Supernumerary Kidneys

  According to Rehder et al. (2019), the term for normally 1, but can be two, additional kidneys are supernumerary kidneys (SK), with the estimated number of occurrences being 1:26,750. Most people, if they have supernumerary kidneys, only have one additional kidney, which is normally on the left side. It is hard to know, however, truly how many people have supernumerary kidneys because unless there are additional problems, people normally do not have the scans needed to reveal the additional kidneys. Some of these problems could include kidney infections or problems with the ureters. Supernumerary kidneys are much rarer than the more common duplex kidneys, with the latter being fused with the regular kidney and having the same blood supply. With the additional kidneys, the ureters, which drain the kidneys, can also have variation, with some ureters joining to the ureter of the kidney below, which is more common, or each kidney having its own ureter. Altogether, to show the rarity of this condition, Rehder et al. (2019) looked at scans of 461,500 people taken between 2000 and 2017 and found 9 with the condition. 

I am very interested in supernumerary kidneys because I was diagnosed with two additional kidneys when I was younger. What led to this diagnosis was that I would constantly have kidney infections, which were caused by a problem in one of my ureters. While my parents don’t remember much of what the doctors told them about the condition, I do have a scan of my four kidneys. Mine are currently all still functioning, which according to the article is pretty rare since only two of the people that they found with SKs had fully functional ones. As well as having two SKs, on one side I have two separate ureters, while on the other side, both kidneys are connected to the same ureter. This article highlights how SKs can have an increased morbidity rate, but it explains further that this increase is normally caused by complications from unneeded surgery due to misdiagnosis because of how rare they are. I almost experienced this, with the first set of doctors misdiagnosing and telling my mom that I had cysts on my kidneys and would die within a year. Luckily, the next doctors discovered the problem and fixed the small issue with my ureter by stretching the tube out at the connection to the kidney. 

Reference:
Rehder, P., Rehwald, R., Böhm, J. M., Grams, A. E., Loizides, A., Pedrini, M., Stühmeier, J., & Glodny, B. (2019). Supernumerary kidneys: a clinical and radiological analysis of nine cases. BMC Urology, 19(1). https://doi.org/10.1186/s12894-019-0522-0