“One’s Company, two’s a crowd, and three’s a party.” Right? While that may be true for people, it certainly isn’t true for our organs.
Normally, human beings are born with a single pair of kidneys, one on either side. However, there have been reports of people being born with just one kidney and surviving without any major complications. But, possessing three kidneys? That’s something that’s hardly ever heard of.
A recent case published in the New England Journal of Medicine (NEJM), reports the incidental finding of three kidneys in a man being evaluated for back pain. The 38-year old had presented to the Hospital do Rim in São Paulo, Brazil, with a history of severe lower back pain. The doctors referred him for a computed tomography (CT) scan to investigate the origin of his back pain.
The CT scan was successful in diagnosing the patient with a herniated disk in the lumbar region between L4 and L5. But, that’s not all. To their surprise, the scan also showed the presence of three kidneys; a normal-appearing one on the left and two fused kidneys below in the pelvis. The right kidney was seen to be directly connected to the bladder via a ureter. However, on the left side, the ureter from the left pelvic kidney was seen to join the ureter from the other left kidney just above its entrance into the bladder. The ureter is usually a single tube on either side that directs urine from the kidney to the bladder.
Supernumerary Kidneys – How do they arise?
During fetal development, the kidneys are formed from a single ureteral bud and are later seen to ascend from the pelvic to the abdominal region. This particular renal abnormality, known as supernumerary kidneys, seems to have occurred due to premature division of the left ureteral bud. Additionally, the right and lower left kidneys fused and failed to ascend to the abdomen during development.
According to studies, there are currently less than 100 such cases in the medical literature of supernumerary kidneys.
Despite the unusual anatomy, the man was not found to have any renal symptoms and his renal function tests were completely normal. His back pain was attributed to the herniated disk and he was sent home with oral painkillers.
Foresto, R. D., & Medina-Pestana, J. O. (2020, May 7). Three Kidneys. The New England Journal of Medicine, 382:1843.
Mejia, M., Limback, J., Ramirez, A., & Burt, J. R. (2018). A Case of Supernumerary Kidney. Cureus, 10(12), e3686.