The value of renal color Doppler ultrasound as an objective tool in the diagnosis of renal affection in SLE patients

Abstract
Background
Systemic lupus erythematosus (SLE) is an autoimmune disease with diverse manifestations, which resembles a clinical challenge to be managed. Lupus nephritis is a life-threatening condition as about 10% of patients develop chronic kidney disease.

Aim of the work
To assess the role of resistive index (RI) as a noninvasive parameter in detecting renal affection in SLE patients.

Results
A case–control study included 3 matched groups: 30 patients, 15 SLE with no renal affection, and 15 SLE lupus nephritis patients, who were selected, diagnosed according to ACR criteria 2019 for SLE, beside 15 age- and gender-matched healthy controls without any risk factors of chronic diseases. Written informed consent was obtained from all the three groups, and the study was approved by ethical committee. There was a statistically significant increase in both SLEDAI and renal SLEDAI scores, serum BUN, creatinine, urinary pus cells, RBCs, casts and proteins, 24-h urinary proteins, and protein/creatinine ratio beside a statistically significant increase in both right and left resistive indices in the group of lupus nephritis than the other group. There was highly statistically significant difference between SLE without nephritis and SLE with nephritis regarding renal echogenicity. There was statistically significant positive correlation between average RI and SLEDAI, rSLEDAI, serum creatinine, BUN, 24-h urinary proteins, protein/creatinine ratio, and renal echogenicity. Relation between renal echogenicity and demographic, laboratory, and clinical data was highly statistically significant with rSLEDAI, serum creatinine, BUN, 24-h urinary proteins, and P/C ratio. Our study highlighted that the best cutoff point of Rt average RI to detect SLE with nephritis group was found > 0.68 with sensitivity of 86.7% and specificity of 100.0%, while the best cutoff point of left average RI to detect SLE with nephritis group was found > 0.7 with sensitivity of 80.0% and specificity of 100.0%.

Conclusion
Renal RI is a noninvasive technique that can be used for detection renal disease activity in SLE patients, together with renal parenchymal echogenicity by grayscale US.