Blood in Urine (Haematuria) — Nephrologist

What is haematuria?

Haematuria simply means blood in the urine. It comes in two forms. Visible (macroscopic) haematuria turns the urine pink, red or cola-coloured and is obvious to the naked eye. Microscopic haematuria is invisible and detected only when a urine test reveals red blood cells under the microscope, often as an incidental finding during a routine check-up.

Both types matter. Visible blood is always a reason for prompt evaluation, but persistent microscopic blood should never be ignored either, because it can be the first sign of significant kidney or urinary-tract disease.

Kidney (nephrological) causes

When bleeding originates in the kidneys themselves, the cause often lies in the filtering units:

• Glomerulonephritis — inflammation of the glomeruli, which can leak blood and protein together. This is a classic nephrological cause and may follow an infection or accompany an autoimmune condition.
• Kidney stones — these can scratch the urinary tract and cause bleeding, usually with severe loin-to-groin pain.
• Kidney cysts and polycystic kidney disease — cysts can bleed, sometimes painlessly.
• Kidney cancer — less common but important to exclude, particularly when bleeding is painless.

A useful clue is that kidney-origin blood is often associated with protein in the urine, abnormally shaped red cells, raised blood pressure or a rise in creatinine.

Urological versus nephrological causes

Not all blood in urine comes from the kidneys. Urological causes include bladder infections, bladder or prostate tumours, an enlarged prostate, and stones lower in the tract. Distinguishing urological from nephrological bleeding shapes the entire workup: nephrological causes are managed by a kidney specialist, while urological causes may need a urologist and imaging of the bladder.

How urgent is evaluation?

Visible blood in the urine should be assessed without delay, even if it settles on its own and even if there is no pain. Painless visible haematuria in particular must always be investigated, because it can be the only early sign of a tumour. Persistent microscopic blood, while less urgent, still warrants a structured assessment rather than a wait-and-see approach.

What the workup involves

A nephrologist works through the problem methodically:

• Urine testing — confirming red cells, checking for protein, and examining red-cell shape, which helps localise the source.
• Blood tests — creatinine, eGFR and markers of inflammation or autoimmune disease.
• Blood pressure measurement — often raised when the kidney is the source.
• Imaging — a kidney ultrasound or CT scan to look for stones, cysts or masses.
• Onward referral — to urology for cystoscopy when a bladder or prostate source is suspected.

What you should do

If you ever see blood in your urine, do not wait for it to happen again — arrange an assessment. Bring any recent blood or urine results with you. Early evaluation is the difference between catching a serious cause in time and missing a narrow window for treatment.

Dr. Juan Luis Villaro Gumpert evaluates haematuria at Hospital Vithas 9 de Octubre in Valencia, working in English and Spanish and coordinating with urology when a urinary-tract cause is suspected.