Premature babies typically have smaller kidneys and fewer nephrons, which are responsible for filtering the blood. This can negatively impact kidney function.

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Each year, it’s estimated that around 15 million babies are born prematurely worldwide, accounting for about 11% of all live births.

Preterm births — those between 20–37 weeks of gestation — are associated with many health problems and can interrupt a baby’s growth and development.

Babies born prematurely are also more susceptible to kidney dysfunction, impacting their ability to remove waste products from the blood and produce urine.

This article will cover some of the signs and symptoms, causes, and treatments of kidney problems in premature infants.

Premature infants tend to have smaller kidneys and fewer nephrons, which are the functional units of the kidney responsible for filtering the blood.

Though a baby’s kidneys usually mature quickly after birth, problems balancing the body’s fluids, salts, and wastes can occur during the first 4–5 days of life, especially in babies less than 28 weeks of gestation.

During this time, a baby’s kidneys may have difficulty:

  • Filtering waste: This can create a blood imbalance of substances like potassium, urea, and creatinine.
  • Concentrating urine: This means getting rid of wastes from the body without excreting excess fluids.
  • Producing urine: This can be a problem if the kidneys were damaged during delivery or if the baby has been without oxygen for a prolonged period of time.

Though many kidney issues can often be managed with medical treatment, some research suggests that preterm infants may be at a higher risk of neonatal acute kidney injury and several other conditions later in life, including high blood pressure, chronic kidney disease, and proteinuria, or protein in the urine.

Monitoring children who were born preterm throughout childhood and adolescence is important. Some signs of kidney problems — such as high blood pressure or increased creatine or albumin levels in the blood — may develop later and may be identified before other symptoms.

Because the kidneys are responsible for producing urine, kidney dysfunction may cause low or no urine output (oliguria or anuria) in preterm infants.

Swelling of the extremities, such as the arms or legs, can also occur due to fluid buildup in the body.

However, kidney problems, such as kidney dysplasia, may not cause symptoms if only one kidney is affected.

Premature birth can interrupt the development of the kidneys, resulting in fewer nephrons and smaller kidneys.

A 2019 study found that around 60% of nephrons are formed during the third trimester of pregnancy.

This can make it more challenging for a baby’s kidneys to filter the blood, produce urine, and balance fluid levels.

Other factors that can contribute to kidney dysfunction may include:

  • genetics
  • lack of oxygen, protein, or micronutrients during fetal development
  • inflammation
  • blood clots in the kidneys
  • exposure to compounds that can harm the kidneys, including certain medications

Because of the potential for kidney problems, a doctor may record the amount of urine a baby produces after birth to ensure that the kidneys function properly.

This is usually necessary in significantly premature babies or babies with certain underlying conditions. It is not needed if the baby is slightly preterm and otherwise healthy.

They may also test the blood for certain markers used to evaluate kidney function, including:

  • potassium
  • urea
  • creatinine
  • cystatin C

Staff must also be watchful when giving medications, especially antibiotics, to make sure that the medicines are excreted from the body.

Treatment options for kidney problems in preterm infants can vary depending on the specific cause, symptoms, and severity.

In many cases, balancing electrolyte and fluid levels is key. This may involve administering insulin or glucose infusions, fluids, medications such as diuretics, or sodium bicarbonate (baking soda).

Additionally, providing adequate nutrition while avoiding fluid overload, electrolyte imbalances, and high blood sugar levels is also important. Protein or fluid intake may also sometimes need to be limited.

Infusions with albumin, a type of protein produced by the liver, might also be beneficial in some cases.

Peritoneal dialysis, a treatment that helps remove waste products from the blood through a small catheter in the stomach, may be recommended, as well.

Premature infants often have health problems, which can affect many parts of the body.

Some of the most common conditions in premature babies include:

  • Respiratory distress syndrome: This is a breathing problem that occurs because the lungs of preterm infants often lack surfactant, a substance that helps the lungs expand.
  • Bronchopulmonary dysplasia: Also known as chronic lung disease, this condition often affects premature infants and requires treatment with oxygen therapy.
  • Apnea: Preterm infants often experience apnea, characterized by a pause in breathing of more than 15 seconds. It can also cause a decrease in heart rate, also known as bradycardia.
  • Jaundice: This condition occurs because the liver cannot filter excess bilirubin levels in the blood.
  • Anemia of prematurity: This type of anemia is common in premature infants and is characterized by a low level of red blood cells.

Can a baby survive with small kidneys?

Kidney atrophy, or a smaller than typical kidney, is often a congenital problem, meaning that it’s present from birth. In this case, it doesn’t usually require any medical treatment or cause any negative effects on health.

However, if this condition occurs due to a blocked blood supply or chronic infection, treatment is required to help maintain kidney function and prevent kidney failure.

Can a newborn survive kidney failure?

The prognosis for kidney failure depends on many factors, including the cause and severity. However, early diagnosis and treatment may help improve outcomes.

Can a baby live a normal life with one kidney?

Having only one kidney from birth is called renal agenesis. In most cases, babies born with one kidney are able to lead a healthy life if the kidney is working well. There is a chance of mild kidney function loss later in life, usually after at least 25 years. Regular check-ups with a pediatrician or primary care doctor are recommended.

Preterm infants are at an increased risk of developing kidney problems, affecting the body’s ability to filter waste products from the blood and produce urine.

Monitoring a baby’s urine output and kidney function is essential and can help diagnose kidney problems early to improve outcomes.

Treatment may involve balancing electrolyte and fluid levels, ensuring that the baby receives adequate nutrition. In cases when the baby’s kidneys are nearly losing function, the baby may need peritoneal dialysis, which can help remove waste products from the blood.