Yes, kidney stones very frequently lead to blood in the urine, a condition known as haematuria. Because stones are hard, crystalline masses with often jagged or irregular edges, they can scrape and irritate the delicate lining of the urinary tract as they move from the kidney toward the bladder. This irritation causes the lining to bleed, which can turn the urine pink, red, or even brown. While this is a hallmark sign of kidney stones, it is almost always accompanied by significant pain and requires a formal medical diagnosis to manage safely.
What We’ll Discuss in This Article
- The physical mechanism of how stones cause bleeding
- Differentiating between visible and non-visible blood in stone cases
- Common symptoms that occur alongside haematuria
- How the location of the stone affects the appearance of blood
- Diagnostic tests used by the NHS to confirm kidney stones
- When blood and pain become a medical emergency
How Kidney Stones Cause Bleeding
Kidney stones (nephrolithiasis) develop when waste products in the blood form crystals that collect inside the kidneys. Over time, these crystals build up to form a hard, stone-like lump. When a stone stays in the kidney, it may not cause any symptoms at all. However, if it starts to move into the ureter the narrow tube connecting the kidney to the bladder it can cause a blockage and physical trauma.
The ureter is a muscular tube designed to move liquid, not solid objects. As the stone is pushed through, its sharp edges can scratch the mucosal lining (the ‘skin’ inside the tube). This is like a graze on your skin, but because it happens inside the urinary tract, the resulting blood mixes with the urine. According to the British Association of Urological Surgeons (BAUS), haematuria is present in approximately 85% to 90% of patients with symptomatic kidney stones.
The Journey of a Stone
| Location | Potential for Bleeding | Typical Pain Type |
| Kidney Calyx | Low (unless very large) | Dull ache in the back |
| Ureter | High (due to friction) | Intense, ‘colicky’ waves of pain |
| Bladder | Moderate | Discomfort when finishing urination |
| Urethra | High (during passage) | Sharp, stinging sensation |
Visible vs. Non-Visible Blood
While many people with kidney stones see blood (macroscopic haematuria), it is even more common for the blood to be ‘non-visible’ (microscopic haematuria). This means the urine looks normal to the naked eye, but a urine dipstick test or a microscopic lab exam will reveal the presence of red blood cells.
Research indicates that even if the urine appears clear, the presence of microscopic blood combined with ‘loin-to-groin’ pain is a strong clinical indicator of a stone. In UK emergency departments, a urine dipstick is one of the first tests performed on anyone presenting with sudden side pain to check for these hidden red blood cells.
Symptoms Accompanying Blood in Urine
It is rare for a kidney stone to cause visible blood without other noticeable symptoms. The most characteristic sign is ‘renal colic’ a severe, cramping pain that often comes in waves.
Stone Symptom Checklist
- Severe Pain: Usually felt in the side of the tummy (flank) or the back, often radiating down to the groin.
- Nausea and Vomiting: The intense pain can frequently make patients feel or be sick.
- Urinary Urgency: Feeling a constant, strong need to pee, even if very little comes out.
- Restlessness: Patients often find it impossible to stay still, pacing around to try and find a comfortable position.
Differentiation: Kidney Stones vs. UTI
Because both kidney stones and urinary tract infections (UTIs) can cause blood in the urine, GPs use specific clues to tell them apart.
| Feature | Kidney Stones | Urinary Tract Infection (UTI) |
| Nature of Pain | Sudden, excruciating waves | Burning or stinging during urination |
| Urine Clarity | Usually clear (but red/pink) | Often cloudy or smelly |
| Fever | Rare (unless an infection is also present) | Common (especially if in the kidneys) |
| Movement | Patient cannot sit still | Patient often stays still |
To Summarise
Kidney stones are a very common cause of visible blood in the urine. The bleeding occurs due to the physical irritation and scratching of the urinary tract lining as the stone attempts to pass. While the sight of blood can be frightening, it is the accompanying pain that usually drives patients to seek medical help. Most stones are diagnosed through a combination of urine tests and imaging, such as a CT scan or ultrasound.
If you experience severe, sudden, or worsening symptoms, call 999 immediately.
Can a kidney stone cause blood without any pain?
It is possible, especially if the stone is sitting quietly in the kidney, but most stones cause pain when they start to bleed or move.
How long does the bleeding last?
The blood usually persists as long as the stone is moving or causing irritation. It should clear once the stone is passed or treated.
Can drinking more water help?
Yes, increasing fluid intake is the primary recommendation to help ‘flush’ the stone through, which eventually stops the bleeding.
Do all kidney stones require surgery?
No, many small stones (under 5mm) pass on their own with pain relief and hydration, but larger stones may need laser or soundwave treatment.
Is it dangerous if my urine is dark red from a stone?
The colour can be alarming, but the actual volume of blood lost is usually small. However, you must see a doctor to rule out other causes.
Can a stone cause protein in the urine too?
Yes, the presence of blood and the stress on the kidney can often lead to a ‘positive’ result for protein on a dipstick test.
What is a ‘CT KUB’ scan?
It is a specific type of CT scan used in the UK to look at the Kidneys, Ureters, and Bladder to locate and measure stones.
Authority Snapshot
This article was reviewed by Dr. Stefan Petrov, a UK-trained physician with experience in general medicine and surgical specialities. The information follows the clinical pathways for renal colic management established by the NHS and NICE. Our goal is to provide clear, factual guidance on why kidney stones cause bleeding and to help patients identify the specific symptoms that require professional medical investigation.
