I can only imagine the whirlwind of emotions when you first hear the words. Maybe it was during a routine pregnancy scan, the sonographer suddenly quiet, pointing to an image that didn’t look quite… complete. Or perhaps it was after your little one arrived, and tests started revealing something unexpected. Hearing that your baby might be missing a kidney, or even both, is a shock. It’s okay to feel overwhelmed. We’re here to walk through what renal agenesis means, together.
What Exactly is Renal Agenesis?
So, let’s break it down. “Renal” is just our medical way of saying “kidneys.” And “agenesis”? That means an organ didn’t quite finish forming while your baby was developing in the womb. So, renal agenesis simply means your baby was born without one or, much more rarely, both kidneys. Most of us have two, and they’re pretty important – they filter waste from our blood, which we then pee out. You absolutely need at least one functioning kidney to live.
There are two main types we see:
- Unilateral renal agenesis: “Uni” means one. So, your child is missing one kidney. The good news? Many children with this live perfectly full and healthy lives. Often, the remaining kidney steps up, growing a bit larger to do the work of two. It’s quite amazing, really.
- Bilateral renal agenesis: “Bi” means two. This is when a baby is born without either kidney. This is much tougher, I won’t sugarcoat it. Often, the tubes that carry urine (we call them ureters) are missing too, and very critically, the baby’s lungs are usually small and underdeveloped (a condition called pulmonary hypoplasia). When these things happen together, it’s known as Potter syndrome, and sadly, it’s often fatal.
Unilateral renal agenesis happens in about 1 out of every 2,000 babies. Bilateral is rarer, maybe 1 in 8,500 newborns, and for reasons we don’t fully understand, it seems to affect little boys more often.
Why Does Renal Agenesis Happen?
This is the big question every parent asks. Most of the time, renal agenesis is linked to a change, or what we call a mutation, in a gene. Think of genes as the instruction manual for building a body. If there’s a tiny typo in the instructions for kidney development, they might not form correctly. This usually happens very early in pregnancy, in the first trimester.
Sometimes, other things might play a role, though these are less common:
- Having gestational diabetes (diabetes during pregnancy).
- Expecting more than one baby (twins, triplets).
- Using certain medications during pregnancy.
Now, about how it’s passed on. It can be a bit different for the two types:
- Unilateral renal agenesis often follows what we call an autosomal dominant pattern. This means if one parent has the gene change (and they might even have the condition themselves), there’s a 50/50 chance of passing it to each child.
- Bilateral renal agenesis can sometimes be autosomal recessive. This is a bit more complex. It means both parents carry a copy of the changed gene (but don’t have the condition themselves). If a child inherits that specific changed gene from both parents, then they might develop bilateral renal agenesis. In this scenario, with each pregnancy, there’s a 1 in 4 chance the baby will have it, a 1 in 2 chance they’ll be a carrier like the parents, and a 1 in 4 chance they won’t get the gene change at all.
It’s a lot to take in, I know. Genetic counselors are wonderful at explaining these patterns in more detail if it’s relevant to your family.
Spotting the Signs of Renal Agenesis
For a baby born with bilateral renal agenesis (Potter syndrome), the signs are usually immediate and serious. Because their lungs haven’t developed properly, they’ll have significant breathing problems right after birth.
With unilateral renal agenesis, your little one might not show any symptoms at all, especially when they’re young. The one kidney often does a brilliant job. If symptoms do appear, they might include:
- High blood pressure (yes, even in children).
- Higher than normal protein levels in their urine (we call this proteinuria).
- Something called vesicoureteral reflux, where urine flows backward from the bladder up towards the kidney.
Some children with one kidney might also have other things going on, like:
- Clubfoot.
- Heart conditions they were born with, like an atrial septal defect (ASD) or ventricular septal defect (VSD) (holes between the heart chambers).
- Other differences in their urinary tract or genitals.
- An imperforate anus, where the opening for stool hasn’t formed.
How We Figure This Out: Diagnosis
Often, we get the first clue about renal agenesis during pregnancy. Routine prenatal ultrasounds can show if the kidneys are present. They can also show if there’s a low level of amniotic fluid (the fluid surrounding the baby in the womb). This is called oligohydramnios. A baby’s urine actually makes up a lot of this fluid, so if the kidneys aren’t working or aren’t there, fluid levels can drop. This low fluid is what impacts lung development.
If it’s not picked up before birth, or if it’s unilateral and not causing early problems, we might discover it later. Perhaps your child has symptoms that lead us to do some scans, or maybe an ultrasound is done for another reason, like a urinary tract infection (UTI), and we spot it then.
The imaging tests we might use include:
- Abdominal ultrasound or kidney ultrasound (these are the same, just focused on the kidney area).
- A CT scan.
- An MRI.
Navigating Treatment and What to Expect
The path forward really depends on whether one or both kidneys are affected.
For Bilateral Renal Agenesis
This is, as I said, a very challenging situation. Historically, babies born without any kidneys and with underdeveloped lungs usually couldn’t survive for more than a few hours. However, there’s some hope on the horizon with new, experimental treatments. These involve carefully injecting a sterile saltwater solution (saline) into the womb during pregnancy to try and mimic amniotic fluid, giving the lungs a chance to develop. After birth, the baby would need dialysis (a machine to clean the blood) right away, until they are strong enough for a kidney transplant. It’s important to know this is still very new and not widely available, but it’s a step. About 40% of fetuses with this condition sadly don’t make it to term (stillbirth) or are born very early (premature birth).
For Unilateral Renal Agenesis
The outlook here is generally much brighter. Your baby might be born a bit early or be smaller, perhaps needing some time in the neonatal intensive care unit (NICU).
The main thing is protecting that one precious kidney. Up to half of children born with one kidney might develop some kidney-related issues by the time they’re 30, such as:
- High blood pressure.
- Proteinuria.
- Chronic kidney disease, which in some cases can progress to end-stage kidney disease, possibly needing dialysis or a kidney transplant down the line.
So, how do we manage this?
- Sometimes, medications are needed to keep blood pressure in a healthy range.
- Regular check-ups with a nephrologist (that’s a kidney specialist) are key. These will likely be yearly, or more often if needed.
- At these visits, we’ll do a physical exam, check urine (urinalysis), and sometimes do imaging.
- We’ll also keep an eye on how well the kidney is working with kidney function tests and urine protein tests.
There are also things you can do as a family to help protect that single kidney:
- Follow a kidney-friendly diet, often similar to the DASH diet. This usually means lower salt and sugar, and plenty of fiber and potassium. Your doctor or a dietitian can guide you.
- Be careful with medications. Some common painkillers like nonsteroidal anti-inflammatory drugs (NSAIDs) can be hard on kidneys. Acetaminophen is usually a safer choice, but always check with us.
- Maintaining a healthy weight and staying active is great. However, we generally advise against high-contact sports – things like football, competitive soccer, or martial arts – just to reduce the risk of an injury to that solitary kidney.
- Learning to check blood pressure at home can be helpful.
What Does the Future Hold?
For most children with one kidney, the future is bright. They can lead full, active lives. The key is regular monitoring to catch any potential issues early. For the very rare cases of bilateral renal agenesis, while the road is incredibly tough, those experimental therapies are offering a sliver of hope where there was very little before.
If there’s a known gene mutation in your family linked to renal agenesis, a genetic counselor can be an invaluable resource. They can talk about the risks for future pregnancies and options like preimplantation genetic diagnosis (PGD), which can be used with in vitro fertilization (IVF) to select embryos without the gene change.
When to Reach Out to Us
It’s always important to be aware. If your child (or you, if you have unilateral renal agenesis) starts showing any signs that might suggest kidney trouble, please give us a call. Things like:
- Sudden confusion or memory issues.
- Peeing less than usual.
- Swelling (edema) in the legs, feet, or ankles.
- Feeling extremely tired (fatigue).
- Headaches.
- Really itchy skin (pruritus).
- Loss of appetite.
- Muscle cramps.
- Feeling sick to the stomach (nausea) or vomiting.
One Last Thing: Renal Agenesis vs. Kidney Dysplasia
You might hear another term, kidney dysplasia, and wonder if it’s the same. It’s a bit different. With renal agenesis, a kidney is missing. With kidney dysplasia, there are two kidneys, but one (or sometimes both) didn’t develop properly – it might be small or not work as well as it should.
Take-Home Message: Key Points on Renal Agenesis
I know this is a ton of information. Let’s boil it down to the essentials:
- Renal agenesis means being born with one (unilateral) or no (bilateral) kidneys.
- Unilateral is more common; many live normal lives with careful monitoring.
- Bilateral is rare and very serious, often linked to underdeveloped lungs (Potter syndrome).
- Gene changes are a common cause.
- Diagnosis can happen during pregnancy via ultrasound or later in life.
- Management for unilateral renal agenesis focuses on protecting the remaining kidney through diet, lifestyle, and regular check-ups.
- Experimental treatments offer some hope for bilateral cases, but it’s early days.
- Always talk to us about any concerns or new symptoms.
This journey might feel daunting, especially at first. But please know you’re not alone in this. We’re here to support you and your child every step of the way, providing the best care and information we can.