The kidneys play a critical role in the body: Acting as the body's filtering system, they help control water levels and eliminate wastes through urine (pee). They also help regulate blood pressure, red blood cell production, and the levels of calcium and minerals.
But sometimes the kidneys don't develop properly and, as a result, don't function as they should. Often these problems are 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 medication or surgery while the child is still young. Other problems may appear later, with symptoms such as urinary tract infections (UTIs), growth problems, or high blood pressure (hypertension).
In some cases, the problems can be severe and require surgical treatment.
How the Kidneys Work
The kidneys are like the body's garbage collection and disposal system. Through microscopic units called nephrons, the kidneys remove waste products and extra water from the food a person eats, returning chemicals the body needs (such as sodium, phosphorus, and potassium) back into the bloodstream. The extra water combines with other waste to become urine, which flows through thin tubes called ureters to the bladder, where it stays until it exits through the urethra (the tube that carries urine out of the body from the bladder) when someone goes to the bathroom.
The kidneys also produce three important hormones:
- erythropoietin, which stimulates the bone marrow to make red blood cells;
- renin, which helps regulate blood pressure; and
- the active form of vitamin D, which helps control the calcium balance in the body and maintain healthy bones.
Kidney failure, which is also called renal failure, is when the kidneys slow down or stop properly filtering wastes from the body, which can cause buildups of waste products and toxic substances in the blood. Kidney failure can be acute (sudden) or chronic (happening over time and usually long lasting or permanent).
Acute kidney injury (sometimes called acute kidney failure) may be due to bacterial infection, injury, shock, heart failure, poisoning, or drug overdose. Treatment includes correcting the problem that led to the kidney injury and, in some cases, dialysis .
- Chronic kidney failure involves a deterioration of kidney function over time. In kids and teens, it can result from acute kidney failure that fails to improve, birth defects, chronic kidney diseases, or chronic severe high blood pressure. If diagnosed early, chronic kidney failure can be treated. The goal of treatment usually is to slow the decline of kidney function with medication, blood pressure control, and diet. At some point, a kidney transplant may be needed.
Childhood Kidney Diseases
The most common kidney diseases in children are present at birth. They include:
- Posterior urethral valve obstruction: This narrowing or obstruction 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 enlargement of one or both of the kidneys is caused by either an obstruction in the developing urinary tract or a condition called vesicoureteral reflux(VUR) in which urine abnormally flows backward (or refluxes) from the bladder into the ureters. Fetal hydronephrosis is usually diagnosed before the child is born and treatment varies widely. In some cases the condition only requires ongoing monitoring; in others, surgery must be done to clear the obstruction from the urinary tract.
- Polycystic kidney disease (PKD): This is a condition in which many fluid-filled cysts develop in both kidneys. The cysts can multiply so much and grow so large that they lead to kidney failure. Most forms of PKD are inherited. Doctors can diagnose it before or after the child is born. In some cases, there are no symptoms; in others, PKD can lead to UTIs, kidney stones, and high blood pressure. Treatment for PKD varies — some cases can be managed with dietary changes; others require a kidney transplant or dialysis.
- Multicystic kidney disease (MKD): This is when large cysts develop in a kidney that hasn't developed properly, eventually causing it to stop working. (While PKD always affects both kidneys, MKD usually affects just one kidney.) Fortunately, the unaffected kidney takes over and most people with MKD will have normal kidney function. MKD usually is diagnosed by prenatal ultrasound before birth. Doctors manage it by monitoring blood pressure and screening for UTIs when needed. Very rarely, surgical removal of the kidney might be necessary.
- Renal tubular acidosis
- Wilms tumor
- Nephrotic syndrome
Congenital problems with the urinary tract: As a baby develops in the womb, part of the urinary tract can grow to an abnormal size or in an abnormal shape or position. These problems include:
- duplication of the ureters, in which a kidney has two ureters instead of one. This can lead to urinary tract infections over time and can be treated with medication or, in some cases, with surgery.
- horseshoe kidney, where the two kidneys are fused (connected) into one arched kidney that usually functions normally, but is more prone to develop problems later in life. An uncomplicated horseshoe kidney does not need medical or surgical treatment, but it does need to be checked regularly by doctors.
Other Problems With the Kidneys
Sometimes a child can have other health problems that affect how well the kidneys function. These can include:
Symptoms of Kidney Problems
The signs and symptoms of urinary tract or kidney problems vary and include:
- swelling around the eyes, face, feet, and ankles (called edema)
- burning or pain during peeing
- significant increase in the frequency of urination
- difficulty in controlling urination in kids who are mature enough to use the toilet
- recurrence of nighttime bedwetting (in kids who have been dry for several months)
- blood in the urine
- high blood pressure
Diagnosis of Kidney Diseases
If a kidney disease is suspected, the doctor will take a medical history, do a physical 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 specializes in the diagnosis and treatment of kidney diseases.
With urinalysis (a type of urine test), the doctor can quickly detect abnormalities (such as too many red blood cells) that may signal inflammation or irritation in the urinary tract. Urinalysis can also detect an of excess white blood cells, which is most commonly associated with bladder and kidney infections.
Certain blood tests tell doctors how well the kidneys are filtering waste products and balancing the bloodstream's chemical makeup.
Two other important diagnostic tools doctors use are blood pressure and growth measurements. Along with the heart, the kidneys are crucial to determining blood pressure. High blood pressure in a child is an important sign that the kidneys need to be evaluated. Accurate growth measurements can provide a clue to diagnosing some kidney diseases because kids with chronic kidney disease often have growth problems.
The doctor may use a kidney biopsy to evaluate kidney function. A biopsy is a procedure in which a small piece of the kidney tissue is removed with a needle. Performed while a child is under anesthesia, it's a simple procedure that can help make an accurate diagnosis of the kidney problem in about 9 out of 10 cases. It's especially helpful in the diagnosis of nephritis and nephrosis.
In addition to standard X-rays, other imaging studies a doctor may use to help diagnose kidney diseases include:
- Computerized tomography (CAT) scan
- Renal nuclear scan. A renal nuclear scan involves having special radioactive material injected into a vein. The radiation dose is less than that of a simple X-ray. The scan shows how the kidneys compare with each other in size, shape, and function. It also can detect scarring or other evidence of recurrent or chronic kidney infection.
- Voiding cystourethrogram (VCUG)