What Do the Kidneys Do?

The kidneys have many important jobs. As the body's filtering system, they help control water levels and get rid of wastes through urine (pee). They also help control blood pressure, red blood cell production, and the levels of calcium and minerals.

Tiny units called nephrons remove waste products and extra water from the food we eat, returning chemicals the body needs (such as sodium, phosphorus, and potassium) to the bloodstream. The extra water mixes with other waste to become urine. Urine flows through thin tubes called ureters to the bladder, where it stays until it leaves the body through the urethra when someone pees.

The kidneys also make three important hormones:

• erythropoietin, which stimulates the bone marrow to make red blood cells
• renin, which helps regulate blood pressure
• the active form of vitamin D, which helps maintain healthy bones and control the body's calcium balance

What Is Kidney Disease?

In kidney disease, the kidneys don't work as they should. Many things can cause problems, such as when:

• The blood doesn't flow to the kidneys as well as it should.
• Tissues of the kidneys are damaged.
• The flow of urine from the kidneys gets blocked and causes kidney damage.

What Can Cause Kidney Disease in Kids?

Sometimes the kidneys don't develop properly before a baby is born, so they don't work as they should. These problems are often genetic and not due to anything a parent did or didn't do. Many of these problems can be diagnosed before a baby is born through routine prenatal testing and treated with medicine or surgery while the child is still young.

Kidney diseases that babies can be born with include:

• Posterior urethral valve obstruction: This narrowing or blockage of the urethra affects only boys. It can be diagnosed before the baby is born or just after and is treated with surgery.
• Fetal hydronephrosis: This is when one or both kidneys become enlarged, either by an obstruction in the developing urinary tract or a condition called vesicoureteral reflux (VUR) in which pee flows backward (or refluxes) from the bladder into the ureters. It's usually diagnosed before birth and treatment varies widely. In some cases, it only requires ongoing monitoring; in others, a child will need surgery to clear the urinary tract blockage.
• Polycystic kidney disease (PKD): This is when many fluid-filled cysts develop in both kidneys. The cysts can multiply so much and get so big that they lead to kidney failure. Most types of PKD run in families. Doctors can diagnose PKD before birth or after the child is born. Sometimes it causes no symptoms. But other kids can have UTIs, kidney stones, and high blood pressure. Treatment varies — sometimes, PKD is managed with diet changes; other kids will need a kidney transplant or dialysis.
• Multicystic kidney disease (MKD): This is when large cysts form in a kidney that hasn't developed properly, eventually causing it to stop working. Because MKD usually affects just one kidney, the unaffected kidney often can take over. So, most kids with the condition will have normal kidney function. MKD usually is found on a prenatal ultrasound before birth. Doctors manage it by monitoring blood pressure and screening for UTIs when needed. Very rarely, the affected kidney might need to be removed surgically.
• Congenital problems with the urinary tract: As a baby develops in the womb, part of the urinary tract can grow to an unusual size or in an unusual shape or position. These problems include:
  • duplication of the ureters: A kidney has two ureters instead of one, which can lead to urinary tract infections over time. It's treated with medicine or, in some cases, surgery.
  • horseshoe kidney (renal fusion): The two kidneys are fused (connected) into one arched kidney. The kidney usually works normally but is more likely to develop problems later. A child who has an uncomplicated horseshoe kidney won't need medical or surgical treatment, but will be checked regularly by doctors.

Other kidney conditions that can affect children include:

• renal tubular acidosis
• Wilms tumor
• glomerulonephritis
• nephrotic syndrome

Sometimes a child can have other health problems that affect how well the kidneys work, such as:

• high blood pressure (hypertension)
• kidney stones
• nephritis. This is any inflammation of the kidney. It can be caused by infection, an autoimmune disease (such as lupus), or an unknown reason. The first symptoms of nephritis usually are high levels of protein and blood in the urine.
• urinary tract infections (UTIs)

What Is Kidney Failure?

Kidney failure, also called renal failure, is when the kidneys slow down or stop properly filtering wastes from the body. This can cause buildups of waste products and toxic substances in the blood.

Kidney failure can be acute (sudden) or chronic (happening over time and long-lasting):

• Acute kidney failure (acute kidney injury) may be due to a bacterial infection, injury, shock, heart failure, poisoning, or drug overdose. Doctors will treat the problem that caused the injury, though some kids will need dialysis.
• Chronic kidney failure (chronic kidney disease) happens when kidney function declines over time. In kids and teens, it can happen due to a problem they were born with, acute kidney failure that doesn't get better, chronic kidney diseases, or chronic severe high blood pressure. Chronic kidney disease that's found early can be treated. The goal of treatment usually is to slow the decline of kidney function with medicine, blood pressure control, and diet. Sometimes, a person will need a kidney transplant.

What Are the Signs & Symptoms of Kidney Problems?

Kids with urinary tract or kidney problems might:

• have a fever
• have swelling around the eyes, face, feet, and ankles (called edema)
• feel burning or pain during peeing
• need to pee often
• have trouble controlling their peeing, if potty trained
• have nighttime bedwetting (after being dry for several months)
• have blood in the urine (hematuria)
• have high blood pressure

How Are Kidney Diseases Diagnosed?

If a kidney disease is suspected, the doctor will take a medical history, do an exam, and order urine tests, blood tests, imaging studies, or a biopsy to help make a diagnosis. These studies are usually suggested by a nephrologist (a doctor who diagnoses and treats kidney problems).

With urinalysis (a type of urine test), the doctor can quickly find problems (such as too many red blood cells) that may a sign of inflammation or irritation in the urinary tract. It also can see if there are too many white blood cells, a sign of a bladder and kidney infection.

Some blood tests tell doctors how well the kidneys are filtering waste products and balancing the bloodstream's chemical makeup.

Doctors also will check a child's:

• blood pressure: Along with the heart, the kidneys are vital to a healthy blood pressure. High blood pressure in a child is an important sign that the kidneys need to be checked.
• growth: Accurate growth measurements are important because kids with chronic kidney disease often have growth problems.

The doctor may use a kidney biopsy to check kidney function. This simple procedure to get and test a tissue sample can help doctors make an accurate diagnosis of a kidney problem in most cases.

Besides standard X-rays, doctors also might order these imaging studies:

• renal ultrasound
• computerized tomography (CAT) scan
• renal nuclear scan: A small amount of special radioactive material (less than that of a simple X-ray) is injected into a vein. The scan shows how the kidneys compare with each other in size, shape, and function. It also can detect scarring or other signs of recurrent or chronic kidney infection.
• voiding cystourethrogram (VCUG)

What Else Should I Know?

If your child has a kidney condition, turn to the care team for help and support before, during, and after treatment.

It also can help to find a support group. The care team might be able to recommend one in your area. You also can find more information online at:

• National Kidney Foundation
• Renal Support Network