when extending into the lower pelvis, from lymphoceles, large ovarian cysts, and metastatic lymph nodes with central necrosis (57).

Checklist Right cardiac Insufficiency:

• Dilatation of the

to > 2.0 cm (2.5 cm in

inferor vena cava

trained athletes)

• Dilated hepatic veins

> 6 mm in the hepatic

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