Blood in the urine (hematuria): what you should know

If the urine is reddish in color, it is important to pay attention. Blood in the urine must always be checked by a doctor. The causes often lie in the urinary tract, kidneys or prostate

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Urine sample with test strips: A change in urine color can have harmless but also pathological causes

© BrandXPictures / RYF

Blood in the urine: at a glance

  • Most common causes: urinary tract infections, urinary stones, kidney disease, blood from the bladder or intestines.
    In addition, bei women (before menopause):
    Endometriosis with growths of the lining of the uterus in the bladder and ureters
    Also in men:
    Diseases the prostate
  • Possible accompanying symptoms: burning sensation or pain when urinating, increased urination, changes in the amount of urine, pain in the lower abdomen or in the groin area, colic pain, fever.
    Also in women (before menopause): painful menstrual and intermenstrual bleeding
    Also in men: Blood in semen
  • Important technical terms:
    Blood in the urine: hematuria
    Blood in the urine visible to the naked eye: macrohematuria
    Blood in the urine, only visible in a urine test: microhematuria
  • Is blood in the urine dangerous? There is not always a disease behind it. There are quite harmless causes, such as discoloration from certain foods or drugs. Nevertheless, to be on the safe side, a doctor should check the findings and, if necessary, clarify the cause.
  • What to do? So always see a doctor if you notice that the urine is reddish in color.

What is hematuria?

It is always alarming when the urine suddenly turns red instead of yellow. But sometimes the reason is quickly found, the beetroot salad or a mushroom dish (for example certain types of irritant) for lunch, the dessert with the blueberry compote.

There are foods that not only color the tongue red or blue, they also temporarily leave traces of color in the urine.

But that has nothing to do with blood. One or two visits to the toilet later, the urine will be back to its normal color. It ranges from light to dark yellow. Some medications can also change the color of the urine (see below).

Blood in the urine, on the other hand, means that there are more red blood cells in the excreted fluid. Doctors speak of hematuria.

The urine then takes on a reddish tone, which can go from flesh-colored, pink or light red to bright red. Bloody urine very often has pathological causes. Sometimes, however, the reason for the hematuria remains unclear despite thorough examinations.

The majority of the identified causes are benign. Do not panic if you notice that the urine looks different, for example it is reddish in color or has traces of blood. However, consult the doctor in order to start the necessary examinations promptly. Usually there is the all-clear afterwards.

Figure 1: How the kidneys are structured and how the urine reaches the bladder and urethra via the ureter

© W & B / Martina Ibelherr

How is urine created?

The urine or urine is the filter product from the kidneys. These continually purify the blood flowing through them. To do this, like a filter, they squeeze out metabolic products, pollutants, salts and water. Blood cells and proteins usually remain in the blood.

Much of the water and salts required for the body also return to the circulation. The remaining concentrate, the urine, flows from the renal pelvis into the ureter and the urinary bladder. From there, it is released to the outside via the urethra and disposed of in this way (see Figure 1).

How does the blood get into the urine?

If the "filter stations" in the kidney malfunction, more red blood cells can get into the urine. Kidney diseases are possible triggers here.

Likewise, inflammation or tissue growth in the ureters and bladder sometimes leads to bleeding, which leaves visible traces in the urine (technical term: macrohematuria), recognizable from an admixture of one milliliter of blood per liter of urine.

Even the finest injuries to the mucous membrane in the lower urinary tract caused by mechanical stimuli, such as urinary stones, or increased vascular permeability can cause blood cells to leak into the urine.

Sometimes the amount of blood in the urine is so small that it cannot be seen with the naked eye (technical term: microhematuria). The doctor often only detects the red blood cells during urine tests, for example as part of a check-up for a urinary tract infection, a urinary stone or a prostate problem.

Urine strip tests, for example used as a self-test, are quite sensitive to red blood cells and can show a positive result for blood in the urine, even though there is no abnormal finding. Conversely, a test may be negative and blood may only appear intermittently in the urine. You should always leave the exact evaluation and use of urine test strips to the doctor (see also under "Urine examination"). You can also find out more at the pharmacy.