A 17-year-old male presents to the office because he had an episode of cola-colored urine. He appears scared and says that he ran 12 miles two days ago as a part of 'a run for heart disease awareness.' His past medical history is insignificant. He denies any recent upper respiratory or skin infections. He does not smoke or consume alcohol, and says that he has never used any recreational drugs. His father has hypertension and coronary artery disease. His temperature is 37.2 C (98.9 F), blood pressure is 118/76 mmHg and pulse is 78/min. His BMI is 23 kg/m². The physical examination is unremarkable. Urinalysis is positive for blood; there are numerous (100+) RBCs/hpf. Urine sediment did not show any RBC casts. Which of the following is the most appropriate next step in management?

Question

Quizplus · Accepted Answer

Explanation: The differential diagnosis for this patient's cola-colored urine following exercise includes exercise-induced hematuria, myoglobinuria from rhabdomyolysis, and march hemoglobinuria from RBC trauma. All of these entities may result in a positive result for blood on urinalysis, although identifying intact RBCs on microscopy excludes myoglobinuria and hemoglobinuria. The absence of red blood cell casts also makes a glomerular cause of his hematuria less likely. Exercise-induced hematuria is therefore the most likely diagnosis in this patient. Up to 24% of participants in marathons may have exercise induced hematuria. This hematuria may be caused by repetitive up and down movements of the bladder during running. In contact sports, direct trauma to the kidneys or bladder may result in hematuria. Shunting of blood flow towards the muscles and away from the kidneys may also contribute. Even when an appropriate history is present, exercise hematuria should be considered a diagnosis of exclusion and repeat urinalysis should be done in one week to ensure resolution. Further evaluation would then be necessary if hematuria were still present, particularly in patients over the age of 50. (Choice A) Cystoscopy would not be needed unless this patient's hematuria persisted beyond one week. Bladder contusions are frequently seen if cystoscopy is performed, and their presence does not change management. (Choice B) CT has largely replaced intravenous pyelography in the evaluation of hematuria, but neither would be needed at the current time. (Choice C) Renal biopsy is indicated if he were suspected to have glomerulonephritis. (Choice E) Myoglobinuria from rhabdomyolysis would be on the differential diagnosis for this patient, but it is excluded by the visualization of RBCs on urine microscopy. If rhabdomyolysis is suspected, serum CPK would be more helpful than serum myoglobin level. Educational objective: Hematuria frequently occurs with extremely strenuous exercise, and can occur in both contact and non-contact sports. The diagnosis should be considered one of exclusion even with the appropriate history, and follow up urinalysis is needed in 1 week to ensure that the hematuria has resolved. References: Renal alterations during exercise. (http://www.ncbi.nlm.nih.gov/pubmed/18089464) Exercise-induced hematuria. (http://www.ncbi.nlm.nih.gov/pubmed/8594866)

A 17-Year-Old Male Presents to the Office Because He Had