Acute splenic sequestration (ASS) and chronic hypersplenism are common features of homozygous sickle cell (SS) disease in the first 5 years of life affecting one-third of subjects in the Jamaican Cohort Study. The risk factors are largely unknown and the current study explores a possible role of genetic factors. We have explored these in subjects who received splenectomy in the management of ASS (n=8) or chronic hypersplenism (n=9) along with age, gender, and genotype matched controls using Luminex Technology to assess 42 human cytokines/chemokines, including IL-1α and CXCL10 (IP-10). Levels of IL-1α (p=0.008) and CXCL10 (p=0.009) were significantly elevated in patients treated by splenectomy compared with the control group. Levels of IL-1α were significantly higher in those with a history of ASS compared with matched normal controls (p= 0.028) but not in those treated for hypersplenism (p=0.093). Furthermore, several significant differences were found in the median ratios of some cytokine biomarkers between the splenectomized group and the normal controls. These observations are consistent with acute splenic sequestration having a distinct phenotype which may be helpful in predicting those at risk of this complication and suggest that the mechanism of these differences merit further study.
Sickle cell anemia; biomarkers; splenectomy; spleen; interleukins; cytokine; acute splenic sequestration; chronic hypersplenism
The aim of this study was to evaluate our experience with laparoscopic surgery in children with sickle cell disease.
A retrospective chart review was performed to analyze the indication for surgery, perioperative management, surgical technique, complications, duration of hospitalization, and outcome. One pediatric surgeon performed all procedures.
Thirteen children underwent laparoscopic surgery for the following indications: symptomatic cholelithiasis/cholecystitis in 9; recurrent splenic sequestration in 3; and hypersplenism/symptomatic cholelithiasis in 1. The 7 boys and 6 girls had a median age of 7.8 years. Patients undergoing splenectomy only were younger than those undergoing cholecystectomy (median age, 3.6 years versus 11.5 years, respectively). Four children underwent endoscopic retrograde cholangiopancreatography (ERCP) and sphincterotomy because of common bile duct dilatation and stones. Twelve patients received packed red blood cell transfusions prior to surgery. The median operative time was 150 minutes, and the median hospitalization was 3 days. Four patients suffered postoperative complications (2 with acute chest syndrome, 1 with recurrent abdominal pain, and 1 with priapism). The patient with abdominal pain was found to have a retained stone in the common bile duct, which was retrieved via endoscopic retrograde cholangiopancreatography and sphincterotomy. All complications resolved with medical management.
Laparoscopic surgery is safe in children with sickle cell disease. Meticulous attention to perioperative management, transfusion guidelines, and pulmonary care may decrease the incidence of acute chest syndrome.
Sickle cell anemia; Laparoscopic surgery; Child; Adolescence
Sickle-cell trait is a common genetic abnormality in the African American population. A sickle-cell crisis in a patient with sickle-cell trait is uncommon at best. Abdominal painful crises are typical of patients with sickle cell anemia. The treatment for an abdominal painful crisis is usually medical and rarely surgical. We present the case of a cocaine-induced sickle-cell crisis in a sickle-cell trait patient that resulted in splenic, intestinal, and cerebral infarctions and multisystem organ failure necessitating a splenectomy, subtotal colectomy, and small bowel resection. This case highlights the diagnostic dilemma that abdominal pain can present in the sickle-cell population and illustrates the importance of recognizing the potential for traditionally medically managed illnesses to become surgical emergencies.
During infancy and early childhood, the spleen commonly enlarges in patients with sickle cell anemia (SCA), and it thereafter undergoes progressive atrophy due to repeated episodes of vaso-occlusion and infarction, leading to autosplenectomy in adult life. However, this may not always be the case as some studies have reported splenomegaly persisting into adult life. This study aims to determine and review the prevalence of autosplenectomy by abdominal ultrasonography in sickle cell anemic patients in Zaria, Nigeria.
An ex-post-facto cross study of 74 subjects was carried out between May to July in 2010. Hematological parameters were determined by an analyzer while B mode Ultrasonography was used to determine the craniocaudal length of the spleen, if visualized.
The mean age of the sickle cell subjects was 23.2 ±5.3 years, while that of the controls was 22.7±12.4 years. Of the 74 sickle cell subjects, 55.4% were females; while of the 20 controls, 50% were females. Forty one subjects (55.4%) had autosplenectomy and a significant difference existed in the mean splenic size compared with the control (p<0.0001). Only 3 (4.05%) subjects had splenomegaly, while 23 (31%) had a shrunken spleen.
Anatomical autosplenectomy is not an uncommon finding in SCA patients. This may be related to inadequate clinical care due to the lack of good health education, ignorance, poverty, and poor standard of care, as well as the lack of newer therapeutic agents.
Sickle cell anemia; Autosplenectomy; Ultrasonography
Partial splenectomy was carried out in four children with homozygous sickle cell disease and eight children with sickle cell beta thalassaemia. It was performed in order to preserve splenic contribution to the host defence against infections while suppressing hypersplenism or the risk of recurrence of acute splenic sequestration. Indications for this surgical operation were acute splenic sequestration (n = 1), hypersplenism (n = 5), and acute splenic sequestration and hypersplenism (n = 6). Surgery was uneventful in 11 patients. A significant reduction of blood requirements and a significant decrease of the number of hospitalisations/patient/year were observed after splenectomy. No recurrence of hypersplenism or acute splenic sequestration occurred and no severe infection was noticed during the follow up period after surgery (mean (SD) 4.2 (2.8) years; range 6 months-7 years). Mean haemoglobin concentration and leucocyte and platelet counts increased after surgery. The benefit of partial splenectomy compared with total splenectomy to treat acute splenic sequestration or hypersplenism in sickle cell disease is discussed.
Idiopathic portal hypertension (IPH) is a disorder of unknown etiology and is characterized clinically by portal hypertension, splenomegaly, and hypersplenism accompanied by pancytopenia. This study evaluates the pathogenic concept of the disease by a systematic review of the literature and illustrates novel pathologic and laboratory findings.
We report the first case of uncontrolled splenic hyperperfusion and enlargement with subsequent hypersplenism leading to life-threatening complications of IPH in infancy and emergent splenectomy.
Our results suggest that splenic NO and VCAM-1, rather than ET-1, have a significant impact on the development of IPH, even at a very early stage of disease. The success of surgical interventions targeting the splenic hyperperfusion suggests that the primary defect in the regulation of splenic blood flow seems to be crucial for the development of IPH. Thus, beside other treatment options splenectomy needs to be considered as a prime therapeutic option for IPH.
To assess the effects of chronic erythrocyte transfusions on prevalence of sonographic incidence of organ damage in children with sickle cell anemia (SCA).
Children (n=148; mean age, 13.0 years) with SCA, receiving chronic transfusions (average, 7 years) underwent abdominal sonography at 25 institutions. After central imaging review, spleen, liver and kidney measurements were compared with published normal values. Potential relations between ultrasound, clinical and laboratory data were explored via Analysis of Variance, Student t-test and Cochran Mantel Haenzel tests of non-zero correlation.
Average spleen length was similar to normal children, but over one-third had spleen volumes > 300mL, 15 had previous splenectomy for splenomegaly and 24 had abnormal splenic echotexture. Two-thirds had hepatobiliary disease; 37 had prior cholecystectomy, 46 had gallstones, 16 had gallbladder sludge. Gallbladder disease correlated with older age (p = 0.002), longer liver length (p < 0.001), longer duration of transfusions (p = 0.034) and higher total bilirubin (p < 0.001). Liver (p < 0.001) and renal lengths (p ≤ 0.005) were larger than published norms.
In children with SCA, long-term transfusion therapy may not prevent development or progression of abdominal organ dysfunction.
sickle cell anemia; iron overload; splenomegaly; gallstones; hepatomegaly; nephromegaly
The relevance of fetal haemoglobin (HbF) concentration to the development of early clinical manifestations of homozygous sickle (SS) disease has been investigated by examining the time to first occurrence and the proportional hazard of these complications in three groups of the HbF distribution at age 5 years. HbF was significantly related to dactylitis, painful crises, acute chest syndrome, and acute splenic sequestration. The relationship suggested that a critically low HbF concentration increased the risk, little difference in risk occurring between the medium and high HbF groups. The abdominal painful crisis and hypersplenism were not related to HbF concentration suggesting that the degree of sickling may not be important in their genesis. Parental education on acute splenic sequestration should be focused on children with HbF concentrations in the lowest part of the HbF distribution for age.
Enlarged spleen without a clear-cut etiology, and believed to be related to malarial infestations, has been referred to as “tropical splenomegaly” and “cryptogenetic splenomegaly.” Splenectomy performed in such cases after a failure of antimalarial therapy shows histopathologically, while some of these meet the criteria for tropical splenomegaly, that most were cases of splenic abscess in various stages of formation, and some were lymphosarcoma. In sickle cell disease, one sequence of events involving the spleen is intermittent painful splenic infarction leading to splenic abscess or shrunken, fibrotic, and probably functionless spleen. It is proposed that an elective splenectomy may be indicated in cases of sickle cell disease to forestall this outcome. It is also proposed that an enlarged spleen that fails to respond to antimalarial medication after a certain period should be removed to establish the correct diagnosis, to prevent rupture, and to determine definitive management.
The aim of this study was to evaluate our experience with laparoscopic splenectomy in pediatric patients with hematologic diseases.
A retrospective chart review was performed to analyze the following: indication for splenectomy, pre- and peri-operative management, surgical technique, complications, duration of hospitalization, and outcome.
Eleven patients underwent laparoscopic splenectomy for the following indications: recurrent thrombocytopenia (<10,000) in seven with chronic immune thrombocytopenic purpura; anemia in two with hereditary spherocytosis; and hypersplenism in one and recurrent splenic sequestration in another with homozygous hemoglobin S. The six girls and five boys had a median age of 7 years. The median operative time was 180 minutes, and the median hospitalization was 72 hours. Among the patients with immune thrombocytopenic purpura (median platelet count, 153,000), those patients (n=3) with platelet counts of <100,000 did not suffer any bleeding complications. The patient with hypersplenism and homozygous hemoglobin S required a small incision in the left lower quadrant to facilitate removal of a 558-gram spleen. This patient also underwent cholecystectomy for cholelithiasis. The operative time was 295 minutes, and he was hospitalized for 5 days because of atelectasis.
Laparoscopic splenectomy is a safe and effective procedure in children with hematological disorders.
Hematologic diseases; Splenectomy; Laparoscopic surgery; Child; Adolescence
A cord blood screening programme initiated in June 1973 had screened 68 000 normal deliveries by February 1979 with the detection of 216 cases of homozygous sickle cell disease. Regular review of these children in the Medical Research Council paediatric clinic has identified acute splenic sequestration as a major cause of morbidity and mortality in the first 5 years of life. In addition to classical episodes characterised by peripheral circulatory failure, minor episodes of increasing anaemia associated with an enlarging spleen and an active marrow were also common. These minor episodes appeared to have predictive value in children who later developed severe life-threatening episodes of acute splenic sequestration. Sequestration. Sustained hypersplenism was also appreciably more common in children developing minor or major episodes of acute splenic sequestration compared with those without such a history. It is proposed that the classification of acute splenic sequestration be expanded to include these minor episodes, and that consideration be given to prevention of recurrences by splenectomy particularly in patients who also develop sustained hypersplenism.
Hypersplenism due to chemotherapy-related liver injury has been associated with severe thrombocytopenia that may preclude continuation of systemic therapy for cancer patients. Patients treated for metastatic colorectal cancer (mCRC) are among the most common patients affected by hypersplenism. Cessation of systemic therapy invariably leads to progression of disease. While partial splenic embolization has been employed successfully to reverse the effects of hypersplenism, the role of laparoscopic splenectomy for this problem has not been completely defined.
A retrospective review was conducted of mCRC patients treated with laparoscopic splenectomy at our institution to reverse severe thrombocytopenia due to chemotherapy-related hypersplenism. An endpoint assessed was the ability to resume therapy after splenectomy.
Six patients with mCRC and hypersplenism requiring cessation of systemic therapy underwent laparoscopic splenectomy. All (6) patients had a postsurgical platelet count >150 × 103/μl and resumed chemotherapy after surgery. Median platelet count prior to surgery was 66 × 103/μl, and just prior to resuming systemic therapy it was 399.5 × 103/μl. Median spleen size was 14.0 cm. There were no surgical complications. Mean hospital stay was 2.8 days and the median time from surgery to resumption of therapy was 23.5 days.
Laparoscopic splenectomy appears to offer selected patients with mCRC the opportunity to resume systemic therapy that otherwise would be discontinued due to thrombocytopenia from hypersplenism.
Laparoscopic surgery; Splenectomy; Hypersplenism; Splenomegaly; Thrombocytopenia; Colorectal cancer; Neoplasm metastasis
During the 25 years 1952--77 31 surgical procedures were performed on children aged up to 16 years with sickle cell anaemia (SCA). Six emergency operations were carried out, all for complications of SCA indistinguishable from the acute surgical conditions they mimicked. Seventeen minor operations were well tolerated and major surgery was undertaken 8 times, including 5 splenectomies for hypersplenism and increased transfusion requirements. The preparation for surgery by planned multiple transfusions and the indications for splenectomy are discussed. Recommendations are made for the preparation of patients for acute and routine surgery.
Wandering spleen is a rare clinical condition caused by incomplete fusion of the 4 primary splenic ligaments, allowing the spleen to be mobile within the abdomen, predisposing to splenic torsion along the vascular pedicle leading to splenomegaly and infarction, often diagnosed in an emergency setting.
The wandering spleen diagnosis was achieved by ultrasound in our case. We successfully treated the patient with laparoscopic splenopexy because the size was almost normal, and no infarction or evidence of hypersplenism was present. We used the sandwich technique in which 2 meshes sandwich the spleen.
This technique was found to be highly satisfactory as a treatment for wandering spleen. The patient was discharged on the third postoperative day with no intra-operative or postoperative complications.
Laparoscopy usually confirms the diagnosis.Recommended surgical procedures are splenopexy or splenectomy. Splenopexy is feasible, less invasive, and does not diminish splenic function.
Splenoptosis; Pedicle torsion; Splenopexy; Sandwich technique
We report on 106 elective splenectomies performed for haematological disorders between March 1979 and January 1986. The most common indications were immune thrombocytopenic purpura (30 patients) and Hodgkin's disease (19 patients). However, staging laparotomy is no longer performed routinely for patients with Hodgkin's disease and the reasons for this are discussed. Other indications for splenectomy included splenic pain (13 patients), autoimmune haemolytic anaemia (12 patients), hereditary spherocytosis (11 patients) and hypersplenism (9 patients). The overall morbidity and mortality was 48% and 5% respectively. The most common postoperative complication was thrombocytosis (defined as a platelet count greater than 800 X 10(9)/l) and occurred in 26 patients. This review confirms that splenectomy continues to have an important role in the management of certain haematological disorders.
Sixteen episodes of acute anaemia necessitating urgent blood transfusion have been investigated in 13 children with sickle cell anaemia. In five out of seven episodes there was evidence of increased haemolysis while in 10 out of 16 episodes a profound fall in reticulocyte count indicated marrow erythroid cell failure. Cold agglutinins active at room temperature were detected in 13 episodes, and anti-I specificity was demonstrated in 11. Warmed blood of homologous ABO and Rhesus groups was administered without complication despite difficulty with cross-matching. The exacerbation of anaemia was not due to folate lack, glucose-6-phosphate dehydrogenase deficiency or splenic sequestration, and an infectious agent appeared responsible. The degree of anaemia in homozygous sickle cell disease is usually constant during asymptomatic periods. An episode of sudden profound anaemia (anaemic crisis) may, however, result from marrow hypoplasia, an exacerbation of haemolysis, splenic sequestration, or folate deficiency.
Laparoscopic splenectomy (LS) has several advantages over the open procedure but can be technically demanding when performed in patients with massive splenomegaly. We hypothesized that patients who undergo hand-assisted LS (HALS) may experience the benefits of LS while having their enlarged spleens removed safely.
We reviewed the charts of patients who underwent HALS or LS between January 2003 and June 2008. Evaluated parameters included intraoperative and early postoperative morbidity and mortality, conversion to open surgery, need for blood transfusion, length of postoperative hospital stay, patient demographics, diagnosis leading to splenectomy, splenic weight and number of postoperative days to resuming normal diet. Differences were analyzed while controlling for splenic weight and malignant diagnosis using multiple linear and logistic regression analysis.
In all, 103 patients underwent splenectomy (23 HALS, 80 LS). Patients who had HALS were older and had larger spleens, and a greater proportion had malignant diagnoses. We observed no significant differences in morbidity, conversion to open surgery or need for blood transfusion. The mean length of postoperative stay, duration of surgery and days to resuming full diet were longer in the HALS group. No patients died. No group differences were significant after controlling for splenic weight and malignant diagnosis.
The morbidity associated with HALS is comparable to that with LS. The longer duration of surgery and hospital stay for HALS patients was likely related to greater splenic weight, older age and greater proportion of malignant diagnoses. Hand-assisted LS is a viable alternative to open surgery in patients with massive spleens.
Splenic involvement of tuberculosis, which is rare, warrants better definition in the current era of resurgence of tuberculosis.
Out of 339 splenectomies performed between January 1989 and December 2008 for indications other than trauma, histopathologic analysis of the spleen revealed tuberculosis in 8 patients.
All eight patients were referred for splenectomy due to fever of unknown origin (FUO). No patient was infected with HIV, and all had at least moderate splenomegaly and hepatomegaly. Three patients had hypersplenism with bleeding manifestations. Radiologic evaluations demonstrated that splenic lesions were present in five patients. Five patients had evidence of tuberculosis manifested as enlarged splenic hilar lymph nodes, cystic lymph nodes, or liver. Two patients exhibited tubercle bacilli in their sputum during the postoperative period.
In areas where tuberculosis is prevalent, tuberculosis should be considered in the differential diagnosis of patients presenting with FUO and splenomegaly. Extrasplenic involvement is usually seen in splenic tuberculosis, although it may not be apparent at presentation. Splenic tuberculosis can present in isolation without extrasplenic involvement, and even in immunocompetent individuals.
Splenic tuberculosis; Fever of unknown origin; Splenomegaly
BACKGROUND: Laparoscopic surgery is arguably the treatment of choice for patients undergoing elective splenectomy; however, for those patients with massive splenomegaly, laparoscopic surgery may prove difficult. PATIENTS AND METHODS: 6 years' experience of elective splenectomy was reviewed, in particular looking at the outcome of laparoscopic splenectomy in relation to the degree of splenomegaly. RESULTS: The conversion rate for laparoscopic splenectomy on patients with spleens weighing less than 1 kg was 0% whereas the conversion rate for those with spleens weighing more than 1 kg was 60%. In addition, a good correlation between both operative time and intra-operative blood loss in relation to splenic weight was observed. Open splenectomy on patients with spleens weighing more than 1 kg reduced the operative time and intra-operative blood loss without affecting hospital stay. CONCLUSIONS: Laparoscopic splenectomy is the method of choice for elective splenectomy in patients with splenic weight estimated to be < 1 kg; however, the operation takes longer, there is a high risk of conversion and there is an increase in blood loss/morbidity associated with massive splenomegaly (spleen > 1 kg) if splenectomy is attempted laparoscopically.
Clinical outcomes of children with sickle cell disease (SCD) who undergo total or partial splenectomy are poorly defined. The purpose of this retrospective study was to initiate an internet-based registry to facilitate analysis of clinical outcomes for these children. We hypothesized that both surgical procedures would be well tolerated and would eliminate risk of splenic sequestration.
We developed a web-based registry using the Research Electronic Data Capture (REDCap) platform. Children were included if they had SCD and underwent total splenectomy (TS) or partial splenectomy (PS) between 2003 to 2010. Clinical outcomes were compared between cohorts, with follow-up to one year.
Twenty-four children were included, total splenectomy (n=15) and partial splenectomy (n=9). There were no differences in surgical time or intraoperative blood loss. The length of stay was longer after PS (4.1±1.7 days) compared to TS, (2.4±1.2 days, p=0.02). Within 30 days of surgery, 2 (20%) patients had acute chest syndrome following TS and 2 (15%) patients had acute chest syndrome after PS. During one year follow-up, no patient in either cohort had recurrent splenic sequestration, venous thrombosis or overwhelming post-splenectomy sepsis. All children who were transfused preoperatively to prevent recurrent splenic sequestration successfully discontinued transfusions.
Both TS and PS result in favorable hematologic outcomes and low risk of adverse events for children with SCD. A REDCap based registry may facilitate data entry and analysis of clinical outcomes to allow for comparison between different types of splenectomy.
Sickle cell disease; partial splenectomy; total splenectomy; electronic data capture; medical informatics
Laparoscopic splenectomy in a pediatric patient was performed through a single umbilical incision by using 3 ports.
Single incision laparoscopic surgery (SILS) is an emerging technique that has been used as an approach for appendectomy, cholecystectomy, and splenectomy. We describe the technique of single incision laparoscopic splenectomy for hypersplenism in a 5-year-old boy with spherocytosis.
The patient required blood transfusions for anemia secondary to hypersplenism. His spleen measured 9.8 cm in cranio-caudal length on ultrasound. SILS splenectomy was performed through a 2-cm umbilical incision by using 3 ports. The splenic attachments were taken down using an electrosurgical sealing and cutting device, and the hilum was transected with an endosurgical stapler. The spleen was placed in an endosurgical bag, morcellated, and removed from the abdomen via the umbilical incision without complications. Operative time was 84 minutes; blood loss was minimal.
SILS splenectomy is feasible in pediatric patients. More experience is needed to assess advantages and disadvantages compared with the standard laparoscopic approach.
Single incision; Laparoscopy; Splenectomy; Child
Acute splenic sequestration crisis in a 20 year old female with homozygous sickle cell anaemia (Hb SS) is described. The resemblance of this complication to that of splenic vein ligation is discussed. This is the first case report known to the author of acute splenic sequestration crisis in an adult with homozygous sickle cell anaemia treated successfully.
Several episodes of acute hepatic enlargement associated with a dramatic fall in haemoglobin concentration were observed in two patients with sickle cell anaemia. No appreciable disturbances of liver function or signs of cardiac failure were evident. The most likely mechanism was sequestration of sickled erythrocytes in the liver. This complication, which may have a basis similar to that of splenic sequestration and the sickle lung syndrome, may be easily overlooked unless the size of the liver is regularly monitored in patients with sickle cell crisis.
Although sickle-cell anemia (SCA) is common in black Americans, Sub-Saharan Africa and in the Mediterranean area, the disease is rare in the temperate climate zone. The manifestations of the disease are related mainly to the production of abnormal hemoglobin that leads to organ ischemia and increased susceptibility to infection caused by functional asplenia.
The authors present CT findings in a 39-year-old black woman diagnosed due to abdominal pain, lymphadenopathy and fever. CT of the thorax and abdomen demonstrated changes in the liver, spleen, and skeletal system suggestive of SCA complicated with spondylodiscitis in the thoracic spine.
Hepatomegaly and small calcified spleen are typical findings in older homozygotic patients with SCA. The lesions in the skeleton may be related either to intramedullary hematopoiesis or osteonecrosis and osteomyelitis. In the latter case, diffuse osteosclerosis and H-shaped vertebrae are most typical. Tuberculous spondylodiscitis is characterized by the location in the thoracic region, preferential involvement of anterior elements, relative sparing of intervertebral discs, and cold abscesses.
sickle-cell disease; tuberculous spondylodiscitis; computed tomography
Low hemoglobin oxygen saturation (SpO2) is common in Sickle Cell Anemia (SCA) and associated with complications including stroke, although determinants remain unknown. We investigated potential hematological, genetic, and nutritional predictors of daytime SpO2 in Tanzanian children with SCA and compared them with non-SCA controls. Steady-state resting pulse oximetry, full blood count, transferrin saturation, and clinical chemistry were measured. Median daytime SpO2 was 97% (IQ range 94–99%) in SCA (N = 458), lower (P < 0.0001) than non-SCA (median 99%, IQ range 98–100%; N = 394). Within SCA, associations with SpO2 were observed for hematological variables, transferrin saturation, body-mass-index z-score, hemoglobin F (HbF%), genotypes, and hemolytic markers; mean cell hemoglobin (MCH) explained most variability (P < 0.001, Adj r2 = 0.09). In non-SCA only age correlated with SpO2. α-thalassemia 3.7 deletion highly correlated with decreased MCH (Pearson correlation coefficient −0.60, P < 0.0001). In multivariable models, lower SpO2 correlated with higher MCH (β-coefficient −0.32, P < 0.001) or with decreased copies of α-thalassemia 3.7 deletion (β-coefficient 1.1, P < 0.001), and independently in both models with lower HbF% (β-coefficient 0.15, P < 0.001) and Glucose-6-Phosphate Dehydrogenase genotype (β-coefficient −1.12, P = 0.012). This study provides evidence to support the hypothesis that effects on red cell rheology are important in determining SpO2 in children with SCA. Potential mechanisms and implications are discussed.