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The kidneys

The kidneys do vital work in the body filtering blood removing waste into urine, and balancing electrolyte levels.

Our blood in our bodies passes through the kidneys several times a day.

Picture of the Human Kidney

The kidneys are located at the back of the abdomen. Each kidney is about the size of a fist - 10-12.5cm long.

Each kidney contains millions of tiny filters called nephrons. These filter blood and the waste product they produce is urine. This passes through tubes called ureters into the bladder.

A person can sometimes lose as much as 90% of their kidney function without noticing.

A person can survive with just one kidney if the other is lost through an accident, disease, or is donated to someone else.

If both kidneys fail, a person will need kidney dialysis or a kidney transplant to stay alive.

Kidney conditions

Conditions affecting the kidneys include:

  • Kidney infection (pyelonephritis) often causing back pain and fever. The infection often spreads to the kidneys from the bladder.
  • Glomerulonephritis, where the body's immune defence mistakenly attacks the kidneys. Symptoms can include blood in urine and kidney failure.
  • Kidney stones, crystals can build-up in the kidneys which can cause blockages and can be very painful.
  • Nephrotic syndrome, where protein is released into the urine by damaged kidneys.
  • Polycystic kidney disease, this genetic condition causes large cysts in the kidneys affecting how they work.
  • Acute kidney failure (acute renal failure, acute kidney injury), where the kidneys stop working for some time. This can be caused by dehydration, infection or a blockage.
  • Chronic kidney failure (long-term renal failure), causing a permanent loss of some kidney function, often due to diabetes complications or high blood pressure.
  • End-stage renal failure (ESRF), meaning a complete loss of kidney function.
  • Renal papillary necrosis, where tissue breaks up inside a kidney causing blockages or kidney failure.
  • Diabetic nephropathy, long-term high blood sugar from unmanaged diabetes can cause kidney damage and protein in the urine.
  • Hypertensive nephropathy, damage to kidneys from high blood pressure over time.
  • Kidney cancer, with renal cell carcinoma being the most common type of kidney cancer.
  • Interstitial nephritis, with inflammation of connective tissue inside the kidney.
  • Minimal change disease, a type of nephrotic syndrome where there are problems despite cells looking almost normal under a microscope.
  • Nephrogenic diabetes insipidus (NDI), where the kidneys are unable to concentrate the urine, usually due to a medication reaction.
  • Renal cyst, a benign space in the kidney.


Kidney tests

Kidney tests include:

  • Urinalysis: Urine tests for kidney or bladder issues, sometimes with a special dipstick with colour changes to indicate problems, or with laboratory tests.
  • Urine cultures: Cultures of urine samples are grown in the laboratory to help identify bacteria before antibiotics are given.
  • Kidney ultrasound: To look for blockages, kidney stones, cysts or other problems.
  • CT scan: to get a clearer image than with an ultrasound.
  • MRI scan: High definition images of the kidneys created using a magnetic field.
  • Kidney biopsy: Sample of kidney tissue taken with a special needle for laboratory testing.
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