A man recently discovered he was born with three kidneys after receiving medical scans for his back pain.
Reported in The New England Journal of Medicine (NEJM) this week, the 38-year-old man visited a hospital in the Brazilian city of São Paulo with low back pain from a slipped disk. A computed tomography (CT) scan showed that the man was suffering from a slipped disk, but it also incidentally revealed the presence of not two but three kidneys in his abdomen: a normal-appearing left kidney and two fused kidneys.
The ureter – the skinny tubes that propel pee from the kidneys into the bladder – from the left pelvic kidney joined the ureter from the other left kidney just above its entrance into the bladder, while the ureter from the right pelvic kidney entered the bladder on the right side.
"We had never seen anything like this," Dr Renato Foresto, one of the case study authors from Hospital do Rim in São Paulo, told IFLScience. "The surprise was great, followed by concern there was something wrong with the patient's health."
Oddly enough, the condition did not appear to affect the man’s health. Blood tests showed that his kidney function was normal and his wider health, except for the slipped disk, appeared to be fine. The patient was treated for his slipped disk with oral painkillers and sent on his way with no apparent complications.
"His renal function... was completely normal. Further investigation with abdominal ultrasound and tomography was considered sufficient since the cause of the pain had already been diagnosed and there were no other changes in laboratory tests," added Dr Foresto.
His doctors say his kidneys are an uncommon congenital abnormality that likely occurred during the embryonic development when a single primitive kidney-like structure splits in two. While extremely rare, this condition has been documented a number of times before. Known as a supernumerary kidney, there’s thought to be less than 100 cases of the condition officially reported in medical literature, including a number of case reports from over a century ago. One case report from 1915 reads: “true supernumerary kidney may be considered one of the rarest of all pathologic renal conditions.”
However, as the doctors of this case study explain, many people with a supernumerary kidney are not even aware of their condition. “Affected persons are commonly asymptomatic, and as in this case, the condition may not become known until imaging is performed for another reason,” the doctors write.
Another congenital condition that affects the placement of internal organs is known as Situs inversus, in which the organs are positioned in a mirror image from their normal positions. So, the heart is inside the right of the chest and the liver is found on the left side of the abdominal cavity. Much like a supernumerary kidney, people with Situs inversus are often unaware they have the condition until medical examinations incidentally bring them up.