Yes, a person can be born with only one kidney. This congenital condition is medically termed a solitary functioning kidney. While having a single kidney may raise concerns, the body possesses a remarkable ability to adapt. Most individuals are unaware they have it for many years, often discovering it incidentally during routine medical imaging for an unrelated issue.
Defining Congenital Solitary Kidney
Congenital solitary kidney is a condition where one kidney fails to develop completely during fetal growth. This failure to form the kidney is called unilateral renal agenesis (URA), which accounts for most cases. Another form of congenital solitary functioning kidney occurs when a person is born with two kidneys, but only one is functional. This typically happens when one kidney develops as a multicystic dysplastic kidney (MCDK), meaning it is non-functional and often shrinks over time. Both URA and MCDK are part of a broader group of conditions known as congenital anomalies of the kidney and urinary tract. The prevalence of being born with a single kidney is estimated to be approximately 1 in 1,000 to 1 in 2,000 live births. In some cases, a single kidney is associated with other anomalies, particularly in the reproductive system, such as Müllerian anomalies in females.
How the Single Kidney Compensates
The body’s primary response to the absence of one kidney is a physiological change known as compensatory hypertrophy. This natural adaptation causes the remaining single kidney to increase in both size and functional capacity. The enlargement occurs through cellular hypertrophy, where existing kidney cells grow bigger to handle the increased workload. The functional adaptation involves hyperfiltration, which takes place at the level of the nephrons, the kidney’s microscopic filtering units. Each nephron filters a greater volume of plasma, significantly increasing the single nephron glomerular filtration rate (SNGFR). This enhanced filtering effort allows the total Glomerular Filtration Rate (GFR)—a measure of overall kidney function—to often reach levels near that of two normal kidneys. However, this long-term increase in filtration pressure can potentially put the kidney under strain. This sustained hyperfiltration is believed to contribute to an elevated risk of developing issues like hypertension or protein in the urine over many decades.
Long-Term Health and Lifestyle Management
Individuals living with a single kidney generally lead full, normal lives but require consistent, focused health monitoring to protect their sole organ. Regular medical surveillance is recommended, typically involving annual or semi-annual check-ups with a healthcare provider. These appointments should include monitoring blood pressure, as hypertension is a common complication that can damage the kidney over time. Screening for proteinuria, or protein in the urine, is another important part of routine care, as this can be an early indicator of kidney stress. Early detection of either elevated blood pressure or proteinuria allows for timely intervention, such as medication, which can help preserve long-term kidney function.
Dietary and Hydration Management
Excellent hydration is advised to help the kidney efficiently process waste products and maintain fluid balance. Dietary considerations center on moderation, particularly avoiding excessively high protein intake, which increases the workload on the nephrons. While a low-protein diet is not necessary for a healthy single kidney, avoiding consumption of protein exceeding one gram per kilogram of body weight per day is a cautious approach. A balanced diet should also be low in sodium, with a goal of less than four grams per day, as high salt intake can contribute to elevated blood pressure and hyperfiltration.
Avoiding Contact Sports
A significant precautionary measure involves avoiding high-impact contact sports, such as football, hockey, boxing, and wrestling. Though the kidney is somewhat protected by the rib cage and surrounding muscle, a severe blow to the flank area could cause a life-threatening injury. For those participating in moderate-risk activities, wearing protective gear, such as padded vests, is appropriate to minimize the chance of trauma to the remaining organ.