In case of RBCs found in urine, what does normally-shaped RBCs indicate?

The presence of normally-shaped red blood cells (RBCs) in urine typically suggests an extrinsic source of bleeding. This scenario implies that the RBCs are likely originating from areas outside the kidneys, such as the urinary tract, bladder, or urethra. When bleeding occurs in these structures, the RBCs maintain their normal morphology as they are not subjected to the pathologic changes that occur with glomerular damage.

This understanding is crucial because normally-shaped RBCs point away from disorders that affect the glomeruli, like glomerulonephritis or systemic illnesses that lead to intrinsic renal disease. In those cases, one would expect dysmorphic RBCs or casts in the urine due to the process of filtration and potential damage within the nephron.

Moreover, conditions like kidney stones can sometimes result in hematuria, but RBCs might also be affected depending on the severity of the injury and the location of the stone. Kidney stones can cause extrinsic bleeding, so while there is overlap, the focus on normally-shaped RBCs is distinctly indicative of bleeding from the urinary tract rather than from glomerular or intrinsic sources.