Author: Dr Peter de Souza
Last modified: 17 December 2020


This tutorial is on the kidneys. In this tutorial, I'm going to talk about the relations of the kidneys, its location and relation to other structures in the abdomen. And I'll talk about some of the external features of the kidneys. In another tutorial, I'll talk about the internal structure of the kidneys.

The function of the kidneys is really to filter blood and excrete waste and excess water as urine. It also regulates blood pressure, blood pH, blood volume and it's important in salt balance and electrolyte balance.


Let's just bring in some other structures in and take a look at the relative location of the kidneys. You can see here that they sit in the posterior abdominal wall. They sit either side of the vertebra. They sit at roughly the level of T12 down to L3. We've got T12 up here and L3 is down here.   They’re not quite shown as extending quite that far, but most textbooks say they extend from T12 down to L3.


If I just bring in the rest of the abdominal organs and fade away the muscles again, we can see how the kidneys sit behind these organs. They sit quite far back in the abdomen. They sit on the posterior abdominal wall. The kidneys are retroperitoneal, so they're not contained within the folds of the peritoneum, which some of the other organs of the abdominal cavity are.


Each kidney has a superior and inferior pole. Medially, you've got these vertical slit where various structures enter and exit the kidney. This is called the hilum. The structure that you can see here coming out of the kidney is called the ureter, but you also have the artery and vein, the renal artery and vein entering the kidney and you've also got nerves and lymphatics.


I just brought in the cardiovascular system here and you can see the large inferior vena cava and the abdominal aorta here and coming off it, you can see the renal veins and arteries on either side entering the hilum together with the ureter.


On this model, it's not really demonstrated that well. It's kind of shown just sticking on to the side of the kidney, but they actually enter medially into this vertical little slit into the inside of the kidney. This is called the hilum.


The hilum lies at vertebral level L1.   This is L1 vertebra.


We'll just take a quick look at some of the posterior relations of the kidney. If we look at back, we can see that the 12th rib lies behind the kidney. And if I bring in some other structures like some of the musculature, we can see some of the muscles which sit behind it.


You can see the psoas major on either side. It sits behind it. It's this muscle here on either side. And you've got the diaphragm, so the posterior parts of the diaphragm sitting behind the kidney. You've got the quadratus lumborum, which is this muscle here. It's kind of obscured in this model by the huge psoas major muscle. If I just rotate it around to the front, you can see that the quadratus lumborum is hidden because the psoas major is so big in this model. And then you've also got the transversus abdominis muscle, which is not shown in this model.


And then you've got a couple of nerves. You've got the subcostal nerve, the iliohypogastric nerve, the ilioinguinal nerves.   You can see these two here. You can see the iliohypogastric and the ilioinguinal nerve here.


That’s what lies behind both the kidneys. But what lies in front of the kidneys is different for the right and the left kidney. We'll take a look first at the right kidney.


If you look at the kidneys from this view, you can see that the right kidney is slightly lower than the left kidney. There's a reason for this. It's because of this large organ, the liver, which sits on top of it.   The right lobe of the liver is kind of big and it sort of pushes it down, so the right kidney is a little bit low than the left kidney.


I'll get rid of that and we can see what else is in front of the kidney – and the gallbladder.


You can see the colon runs in front of the kidney. You can see this hepatic flexure or the right colic flexure lies in front of the kidney. It runs in front of the lower part of the kidney, the inferior pole of the kidney. That's the hepatic flexure. We'll get rid of that.


And now you can see that the descending part of the duodenum sits in front of the medial part of the kidney.   The descending part of the duodenum is retroperitoneal as well and it sits right up against the kidney.


And if I just rotate the model around a bit further, you can see this thing on top of the kidney. This is the suprarenal gland or the adrenal gland.


I've just brought those structures back and we'll take a look at what sits in front of the left kidney that you can already see a lot of.


Anyway, the other side of the colon sits in front of the left kidney. We've got the splenic flexure or the left colic flexure.   I'll just get rid of that.


And then you can see the stomach and the spleen sitting in front of it. We'll get rid of those two. And then you can see the end of the pancreas sitting in front of it as well. The pancreas is a retroperitoneal structure whereas the stomach and spleen are both intraperitoneal structures. And then it's also got this suprarenal gland sitting on top of it.   Not the other adrenal gland.


Hopefully, that's orientated you a bit and you know exactly where the kidneys lie now. Next, we'll talk a little bit about the capsules of the kidney and the blood supply to the kidney. Then we'll do another tutorial on the internal structure of the kidney.