The smoky, brown-colored urine in acute poststreptococcal glomerulonephritis is primarily due to what?

The smoky, brown-colored urine observed in acute poststreptococcal glomerulonephritis is primarily due to the presence of red blood cells. This condition is characterized by inflammation of the glomeruli, often triggered by a preceding streptococcal infection. The inflammatory process can lead to increased permeability of the glomerular capillaries, allowing red blood cells to escape from the bloodstream into the urine, causing the characteristic discoloration.

While other factors such as proteinuria and altered urine composition may be present during this condition, they do not contribute to the smoky brown appearance to the same extent as hematuria (the presence of red blood cells) does. Urobilinogen is typically associated with liver dysfunction or hemolysis but is not responsible for the smoky appearance in this scenario. Similarly, sloughing of the collecting tubules and excessive proteins in the urine do not lead to the brown coloration as prominently as red blood cells. Hence, the presence of red blood cells is the definitive cause of the smoky, brown-colored urine in this context.