The Kidney Connection: Renal Agenesis and CBAVD
At a Glance
About 11% to 12% of men with Congenital Bilateral Absence of the Vas Deferens (CBAVD) are also born missing one kidney. Because the reproductive and urinary systems develop from the same structure, the standard of care is for all men diagnosed with CBAVD to undergo a kidney ultrasound.
When you are diagnosed with CBAVD, your doctor will likely recommend looking at an organ that seems completely unrelated to your fertility: your kidneys. This is because the reproductive system and the urinary system are “developmental neighbors” [1].
The Embryological Link
During the first few weeks of life in the womb, the male reproductive tract and the kidney collecting system both grow from the same structure, called the Wolffian duct (or mesonephric duct) [2][3].
- The Wolffian duct eventually becomes the epididymis and the vas deferens [3].
- A small bud, called the ureteric bud, grows off the side of this same duct to form the kidneys [2][4].
Because they share this common “parent” structure, a developmental “hiccup” that prevents the vas deferens from forming can also prevent one of the kidneys from developing [1][5].
Unilateral Renal Agenesis (URA)
About 11% to 12% of men with CBAVD are also born with Unilateral Renal Agenesis (URA)—the medical term for being born with only one kidney [6][7].
Most men with URA have no idea they are missing a kidney because the remaining kidney is usually healthy and grows slightly larger to handle the work of two [6]. It does not cause pain or obvious symptoms, and it is usually only discovered during a routine ultrasound for infertility [8][9].
The Genetics of the Kidney Connection
The relationship between kidneys and genetics in CBAVD is very revealing. Specialists often use the presence or absence of a kidney to help guess the underlying genetic cause:
- CFTR-Related CBAVD: When the cause is a CFTR mutation (linked to Cystic Fibrosis), it is usually a “late” developmental issue where the tubes form but then waste away. In these cases, the kidneys are almost always present and normal [1][10].
- Non-CFTR CBAVD: When a man is missing both a vas deferens and a kidney, he is less likely to have a CFTR mutation [11][12]. This suggests the developmental issue happened much earlier in the womb, affecting the entire Wolffian duct before the kidneys could even start to grow [1].
Standard of Care: Kidney Screening
Because you cannot “feel” a missing kidney during a physical exam and standard blood tests often look normal, the standard of care for any man diagnosed with CBAVD is a transabdominal ultrasound [6][9]. This is a painless, non-invasive scan to confirm you have two functioning kidneys.
Living with One Kidney
If you find out you have only one kidney, the news is generally very positive. Most people with a single healthy kidney live full, normal lives without restriction [6]. However, there are a few long-term health considerations:
- Monitoring: You should have your blood pressure and kidney function (via a simple urine or blood test) checked annually, as a single kidney can be more sensitive to high blood pressure over many decades [6].
- Protection: It is wise to mention your single-kidney status to doctors before starting certain medications (like long-term high-dose ibuprofen) that can be hard on the kidneys.
Knowing your kidney status provides a clearer picture of your overall health and helps your care team understand the root cause of your CBAVD.
Common questions in this guide
Why do men with CBAVD need a kidney ultrasound?
Does missing a kidney mean my CBAVD is caused by a CFTR mutation?
Will being born with only one kidney affect my long-term health?
Are there symptoms if I am born missing a kidney?
Questions to Ask Your Doctor
Curated prompts to bring to your next appointment.
- 1.Since I have CBAVD, do I need a transabdominal ultrasound to check if I am missing a kidney?
- 2.If I am missing a kidney, does that make it more or less likely that my CBAVD is caused by a CFTR gene mutation?
- 3.Does having only one kidney put me at a higher risk for high blood pressure or other long-term health issues?
- 4.Are there any medications or lifestyle habits I should avoid if I only have one functioning kidney?
- 5.How often should I have my remaining kidney’s function checked?
Questions For You
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References
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This page is for informational purposes only and does not replace professional medical advice. Always consult your urologist or healthcare provider regarding CBAVD, kidney screening, and genetic testing.
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