Why does sickle cell disease cause blood in urine?

The kidneys filter blood and make urine through a network of very small vessels. In sickle cell disease, red blood cells can change shape and affect flow in these vessels, particularly in the kidney’s inner area. This can allow blood to enter the urine, which may look pink, red, brown or tea-coloured. Blood in Urine is a common presentation of Sickle Cell Disease, but blood in urine also has other possible causes and should be assessed rather than assumed to be from sickle cell disease.

Contact your sickle cell team or a clinician promptly whenever blood is visible in the urine. They may ask about pain, fever, clots, recent dehydration, medicines and changes in urine amount, then arrange urine and blood tests or imaging if appropriate. Drink fluids in line with your usual medical advice unless you have been told to limit fluids. Keep a note of the urine colour and any associated symptoms, but do not delay assessment to monitor it at home.

Seek urgent medical care now for heavy bleeding, blood clots, inability to pass urine, severe side or abdominal pain, fever with feeling very unwell, dizziness, fainting, or a marked reduction in urine. Emergency assessment is also appropriate when symptoms are rapidly worsening. These signs can indicate a problem needing prompt treatment, whatever the underlying cause of the bleeding.

Ask whether the bleeding is likely from the kidney or another part of the urinary tract, which tests are needed, and whether your current medicines need review. Ask what hydration plan suits you and exactly when recurrent bleeding, pain or reduced urine output should lead to urgent care.