Hematuria. When is it cause for alarm?

Abstract

The urine of less than 3% of healthy persons shows more than three red cells per high-power field, which is about the limit of sensitivity of test strips for occult blood. Even minimal hematuria may herald serious problems and must be investigated. Common causes include infection, urethritis, and urethrotrigonitis (25%); stone (20%); and tumor (15%). Although hematuria may be caused by coagulopathy, patients with anticoagulant-induced hematuria must be examined for anatomic defects. Hematuria may originate from the kidney or the urinary tract; red cell casts and dysmorphic red cells suggest a renal source. Hematuria arising from the kidney is classified as glomerular (eg, various forms of glomerulonephritis) or nonglomerular (eg, polycystic kidney disease, cancer). If the urine is pigmented but test strips are negative, or test strips are negative but no red cells are seen, pseudohematuria must be considered.