From the Guidelines
Asymptomatic microscopic hematuria (AMH) is a condition that requires a comprehensive evaluation to determine its underlying cause, with the most common causes including urinary tract infections, benign prostatic hyperplasia, kidney stones, and urologic malignancies. The evaluation of AMH should begin with a thorough history and physical examination, followed by a repeat urinalysis to confirm persistence 1. If hematuria persists, patients should undergo a comprehensive workup including renal function tests (BUN, creatinine), urine culture, and imaging studies, with the preferred imaging being a CT urogram, though ultrasound may be used initially in lower-risk patients 1. Some of the key causes of AMH include:
- Urinary tract infections
- Benign prostatic hyperplasia
- Kidney stones
- Urologic malignancies (bladder, kidney, or prostate cancer)
- Glomerular disorders
- Exercise-induced hematuria
- Medications (anticoagulants, aspirin)
- Recent urologic procedures Cystoscopy is recommended for all patients over 35 years with persistent AMH to evaluate for bladder cancer, particularly in those with risk factors such as smoking or chemical exposures 1. For patients with suspected glomerular disease (suggested by proteinuria, red cell casts, or dysmorphic RBCs), referral to nephrology is appropriate 1. The urgency of evaluation depends on risk factors, with expedited workup for older patients, smokers, and those with occupational exposures 1. This systematic approach is essential because while most cases of AMH are benign, approximately 5% will reveal significant urologic pathology, including malignancy, making thorough evaluation necessary despite the absence of symptoms 1.
From the Research
Causes of Asymptomatic Microscopic Hematuria
- Urinary tract infection 2, 3, 4
- Benign prostatic hyperplasia 2, 3
- Urinary calculi 2, 3, 4
- Urologic malignancy, which can be found in up to 5% of patients with asymptomatic microscopic hematuria 2
- Intrinsic renal disease 3
Evaluation of Asymptomatic Microscopic Hematuria
- A thorough history and physical to determine potential causes and assess risk factors for malignancy 3
- Laboratory tests to rule out intrinsic renal disease 3
- Imaging of the urinary tract, with multiphasic computed tomography urography being recommended for the upper urinary tract 2 and cystoscopy for the lower urinary tract 2, 5
- Referral to nephrology and urology subspecialists if no benign cause is found or if there are risk factors for malignancy 2, 3
- Use of the Hematuria Risk Index to stratify risk of urinary tract malignant tumors 6
- Renal ultrasound as a cost-effective first-line imaging modality in patients with asymptomatic microscopic hematuria 5