Comparative Sonographic Assessment Of The Spleen In Patients With Sickle Cell Disease In Stable State And Subjects With Normal Haemoglobin At Abakaliki

SUMMARY

BACKGROUND: Sickle cell disease (SCD) is one of the major public health burdens in Sub-Saharan Africa. The spleen is one of the most commonly affected organs in sickle cell disease with associated increase in morbidity and in some cases, may lead to mortality. Ultrasonography of the spleen together with splenic artery Doppler studies is an important diagnostic tool in the management of patients with sickle cell disease.

AIM AND OBJECTIVES: The aim of this study is to compare the ultrasonographic findings of the spleen including the Doppler indices of the splenic artery in patients with sickle cell disease in stable state and subjects with normal haemoglobin in Abakaliki.

MATERIALS AND METHODS: This was a comparative cross-sectional study of 60 patients with sickle cell disease in stable state and an equal number of sex- and age- matched subjects with haemoglobin AA. The spleen was scanned using the trans-abdominal route with a 2-5 MHz multi-frequency curved transducer of Sonoscape model S40 (Sonoscape Medical Corp, China, 2018) ultrasound scanner. The study was conducted over a period of 6 months. The splenic size, splenic echopattern and splenic artery Doppler indices (PSV, EDV, PI, RI and S/D) were assessed.

DATA ANALYSIS: Data analysis was carried out using Statistical Package for Social Sciences (SPSS) version 20.0 (SPSS Inc Chicago, IL, USA). Statistical tests were considered significant at 95% confidence interval and p values less than 0.05.

RESULTS: Sixty patients with sickle cell disease and 60 patients with normal haemoglobin were studied with a mean age of 15.78±7.20 and 15.80±7.52 respectively. The age range was 2-32 years in both groups. Thirteen (21.7%) patients with sickle cell disease had autosplenectomy while, 11.7% had splenomegaly, 10% had shrunken spleen and 56.7% had normal sized spleen on ultrasonography. All the subjects with normal haemoglobin had normal splenic size for age with normal homogenous splenic echopattern. Of the 47 patients with sickle cell disease whose spleen were visualized, 27 (57.4%) had normal echopattern, while 42.6% had abnormal splenic echopattern. The mean longitudinal, anteroposterior, and transverse dimensions of the spleen, splenic index, as well as splenic volume were significantly lower in patients with sickle cell disease compared with those with normal haemoglobin with p values of 0.02, 0.004, 0.001, 0.006, and 0.008, respectively. There was significantly higher abnormal splenic echopattern in patients with sickle cell disease when compared with their counterparts with normal haemoglobin. There was no significant difference in the peak systolic velocity (PSV) of the splenic artery in patients with sickle cell disease in stable state compared with those with normal haemoglobin (p=0.74). The end diastolic velocity (EDV) of the splenic artery was significantly lower in patients with sickle cell disease in stable state compared with those with normal haemoglobin (p value of < 0.001). The pulsatility index PI, resistivity index RI, and systolic-diastolic S/D ratio of the splenic artery were significantly higher in patients with sickle cell disease in stable state compared with those with normal haemoglobin (p values of <0.001, <0.001 and <0.001, respectively). There was a weak negative non-significant correlation between the splenic size and haemoglobin in patients with sickle cell disease.

CONCLUSION: Many subjects with sickle cell disease have abnormal splenic size and show higher rate of abnormal splenic echopattern with significant higher values of  PI, RI, and S/D ratio of the splenic artery compared with that of subjects with normal haemoglobin.

KEYWORDS: Haemoglobin, Sickle Cell Disease, Spleen, Ultrasonography

INTRODUCTION

The spleen is the largest lymphoid organ in the body. It has a combined function of immune defense, reservoir of blood cells and quality control of altered or senescent red cells.² The spleen is affected by a wide range of pathologic conditions and sickle cell disease is one of those conditions that frequently affect the spleen.³

Sickle cell disease (SCD) is an important hereditary haemoglobinopathy caused by a qualitative mutation of the haemoglobin structure in the red blood cells resulting in red blood cells that assume an abnormal, rigid and sickle shape with associated characteristic vaso-occlusive events and accelerated haemolysis.⁴ It is a significant cause of morbidity and mortality in Africa.⁵ Sickle cell disease is most common in people of African ancestry, but it is prevalent in other racial groups.^5,6 It constitutes a major health problem in Nigeria, a country with highest burden of the sickle cell disease worldwide and a top sickle cell endemic country in Africa.^5,7

Sickle cell disease encompasses a group of genetic conditions in which pathology results from the inheritance of gene for sickle cell haemoglobin (HbS) either homozygously or as a double heterozygote.⁷ Homozygous inheritance of sickle cell haemoglobin gene is termed homozygous sickle cell disease (HbSS), commonly known as sickle cell anaemia.^6,7 Other forms of sickle cell disease include sickle cell haemoglobin C disease (HbSC), sickle cell-β^o thalassemia (HbSβ^o), sickle cell- β_­­⁺ thalasemia (HbSβ⁺) , sickle cell haemoglobin D disease (HbSD), and sickle cell haemoglobin E disease (HbSE).^6,7 The common sickle cell disease variants in Africa and Nigeria include homozygous sickle cell disease  and sickle cell haemoglobin C disease.⁵ Interestingly, sickle cell trait which is heterozygous inheritance of sickle cell haemoglobin gene (inheritance of normal haemoglobin βA in addition to sickle cell haemoglobin βS gene) is not considered as part of sickle cell disease spectrum because individuals with this condition do not show severe signs and symptoms of sickle cell disease and are essentially normal.⁶ However, it is worthy of note that in much of the time, a greater number of patients with sickle cell disease are relatively stable and are said to be in a steady or stable state.⁸ This steady state may be interrupted by painful episodes from time to time.⁸ Steady state refers to a period of time during which a patient with sickle cell disease has no history of acute painful episodes that required treatment in the hospital for at least four consecutive weeks after a previous painful crisis.⁹

The spleen is one of the most common and early organs to be affected in SCD.^10,11 This is because the microvasculature of the spleen possesses a slow tortuous circulation which prolongs microvascular transit time. This renders it susceptible to congestion, sludging and polymerization. These events will subsequently lead to vascular occlusion with associated infarction.^4,10,12 Furthermore, splenic immune function is compromised which has important consequences for infection susceptibility as individuals with sickle cell disease are prone to infection with encapsulated bacteria.^6,12 Abnormal splenic function is a major determinant of the morbidity and mortality of sickle cell disease especially in childhood.¹¹

In patients with sickle cell disease the spleen commonly becomes enlarged during infancy and childhood, and subsequently, it suffers progressive regression in size with fibrosis due to repeated episodes of vaso-occlusion and infarction.^6,10 This ultimately results in autosplenectomy. Autosplenectomy tends to occur by the age of 8 – 10 years.⁶ However, this is not always the case as splenomegaly can persist into adulthood.^6,10

The presence of persistent splenomegaly in adult may infer a differential severity of disease when compared with those whose spleen have undergone autosplenectomy as patients with autosplenectomy are more likely to show evidence of greater immune dysfunction due to absence of the spleen.¹³ Occasionally, patients with persistent splenomegaly may show evidence of hypersplenism, splenic abscess and acute splenic sequestration which are frequently associated with serious morbidity and mortality.^6,10

The routine method of assessment of the spleen by palpation and percussion is not always accurate. In fact, before the spleen becomes clinically palpable, the volume will be about twice normal in size.¹⁴ This is because it is located laterally and lies deep to the ribs making palpation and percussion difficult.¹⁴  Therefore, mild enlargement of the spleen is often not detected by palpation and a non- palpable spleen does not certainly indicate splenic atrophy or normal sized spleen.¹⁵ Ultrasonography is a more reliable and accurate method for measuring the actual splenic size as well as assessing the splenic appearances^14,15

Ultrasonography has become the most common and the first choice of imaging modality used in the assessment of the intra-abdominal organs in which assessment of the spleen is an integral part.^14–16 Doppler ultrasonography is used to assess the vascular changes. Ultrasonography is a simple, affordable, non-invasive, non-ionizing, repeatable, easily accessible and readily available technique of imaging the spleen. Other imaging modalities that can be used to evaluate the spleen include conventional radiography, computerized tomography and magnetic resonance imaging.

Conventional radiography and computerized tomography involve the use of ionizing radiation. Computerized tomography and magnetic resonance imaging are expensive and not readily available. Magnetic resonance imaging provides good soft tissue details but at the expense of a higher cost and increase scan time.

This study therefore aims at comparing the various spectrums of ultrasonographic findings of the spleen including splenic artery Doppler indices in SCD patients in steady state with the findings in age and sex matched subjects with normal haemoglobin (HbAA).

AIM AND OBJECTIVES

BROAD OBJECTIVE

To compare the ultrasonographic findings of the spleen as well as Doppler indices of the splenic artery in patients with sickle cell disease in stable state and that of age- and sex- matched subjects with normal haemoglobin in Abakaliki.

SPECIFIC OBJECTIVES

1. To evaluate the size and echopattern of the spleen in patients with sickle cell disease in stable state.
2. To compare the splenic size of patients with sickle cell disease in stable state, and splenic size of age- and sex- matched subjects with normal haemoglobin.
3. To evaluate the relationship between splenic size and age in patients with sickle cell disease in stable state and compare with that of age- and sex-matched subjects with normal haemoglobin.
4. To compare splenic echopattern of patients with sickle cell disease in stable state and that of age- and sex- matched subjects with normal haemoglobin.
5. To compare the Peak Systolic Velocity(PSV), End Diastolic Velocity(EDV), Pulsatilily Index(PI), Resistivity Index(RI), Systolic Diastolic ratio(S/D) of the splenic artery in patient with sickle cell disease in stable state and that of age- and sex-matched subjects with normal haemoglobin.
6. To correlate the splenic size with haemoglobin levels of patients with sickle cell disease in stable state.

HYPOTHESIS

NULL HYPOTHESIS

1. There is no statistically significant difference in the splenic size of patients with sickle cell disease in stable state compared with that of age- and sex- matched subjects with normal haemoglobin.
2. There is no statistically significant difference in splenic size with age in patients with sickle cell disease in stable state compared with that of age- and sex- matched subjects with normal haemoglobin.
3. There is no statistically significant difference in splenic echopattern of patients with sickle cell disease in stable state compared with that of age- and sex- matched subjects with normal haemoglobin.
4. There is no statistically significant difference between the Peak Systolic Velocity (PSV), End Diastolic Velocity (EDV), Pulsatility Index (PI), Resistivity Index (RI), Systolic Diastolic ratio(S/D) of the splenic artery in patient with sickle cell disease in stable state and that of age- and sex-matched subjects with normal haemoglobin.
5. There is no correlation between splenic size and haemoglobin level in patients with sickle cell disease in stable state.

ALTERNATE HYPOTHESIS

1. There is statistically significant difference in splenic size of patients with sickle cell disease in stable state compared with that of age- and sex- matched subjects with normal haemoglobin.
2. There is statistically significant difference in splenic size with age in patients with sickle cell disease in stable state compared with that of age- and sex- matched subjects with normal haemoglobin.
3. There is statistically significant difference in splenic echopattern of patients with sickle cell disease in stable state compared with that of age- and sex- matched subjects with normal haemoglobin.
4. There is statistically significant difference between the Peak Systolic Velocity (PSV), End Diastolic Velocity (EDV), Pulsatility Index (PI), Resistivity Index (RI), Systolic Diastolic ratio(S/D) of the splenic artery in patient with sickle cell disease in stable state and that of age- and sex-matched subjects with normal haemoglobin.
5. There is correlation between splenic size and haemoglobin level in patients with sickle cell disease in stable state.

 JUSTIFICATION

Sickle cell disease is the most common genetic disease in Nigeria with prevalence ranging from 3% to 7.5% in different regions and it is a major public health problem.^6,17–22  There is prominent organ involvement in which the spleen is usually the earliest organ to be affected and it responds to the disease by dimensional changes, parenchymal changes, or both.^2,10

Ultrasonography plays an important role in the evaluation of the spleen accurately and at a relatively low cost and it is more reliable than palpation.¹⁵ It may help in the detection of early splenic changes in the spleen in sickle cell disease.¹⁰ Furthermore, knowledge of the ultrasonographic findings of the spleen in sickle cell disease is of great importance as the radiologist may be the first to anticipate a case of sickle cell disease in unscreened individual when routine investigation for other diseases are being carried out.²³

Early detection and constant monitoring of the spleen by ultrasonography will enable the caregivers of patients with sickle cell disease to take proper preventive measures.²⁴

Some studies,^4,7 have shown that there is regional, ethnic and racial variation in splenic changes in patients with sickle cell disease.

This study will provide the current information on the different ultrasonographic changes of the spleen that occur in sickle cell disease patients in our environment which will be helpful in making informed treatment and management decisions.

Although there are documented reports of sonographic findings of the spleen in patients with sickle cell disease in other parts of Nigeria, there is paucity of information in our environment (Abakaliki).

Pages:  120

Category: Project

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Material contains Table of Content, Abstract and References.