I dare you!
A 23-year-old man presented to the emergency department with thigh and flank pain. His medical history was unremarkable. Serum test results included the following: aspartate aminotransferase, 4007 U/L (reference interval, 11-47 U/L); alanine aminotransferase, 715 U/L (reference interval, 7-53 U/L); alkaline phosphatase, 67 U/L (reference interval, 38-126 U/L); lactate dehydrogenase, 6150 U/L (reference interval, 100-250 U/L); creatinine, 1.6 mg/dL (141 [micro]mol/L) [reference interval, 0.7-1.3 mg/dL (62-115 [micro]mol/L)]. A urine sample (Fig. 1) was also collected at the time of presentation.
[FIGURE 1 OMITTED]
1. What conditions might cause urine to have this appearance?
2. What laboratory tests might be useful for patients with dark brown urine?
The answers are below.
Dark brown urine can be caused by foods, medications, bilirubin, hematuria or hemoglobinuria, and myoglobinuria. Tests for markers of renal and liver function, urinalysis, and assays of muscle enzymes and hemoglobin are useful. The urine was positive for "blood" but not for red blood cells, suggesting the presence of hemoglobin or myoglobin. Further questioning of the patient revealed that he had performed 2500 squats 3 days prior, on a dare. The patient's serum creatine kinase activity was 310 000 U/L (reference interval, 30-200 U/L), and his serum myoglobin result was 68 860 [micro]g/L (reference interval, 0-110 [micro]g/L). Damaged muscle cells release creatine kinase (MM isoform), myoglobin, and aspartate aminotransferase, as well as lesser amounts of alanine aminotransferase and lactate dehydrogenase.
Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements:
(a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.
Authors' Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts of interest
Employment or Leadership: A.M. Gronowski, Clinical Chemistry, AACC; M.G. Scott, Clinical Chemistry, AACC.
Consultant or Advisory Role: None declared.
Stock Ownership: None declared.
Honoraria: None declared.
Research Funding: None declared.
Expert Testimony: None declared.
Patents: None declared.
Ann M. Gronowski * and Mitchell G. Scott
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO.
* Address correspondence to this author at: Washington University School of Medicine, Campus Box 8118, 660 S. Euclid Ave., St. Louis, MO 63110-1093. Fax 314-362-1461; e-mail email@example.com.
Received July 3, 2012; accepted July 11, 2012.
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|Title Annotation:||the Clinical Chemist: What Is Your Guess?|
|Author:||Gronowski, Ann M.; Scott, Mitchell G.|
|Date:||Dec 1, 2012|
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