Hematuria, which means blood in the urine, is a very common clinical problem and will be covered on the Physician Assistant Exam. Being able to evaluate this condition is important because the causes are many and they affect people of any age or gender. Not fully evaluating the cause of hematuria can have dire consequences for the patient — for example, you may miss a potential cancer or nephritis.
Hematuria can be gross (macroscopic) or invisible to the naked eye (microscopic). Microscopic hematuria is diagnosed by urinalysis, with blood dipping positive.
The key to answering test questions about hematuria is figuring out where the hematuria originates. The clinical presentation and urinalysis are vital in determining this. Ask yourself the following questions:
Is the hematuria coming from the glomerulus itself? When the source of the hematuria is the glomerulus, the urinalysis dips positive for blood and, in most cases, protein. The microscopic examination can show red cells, dysmorphic red cells, and/or red cell casts.
Is the hematuria coming from somewhere along the GU tract (for example, the bladder, ureters, or somewhere in the kidney, as you might see in a renal cell carcinoma)? Causes of bleeding where the urinalysis is positive for blood and the microscopic evaluation shows red blood cells include cystitis, kidney or bladder cancer, infection, or a kidney stone.
Is the hematuria due to another process? Rhabdomyolysis is caused by any process that damages muscle enzymes, causing excess release of creatine phosphokinase from the damaged muscle. Common causes include trauma or crush injuries and side effects of medications, including statins used in the treatment for cholesterol. These muscle enzymes can cause acute renal failure, usually secondary to acute tubular necrosis. Treatment includes aggressive hydration, usually with intravenous saline.
Hematuria can occur by a mechanism where the urinalysis dips positive for blood but the urine sediment doesn’t show any red blood cells. The urinalysis-dip false positive is due to the presence of the myoglobin. Rhabdomyolysis and intravascular hemolysis are two important causes of such hematuria.