Spectral pulsed Doppler sonography of renal vascular resistance in sickle cell disease: clinical implications

Pattern of Renal Blood Flow and Renovascular Parameters in Adult Patients With Sickle Cell Disease

OBJECTIVES

To evaluate renal blood flow patterns and renovascular parameters in adult patients with sickle cell disease (SCD) without laboratory evidence of renal impairment.

METHODS

Sixty-five steady-state adult patients with SCD (50 hemoglobin SS [HbSS], 12 HbSβ⁰ , and 3 HbSD) and 30 age- and sex-matched healthy controls were studied. The kidney length, echo pattern, peak systolic velocity (PSV), end-diastolic velocity, renal-to-aortic ratio, resistive index (RI), acceleration time (AT), and renal vein velocity were acquired, recorded, and analyzed with a 1-5-MHz curvilinear transducer through the abdomen.

RESULTS

The mean age ± SD of the patients with SCD was 32.89 ± 13.89 years. The highest means for the ultrasound-measured renal length and cortical thickness in the SCD and control groups were 11.78 ± 1.30 and 11.27 ± 0.77 cm and 1.86 ± 0.41 and 1.78 ± 0.28 cm, respectively. The figures were significantly higher in the SCD group than the control group (P < .05). Fifty-nine (90.8%) patients had a mild diffuse increase in cortical echogenicity with preserved renal cortical thickness. The highest mean extrarenal PSVs in the SCD and control groups were 138.46 ± 56.32 and 101.75 ± 31.48 cm/s (P < .05). However, the highest intrarenal RI and AT in SCD and control groups were 0.69 ± 0.07 and 0.06 ± 0.02 seconds and 0.63 ± 0.05 and 0.04 ± 0.01 seconds (P < .05). There was no significant correlation between the RI, AT, and PSV among the patients with SCD (P > .05).

CONCLUSIONS

Increased renal length and cortical echogenicity with elevated PSV, RI, and AT values can serve as early ultrasound changes in adult patients with SCD without renal impairment.

Association between Endothelial Dysfunction, Biomarkers of Renal Function, and Disease Severity in Sickle Cell Disease

Background

Endothelial dysfunction (ED), as ascertained by brachial artery flow-mediated dilation (FMD), is a known feature of sickle cell disease (SCD), which is present both in crisis and in steady state. The assessment of FMD was introduced to examine the vasodilator function. Our objective was to establish the relationship between ED determined by FMD, biomarkers of renal dysfunction, and biomarkers of disease severity in SCD subjects asymptomatic of renal disease.

Methods

We enrolled 44 patients with homozygous SCD in steady state and 33 age- and sex-matched controls between 2013 and 2014 in a tropical tertiary hospital. Ultrasonographic FMD of the right brachial artery, renal arterial Doppler, complete blood count, creatinine, fetal hemoglobin, soluble P-selectin, and cystatin C (Cys-C) levels were determined. Using the median FMD value of the control group, the SCD subjects were further classified into two groups for comparison.

Results

The median FMD in SCD subjects of 3.44 (IQR, 0.00-7.08) was significantly lower than that of controls, which was 5.35 (IQR, 3.60-6.78; P=0.04). There was negative correlation between FMD and Cys-C levels (r=-0.372; P=0.01) along with renal artery resistivity index (RARI; r=-0.307; P=0.04) in SCD subjects. Additionally, Cys-C level was significantly higher in SCD subjects with FMD<5.35.

Conclusions

Brachial artery FMD was significantly lower in SCD subjects compared with a control group. Cys-C and RARI show a negative correlation with FMD, indicating that renal function is related to ED in SCD.

Doppler assessment of renal hemodynamic alterations in homozygous sickle cell disease and sickle Beta-thalassemia

We evaluated the renal vascular indices in children and adolescents with sickle cell disease (SCD) using Doppler ultrasonography. We also assessed the renal hemodynamics alterations in patients with homozygous SCD and sickle beta-thalassemia (sickle β-thalassemia). We studied 75 patients (age range = 3-20 years; M = 9.95 ± 4.15) with SCD: 42 patients suffering from homozygous SCD and 33 patients diagnosed with sickle β-thalassemia. Thirty, age- and sex-matched, normal subjects were also included as a control group. Both patients and control groups had Doppler assessment of pulsatility (PI) and resistivity (RI) indices of main renal, segmental, interlobar, and arcuate arteries. Both PIs and RIs were significantly higher in SCD patients, compared with the control group. Among patients, PIs and RIs in the main renal, segmental, interlobar, and arcuate arteries were significantly higher in patients with homozygous SCD as compared with those with sickle β-thalassemia (p values <0.01, <0.001, <0.001, and <0.001 for PIs and <0.001, <0.001, <0.001, and <0.01 for RIs, respectively). We concluded that renal vascular resistance is raised in children and adolescents with SCD. This is more pronounced in patients with homozygous SCD as compared with those with sickle β-thalassemia.

Thyroid Doppler indices in patients with sickle cell disease

OBJECTIVE

To evaluate the intrathyroidal hemodynamic changes and thyroidal volume in sickle cell disease (SCD) patients.

METHODS

Thirty-two patients with homozygous SCD and 32 control subjects were examined with color Doppler ultrasonography. None of the patients and control subjects had clinical or laboratory evidence of thyroid disease.

RESULTS

SCD patients had significantly higher resistance index (RI) and pulsatility index (PI) values and lower thyroid volume compared with control group.

CONCLUSION

Increased intrathyroidal RI and PI and decreased thyroid volume may be due to impaired thyroidal microcirculation. Further and follow-up studies are needed to explain the relationship between Doppler parameters and thyroid functions.

Ultrasound imaging of renal vaso-occlusive events in transgenic sickle mice exposed to hypoxic stress

One of the major clinical manifestations of sickle cell disease (SCD) is vaso-occlusive crisis in response to hypoxic exposure, leading to acute and chronic organ damages, especially in kidneys. In a SCD transgenic murine model, ultrasound imaging allowed us to characterize the circulatory changes in renal arteries during vaso-occlusive crisis. Cardiac output, heart rate and renal blood flow velocities (BFV) were measured in 10 male transgenic and 10 male wild-type (WT) mice with a conventional echograph (Vivid 7, GE Medical), before and after hypoxic exposure (8%O(2), 18h). To assess entrapment of red cells, histologic study of the kidneys was performed in both groups. Hypoxic exposure decreased heart rates in both groups (-17%, p < 0.001). Cardiac output remained stable in WT, and decreased in transgenic (-26%, p < 0.01). Peak systolic BFV in the renal artery was not modified in both groups. End-diastolic and mean BFV remained stable in WT, but decreased in sickle transgenic (-56%, p < 0.01 and -47%, p < 0.001, respectively). Transgenic mice displayed marked congestion in peritubular capillaries and glomerular abnormalities with trapped sickle red cells, whereas WT did not present any histologic injury. Five hours after hypoxic exposure, blood flow velocities returned to basal values in both groups. Decrease in end-diastolic and mean BFV in absence of peak systolic BFV after hypoxic exposure strongly indicated that the increase in vascular resistance in kidneys related to sickling of red cells. Thus, ultrasound imaging of the renal artery in mouse is a powerful, noninvasive, easy-to-repeat method to evidence circulatory changes in murine models of vascular renal human diseases.

Renal vascular resistance in sickle cell painful crisis

Vaso-occlusive painful crisis is one of the characteristic manifestations of sickle cell disease (SCD). We aimed to investigate the state of renal vascular resistance by means of Doppler ultrasonography during vaso-occlusive painful crisis in patients with SCD. The 60 patients with homozygous SCD who entered the study were divided into 2 groups. Group 1 included 45 patients who were living in steady-state conditions and had no history of transfusions within the 3 months before the initiation of the study. Group 2 consisted of 15 patients with signs of painful vaso-occlusive crisis during evaluation. Group 2 patients had significant reductions in 3 measures of flow velocity in both main renal arteries, compared with group 1 patients (P < .04, P < .001, and P < .01). Mean and end-diastolic velocities in the segmental arteries (P < .01, and P < .001, respectively) and end-diastolic velocities in the interlobar arteries (P < .04) were lower in group 2 patients than in group 1 patients. Analysis of resistive (RI) and pulsatile (PI) indices in the investigated arteries demonstrated that the RI of the renal (P < .001; P < .0001), segmental (P < .002; P < .0001) and interlobar (P < .001; P < .0001) arteries of both kidneys in group 2 < .0001; P < .0001) for both kidneys were markedly higher in group 2 patients than in group 1 patients and the healthy subjects, respectively. Our preliminary results suggest a reduction of renal blood flow and an increase in renal vascular resistance during painful crisis compared with steady-state SCD.

Abdominal ultrasonographic findings in patients with sickle-cell anaemia and thalassaemia intermedia

BACKGROUND

The high prevalence and heterogeneity of clinical and haematological phenotypes of sickle-cell anaemia and thalassaemia intermedia (TI) syndromes in the Greek population constitute a major challenge in routine medical practice.

PURPOSE

To investigate the spectrum and prevalence of abdominal US findings in these patients.

MATERIALS AND METHODS

The study included 105 patients, 13 homozygous for sickle-cell anaemia (S/S) and 92 with TI syndromes (Th/S, beta(thal)/beta(thal )or beta(thal)/deltabeta(thal)). The patients' ages ranged from 1 to 54 years, with 49 males and 56 females.

RESULTS

At the time of the examination, 41% of the patients had undergone splenectomy and 23.8% had undergone cholecystectomy. The most frequent US findings (percentages refer to all patients) were: hepatomegaly (70.5%), splenomegaly (48.6%) and cholelithiasis (20%). A bright liver was identified in 3.8% and focal hepatic lesions were present in two patients of the TI group. Functional disorders of the gallbladder concerned mainly patients with sickle-cell syndromes. Of those with S/S, 30.8% had a shrunken spleen. An echogenic pancreas was identified in one patient in each group. Increased renal echogenicity was observed in 17.6% of patients with sickle-cell syndromes. One case of polycystic kidney disease was diagnosed and coexisted with S/S.

CONCLUSIONS

The value of US imaging in detecting complications of sickle-cell and TI syndromes is still debated. To our knowledge, there are no previous reports concerning the frequency and spectrum of abdominal US findings in patients with these syndromes.