Non-visible hematuria (NVH), also known as microhematuria, is the presence of three or more red blood cells (RBCs) per high-power microscope field on a midstream, clean-catch urine sample.
A positive dipstick result for blood (trace blood or greater) does not confirm NVH, but should prompt further investigation with microscopy.
Many cases of NVH are idiopathic; discrepancies between study populations may be attributable to factors including age, sex, ethnicity, occupation, and smoking status. AUA: diagnosis, evaluation and follow-up of asymptomatic microhematuria (AMH) in adults Opens in new window
The most important initial diagnostic step is a detailed history, with the aim of identifying risk factors for malignancy and medical renal disease. History may also indicate less serious causes (e.g., recent exercise or sexual activity, urinary tract infection, and menstruation).
Cancer risk factors
The risk of urinary tract malignancy increases with age >40 years, male sex, degree of hematuria, persistence of hematuria, history of visible hematuria, tobacco use, previous radiation exposure, family history of urothelial cancer or Lynch syndrome, and certain occupational exposures (dyes, benzenes, aromatic amines) and medications such as phenacetin (available only in Japan), cyclophosphamide or ifosfamide chemotherapy, and aristolochic acid in some herbal weight loss preparations). Asymptomatic NVH is more likely to be associated with urinary tract malignancy in men. Obesity and hypertension are risk factors for renal cell carcinoma.
If malignancy is suspected, based on a high-risk or intermediate-risk profile, then evaluation of the entire urinary tract, including upper tract imaging and cystoscopy for the lower tract, is required. By contrast, the workup of low-risk patients can be more focused toward the suspected cause without a complete urinary tract survey.
Considering the source of bleeding by anatomic site offers an organized approach. The upper urinary tract includes the kidneys (glomerular or nonglomerular) and ureters, with remaining structures in the lower urinary tract. These dividing lines are useful to apply during the history and physical exam, as well as when ordering diagnostic tests, because no single diagnostic test evaluates the urinary tract completely.
Diagnostic testing must first confirm the presence of NVH. Thereafter, testing may distinguish an upper tract glomerular source from other causes, allowing a more refined workup. However, upper and lower tract diagnostic tests (imaging and cystoscopy) remain necessary in all patients with risk factors for urinary tract malignancy.
- Cystitis (urinary tract infection)
- Acute prostatitis
- Benign prostatic hyperplasia (BPH)
- Trauma (sexual activity, exercise, contusion)
- Bladder stone
- Renal cell carcinoma
- Transitional cell carcinoma (kidney or ureter)
- Simple renal cyst
- Polycystic kidney disease
- Medullary sponge kidney
- Atrophic kidney
- Calyceal diverticulum
- Renal infarction
- Renal vein thrombosis
- Arteriovenous malformations
- Papillary necrosis
- Sickle cell disease
- Ureteropelvic junction obstruction
- Vesicoureteral reflux
- IgA nephropathy
- Thin glomerular basement membrane disease
- Acute glomerulonephritis
- Lupus nephritis
- Hereditary nephritis (Alport syndrome)
- Transitional cell carcinoma (bladder)
- Cystitis (interstitial)
- Cystitis (radiation-induced)
- Cystitis (eosinophilic)
- Bladder diverticulum
- Bladder papilloma
- Prostate cancer
- Prostate stone
- Bladder neck contracture
- Urethral stricture
- Penile cancer
- Multiple myeloma
- Urinary tract tuberculosis
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