My Baby Has Renal Agenesis (Absent Kidney)
Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist
Content reviewed against published NIH, AAP, Children's Hospital guidelines
Last reviewed:
If your baby has been diagnosed with or you suspect has renal agenesis (absent kidney), here is what the evidence says.
The short answer
Renal agenesis means one or both kidneys did not develop. Unilateral renal agenesis (one kidney missing) occurs in about 1 in 1,000 births and is usually found incidentally on imaging - the remaining kidney compensates by growing larger and typically provides completely normal kidney function. Bilateral renal agenesis (both kidneys missing) is fatal and results in Potter sequence due to absence of fetal urine and amniotic fluid. For unilateral renal agenesis, the prognosis is generally excellent, though the single kidney should be protected and monitored throughout life.
Key takeaways
- Renal agenesis means one or both kidneys did not develop. Unilateral renal agenesis (one kidney missing) occurs in about 1 in 1,000 births and is usually found incidentally on imaging - the remaining kidney compensates by growing larger and typically provides completely normal kidney function. Bilateral renal agenesis (both kidneys missing) is fatal and results in Potter sequence due to absence of fetal urine and amniotic fluid. For unilateral renal agenesis, the prognosis is generally excellent, though the single kidney should be protected and monitored throughout life.
- Usually normal when: Your baby has one functioning kidney that is working well and growing to compensate
- Call your doctor if: Your baby has a high fever with no clear source, which could be a UTI and requires urgent evaluation to protect the only kidney
- Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
Parents everywhere have the same worry. You are doing the right thing by looking into it.
What Parents Should Know
According to NIH, AAP, Children's Hospital guidelines, renal agenesis means one or both kidneys did not develop. Unilateral renal agenesis (one kidney missing) occurs in about 1 in 1,000 births and is usually found incidentally on imaging - the remaining kidney compensates by growing larger and typically provides completely normal kidney function. Bilateral renal agenesis (both kidneys missing) is fatal and results in Potter sequence due to absence of fetal urine and amniotic fluid. For unilateral renal agenesis, the prognosis is generally excellent, though the single kidney should be protected and monitored throughout life. At Prenatal, unilateral renal agenesis may be detected on prenatal ultrasound when only one kidney is visible, or it may be missed. The remaining kidney often undergoes compensatory hypertrophy (grows larger). Amniotic fluid levels are usually normal with one functioning kidney. Bilateral renal agenesis causes severe oligohydramnios (very low amniotic fluid) leading to Potter sequence: pulmonary hypoplasia (underdeveloped lungs), characteristic facial features, and limb abnormalities. Bilateral renal agenesis is not compatible with life. It is generally considered normal when your baby has one functioning kidney that is working well and growing to compensate. However, you should contact your pediatrician promptly if your baby has a high fever with no clear source, which could be a UTI and requires urgent evaluation to protect the only kidney.
Normal vs. Concerning
When to Seek Immediate Care
- Your baby has a high fever with no clear source, which could be a UTI and requires urgent evaluation to protect the only kidney
- Your child has blood in the urine, especially after an injury
- Your child has signs of decreased kidney function: significant swelling, decreased urine output, nausea, or fatigue
- Your child sustained a significant abdominal or flank injury and has pain, swelling, or blood in urine
- Your child has persistently elevated blood pressure
By Age
What to expect by age
Prenatal
Unilateral renal agenesis may be detected on prenatal ultrasound when only one kidney is visible, or it may be missed. The remaining kidney often undergoes compensatory hypertrophy (grows larger). Amniotic fluid levels are usually normal with one functioning kidney. Bilateral renal agenesis causes severe oligohydramnios (very low amniotic fluid) leading to Potter sequence: pulmonary hypoplasia (underdeveloped lungs), characteristic facial features, and limb abnormalities. Bilateral renal agenesis is not compatible with life.
0-1 month
If unilateral renal agenesis is diagnosed or suspected, a renal ultrasound confirms the absence of one kidney and evaluates the remaining kidney. The solitary kidney is often already larger than expected (compensatory hypertrophy), which is a normal adaptive response. A VCUG (voiding cystourethrogram) may be recommended to check for vesicoureteral reflux in the remaining kidney. Kidney function tests (creatinine) are usually normal. Your baby will be referred to pediatric urology or nephrology for initial evaluation.
1-12 months
Your baby with a single kidney should grow and develop completely normally. The remaining kidney provides adequate function for a healthy life. Follow-up imaging may be done to monitor the solitary kidney. Prompt evaluation of fevers is recommended since UTIs need to be treated quickly to protect the only kidney. Your pediatrician will monitor blood pressure at routine visits, as people with a solitary kidney have a slightly higher risk of developing hypertension later in life.
1-5 years
Most children with a solitary kidney live entirely normal lives. Your pediatrician will monitor blood pressure and kidney function periodically. It is important to treat any UTIs promptly to protect the single kidney. As your child grows, discuss with your doctor whether contact sports that could cause kidney injury (like football or martial arts) should be limited or played with protective equipment. Adequate hydration and a healthy diet support kidney health.
5 years+
People with a single kidney generally have an excellent long-term prognosis. The main considerations are protecting the kidney from injury and monitoring kidney function and blood pressure over time. The American Academy of Pediatrics recommends individual risk assessment for contact sports rather than a blanket ban. Your child should know about their condition so they can inform future healthcare providers. Kidney donations from people with a solitary kidney are not possible, which is important for family planning purposes.
What to Tell Your Pediatrician
- Describe when you first noticed has renal agenesis (absent kidney) and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your baby has an unexplained fever that could indicate a UTI - prompt evaluation protects the single kidney.
- Mention if you have questions about activity restrictions or sports participation for your child.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Your baby has one functioning kidney that is working well and growing to compensate
- Kidney function tests are normal
- Blood pressure is normal at routine checks
- Your baby is growing and developing at expected rates
- You are following up with nephrology or urology as recommended
- Your baby has an unexplained fever that could indicate a UTI - prompt evaluation protects the single kidney
- You have questions about activity restrictions or sports participation for your child
- You want to discuss long-term monitoring for your child's solitary kidney
- You are concerned about genetic implications for future pregnancies
- Your baby has a high fever with no clear source, which could be a UTI and requires urgent evaluation to protect the only kidney
- Your child has blood in the urine, especially after an injury
- Your child has signs of decreased kidney function: significant swelling, decreased urine output, nausea, or fatigue
- Your child sustained a significant abdominal or flank injury and has pain, swelling, or blood in urine
- Your child has persistently elevated blood pressure
What You Can Do at Home
- Keep track of when you notice has renal agenesis (absent kidney) — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your baby has one functioning kidney that is working well and growing to compensate — this is generally within the range of normal.
- At Prenatal, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
- While monitoring at home, seek immediate care if your baby has a high fever with no clear source, which could be a UTI and requires urgent evaluation to protect the only kidney.
Related Conditions
20-Week Anatomy Scan Unexpected Findings
The 20-week anatomy scan checks your baby's major organs, structures, and growth. Most scans are completely normal. When unexpected findings are identified, they range from minor variants that resolve on their own to conditions that need further evaluation. Many findings require nothing more than a follow-up ultrasound to confirm the baby is developing well.
My Baby Has a Horseshoe Kidney
A horseshoe kidney is the most common kidney fusion anomaly, occurring in approximately 1 in 400-600 people. The lower portions of both kidneys are fused together by a bridge of tissue (isthmus), forming a U or horseshoe shape. Most horseshoe kidneys are found incidentally on imaging done for other reasons and cause no problems at all. People with horseshoe kidneys have a slightly higher risk of urinary tract infections, kidney stones, and hydronephrosis (urine backup), but many go through life without ever knowing they have this condition.
Related Resources
Frequently asked questions
Is has renal agenesis (absent kidney) normal?
When should I call the doctor about has renal agenesis (absent kidney)?
When is has renal agenesis (absent kidney) normal?
What causes has renal agenesis (absent kidney)?
What should I mention to my pediatrician about has renal agenesis (absent kidney)?
Is has renal agenesis (absent kidney) normal at Prenatal?
Is has renal agenesis (absent kidney) normal at 0-1 month?
Should I go to the ER for has renal agenesis (absent kidney)?
Does has renal agenesis (absent kidney) go away on its own?
References
- [1]National Institutes of Health. Unilateral Renal Agenesis. Genetic and Rare Diseases Information Center (GARD), 2024. NIH
- [2]Urology Care Foundation. Solitary Kidney. American Urological Association, 2024. AAP
- [3]Boston Children's Hospital. Renal Agenesis. Children's Hospital
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss My Baby Has Renal Agenesis (Absent Kidney).
Things to mention
- Describe when you first noticed has renal agenesis (absent kidney) and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your baby has an unexplained fever that could indicate a UTI - prompt evaluation protects the single kidney.
- Mention if you have questions about activity restrictions or sports participation for your child.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- Your baby has an unexplained fever that could indicate a UTI - prompt evaluation protects the single kidney
- You have questions about activity restrictions or sports participation for your child
- You want to discuss long-term monitoring for your child's solitary kidney
Urgent signs to report immediately
- Your baby has a high fever with no clear source, which could be a UTI and requires urgent evaluation to protect the only kidney
- Your child has blood in the urine, especially after an injury
- Your child has signs of decreased kidney function: significant swelling, decreased urine output, nausea, or fatigue
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members
Related Resources
Bottom line
Most cases of has renal agenesis (absent kidney) are normal. Talk to your pediatrician if your baby has a high fever with no clear source, which could be a uti and requires urgent evaluation to protect the only kidney.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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The 20-week anatomy scan checks your baby's major organs, structures, and growth. Most scans are completely normal. When unexpected findings are identified, they range from minor variants that resolve on their own to conditions that need further evaluation. Many findings require nothing more than a follow-up ultrasound to confirm the baby is developing well.
My Baby Has a Horseshoe Kidney
A horseshoe kidney is the most common kidney fusion anomaly, occurring in approximately 1 in 400-600 people. The lower portions of both kidneys are fused together by a bridge of tissue (isthmus), forming a U or horseshoe shape. Most horseshoe kidneys are found incidentally on imaging done for other reasons and cause no problems at all. People with horseshoe kidneys have a slightly higher risk of urinary tract infections, kidney stones, and hydronephrosis (urine backup), but many go through life without ever knowing they have this condition.
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