Unexplained Fever

Basic Principles

Principal signs and symptoms: malaise; undulating subfebrile temperatures are most common, but fever may occur. Hematologic changes, anemia, elevated ESR. Weight loss, night sweats; constipation or diarrhea, or an alternation of both.

ESR. Weight loss, night sweats; constipation or diarrhea, or an alternation of both.
x Basically, all infectious diseases should be excluded.
x An occult abscess is frequently responsible for the disease and fever. A systematic search should be conducted and may include CT scans if required.
x Virtually any tumor may cause unexplained fever.
x If enlarged lymph nodes are found, the anatomy of the lymphatic drainage
pathways can help direct the search for a primary tumor

Visceral lymph node metastases and their relationship to primary
tumor sites

Sites of nodal metastases

Primary tumor sites

Inferior mesenteric lymph nodes

Left side of the colon, sigmoid colon

Superior mesenteric lymph nodes

Right side of the colon, small intestine, pancreas

Celiac lymph nodes

Lower esophagus, stomach

Lymph nodes at the porta hepatis

Lower esophagus, stomach, colon, liver, gallbladder,
pancreas, urogenital system

Differential diagnosis of unexplained fever


Sonographic signs


Gastrointestinal tumors

Hypoechoic round lesions, intestinal target patterns, signs of
partial bowel obstruction

Pancreatic tumor

Hypoechoic mass, dilatation of pancreatic and bile duct


Hypoechoic, sharply circumscribed mass that may show highlevel internal echoes

Differential diagnosis of unexplained fever ñ continued


Sonographic signs

Less common


Nonhomogeneous mass, variable echogenicity, pseudocapsule

Adrenal tumor

Hypoechoic mass between the vena cava or aorta and the
superior renal pole

Malignant lymphoma

Diffuse organ infiltration or multiple, hypoechoic extra- and intraabdominal round lesions distributed along vascular pathways

Breast carcinoma

Variable echogenicity, ill-defined margins with tumor extensions,
usually a nonhomogeneous internal echo pattern


Thickened valves, echogenic deposits, valvular regurgitation



Atrial myxoma

Intracavitary echogenic mass, usually very mobile

Conditions that cannot be diagnosed with ultrasound
Common: Central bronchial carcinoma  (chest wall tumors can be detected sonographically
and sampled by ultrasound-guided percutaneous biopsy)

Less common: Leukemia
Rare: Melanoma

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