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In medicine, hematuria, or haematuria, is the presence of red blood cells (erythrocytes) in the urine. It may be idiopathic and/or benign, or it can be a sign that there is a kidney stone or a tumor in the urinary tract (kidneys, ureters, urinary bladder, prostate, and urethra), ranging from trivial to lethal. If white blood cells are found in addition to red blood cells, then it is a signal of urinary tract infection.
Red discoloration of the urine can have various causes:
- Red blood cells
- Hemoglobin (only the red pigment, not the red blood cells)
- Other pigments
Often, the diagnosis is made on the basis of the medical history and some blood tests—especially in young people in whom the risk of malignancy is negligible and the symptoms are generally self-limiting.
The most common causes of hematuria are:
- Urinary tract infection with viruses, other sexually transmitted diseases (particularly in women) or some bacterial species including strains of EPEC, Streptococcus pyogenes, and Staphylococcus saprophyticus
- Bladder stones
- Kidney stones or ureter stones
- Benign prostatic hyperplasia, in older men, especially those over 50
Other, less common causes of hematuria include:
- IgA nephropathy ("Berger's disease") - occurs during viral infections in predisposed patients
- Trauma (e.g., a blow to the kidneys)
- Tumors and/or cancer in the urinary system, for example bladder cancer or renal cell carcinoma
- Kidney diseases
- Urinary Schistosomiasis (caused by Schistosoma haematobium) - a major cause for hematuria in many African and Middle-Eastern countries;
- Prostate infection or inflammation (prostatitis)
Rare causes include:
- Benign familial hematuria
- Paroxysmal nocturnal hemoglobinuria - a rare disease where hemoglobin of hemolyzed cells is passed into the urine
- Sickle cell trait can precipitate large amounts of red blood cell discharge, but only a small number of individuals endure this problem
- Arteriovenous malformation of the kidney (rare, but may impress like renal cell carcinoma on scans as both are highly vascular)
- Nephritic syndrome (a condition associated with post-streptococcal and rapidly progressing glomerulonephritis)
- Fibrinoid necrosis of the Glomeruli (as a result of malignant hypertension)
- Vesical varices may rarely develop secondary to obstruction of the inferior vena cava
- Allergy may rarely cause episodic gross hematuria in children 
- Left renal vein hypertension, also called "nutcracker phenomenon" or "nutcracker syndrome," is a rare vascular abnormality responsible for gross hematuria 
- Ureteral Pelvic Junction Obstruction (UPJ) is a rare condition beginning from birth in which the ureter is blocked between the kidney and bladder. This condition may cause blood in the urine 
- March hematuria secondary to repetitive impacts on the body, usually the feet
- Athletic nephritis secondary to strenuous exercise
- Medications can cause red discoloration of the urine, but not hematuria. Some examples include: sulfonamides, quinine, rifampin, phenytoin
- Alport syndrome
- Spetie, DN.; Nadasdy, T.; Nadasdy, G.; Agarwal, G.; Mauer, M.; Agarwal, AK.; Khabiri, H.; Nagaraja, HN. et al. (Mar 2006). "Proposed pathogenesis of idiopathic loin pain-hematuria syndrome". Am J Kidney Dis 47 (3): 419–27. doi:10.1053/j.ajkd.2005.11.029. PMID 16490620.
- Hematuria Causes Original Date of Publication: 15 Jun 1998. Reviewed by: Stacy J. Childs, M.D., Stanley J. Swierzewski, III, M.D. Last Reviewed: 10 Jul 2008
- Koshy, CG.; Govil, S.; Shyamkumar, NK.; Devasia, A. (Jan 2009). "Bladder varices--rare cause of painless hematuria in idiopathic retroperitoneal fibrosis.". Urology 73 (1): 58–9. doi:10.1016/j.urology.2008.06.039. PMID 18722652.
- Graham, DM.; McMorris, MS.; Flynn, JT. (Nov 2002). "Episodic gross hematuria in association with allergy symptoms in a child.". Clin Nephrol 58 (5): 389–92. doi:10.5414/cnp58389. PMID 12425491.
- Russo, D.; Minutolo, R.; Iaccarino, V.; Andreucci, M.; Capuano, A.; Savino, FA. (Sep 1998). "Gross hematuria of uncommon origin: the nutcracker syndrome.". Am J Kidney Dis 32 (3): E3. doi:10.1053/ajkd.1998.v32.pm10074588. PMID 10074588.
- Ureteral Pelvic Junction Obstruction (UPJ) / Ureteral Obstruction
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