CaliToday (22/8/2025): A 38-year-old man went to a hospital in Brazil suffering from severe lower back pain. Doctors initially diagnosed him with a herniated disc, a common cause for such symptoms. However, when they performed a CT scan to confirm, they discovered something completely unexpected and incredibly rare: the man didn't have two kidneys, but three.
Remarkably, he had lived his entire 38 years as a perfectly normal life without ever knowing about the extra "spare part" inside his body. He had no pain, no symptoms, and not a single clue about his unusual anatomy.
What is a Supernumerary Kidney?
This medical condition is known as a supernumerary kidney. It is an extremely rare congenital anomaly, with fewer than 100 cases recorded in global medical literature. It occurs when a third, completely separate kidney develops during fetal formation.
- Anatomy: Typically, an individual with this condition will have one normal kidney on one side of the body and two kidneys on the other. The extra kidney is usually smaller than the normal ones and may be fused to the other kidney on the same side.
- Function: In most cases, all three kidneys are fully functional. Each kidney often has its own separate ureter (the tube that carries urine to the bladder), but sometimes two of them may merge and drain into a single shared ureter.
- Symptoms: The vast majority of supernumerary kidney cases are asymptomatic. This is why most people with the condition live their entire lives without knowing they have it. It is usually discovered by accident when they undergo medical imaging for an unrelated issue, just like the case of the man with back pain.
A Defect or a Lucky Backup System?
This raises an interesting question: is having three kidneys a defect or an advantage?
- From a medical perspective: It is classified as a congenital anomaly or "defect" because it is a deviation from standard human anatomy. In a small number of cases, the extra kidney can cause complications such as urinary tract blockages, kidney stones, or infections.
- From a "lucky" perspective: If all three kidneys are healthy and functioning normally, it can be seen as a natural "backup system." Theoretically, if one of the three kidneys were to fail or need to be removed due to injury or disease, the body would still have two healthy kidneys left to perfectly maintain its blood-filtering function. This also means a person with three kidneys could potentially donate one to a relative and still live a healthy life with two remaining kidneys.
