INTRODUCTION
Chronic kidney disease (CKD) is defined as sustained kidney damage or decrease of estimated glomerular filtration rate (eGFR) to less than 60 ml/min per 1.73 m² body surface area lasting for ≥3 months (1). Diabetes mellitus (DM) is one of the most common causes of kidney damage and dysfunction (2). DM-II causes endothelial dysfunction and increased permeability to proteins (3). Moderate albuminuria, defined as urinary albumin to creatinine ratio (uACR) between 30-300 mg/g, is one of the most commonly used biomarker of early renal injury.
The most common noninvasive imaging tool for the assessment of renal diseases is ultrasonography (US) with renal size, cortical echogenicity and cortical thickness being used as markers of CKD (4, 5). Although these conventional US markers are well correlated with eGFR and severity of albuminuria, they can be recognized relatively late in the disease course where advanced damage to kidneys has already occurred (6). It is well recognized that histological changes in kidneys start before a measurable decline in eGFR and conventional US findings have occurred (3). Typical histological changes in type-II DM (DM-II) include glomerular changes which are related to proteinuria (7). Interstitial fibrosis occur in the later stages, and are associated with a decline in GFR and progressive deterioration of tissue elasticity and increased renal stiffness (3, 6). Hence combination of moderately increased uACR with preserved eGFR can be considered as a surrogate marker of early kidney damage in patients with DM-II.
The so called gold standard method to detect early glomerular changes is biopsy (8) which is invasive and inappropriate for prospective serial follow-up (9). Moreover, biopsy sensitivity remains problematic due to potential sampling errors (8, 10). Hence, elastographic methods have been increasingly investigated to assess kidney stiffness including magnetic resonance imaging (11) and US (6, 9, 12, 13). Among US shear-wave elastography methods, 2D shear-wave velocity (2D-SWV) has emerged as a relatively novel method to assess tissue stiffness and has been reported to provide comparable results as compared to transient elastography point shear-wave elastography (14, 15). There is lack of evidence showing disturbances in renal elasticity caused by early diabetic renal damage. This study aims to compare the renal elasticity DM-II patients with preserved eGFR and healthy controls using US 2D-SWV.