Welcome to the first of our Q & A sessions with Alan S. L. Yu, M.D. Dr. Yu is a practicing nephrologist as well as a professor and scientist with a lab at USC Keck School of Medicine. Visit http://ukrocharity.org/about-ukro/medical-scientific-advisory-board/alan-s-l-yu-md/ for more information about Dr. Yu and his research.
Q: So we decided to start with a really simple question. Can you tell me why we have two kidneys?
A: Actually that is a great question!
Having two kidneys is not essential for adult life. Adults who donate one kidney for transplantation, or who undergo unilateral nephrectomy for some reason, live a normal lifespan and have no increased risk of complications. Thus, we assume that the reason we have two kidneys is so that there is some extra reserve of kidney mass in case we sustain some renal insult (e.g. toxic injury, or traumatic injury).
Having said that, about 1 in 1000 individuals are born with one kidney (unilateral renal agenesis). The limited data available suggest that these individuals have an increased risk of hypertension, proteinuria and focal segmental glomerulosclerosis in later life. Whether this is because of the reduced renal mass since birth, or because of some other factor is unclear.
Q: Why exactly is the kidney mass important?
A: The kidney is made up of nephrons, whose job is to filter, secrete and reabsorb solutes and water. More kidney mass = more nephrons.
So there you have it. If you have any questions or comments regarding this Q & A, please post them on our blog or on Facebook and we will get them answered. Special thanks to my friend Karen for suggesting this first question! And if you have a new question you’d like answered, just ask. We can’t dispense medical advice, but we can certainly enlighten you on the workings of the kidney and kidney disease.