Sickle Cell Anemia

Published on 19/07/2015 by admin

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Last modified 19/07/2015

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 Splenic autoinfarction: Absent or small calcified spleen

image Massive splenic infarction: Rare complication defined as when > 50% of spleen is infarcted
image Splenic sequestration: Massive splenomegaly
image Splenic abscess: Usually due to prior infarcts
• Gallbladder: Gallstones in young patients
• Extramedullary hematopoiesis: Most commonly paravertebral soft tissue masses of homogeneous density
• Kidneys

image Papillary necrosis on CT urography
image Large kidneys in early phase of disease; gradual atrophy with development of chronic renal failure
• Bones

image Widened medullary spaces, thinning of cortex, coarsening of trabecular pattern, and osteopenia
image Osteonecrosis and multiple bone infarcts

– High T2WI MR signal in affected areas with serpiginous low T2 signal outline (double-line sign)
image H-shaped or “Lincoln log” vertebrae 

– Cortical thinning leads to endplate deformities
image Osteomyelitis
image Persistence of red (cellular) marrow in bones with low-signal marrow on T1WI

– Demand for increased production of RBCs prevents normal conversion of red to yellow marrow
• Findings of iron deposition due to repetitive transfusions

image Hyperdense liver on NECT
image Liver, spleen, and bone marrow abnormally low signal on all MR pulse sequences (particularly on T2WI)
image Involved organs demonstrate characteristic signal loss on in-phase GRE images
image
(Left) Axial NECT in a patient who presented with sickle cell anemia and severe left upper quadrant pain demonstrates a heavily calcified and heterogeneous spleen image, indicating chronic and possibly acute infarction.

image
(Right) Splenectomy specimen from the same patient illustrates a mottled spleen with capsular discoloration image that was heavily calcified on microscopy.
image
(Left) Axial NECT in a patient with homozygous sickle cell anemia demonstrates a small and heavily calcified spleen image, also known as autosplenectomy.

image
(Right) Axial CECT in a patient with sickle cell anemia demonstrates multiple wedge-shaped hypodense areas image in the spleen, representing massive splenic infarction, an uncommon complication that rarely results in the formation of a splenic abscess.

TERMINOLOGY

Abbreviations

• Sickle cell anemia (SCA)

Definitions

• Inherited hemolytic anemia arising due to abnormal hemoglobin (hemoglobin S), resulting in deformation of red blood cells and leading to microvascular occlusions and infarcts

IMAGING

General Features

• Best diagnostic clue

image Small, densely calcified spleen on CT
image Papillary necrosis on intravenous pyelogram (IVP) or CT urography
image Cholelithiasis in a young African American patient
• Size

image Spleen may be undetectable (autosplenectomy) but rarely may enlarge due to sequestration syndrome

CT Findings

• Spleen

image Splenic autoinfarction: Absent or small calcified spleen
image Massive splenic infarction

– Splenic infarcts usually small and repetitive, leading to autoinfarction
– Massive splenic infarction defined as when > 50% of spleen is infarcted
– Often no precipitating factor, but may be associated with hypoxia (high altitude or mountain climbing)
image Splenic abscess: Rare (< 1%) complication usually seen in patients with persistent splenomegaly (rather than autoinfarction) and massive infarcts
image Splenic sequestration: Often associated with massive splenomegaly

– Represents severe, life-threatening anemia with massive splenomegaly and reticulocytosis
• Gallbladder: Gallstones in young patients
• Brain: White matter infarcts
• Extramedullary hematopoiesis: May have many different manifestations, including paravertebral soft tissue masses (homogeneous soft tissue density), hepatosplenomegaly, or perinephric soft tissue “rind” encasing kidneys
• Liver: Hyperdense liver due to repeated transfusions
• Kidneys

image Papillary necrosis on CT urography (blunted, irregular calyces, “golf ball-on-tee” appearance, etc.)
image Large kidneys in early phase of disease; gradual atrophy with development of chronic renal failure
image Renal medullary carcinoma

– More common in patients with sickle cell trait than with sickle cell disease
– Very rare, highly aggressive malignancy with high mortality and early metastatic disease
– Poorly marginated, heterogeneous renal mass with infiltrative appearance (similar to transitional cell carcinoma or lymphoma)
• Bones

image Avascular necrosis and multiple bone infarcts
image H-shaped vertebrae with endplate deformities
image Osteomyelitis

MR Findings

• Persistence of red (cellular) marrow in bones with low-signal marrow on T1WI

image Demand for increased production of RBCs (due to RBC destruction and anemia) prevents normal conversion of red to yellow marrow
image Stimulation of RBC production leads to widened medullary spaces, thinning of cortex, coarsening of trabecular pattern, and osteopenia
image T1 images of skull demonstrate low-signal widening of diploic spaces due to bone marrow expansion
image Cortical thinning leads to endplate deformities of vertebral bodies
• Multiple medullary bone infarcts and avascular necrosis (especially humeral and femoral heads)

image High T2 signal in affected areas with serpiginous low T2 signal outline (double-line sign)
• Findings of iron deposition (hemosiderosis) due to repetitive blood transfusions

image Liver, spleen, and bone marrow abnormally low signal on all pulse sequences (particularly on T2WI)
image Involved organs demonstrate characteristic signal loss on in-phase GRE images (opposite of steatosis)
image Iron deposition can be quantified using MR (usually GRE sequences with multiple TEs)
• Osteomyelitis
• White matter infarcts in brain

Ultrasonographic Findings

• Heterogeneous, coarsened liver parenchyma ± hepatomegaly
• Gallstones
• Increased renal echogenicity

Radiographic Findings

• Radiography

image 

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