From the Guidelines
Hematuria, or the presence of blood in urine, can be caused by a variety of factors, including renal parenchymal disease, urolithiasis, infection, benign prostatic hypertrophy, and malignancy, with the most common benign nephrogenic cause being renal parenchymal disease 1. When evaluating the causes of hematuria, it is essential to consider the patient's symptoms, medical history, and risk factors.
- The most common factors associated with the development of a urinary malignancy include gross hematuria, male gender, age >35 years, smoking, occupational exposure to chemicals, analgesic abuse, history of urologic disease, irritative voiding symptoms, history of pelvic irradiation, chronic urinary tract infection, exposure to known carcinogenic agents or chemotherapy, and chronic indwelling foreign body 1.
- Gross hematuria has a high association with malignancy, with up to 30% to 40% of cases being related to cancer, and therefore, all patients with gross hematuria should undergo a full urologic workup 1.
- Conversely, patients with microhematuria have a low risk of malignancy, ranging from 2.6% to 4%, and in most patients with asymptomatic microhematuria, a cause is never found 1. Some common causes of hematuria include:
- Renal parenchymal disease, such as glomerulonephritis or acute kidney injury
- Urogenic causes, such as urolithiasis, infection, or benign prostatic hypertrophy
- Malignant causes, such as bladder or kidney cancer It is crucial to note that patients without risk factors and with an identified benign cause of microhematuria, including vigorous exercise, infection, trauma, menstruation, or recent urologic procedure, are unlikely to gain any benefit from a complete imaging workup of microhematuria 1. Therefore, a thorough history, physical examination, urinalysis, and serologic testing should be performed before any initial imaging, and further evaluation should be tailored to the individual patient's symptoms and risk factors 1.
From the Research
Causes of Hematuria
The presence of blood in urine, also known as hematuria, can be caused by various factors, including:
- Benign conditions such as urinary tract infection, benign prostatic hyperplasia, and urinary calculi 2
- Serious conditions such as bladder cancer, upper urinary tract urothelial cell carcinoma (UUT-UCC), renal cell cancer, and urinary tract stones 3, 4
- Intrinsic renal disease 2
- Anticoagulant therapy, which can increase the risk of hematuria and underlying pathology 5
Classification of Hematuria
Hematuria can be classified as either:
- Gross hematuria, which has a higher risk of malignancy (greater than 10%) and requires prompt urologic referral 2
- Microscopic hematuria, which most commonly has benign causes, but can also be a sign of underlying pathology 2, 5
Evaluation of Hematuria
The evaluation of hematuria should begin with noninvasive techniques such as:
- History and physical examination to determine potential causes and assess risk factors for malignancy 2
- Urinalysis and laboratory data to rule out intrinsic renal disease and other conditions 2, 6
- Imaging of the urinary tract, such as CT urography, which is recommended as the initial imaging test for hematuria in patients at high-risk for UCC 4
- Referral to nephrology and urology subspecialists if no benign cause is found or if the patient is at high-risk for UCC 2, 4