Supplementary Material for: Hyperechoic spots in the renal medulla as a potential indicator of early gouty nephropathy

Introduction: To explore the causes and clinical significance of hyperechoic renal medulla observed by ultrasonography in patients with primary gout.
Methods: This study included 2107 patients with primary gout treated in the Gout Clinic of our hospital from 2016 to 2022. The clinical data and biochemical data of these patients were collected and analyzed. According to the presence or absence of punctate hyper-echogenicity in the renal medulla on ultrasound examination, the patients were divided into the hyperechoic medulla (HM) and the normal hypoechoic medulla (NM) groups, and the HM group was further divided into the partial HM (P-HM) and fulfilled-HM (F-HM) subgroups according to the distribution range of hyper-echogenicity.
Results: Among the 2107 patients with primary gout, 380 had hyperechoic renal medulla on renal ultrasound, including 106 patients with F-HM and 274 with P-HM. There were significant differences in the gout duration, urate arthropathies number, serum urate (SU) level, clinical tophi number, blood urea nitrogen (BUN), sCr, and eGFR between the HM and NM groups or between the F-HM and P-HM subgroups (P < 0.05). Multivariate regression analysis showed that the presence of hyperechoic medulla was positively correlated with gout duration, urate arthropathy number, gout attack frequency, SU, and sCr. The number of clinical tophi and sCr were closely related to F-HM.
Conclusion: Ultrasound examination showed that a high medulla echo in patients with gout was often related to renal function damage. P-HM may be a transitory condition between NM and F-HM in patients with gout.