What is commonly noted in children under 7 years of age presenting with postinfectious glomerulonephritis?

In children under 7 years of age presenting with postinfectious glomerulonephritis, dark brown urine and peripheral edema are commonly noted symptoms. Postinfectious glomerulonephritis often follows an infection, most commonly a streptococcal infection, leading to inflammation of the glomeruli in the kidneys.

The dark brown urine is typically a result of hematuria, where blood is present in the urine, and may give it a tea or cola-like appearance. This is often coupled with proteinuria, which can lead to the presence of protein in the urine contributing to edema. Peripheral edema, swelling in areas like the feet and ankles, occurs due to the kidneys' reduced ability to excrete sodium and water, causing fluid retention.

Thus, the combination of dark brown urine and peripheral edema is characteristic of this condition in young children who have recently experienced a bacterial infection, making it the most relevant symptom pair in this scenario.