From the Guidelines
Microscopic hematuria is most commonly caused by benign conditions such as urinary tract infections, kidney stones, and benign prostatic hyperplasia, but can also be a sign of more serious conditions like kidney disease or cancer, as noted in the American College of Radiology's 2020 guidelines 1. The causes of microscopic hematuria can be divided into nephrogenic and urogenic causes, with renal parenchymal disease being the most common benign nephrogenic cause, and urolithiasis, infection, and benign prostatic hypertrophy being common benign urogenic causes 1. Some key factors associated with the development of urinary malignancy, which can cause microscopic hematuria, include gross hematuria, male gender, age over 35 years, smoking, and occupational exposure to chemicals, as outlined in the 2020 American College of Radiology guidelines 1. The evaluation of microscopic hematuria should include a thorough history, physical examination, urinalysis, and serologic testing, with cystoscopy and imaging studies as needed, according to the American Urological Association's 2012 guidelines 1. In patients with asymptomatic microhematuria, the risk of malignancy is relatively low, ranging from 2.6% to 4%, and a cause is often never found, as noted in the 2020 American College of Radiology guidelines 1. Patients without risk factors and with an identified benign cause of microhematuria are unlikely to benefit from a complete imaging workup, and should instead undergo a focused evaluation based on their individual risk factors and clinical presentation, as recommended in the 2020 American College of Radiology guidelines 1.
From the Research
Causes of Microscopic Hematuria
The causes of microscopic hematuria are varied and can range from benign to life-threatening conditions. Some of the common causes include:
- Urinary tract infection 2, 3, 4
- Benign prostatic hyperplasia 2
- Urinary calculi (urolithiasis) 2, 3
- Malignancy (including renal cell carcinoma, bladder carcinoma, and urothelial carcinomas) 2, 3, 5
- Intrinsic renal disease 2, 4
Evaluation and Diagnosis
The evaluation of microscopic hematuria typically involves a thorough history and physical examination, laboratory tests (such as urine cytology and culture), and imaging studies (such as intravenous urography, computed tomography, or ultrasonography) 2, 3, 4. In some cases, cystoscopy may be necessary to complete the investigation 4.
Risk Factors and Predictive Value
The risk of malignancy with microscopic hematuria is generally lower than with gross hematuria, but it is still important to investigate and rule out underlying conditions 2, 5. The positive predictive value (PPV) of microscopic hematuria for urinary tract malignancies varies depending on the specific type of cancer and the population being screened 5. For example, the PPV for bladder carcinoma in men aged 50 years or older is 6.2% 5.