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Hi, I’m Em and I’m taking part in #GlobalScienceShow! Today I will be answering the age old question “how many kidneys can you fit in a human body?”. You can follow along the whole show at @GlobalSciShow and check out @physicsjo who is up next! #Pint20 #GlaSciFest #SciComm [1/19]
This is one of the strangest/best questions I’ve ever been asked by a school pupil, and today I am (finally) going to work out the answer! Disclaimer: I am a biologist but I am not an anatomist or surgeon so apologies in advance if some of my calculations are a bit off. [2/19]
Firstly, we need to know how big a kidney is. A good estimate for a kidney size is making a fist shape with your hand. After lots of googling, I’m going to be using 134cm3 as my average kidney size. [3/19]
Before we get into it, how many (extra) kidneys do you think you could fit in the human body (by this I mean the main torso) and still keep the vital organs? [4/19]
The internal organs in the torso can be roughly divided into two group: vital and non-vital organs. I’m going to start by working out which of our non-vital organs we could get rid of to make more space for our extra kidneys. [5/19]
The function of the appendix is poorly understood, it might store ‘good’ bacteria or might be an evolutionary leftover. I’ve lived without mine for 10 years, so we can definitely get rid of that. The appendix is very small (~ping pong ball), so gains us 0.03 more kidney. [6/19]
The gallbladder aids in digestion by storing bile - if removed, bile just keeps moving continuously from the liver to the digestive system, which is fine. It’s pretty small (tennis ball size), so that’s another 0.06 kidneys. [7/19]
Let’s assume our torso has female reproductive organs. These are routinely removed for various reasons, the only repercussions being the need to take hormone replacements. In total, these organs are about half the size of a kidney. [8/19]
Spleen removals are fairly common, if a bit more major than our last few. The spleen’s jobs in blood filtration and immune response can be taken over by the liver and the lymphoid tissue. The spleen is our biggest organ so far gaining us 1.15 more kidneys. [9/19]
The Pancreas has important roles in producing enzymes and hormones. Losing the entire pancreas means you’re unable to produce insulin, but removing half still allows for some insulin production and a fairly normal life. Half a pancreas buys us a third of a kidney. [10/19]
Sick of storing urine inside your body? Removing your bladder and having a conduit (a tube from your kidneys to an external storage bag) might be for you! Bladders are surprisingly big, so we’ve just gained 2.2 more kidneys! [11/19]
Our digestive system is made up of lots of bits, and we don’t need all of it really. It is possible to bypass the stomach by connecting the oesophagus to the small intestine. The stomach is pretty big, so that’s another 22 and a bit kidneys! [12/19]
The small intestine is pretty important, especially after removing the stomach, but the large intestine can be largely removed. The large intestine is, unsurprisingly, pretty large and wins us 17 more kidneys. [13/19]
Onto our vital organs then, which are the heart, lungs, liver, kidneys and brain (which isn’t usually in the torso, so we’ll leave that one be). We’ll leave the heart alone, but let’s see what we can do with the liver and lungs. [14/19]
Our liver is pretty important, and we are relying on it for taking over some of the jobs of the gallbladder and spleen. However, we can remove half with little impact, and as the heaviest internal organ, taking out half gains us 5 more kidneys! [15/19]
Most of us have two lungs, but living with one lung is a well documented condition. Lungs are pretty big, so that’s 22 more kidneys. [16/19]
Maths time! Most people are born with two kidneys, but it is possible to be born with four. With all the organs we removed, we’ve gained space for 71 extra kidneys! That means we could theoretically fit a whopping 75 kidneys in a human torso! [17/19]
Of course, it’s important to note that our extra 71 wouldn’t be functional, as the extra wiring and tubing that would be needed to hook them up would loose us a lot of space. This hypothetical person would probably also need a fair amount of medical check-ups… [18/19]
Thanks for joining me on my quest to find out how many kidneys you could fit in the human torso! Remember to follow the rest of the show using the hashtag #GlobalScienceShow. [19/19]
