Diagnostic ultrasound ( PDFDrive )

688 PART II Abdominal and Pelvic Sonography
by deinition involves three main sites—the central nervous
system, solid organs, or the gastrointestinal tract. he liver is
the most common site of intraabdominal involvement, occurring
in 30% to 45% of patients with PTLD. In rare cases, intraosseous
lesions may be present, with imaging features on CT
and MRI similar to those of metastatic disease, infection, or
primary bone lymphoma. Overall, PTLD should be considered
in the diferential diagnosis of any transplant patient with
lymphadenopathy or a new lesion within a solid viscus or the
skeletal system. 107-110
When the solid organs are involved, there are four main
patterns of disease:
1. Iniltrative pattern: here is an ill-deined mass or masses
that are extrinsic to the hilum and can result in secondary
mass efect and/or vascular compromise. For instance, within
the liver it may cause biliary obstruction and obstruction of
blood low within the periportal space. In renal involvement
the mass typically is located extrinsic to the renal pelvis with
resultant mass efect and obstruction of the vessels and the
collecting system. In both instances the mass is usually relatively
hypoenhancing but luorodeoxyglucose (FDG) avid on
positron emission tomography (PET) imaging.
2. Parenchymal pattern: his is characterized by multiple lesions
that are disseminated throughout the afected organ. hese
also tend to be hypoenhancing. In the lung they are typically
solid and may rarely cavitate. here may also be ill-deined
alveolar iniltrates.
3. Solitary mass: A solitary mass in the afected organ is
seen on ultrasound as a hypoechoic lesion with no Doppler
signal on color Doppler imaging. Calciication is unusual but
seen in the context of posttreatment changes or tumor
necrosis.
4. Iniltrative lesion: his lesion involves the organ in question
but also extends to involve regional structures such
as the chest, abdominal wall, and adjacent solid organs.
As a secondary manifestation, there may be dysfunction
of the other organ(s) that are involved. Pancreatic PTLD
tends to produce difuse glandular enlargement, with an
appearance that is indistinguishable from pancreatitis or
rejection. 111
Gastrointestinal disease can involve either bowel or the
peritoneal cavity. When there is peritoneal disease, it can be
nodular or difusely iniltrating. 112 PTLD involving the gastrointestinal
tract is seen in association with mural thickening,
aneurysmal dilatation, ulceration, intussusception, and polypoidal
lesions. Perforation is a rare manifestation of intestinal PTLD;
the decline in perforation rates has been attributed to improved
diagnosis and treatment of PTLD. As with any other
lymphomatous-type lesions of the gut, obstruction of the bowel
segments is rare.
Treatment Options
Stratiication and patient management are determined by the
subtype of PTLD, the distribution of disease, and the type of
allograt. Potential management options include modiication
of immunosuppression, chemotherapy, radiation, and rituximab
therapy as well as surgical resection of isolated lesions. Rituximab
is a monoclonal antibody against B cell receptors, has a low
toxicity proile, and has a response rate on the order of 60%.
Preservation of grat function is an important goal of management
while treating the PTLD. 113,114
PET-CT has a pivotal role to play in monitoring response to
therapy, particularly in patients in whom there are persistent
focal lesions. In this scenario, FDG uptake allows discrimination
between residual tumor and ibrosis.
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