Vaso-occlusive crisis complicating sickle cell disease

21 year-old male with history of sickle cell disease (SCD) was admitted with dyspnea and acute chest and abdominal pain. The clinical examination revealed tachycardia, tachypnea and abdominal guarding. The laboratory tests showed severe anemia, trombocitopenia, coagulopathy, acute renal failure, metabolic acidosis and elevated lactate. A chest x-ray showed diffuse pulmonary infiltrates. A thoraco-abdominal CT scan was requested to rule out pulmonary embolism and mesenteric ischemia (Figure 1). Supportive care was initiated including exchange transfusion. Finally, the patient deceased after multi-organ failure.

The vaso-occlusive crisis (VOC) are acute complications in SCD. They are associated with hypoxia-induced polymerization of the abnormal hemoglobin S, followed by erythrocyte sickling, with resultant microvascular occlusion clinically manifested as acute painful episode. Acute chest syndrome (ACS) and acute mesenteric ischemia (AMI) are potentially lifethreatening complications. ACS is caused by pneumonia, fat embolism from bone marrow infarction, hypoxemia due to painful rib infarction or microvascular occlusion. It is the main cause of mortality, since it may progress to respiratory distress syndrome. The diagnosis is made on the combination of new pulmonary opacity on chest x-ray with at least one new sign or symptom (fever, cough, wheezes, dyspnea, tachypnea). CT scan may show mosaic perfusion pattern, ground glass opacities, consolidation with a lower lobe predilection and sometimes pleural effusion. If bacterial pneumonia is ruled out, areas of ground-glass attenuation could represent hemorrhagic edema and the denser areas of consolidation established infarcts without necrosis. Moreover, signs of pulmonary hypertension and cor pulmonale may be seen. AMI is attributed to microvascular occlusion of the postcapillary venules by sickling erythrocytes that leads to ischemia and infarcts in the mesentery and abdominal viscera. The diagnosis is based on presentation of acute abdominal pain, lack of another unifying diagnosis, and resolution with supportive management in uncomplicated cases. CT scan with IV contrast shows nonspecific findings, including the target appearance of bowel wall thickening (mucosal hyperenhancement and submucosal edema), ileus, perienteric stranding and free fluid. The involvement may be segmental or diffuse. The colon, with its low-flow state is more susceptible, although the small bowel can also be affected. The absence of wall enhancement indicates cessation of arterial flow. If it persists, the bowel will infarct and perforate. Management of VOC includes analgesia, fluids, oxygen, blood transfusion, antibiotics and thromboembolism prophylaxis.

ACS and AMI are potentially life-threatening complications in a VOC. Knowledge of the spectrum of its CT features is important to make the diagnosis and potentially prevent theirprogression.

- Bhalla M, Abboud MR, McLoud TC, Shepard JA, Munden MM, Jackson SM, et al. Acute chest syndrome in sickle cell disease: CT evidence of microvascular occlusion. Radiology 1993, 187:45– 49. - Gardner CS, Jaffe TA. Gastrointestinal Vaso-occlusive crisis co