Diagnostic ultrasound ( PDFDrive )

1740 PART V Pediatric Sonography
A
B
FIG. 51.10 Tyrosinemia and Glycogen Storage Disease (Type I, von Gierke Disease). (A) Longitudinal sonogram shows heterogeneous
echotexture, likely a combination of regenerating nodules and adenomas of the liver, in a patient with tyrosinemia awaiting liver transplant. (B)
Echogenic adenoma (arrow) in the liver of another child with glycogen storage disease type I. Follow-up was done because of this patient’s
increased risk of hepatocellular carcinoma.
he sonographic examination of children with possible
metabolic disease includes a careful analysis of liver size and
architecture, searching for steatosis, cirrhosis, and nodules; an
analysis of renal architecture, searching for increased size and
nephrocalcinosis; and a Doppler examination of the abdomen
searching for signs of portal hypertension.
STEATOSIS
Fat accumulates in hepatocytes ater cellular damage (fatty
degeneration), through the overloading of previously healthy
cells with excess fat (fatty iniltration), or in certain enzyme
deiciency syndromes, through the inability of fat to be mobilized
out of the liver. Drugs (acetylsalicylic acid, tetracycline, valproate,
warfarin [Coumadin]) and toxins (alatoxin, hypoglycine) as well
as alcohol abuse lead to fatty degeneration of liver cells. Steatosis
is also seen in metabolic liver disorders such as galactosemia,
fructose intolerance, and Reye syndrome. Obesity (Video 51.3),
corticosteroid therapy, hyperlipidemia, and diabetes are examples
of increased fat mobilization and its entry into the liver. In
malnutrition, nephrotic syndrome, and cystic ibrosis, not only
does excess fat enter the liver, but mobilization of fat out of the
hepatocyte is deicient as well. When parenteral nutrition does
not include lipids, steatosis results from a deiciency of essential
fatty acids. Most inherited disorders of the liver mentioned
previously involve an enzyme deiciency and result in
steatosis.
Fatty changes are reversible, may be difuse or focal, and are
oten detected on ultrasonography before clinically suspected. 25
On sonography, areas of steatosis are highly echogenic, blurring
vessel walls. he nearby kidney cortex appears much less echogenic.
When focal, steatosis usually has smooth, geometric, or
ingerlike borders 26 (Fig. 51.11). Intervening normal liver may
appear hypoechogenic and masquerade as mass lesions (metastases
FIG. 51.11 Fatty Iniltration of Liver (Steatosis) in Patient With
Cystic Fibrosis. Sagittal view shows increased hepatic echotexture,
with some sparing posteriorly. The cortex of the right kidney is much
less echogenic than the fatty liver.
or abscesses), especially if the ultrasound gain is adjusted by
using the fatty areas as a normal reference. Segments 4 and 5
are oten spared in steatosis, perhaps because of favorable blood
supply by the gallbladder and its vessels. 27 Nodules of steatosis
may mimic metastases on CT. Areas of abnormal echotexture
on sonographic studies can be further evaluated with CT; the
two modalities are complementary in this situation. Ultrasound
grading of steatosis is subjective; magnetic resonance spectroscopy
can reliably quantify fat content. Magnetic resonance imaging
(MRI) sequences and various MRI contrast agents can characterize
focal lesions in the liver. Despite sophisticated imaging, occasionally
biopsy may be necessary.