What are the causes of hematuria (blood in urine)?

From the Guidelines

Hematuria, or blood in the urine, can be caused by numerous conditions affecting the urinary tract, including urinary tract infections, kidney stones, enlarged prostate, kidney diseases, and certain medications, as well as more serious causes like bladder or kidney cancers. The causes of hematuria can be divided into nephrogenic and urogenic causes, with renal parenchymal disease being the most common benign nephrogenic cause, and common benign urogenic causes including urolithiasis, infection, and benign prostatic hypertrophy 1. Some of the key 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. The evaluation of hematuria should involve a thorough history, physical examination, urinalysis, and serologic testing, with cystoscopy and imaging studies as needed, particularly in patients with gross hematuria or those at high risk for malignancy 1. It is essential to seek medical attention promptly if blood is noticed in the urine, as it may indicate a serious condition requiring treatment, and diagnosis typically involves urinalysis, imaging studies, and possibly cystoscopy to visualize the bladder, with the underlying mechanism usually involving damage to blood vessels in the urinary tract, allowing red blood cells to leak into urine 1. Some key points to consider in the evaluation of hematuria include:

• The definition of microhematuria as three or more red blood cells per high power field on microscopic evaluation of urinary sediment from a properly collected, noncontaminated urinalysis 1
• The importance of considering risk factors for cancer, such as age, gender, and smoking history, when evaluating hematuria 1
• The need for a thorough history, physical examination, and serologic testing in the evaluation of hematuria, in addition to urinalysis and imaging studies as needed 1
• The potential for gross hematuria to be a presenting sign of occult cancer, and the importance of urgent urologic evaluation in these cases 1. Overall, the evaluation and management of hematuria should be guided by the principles of high-value care, with a focus on minimizing unnecessary testing and treatment while ensuring prompt diagnosis and treatment of underlying conditions, particularly malignancies 1.

From the Research

Causes of Hematuria

• Hematuria can be caused by various factors, including:
  • Infection
  • Kidney stones
  • Trauma
  • Exercise
  • Spurious causes, such as foods, drugs, or menstruation
  • Tumors 2
• Approximately 20% of patients with hematuria have a urological tumor, and a further 20% are found to have significant underlying pathology 2
• Bladder cancer is a significant cause of hematuria, with 70-80% of patients experiencing painless, gross hematuria 2

Evaluation of Hematuria

• When evaluating a patient with hematuria, primary care physicians must answer three key questions:
  1. Is it really hematuria?
  2. Should this patient with hematuria be worked up, and if so, how?
  3. Should this patient with hematuria be referred, and if so, to which specialty? 3
• The evaluation and management of hematuria can range from benign conditions such as urinary tract infection to serious conditions such as bladder cancer 3