What is the utility of urine dipstick for blood in diagnosing rhabdomyolysis?

Although the dipstick method of detecting blood in the urine is convenient, it cannot differentiate between hemoglobin, myoglobin, or red blood cells. 1

Several reviews suggest that urine myoglobin is unstable with subpar performance in rhabdomyolysis1, often defined as creatine kinase (CK) elevation 5 times the upper limit of normal in the proper context (eg, crush injury, hypoxic/ischemic or drug injury). A sensitivity of 71% and a specificity of 54% for urine hemoglobin by dipstick, and a sensitivity of 25% and specificity of 75%  for urine myoglobin  has been reported in patients with serum CK >10,000 U/L. 3  

So while a positive dipstick for blood with few or no RBCs in the urine may make us think about rhabdomyolysis, its absence should not be used to exclude it in a susceptible host.

Final fun pearl: Did you know that consumption of quail has been associated with rhabdomyolysis, possibly due to their feeding on poisonous plants such as hemlock?

References

  1. Rodriguez-Capote Karina, Balion CM, Hill SA, et al. Utility of urine myoglobin for the prediction of acute renal failure in patients with suspected rhabdomyolysis: A systematic review. Clin Chem 2009;55:2190-97. https://www.ncbi.nlm.nih.gov/pubmed/19797717
  2. Nance JR, Mammen AL. Diagnostic evaluation of rhabdomyolysis. Muscle Nerve 2015;51:793-810. https://www.ncbi.nlm.nih.gov/pubmed/25678154
  3. Grover DS, Atta MG, Eustace JA, et al. Lack of clinical utility of urine myoglobin detection by microconcentrator ultrafiltration in the diagnosis of rhabdomyolysis. Nephrol Dial Transplant 2004;19:2634-38. https://www.ncbi.nlm.nih.gov/pubmed/15280520
What is the utility of urine dipstick for blood in diagnosing rhabdomyolysis?

Is there a connection between cirrhosis and elevated CK or rhabdomyolysis?

Besides the usual causes of rhabdomyolysis such as trauma, drugs, alcohol, sepsis, etc…, cirrhotic patients may also have what some have called “hepatic myopathy”.   One study involving 99 patients with cirrhosis and myopathy (all with elevated serum myoglobin) found “infections” as the most common cause (47%),  followed by “idiopathic” (27%) sources as well as ETOH, herbal medicine, and trauma-related causes (<10% each) (1).  Whether this is truly an entity  or just a non-causal association is unclear to me. The question now is whether we should lower our threshold in ordering CK in these patients.

1. Lee O-J, Yoon J-H, Lee E-J, et al. Acute myopathy associated with liver cirrhosis. World J Gastroenterol 2006;12:2254-2258.

Is there a connection between cirrhosis and elevated CK or rhabdomyolysis?