What are the serious diseases that microscopic hematuria can represent?
Damage to the kidney filtration system (glomeruli) or the rest of the kidney tissue (interstitial or papillary) by diseases or even medications is a serious condition.
Chronic pain medicine use such as arthritis medicine is a common cause of renal damage. Anticoagulants such as coumadin and even aspirin can cause blood in the urine but it is a mistake to assume the cause of microscopic hematuria is the anticoagulant until serious causes have been ruled out.
In the case of someone with diabetes, there is concern for the disease itself causing papillary necrosis of the kidney or a glomerular nephritis. Diabetic medications such as Glucophage® (metformin) can also damage the kidneys.
Women with diabetes are often taking antihypertensive medications and diuretics (water pills) which can sometimes damage the kidneys. Therefore, it is doubly important to investigate any kidney tissue damage when someone with diabetes has microscopic hematuria.
Anatomical causes of bleeding such as kidney stones, kidney cancer, bladder cancer and kidney or bladder infections are also serious conditions meriting early diagnosis.
What studies need to be done to make sure none of the serious conditions are present?
The work-up of microscopic hematuria should be directed toward any known medical problems that could cause blood in the urine. If a woman is entirely asymptomatic, then the work-up usually includes lab studies, an IVP and a cystoscopy.
In most cases, these should be able to indicate a cause or where additional investigative studies or procedures are needed.
Work-up of Asymptomatic Hematuria
|non kidney||lab studies -
coagulation studies, prothrombin time (PT), partial thromboplastin time (PTT), complete blood count (CBC)
|kidney||lab studies -
BUN, creatinine, creatinine clearance, microscopic urinalysis, urine culture
radiologic studies -
intravenous pyleogram (IVP)
|bladder||lab studies -
urinalysis, urine culture, urine cytology
Does the amount of blood in the urine indicate the seriousness of the condition?
In general, no, if we are talking about microscopic blood. With microscopic hematuria, whether there are 5 red blood cells in the urine or 50 does not seem to correlate with how severe a condition is or how long it has been present.
Also, microscopic blood is more often associated with upper tract kidney disease rather than lower tract bladder tumors or infections.
Grossly visible blood in the urine is more commonly associated with lower tract disease. In one study, cancer and other benign tumors were found only about 1% of the time in patients with microscopic hematuria while 22% of patients with gross blood in the urine had either benign or malignant urological tumors.
In summary, once microscopic hematuria is found, a work up for diseases affecting kidney function should be started. While the likelihood of cancer is low (1-2%) other long term problems can be found.
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