From the Guidelines
Microhematuria is typically caused by a variety of conditions, including urinary tract infections, kidney stones, and malignancies, and requires further evaluation to determine the underlying cause. The presence of microscopic blood in the urine, defined as 3 or more red blood cells per high-power field on urinalysis, can be a sign of various conditions, ranging from benign to serious.
Causes of Microhematuria
- Urinary tract infections
- Kidney stones
- Malignancies, such as bladder or kidney cancer
- Vigorous exercise
- Gynecologic or non-malignant genitourinary sources According to the most recent guideline, patients diagnosed with microhematuria should undergo a risk classification system, stratified as low-, intermediate-, or high-risk for genitourinary malignancy, to determine the appropriate diagnostic evaluation and follow-up 1. This approach involves considering factors such as age, sex, smoking, and other urothelial cancer risk factors, degree and persistence of microhematuria, as well as prior gross hematuria.
Diagnostic Evaluation
- Cystoscopy and upper tract imaging are recommended according to patient risk and involving shared decision-making 1
- Urine culture to rule out infection
- Serum creatinine to assess kidney function
- Imaging studies, such as CT urogram or renal ultrasound The American Urological Association (AUA) guideline recommends that all patients 35 years or older should undergo cystoscopy, and upper urinary tract imaging is indicated in all adults with microhematuria in the absence of known benign causation 1. However, the more recent guideline from 2020 provides a more nuanced approach, emphasizing the importance of risk stratification and shared decision-making 1.
Follow-up
- If no cause is found, repeat urinalysis every 6-12 months for 2 years
- If persistent, consider annual evaluation It is essential to note that the evaluation and follow-up algorithm and guidelines provide a systematic approach to the patient with microhematuria, and these guidelines will need to be updated as new evidence becomes available 1.
From the Research
Causes of Microhematuria
The presence of microscopic blood in urine, also known as microhematuria, can be caused by various underlying diseases of the kidneys or the urogenital tract 2. The potential causes of microhematuria range from benign to severe malignant diseases of the kidneys and urinary tract 3. Some of the possible causes of microhematuria include:
- Kidney diseases, such as glomerular diseases 2, 4
- Urogenital tract diseases, such as malignant tumors of the kidneys or urinary tract 3, 5
- Other medical conditions, such as urinary tract infections or kidney stones 2
Risk Factors for Microhematuria
Certain risk factors can increase the likelihood of microhematuria, including:
- Smoking 2, 5
- Advanced age 2, 5
- Male sex 2, 5
- Family history of kidney disease or urinary tract cancer 3
Diagnostic Evaluation of Microhematuria
The diagnostic evaluation of microhematuria typically involves a thorough history and physical examination, measurement of inflammatory parameters and renal function tests, and ultrasonography of the kidneys and bladder 2. In some cases, additional tests such as urethrocystoscopy, urine cytology, and CT urography may be necessary to rule out underlying diseases requiring treatment 2, 3. The American Urological Association has developed a risk-stratified approach for the evaluation of patients with microhematuria, which takes into account factors such as sex, age, degree of hematuria, and smoking history 5.