Picture of the Kidneys

Picture of the Human Kidney
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The kidneys' job is to filter your blood. They remove wastes, control the body's fluid balance, and keep the right levels of electrolytes. All of the blood in your body passes through them several times a day.

Blood comes into the kidney, waste gets removed, and salt, water, and minerals are adjusted, if needed. The filtered blood goes back into the body. Waste gets turned into urine, which collects in the kidney's pelvis -- a funnel-shaped structure that drains down a tube called the ureter to the bladder.

Each kidney has around a million tiny filters called nephrons. You could have only 10% of your kidneys working, and you may not notice any symptoms or problems.

If blood stops flowing into a kidney, part or all of it could die. That can lead to kidney failure.

Kidney Conditions

  • Kidney stones (nephrolithiasis): Minerals in urine form crystals (stones), which may grow large enough to block urine flow. It's considered one of the most painful conditions. Most kidney stones pass on their own, but some are too large and need to be treated.
  • Polycystic kidney disease: A genetic condition resulting in large cysts in both kidneys that hinder their work.
  • Acute renal failure (kidney failure): A sudden worsening in how well your kidneys work. Dehydration, a blockage in the urinary tract, or kidney damage can cause acute renal failure, which may be reversible.
  • Chronic renal failure: A permanent partial loss of how well your kidneys work. Diabetes and high blood pressure are the most common causes.
  • End-stage renal disease (ESRD): Complete loss of kidney strength, usually due to progressive chronic kidney disease. People with ESRD require regular dialysis for survival.
  • Nephrogenic diabetes insipidus: The kidneys lose the ability to concentrate the urine, usually due to a drug reaction. Although it's rarely dangerous, diabetes insipidus causes constant thirst and frequent urination.
  • Renal cyst: A hollowed-out space in the kidney. Isolated kidney cysts often happen as people age, and they almost never cause a problem. Complex cysts and masses can be cancerous.


Kidney Tests

  • Computed tomography (CT) scan: A CT scanner takes a series of X-rays, and a computer creates detailed images of the kidneys.
  • Magnetic resonance imaging (MRI) scan: A scanner uses radio waves in a magnetic field to make high-resolution images of the kidneys.

Kidney Treatments

  • Antibiotics: Kidney infections caused by bacteria are treated with antibiotics. Often, cultures of the blood or urine can help guide the choice of antibiotic therapy.
  • Nephrostomy: A tube (catheter) is placed through the skin into the kidney. Urine then drains directly from the kidney, bypassing any blockages in urine flow.
  • Lithotripsy: Some kidney stones may be shattered into small pieces that can pass in the urine. Most often, lithotripsy is done by a machine that projects ultrasound shock waves through the body.
  • Nephrectomy: Surgery to remove a kidney. Nephrectomy is performed for kidney cancer or severe kidney damage.
  • Dialysis: Artificial filtering of the blood to replace the work that damaged kidneys can't do. Hemodialysis is the most common method of dialysis in the U.S.
  • Hemodialysis: A person with complete kidney failure is connected to a dialysis machine, which filters the blood and returns it to the body. Hemodialysis is typically done 3 days per week in people with ESRD.
  • Peritoneal dialysis: Placing large amounts of a special fluid in the abdomen through a catheter allows the body to filter the blood using the natural membrane lining the abdomen. After a while, the fluid with the waste is drained and discarded.
  • Kidney transplant: Transplanting a kidney into a person with ESRD can restore kidney function. A kidney may be transplanted from a living donor, or from a recently deceased organ donor.

WebMD Image Collection Reviewed by Minesh Khatri, MD on August 29, 2017




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