Ultrasound Diagnosis of Liver Masses in Children

Ultrasound (US) is commonly used for the survey of variousorgans, including the liver. It is often used as the first-lineimage modality, due to easy accessibility and non-radiationsafety. However, diagnostic accuracy depends on thefamiliarity of the operator, as well as the type, size, andlocation of the lesion. US is often arranged in two clinicalscenarios: for screening of potential mass lesions inpatients with chronic liver diseases such as chronic hepatitis B, biliary atresia, glycogen storage disease, etc. or forinitial evaluation of symptomatic patients presenting withhepatomegaly, jaundice, right upper quadrant pain, as wellas nonspecific abdominal pain or fever. Liver masses aremore easily identified on US scanning when the echogenicity is different from the surrounding parenchyma, eitherhypoechoic or hyperechoic. When the masses are small insize (<0.5 cm), isoechoic, or located in segment 8, subtleultrasonic clues such as refractive edge shadow, distortedvenous landmarks, or abnormal Doppler patterns maysuggest an otherwise unremarkable liver mass and warrantcareful multiplanar scanning.For diagnosis and management of a liver mass, not only do we have to identify thelesion, but also the nature (benign or malignant, tumortype, primary origin, vascularity, or resectability). Althougha hepatic mass may sometimes present a characteristicultrasonic appearance, in general, it often requires anadditional modality to get an accurate diagnosis forappropriate treatment.Computed tomography (CT) ormagnetic resonance image (MRI) and invasive proceduressuch as aspiration and biopsy serve the purpose. Be awareof lower sensitivity and the intrinsic technical limitation ofUS, the clinician should never spare a repeated US ora second image modality in a symptomatic patient with aninitial negative US exam, taking into consideration the highmorbidity and mortality of a liver mass without timelydiagnosis and proper management.

In this issue, Chuang et alpresented their experience inUS diagnosis of liver abscesses and other hepatic masses insymptomatic patients mainly presenting with fever andabdominal pain. A tentative diagnosis of a liver abscess wasmade according to at least one criterion in the first USstudy. CT was arranged either for percutaneous drainage oras the second-line imaging. Two rare hepatic tumors(lymphoma and undifferentiated sarcoma) were confirmedafter biopsy. The final diagnoses were inconsistent betweenthe ultrasound and CT in 45% in their series. However, theydid not miss any mass. The US is much like a stethoscopeacoustically “viewing” a silent internal organ like the liver.It is reasonable to arrange a second exam to clarify thenature of the mass identified by US, just as heart murmursor lung crackles audible with a stethoscope justify a chestx ray or echocardiography. The subsequent exam is determined by the facility of the institute and accessibility of thelesion. Interventional US or radiological procedures mayprovide microbiologic diagnoses and serve as core treatment in the situation of a liver abscess, or to define tumorpathology in a neoplasm. In some instances, US or radiological intervention also provide curative or palliativetherapy in malignancies, such as hepatocellular carcinomaand hepatoblastoma.

High index of suspicion is the key to discovering anintrahepatic space-taking lesion in an otherwise normalchild presenting with nonspecific symptoms. If US is to beperformed by an experienced hand, it is less likely to misseven an inconspicuous mass. Pyogenic liver abscesses inchildren are rarely encountered in Taiwan, with anincidence of 20/100,000 (1979w1992) to 8.3/100,000(1986w2001) pediatric admissions.They may sharecommon ultrasonic features with other hepatic tumors. Adetailed history-taking, physical examination and pertinentlaboratory tests, such as tumor markers, should not beignored besides careful multiplanar scanning aided withDoppler flow mapping or contrast enhancement. Initialtherapy may be prompted after a likely diagnosis has beenmade. It is mandatory to monitor the therapeutic responseto adjust the next approach. Judicious US- or CT-guidedaspiration or biopsy is indispensible in establishinga correct diagnosis and treatment. The more the pearls andpitfalls of each diagnostic modality are understood, thebetter the patient’s outcome may be.