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.