ASCP International (ASCPi) Practice Exam

Renal tubular epithelial cells in urine signal tubular injury. When the tubules are damaged, they lose the ability to concentrate urine, leading to a low urine specific gravity around 1.010 (isosthenuria). Acute tubular necrosis classically presents with shedding of tubular epithelial cells and impaired concentrating ability, so this combination points most strongly to ATN. Other conditions have different urine findings: glomerulonephritis centers on glomerular leakage and may show proteinuria or red cell casts, nephrotic syndrome shows heavy proteinuria with lipiduria, and pyelonephritis is typically associated with infection markers such as white blood cells or bacteria.