Increased radiotracer activity in a soft tissue mass of the abdomen, is likely due to splenosis in this postsplenectomy patient.
Anterior and posterior whole-body images following
administration of radiotracer are acquired using single photon emission
computed tomography/computed tomography (SPECT/CT) and an X-ray of the left
shoulder is taken. SPECT/CT images of the abdomen show the liver appears
enlarged and demonstrates a homogeneous distribution of radiotracer. The patient
is status postsplenectomy with surgical clips noted in the splenic bed. There
is a midline soft tissue mass lying midline, anterior to the vertebral column,
demonstrating increased radiotracer activity.
The function of the liver and spleen have vastly different
functions. Nevertheless, phagocytosis is a common function to both. Uptake is
performed by the reticuloendothelial cells. In the liver these cells are called
Kupffer cells. Technitium 99m-sulfur colloid measures an average of 0.3-1.0µm. Technitium
colloid is usually cleared from circulation within minutes—80% to 90% of
particles are sequestered by the liver and 5% to 10% to the spleen. This test
can be used to identify the relative size and function of the liver and spleen.
It is also useful, as in this example, for identifying splenosis.
TAR syndrome is a rare genetic disorder characterized by low
platelet level and radial aplasia.
Unlike most other conditions associated with radial aplasia,
TAR syndrome patients usually have thumbs. The other bones of the upper limb
and shoulder may be absent, hypoplastic, or normal. The lower limbs are less
frequently hypoplastic, but may be bowed. Dislocated hips, ankylosis of the
knees, valgus and varus deformities of the feet, syndactyly and abnormal toe
placement have also been reported.1 Additional anomalies include
congenital heart defects, growth retardation, strabismus, nevus flammeus of
forehead, micrognathia, and brachycephaly. The hematologic defects are usually
present at birth or appear within the first few months. The inheritance pattern
is autosomal recessive.2
Thrombocytopenia, which may be transient, is seen in all cases and will be symptomatic in over
90% of cases within the first four months of life. As age increases, platelet
counts typically improve. Nevertheless, removal of the spleen (splenectomy) may
be necessary to correct thrombocytopenia caused by platelet destruction and to
ultimately increase platelet count. A splenectomy may significantly reduce
platelet destruction and increase platelet count by up to 30% because the
spleen acts as the primary site of platelet removal and antibody production.
The patient above, now an adult, despite splenectomy, remains partially resistant
to transfusions, receiving weekly transfusions of platelets.1
- Greenhalgh KL, Howell RT, Bottani A, et al. Thrombocytopenia-absent
radius syndrome: A clinical genetic study. J
Med Genet. 2002;39:876-81.
- Ward, RE, Bixler D, Provisor AJ, et al. Parent to child
transmission of the thrombocytopenia absent radius (TAR) syndrome. Am J Med
Genet Suppl. 1986;2:207-14.