Hematuria (III)

This is the 3077th article of Da Yi Xiao Hu

Hematuria refers to blood in the urine. If the amount of bleeding is large, it is visible to the naked eye, which is called macroscopic hematuria. If the amount of bleeding is small, the blood is often not visible to the naked eye and must be found under a microscope, which is called microscopic hematuria. If urination is done soon after bleeding, the urine may be bright red; if the bleeding stays in the bladder for a period of time before being discharged, it may become dark brown; in severe bleeding, there may be blood clots in the urine.

When urine is tested, if the red blood cell count exceeds 3 per high-power field of view, it is clinically diagnosed as hematuria. Hematuria is a common symptom of urinary system diseases, and some diseases outside the urinary system can also cause hematuria. Previously, it was discussed that red urine is not necessarily hematuria, and common urological and non-urological diseases that cause hematuria. This is the last article in the hematuria series.

Decoding doctors' thinking on diagnosing and treating hematuria

When encountering patients who are suspected of hematuria, urologists generally diagnose and treat according to the following ideas:

(1) Is it hematuria? (Qualitative)

(2) Where in the urinary tract does it occur (location)

(3) What is the cause? (Determine the cause.)

First, we need to determine whether it is true hematuria, that is, we must rule out false hematuria and red urine caused by certain reasons. As mentioned above, we can go to the hospital to test urine to see if there are red blood cells in it. If the red blood cell count under each high-power microscope field exceeds 3, it is clinically diagnosed as hematuria.

Secondly, after confirming that it is true hematuria, it is necessary to perform a localized diagnosis of hematuria, which can be judged based on the appearance of macroscopic hematuria.

(1) Initial hematuria: There is blood only in the urine at the beginning of urination, and then the urine gradually becomes clear, indicating that the bleeding site is in the urethra or bladder neck.

(2) Terminal hematuria: There is blood only in the urine at the end of urination, indicating that the bleeding site is located in the trigone of the bladder.

(3) Entire hematuria: The urine excreted during the entire urination process contains blood, indicating that the bleeding site is above the bladder neck.

There is also urethral hemorrhage, which is the involuntary flow or dripping of blood from the urethra, unrelated to the act of urination. The bleeding site is generally located below the urethral sphincter.

For patients who have microscopic hematuria but not macroscopic hematuria, a "three-cup urine test" can be performed during urine testing. The so-called "three-cup urine test" means that after cleaning the vulva and the external urethral opening, in a complete urination process, the first 10 to 20 mL of urine is left in the first cup, the middle 30 to 40 mL of urine is left in the second cup, and the final 5 to 10 mL of urine is left in the third cup. If there is blood only in the first cup of urine, it is initial hematuria; if there is hematuria only in the second or third cup, it is terminal hematuria; if there is hematuria in all three cups, it is full-course hematuria.

Urinalysis can also help distinguish whether hematuria comes from the renal parenchyma or the urothelium. If casts are found in urine sediment, especially red blood cell casts, it indicates that the bleeding comes from the renal parenchyma; hematuria accompanied by more severe proteinuria is almost always a sign of glomerular hematuria; in hematuria caused by glomerular diseases, most of the red blood cells are deformed, with different shapes and sizes.

Finally, other auxiliary examinations are also needed, such as imaging examinations (such as B-ultrasound, excretory urography, CT), cytology (urine exfoliated cells), endoscopy (cystoscopy, ureteroscopy), tissue biopsy pathology, etc., combined with medical history and physical examination, to conduct a comprehensive analysis to help accurately locate and identify the cause. Hematuria occurs in many diseases of the human body and can be divided into two categories: urological diseases and non-urological diseases. However, in actual practice, it is sometimes very difficult to determine the cause of hematuria. Some patients even undergo many tests and still cannot be determined in the end.

What to do if the cause of hematuria is unknown?

As mentioned earlier, it is sometimes very difficult to determine the cause of hematuria in actual clinical practice. Some patients even undergo many tests and still cannot determine it in the end. In professional works on urology, there is a special category of hematuria called idiopathic hematuria, which means hematuria without any clear cause. What should patients do for whom the cause of hematuria cannot be determined for the time being? When I see patients in the outpatient clinic, after taking the medical history, physical examination, routine examinations such as urine test and urinary system B-ultrasound, if there is no need for further examination, or the patient is unwilling to undergo invasive examinations (such as cystoscopy), I generally recommend that patients closely follow up with urine tests and urinary system B-ultrasound for dynamic observation, and do not need to worry too much about persistent small amounts of microscopic hematuria. However, if suspicious problems, such as tumors, are found in the medical history and preliminary examinations, timely follow-up is required.

Author: Shanghai Fifth People's Hospital Affiliated to Fudan University

Wang Wei, deputy chief physician