What condition is characterized by hematuria as a presenting sign?

Hematuria, or the presence of blood in the urine, can be associated with several renal and urinary tract conditions, but renal thrombosis is particularly notable for this symptom. In renal thrombosis, a blood clot forms in the renal vein, which can lead to renal swelling, pain, and impaired renal function. This condition often causes damage to the kidney, which can manifest as hematuria due to increased pressure and injury to the renal tissue, allowing blood cells to leak into the urine.

While ureteral obstruction may also lead to hematuria due to distended ducts and increased pressure, it is not as directly characterized by hematuria as renal thrombosis. Chronic renal failure, on the other hand, often does not present with hematuria as a first sign and is more related to changes in waste product management and electrolyte imbalance rather than acute bleeding in the urine. Hypospadias is a congenital condition involving the urethral opening and does not typically present with hematuria as a primary symptom.

Therefore, recognizing that renal thrombosis leads directly to hematuria is crucial in understanding its clinical presentation and justifying it as the most appropriate answer.