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Significant Microscopic Hematuria: Definition and Evaluation

Hematuria is a common finding by primary care physicians and urologists and it should not be ignored. About 4% of patients with microscopic hematuria and up to 40% of patients with gross hematuria will be found to have a malignancy. The first step is to determine if the hematuria is significant. Gross hematuria should always be considered significant, as it should be considered secondary to a malignancy until proven otherwise. In my experience, many patients will resist a workup because it only happened one time. It does not matter if it happened one time or 15 times, it happened and it needs to be worked up. While microscopic hematuria is more common than gross hematuria, the etiology is often more elusive. Significant microscopic hematuria is defined as 2 or more red blood cells per high-power field in a properly collected specimen without any obvious benign etiology. A positive dipstick must be confirmed by microscopy.

Probably the most common cause of both microscopic and gross hematuria is urinary tract infection. However, one should not take for granted that the hematuria is secondary to the UTI. The UTI should be treated appropriately and then urine reevaluated. Another common cause of hematuria is kidney stones. However, hematuria is not always present with a kidney stone. Malignant renal tumors are often associated with hematuria, mostly microscopic and can cause gross hematuria if more centrally located in the kidney. Urothelial cancers in the renal collecting system, ureters and bladder are more often present with gross hematuria. BPH is likely the most common cause of microscopic hematuria in men. These patients should be considered for a referral to a urologist. Children with nephropathies and nephritis may have microscopic hematuria, proteinuria or RBC casts and present with hypertension, edema, and/or renal insufficiency. In these cases referral to a nephrologist should be considered.

Early evaluation of hematuria should include BUN/creatine and estimated glomerular filtration rate. If a patient has a history of bleeding, then INR and PTT may be helpful. Urine cytology and some of the newer genetic testing is often helpful. As imaging has improved, it is more helpful in identifying possible reasons for hematuria than in the past.  IVPs are rarely done these days. Many of the renal lesions that are identified are found coincidentally during ultrasounds and CT scans when being evaluated for other causes. CT urography is the mainstay of evaluation. The final step in the evaluation is cystoscopy which should be performed in all patients with gross hematuria including children.  Patients 35 years old and older who presented with asymptomatic microscopic hematuria and have no risk factors should have cystoscopy.

Patients who are worked up and found to have no obvious reason for their hematuria should not be forgotten. It is reported that 1% to 3% of patients with a negative workup may develop a malignancy within 3 years. These patients should be evaluated with urinalysis every 6 months for 3 years if hematuria persists, even if it is still only microscopic, a repeat evaluation should be undertaken.

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