Medical sequestration refers to the abnormal collection or isolation of substances or tissues within the body. This term encompasses various medical conditions where a part of the body’s normal structure or function becomes a distinct entity due to disease or congenital anomaly. It involves recognizing how different bodily components can become abnormally localized, leading to health implications.
Key Forms of Medical Sequestration
Pulmonary sequestration involves a portion of lung tissue that does not connect to the normal bronchial tree and receives its blood supply from the systemic circulation, rather than the pulmonary arteries. This abnormal lung tissue is non-functional and acts as a detached segment of the lung. Pulmonary sequestrations are classified as either intralobar, where the abnormal tissue is within a normal lung lobe, or extralobar, where it is a separate mass with its own pleural covering outside the normal lung.
Splenic sequestration is primarily seen as a complication of sickle cell disease. It occurs when a large volume of red blood cells becomes trapped within the spleen. This pooling of blood causes the spleen to rapidly enlarge. The trapped blood reduces the amount of circulating blood in the body, leading to a significant drop in hemoglobin levels.
A sequestrum, also known as bone sequestration, is a piece of dead bone that has separated from healthy bone tissue. This dead bone fragment acts as a nidus for ongoing infection, particularly in cases of chronic osteomyelitis. The sequestrum is often surrounded by new bone formation, known as an involucrum, which attempts to wall off the infection.
Causes and How They Present
Pulmonary sequestration is a congenital malformation, resulting from abnormal lung tissue development during fetal growth. Intralobar pulmonary sequestration often presents in late childhood or adolescence with recurrent pulmonary infections, persistent cough, back pain, or shortness of breath. Extralobar sequestration is usually diagnosed earlier, in newborns, and may manifest as respiratory distress or cyanosis.
Splenic sequestration occurs when abnormal, sickled red blood cells block the small blood vessels leading out of the spleen. This blockage causes blood to accumulate within the spleen, leading to its sudden enlargement. Symptoms often include sudden left-sided abdominal pain, rapid heart rate, weakness, dizziness, and pale skin due to severe anemia.
A bone sequestrum primarily results from osteomyelitis, a bone infection, where inflammation and pressure within the bone lead to a compromised blood supply and subsequent bone tissue death. Trauma or certain surgical procedures, like tooth extraction, can also contribute to its formation. Individuals with a sequestrum might experience persistent pain, swelling, and sometimes a draining sinus tract that discharges pus.
Identifying and Treating Sequestration
Identifying medical sequestration often relies on various imaging techniques. Pulmonary sequestration can be diagnosed prenatally with ultrasound, which may show a mass in the fetal chest. Postnatally, computed tomography (CT) scans and magnetic resonance imaging (MRI) provide detailed information. For splenic sequestration, diagnosis typically involves a physical examination to feel for an enlarged spleen and blood tests to check hemoglobin levels, with ultrasound sometimes used for confirmation. A bone sequestrum is usually identified through X-rays, which can show the dead bone fragment separated from healthy bone, and further confirmed with advanced imaging like MRI.
Treatment approaches vary depending on the type of sequestration. For pulmonary sequestration, surgical removal of the abnormal lung tissue is a common treatment, especially if symptoms are present or there is a risk of complications. In cases of splenic sequestration, immediate treatment often involves blood transfusions to address severe anemia and restore blood volume. If a child experiences recurrent episodes, surgical removal of the spleen (splenectomy) may be recommended to prevent future life-threatening events. Treating a bone sequestrum typically involves surgical debridement to remove the dead bone fragment and a prolonged course of antibiotics to clear the underlying infection.