Microscopic Hematuria
/Committee Opinion 703 serves for additional reading today!
Defining Microscopic Hematuria
2012 American Urologic Association (AUA) criteria - 3+ RBC/high power field
The AUA guidelines also noted that if found, recommendation for evaluation for all patients older than age 35 years
This evaluation includes cystoscopy and upper urinary tract imaging with CT, with the primary concern being urothelial malignancy
The data supporting this approach was largely based on male patients - so ACOG and AUGS put together this series of recommendations thinking about the female patient
As an example of how this can be so different: the CO points to a large study where 20% of urinalyses performed had microscopic hematuria, and other studies pointing to incidences between 2% and 31% – that would be a lot of studies!
These studies do carry risks – radiation and malignancy risk, particularly for young patients.
Differential Diagnosis and Risk Factors
ACOG points to specimen collection being potentially more challenging in women:
Hematuria might result from true hematuria, but also from
Menstruation
Urogenital tract atrophy
Pelvic organ prolapse
Other non-threatening urogenital diagnosis (prostatic hypertrophy in men, urethral stricture, etc). – these are much less common in women as well.
The primary concern with microscopic hematuria: urothelial malignancy.
Risk factors:
Male sex
Age over 50
Previous or current smoker
Gross hematuria
HIstory of pelvic radiation
Male sex specifically has 3.3x more new cases of bladder cancer than female sex
4th most common cancer in men, while not in the top 10 cancers for women
Renal cancer is also 1.7x more likely in men.
When is reasonable to consider screening in women?
Studies looking at women have found:
Urologic malignancy rate in women under 40 years with any microscopic hematuria was 0.02%, and older than 40 years was 0.4%
Urologic malignancy rate is higher in women with 25 RBCs / hpf or greater
Smoking also increases risk.
Bottom line: women older than 60, with gross hematuria, and history of smoking have highest risk of urologic cancer.
Low risk, never smoking women, younger than 50 and fewer than 25 RBC/hpf - risk of urologic malignancy is less than 0.5%.
In 2020, the AUA updated their guidelines to incorporate these gender-specific screening pathways, which are helpful to recognize and be aware of:
Low risk women can undergo repeat urinalysis within 6 months, or cystoscopy/renal ultrasound
Intermediate risk women should undergo cystoscopy and renal ultrasound
High risk should undergo cystoscopy and CT urogram
Of course, keep your local urogyn / urologist aware of any patient for whom you have concern based on risk factors to discuss evaluation for urothelial cancers.
AUA/SUFU 2020 Microhematuria Algorithm