Understanding invisible urinary bleeding and its link to bladder cancer
Microhematuria is one of those conditions that often go unnoticed or are underestimated. It is the presence of blood in the urine, not visible to the naked eye but detectable on urinary sediment analysis. It is a frequent finding in daily clinical practice: it may emerge from a simple urine test performed for other reasons, perhaps in asymptomatic patients.
But when is this data really significant? And most importantly: what to do when we find it?
But when is this data really significant? And most importantly: what to do when we find it?
What is microhematuria and when to be concerned?
Microhematuria is defined as the presence of at least 3 red blood cells per high magnification field (RBC/HPF) in the microscopic examination of urine, on at least two separate samples collected correctly.
Microhematuria can be entirely benign, as in the case of intense physical exertion, but it can also be the first sign of a serious urologic condition, such as bladder cancer. The physician's job is to figure out when to investigate further and with what tools.
Microhematuria can be entirely benign, as in the case of intense physical exertion, but it can also be the first sign of a serious urologic condition, such as bladder cancer. The physician's job is to figure out when to investigate further and with what tools.
How widespread is it and what is the real risk?
Although it is quite common-it is estimated to affect about 1 in 8 people-in most cases it is not related to serious disease. However, several studies indicate that up to 10% of patients with microhematuria eventually present with a diagnosis of urothelial cancer, mostly in the bladder.
This finding imposes caution on us. It is true that micro-hematuria may be a transient or harmless phenomenon, but ignoring it could mean missing an opportunity to diagnose cancer early.
This finding imposes caution on us. It is true that micro-hematuria may be a transient or harmless phenomenon, but ignoring it could mean missing an opportunity to diagnose cancer early.
The new guidelines: risk-based assessment
To help clinicians navigate, guidelines from theAmerican Urological Association (AUA)and the Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (SUFU) propose an approach based on risk stratification. Not all patients should undergo the same examinations: it depends on factors such as age, the number of red blood cells in the urine, any smoking habits, or exposure to chemicals.
Three risk bands are identified:
- Low risk: young patients (< 40-50 years), few red blood cells, no risk factors.
- Intermediate risk: middle age (40-60 years), light smoker or limited exposure, moderate RBCs.
- High risk: age > 60 years, history of major smoking, exposure to carcinogens, presence of macroscopic hematuria in the past or high red blood cell count (>25 RBC/HPF).
Three risk bands are identified:
- Low risk: young patients (< 40-50 years), few red blood cells, no risk factors.
- Intermediate risk: middle age (40-60 years), light smoker or limited exposure, moderate RBCs.
- High risk: age > 60 years, history of major smoking, exposure to carcinogens, presence of macroscopic hematuria in the past or high red blood cell count (>25 RBC/HPF).
How is it deepened?
The diagnostic pathway depends on this very classification:
- Low risk: in these cases, you can start with a follow-up at a distance (6 months), repeating the examination. If microhematuria persists, a kidney-bladder ultrasound is evaluated. Cystoscopy, that is, endoscopic examination of the bladder, may be postponed.
- Intermediate risk: here cystoscopy becomes important. Ultrasonography is also useful, but alone may not be enough to rule out neoplastic lesions. Sometimes a CT scan of the urinary tract is associated if there are major suspicions.
- High risk: the patient should be thoroughly evaluated right away. In addition to cystoscopy, a CT scan with urography is indicated to explore the entire urinary tract. If a CT scan is not feasible (e.g., due to contrast medium allergy), an MRI may be considered.
In all cases, a urinary cytology test can be considered, on the 3-day urine; since it is a noninvasive test, it can be performed even in low-risk individuals, unlike more invasive tests, such as cystoscopy.
- Low risk: in these cases, you can start with a follow-up at a distance (6 months), repeating the examination. If microhematuria persists, a kidney-bladder ultrasound is evaluated. Cystoscopy, that is, endoscopic examination of the bladder, may be postponed.
- Intermediate risk: here cystoscopy becomes important. Ultrasonography is also useful, but alone may not be enough to rule out neoplastic lesions. Sometimes a CT scan of the urinary tract is associated if there are major suspicions.
- High risk: the patient should be thoroughly evaluated right away. In addition to cystoscopy, a CT scan with urography is indicated to explore the entire urinary tract. If a CT scan is not feasible (e.g., due to contrast medium allergy), an MRI may be considered.
In all cases, a urinary cytology test can be considered, on the 3-day urine; since it is a noninvasive test, it can be performed even in low-risk individuals, unlike more invasive tests, such as cystoscopy.
Conclusion
Microhematuria is a clinical sign that should not be ignored. Although it is often a benign finding, in a non-negligible proportion of cases it may indicate urothelial cancer, particularly of the bladder. A personalized approach, based on risk stratification and the most up-to-date guidelines, helps to balance the need for early diagnosis with the risk of performing unnecessary or invasive tests.
