A 35-year-old female ultramarathon runner is admitted to the hospital following a day-long, 50-mile race because her urinary volume is drastically decreased and her urine is dark red. Tests indicate that she is in the initiating phase of acute tubular necrosis.
Why is her urine red?
A) Hematuria
B) Hemoglobinuria
C) Myoglobinuria
D) Kidney bleeding

Question

A 35-year-old female ultramarathon runner is admitted to the hospital following a day-long, 50-mile race because her urinary volume is drastically decreased and her urine is dark red. Tests indicate that she is in the initiating phase of acute tubular necrosis.
 Why is her urine red?
A) Hematuria
B) Hemoglobinuria
C) Myoglobinuria
D) Kidney bleeding

Quizplus · Accepted Answer

Myoglobinuria, which can cause acute tubular necrosis via intratubular obstruction, involves the leaching of myoglobin from skeletal muscle into the urine, bypassing the usual filtration by the glomerulus. Excess exercise and muscle trauma can contribute to this. While both hemoglobinuria and myoglobinuria discolor the urine, hemoglobinuria results from hemolysis following a reaction to a blood transfusion, whereas myoglobinuria involves muscle damage.

A 35-Year-Old Female Ultramarathon Runner Is Admitted to the Hospital