Overview

Sickle cell disease (SCD) is an inherited hemoglobinopathy leading to chronic hemolytic anemia and vaso-occlusive crises. Radiology plays a critical role in diagnosing and managing the multisystem complications of SCD.

Key Radiologic Findings

• Bone Infarcts: MRI shows geographic, well-demarcated areas of marrow edema and necrosis; later, sclerosis and periosteal reaction appear on radiographs.
• Avascular Necrosis (AVN): Most commonly affects the femoral and humeral heads. Radiographs demonstrate crescent sign, flattening, and collapse; MRI with T1 and STIR sequences shows characteristic double-line sign.
• Acute Chest Syndrome: Chest X-ray and CT reveal patchy pulmonary opacities, consolidation, and pleural effusions; often indistinguishable from pneumonia but requires prompt treatment.
• Stroke and Silent Infarcts: MRI with DWI shows acute ischemic infarcts in watershed zones; chronic microbleeds and silent infarcts are best seen on T2* GRE or SWI sequences.
• Splenic Infarcts / Autosplenectomy: CT or ultrasound demonstrates a small, calcified spleen with poor or absent enhancement.
• Hepatobiliary Complications: Hepatic infarcts, fibrosis, and hemosiderosis are seen on CT and MRI, with T2* imaging quantifying iron overload.
• Renal Papillary Necrosis: CT urography shows contrast filling defects at the renal papillae; MRI may show increased T2 signal.
• Hand-Foot Syndrome (Dactylitis): Radiographs in young children show periosteal new bone formation and soft tissue swelling of the metacarpals and metatarsals.

Imaging Modalities

• Radiography: Often the first-line for skeletal pain and acute chest syndrome. Low radiation and widely available.
• CT: Useful for acute complications like stroke, pulmonary embolism, and abdominal crises. Faster than MRI but involves radiation.
• MRI/MRA: Gold standard for brain, bone marrow, and joint imaging. Excellent soft tissue contrast without radiation. Essential for detecting silent infarcts and AVN.
• Ultrasound: Bedside tool for evaluating spleen, gallbladder, and kidney complications. No radiation, safe for children and pregnancy.
• Nuclear Medicine: Bone scans may detect early osteomyelitis or infarcts; however, MRI is now preferred for specificity.

Clinical Relevance

Early detection of complications through radiology improves outcomes by guiding treatments such as exchange transfusion, hydroxyurea, or surgical intervention (e.g., hip replacement, splenectomy). Regular brain MRI screening in children with SCD can prevent recurrent strokes.