Your kidneys are fist-sized organs shaped like beans that are located at the back of the middle of your trunk, in the area called your flank. They are under the lower part of your ribcage on the right and left sides of your backbone.

Their main job is to filter waste out of your blood and produce urine to remove that waste along with extra fluid from your body.

When your kidney hurts, it usually means there’s something wrong with it. It’s important to determine whether your pain is coming from your kidney and or from somewhere else so that you receive the right treatment.

Because there are muscles, bones, and other organs around your kidney, it’s sometimes hard to tell if it’s your kidney or something else causing your pain. However, the type and location of the pain and other symptoms you are having can help point to your kidney as the source of your pain.

Kidney pain is usually a constant dull ache deep in your right or left flank, or both flanks, that often gets worse when someone gently hits the area.

Only one kidney is usually affected in most conditions, so you typically feel pain on only one side of your back. If both kidneys are affected, the pain will be on both sides.

Symptoms that may accompany kidney pain include:

  • blood in your urine
  • fever and chills
  • frequent urination
  • nausea and vomiting
  • pain that spreads to your groin
  • pain or burning when you urinate
  • recent urinary tract infection

Kidney pain is a sign that there is something wrong with one or both of your kidneys. Your kidney may hurt for these reasons:

  • There’s an infection, which is called pyelonephritis.
  • There’s bleeding in the kidney.
  • There’s a blood clot in the vein connected to your kidney, which is called renal vein thrombosis.
  • It’s swollen because your urine is backing up and filling it with water, which is called hydronephrosis.
  • There’s a mass or cancer in it, but this usually only becomes painful when it gets very large.
  • There’s a cyst in your kidney that’s getting bigger or has ruptured.
  • You have polycystic kidney disease, which is an inherited condition in which many cysts grow in your kidneys and can damage them.
  • There’s a stone in your kidney, but this usually doesn’t hurt until it has passed into the tube connecting your kidney and bladder. When it does hurt, it causes severe, sharp pain.

Kidney pain is almost always a sign that something is wrong with your kidney. You should see your doctor as soon as possible to determine what’s causing your pain.

If the condition that has caused kidney pain isn’t treated promptly and appropriately, your kidneys can stop working, which is called kidney failure.

It’s especially important to see your doctor right away if your pain is severe and started suddenly because this is often caused by a serious problem — such as renal vein thrombosis or bleeding into your kidney — that needs emergency treatment.