20.1 Splenic Sequestration

CPHON Test Content Outline (TCO) V.D.5 tests acute splenic sequestration as a vascular emergency. This is not the genotype, penicillin, hydroxyurea, or transcranial Doppler lecture from the sickle-cell disease chapter. Those tools stay on the clinic calendar. This section is the hour a toddler with sickle cell disease (SCD) pools a large fraction of circulating red cells into a spleen that has not yet auto-infarcted, hemoglobin crashes, and hypovolemic shock can kill before morning clinic opens.

A 2-year-old with hemoglobin SS (HbSS) who was playing after breakfast and is now gray, limp, and “puffy on the left”; a 3-year-old whose parent felt a new left-upper-quadrant mass at diaper change; and a preschooler whose hemoglobin has fallen from a personal baseline of about 8 g/dL to 4 g/dL with a high reticulocyte count are sequestration patients until the spleen and the reticulocyte count say otherwise. The Oncology Nursing Certification Corporation (ONCC) uses generic drug names. The bedside job is palpation, a complete blood count (CBC) with reticulocytes, type and cross, and a transfusion that does not chase hyperviscosity.

What sequestration is, and who still has a spleen that can do it

Acute splenic sequestration is rapid trapping of red cells—and often platelets—inside an enlarging spleen. The blood has not left the body. It is sequestered. Circulating hemoglobin falls, circulating volume falls, and the child looks as if they hemorrhaged. Hypovolemic shock is the death pathway: tachycardia, delayed capillary refill, cool extremities, lethargy, and hypotension as a late pediatric sign.

The anatomy window matters. In HbSS and similarly severe HbS–β0-thalassemia, repeated infarction usually produces functional asplenia and a small, fibrotic spleen in later childhood. Sequestration is therefore classically a young-child emergency—infants and preschoolers whose spleens are still large and vascular. HbSC and HbS–β+-thalassemia can sequester at older ages because the spleen survives longer. Do not tell a 9-year-old with HbSC that sequestration is “only a baby problem.” Do not skip spleen palpation because last year’s note said “auto-infarcted.”

A first episode can be the first time the family understands that SCD is not only pain. Recurrence is common. After the child is stable, splenectomy is considered to prevent the next shock hour. Splenectomy is not the treatment of active hypovolemic shock.

Recognition: palpate, CBC, type and cross

The recognition cluster is clinical:

• Acute pallor, lethargy, irritability, or collapse in a young child with SCD.
• A rapidly enlarging spleen—a new or suddenly bigger left-upper-quadrant mass. Palpate gently. Compare with the baseline the family and the last clinic note described. Some teams mark the edge on the abdomen for serial exams; the skill is the exam, not the marker.
• Signs of hypovolemia: tachycardia out of proportion to fever, delayed refill, and a child who will not play.
• A CBC showing an acute drop in hemoglobin from that child’s baseline, not from a textbook “normal.”
• A reticulocyte count that is typically elevated or preserved—the marrow is making cells; they are pooled in the spleen.
• Mild thrombocytopenia can accompany pooling.
• Concurrent fever or a pain crisis can coexist; they do not cancel sequestration. Fever in a functionally asplenic child is still an infectious emergency from earlier teaching; treat both maps.

First actions:

• Airway, breathing, circulation. Give oxygen if hypoxic. Obtain rapid vascular access.
• Palpate the spleen and document size. Repeat. A spleen that grows while you watch is this diagnosis.
• Draw CBC with reticulocyte count and type and cross immediately. Do not send the type-and-cross “with morning labs.”
• Resuscitate shock with isotonic fluid as the team directs, then red-cell transfusion. The transfusion is cautious and in small aliquots. When the spleen releases sequestered cells back into the circulation, hemoglobin can rebound and hyperviscosity can injure brain and lung. Overshooting to a “normal” adult hemoglobin is a CPHON trap.
• Notify hematology. Move shock to an intensive-care unit (ICU).
• Emergency-release blood may be required if the child is crashing; a perfect extended-phenotype match does not outrank a dying toddler.

Walk the 2-year-old. Baseline hemoglobin 8.2 g/dL, spleen usually one to two centimeters below the costal margin. Tonight the spleen is at the umbilicus, heart rate is 180, refill is 4 seconds, hemoglobin is 3.9 g/dL, and the reticulocyte count is 14%. This is sequestration with shock. Type and cross, cautious packed-red-cell aliquots, ICU, serial spleen and hemoglobin checks—not a large “catch-up” transfusion aimed at 12 g/dL, and not a lecture about hydroxyurea in the next hour.

Parent teaching: daily spleen palpation

The prevention that belongs in this emergency chapter is teaching parents (and older children) to palpate the spleen daily. Show the left upper quadrant. Describe the child’s usual spleen. Teach that sudden enlargement plus pallor, lethargy, or a bigger belly is a same-hour hematology emergency, not acetaminophen and a morning voicemail. A parent who felt the spleen at 19:00 and feels a new hard edge at 22:00 has already made the diagnosis.

After recovery from an episode, document that recurrent sequestration is likely and that splenectomy after recovery is the usual surgical conversation. Keep penicillin and pneumococcal vaccination teaching aligned with asplenia care from the disease chapter; do not rebuild that chapter here. The emergency product is a family that can find the spleen and a nurse who will not over-transfuse.

A 3-year-old recovering from a first sequestration goes home with a written spleen map: where the edge was at discharge, how often to feel it, and which phone number to call at 02:00 if the abdomen changes and the child looks pale. That teaching visit is part of TCO V.D.5, not optional “clinic education.”

Not parvovirus aplastic crisis

Parvovirus B19 aplastic crisis also drops hemoglobin in SCD because red cells are already short-lived and erythropoiesis has stopped. The reticulocyte count is low or absent. The spleen is not rapidly enlarging. Pallor evolves over days more often than over an hour. Transfuse as needed; isolate per policy; counsel pregnant staff about exposure. Both processes can look like “the child got pale.” The diagnostic fork is the reticulocyte count and the spleen.

Walk the look-alike. A 4-year-old with HbSS had a classmate with slapped-cheek rash last week. Today hemoglobin is 4.1 g/dL, reticulocyte count is 0.2%, and the spleen is the same size as last clinic visit. That is aplastic crisis, not sequestration. Transfuse to a safe symptomatic hemoglobin as the team directs. Do not label it sequestration and do not schedule emergency splenectomy in the shock bay.

Do not call every falling hemoglobin in SCD “vaso-occlusive crisis (VOC).” Pain without a crashing hemoglobin and without a growing spleen is the next section. Do not call every left-sided belly finding constipation. Do not send a gray toddler home because the last transcranial Doppler study was normal. Hepatic sequestration (tender, enlarging liver with a falling hemoglobin) is a rarer cousin; the same cautious-transfusion logic applies, but the CPHON classic for V.D.5 is the spleen.

The CPHON product for TCO V.D.5 is a palpated spleen, a type-and-cross that left with the first CBC, a cautious aliquot that does not chase hyperviscosity, a parent who checks the left upper quadrant every day, and a parvovirus aplastic crisis that was not mislabeled because the reticulocyte count was ignored.