In a patient with a closed tibial fracture, increased leg pain and dark red urine after 24 hours may indicate which condition?

Increased leg pain and dark red urine after 24 hours in a patient with a closed tibial fracture may indicate acute tubular necrosis (ATN) due to muscle injury and subsequent release of myoglobin into the bloodstream, a condition known as rhabdomyolysis. When muscle tissue is injured, myoglobin is released from the damaged muscle cells into the circulation. This myoglobin can then be filtered by the kidneys, where it may cause tubular obstruction and direct tubular cell toxicity, leading to ATN.

The presence of dark red urine suggests myoglobinuria, which is a hallmark of this condition. It typically occurs in the context of significant muscle breakdown, which can happen after trauma or prolonged immobilization, such as might occur with a tibial fracture. The increase in leg pain after the fracture may signify an increase in muscle stress or damage, contributing to the rhabdomyolysis and subsequent kidney injury.

In contrast, conditions such as acute glomerulonephritis or interstitial nephritis would likely present differently, with more systemic symptoms or specific signs that are not directly related to muscle injury. Hemolytic-uremic syndrome typically involves a triad of symptoms: hemolytic anemia, acute renal failure, and thromb