Final answer:
Gross hematuria following an upper respiratory infection is indicative of post-infectious glomerulonephritis, a condition where the immune response to an infection affects the kidneys.
Step-by-step explanation:
Gross hematuria following an upper respiratory infection are the presentation of post-infectious glomerulonephritis (PIGN). This condition can occur after infections like streptococcal pharyngitis or an upper respiratory infection. The body's immune response to the infection can end up affecting the kidneys, leading to glomerulonephritis. Symptoms may include dark urine, typically brown or cola-colored, due to the presence of red blood cells, and thus giving it the characteristic of hematuria. Other signs include hypertension, and in more severe cases, edema may develop.