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


The kidney has three capsules which surround and contain it. It's not shown on this model, so I'll show you some other diagram to explain about these three capsules.  What I'm going to do is now I'm going to take a cross-section.  Imagine that we're going to take a slice of this poor woman at this level, okay?


We've got this cross-section here. Up here is anterior, so you can see the rectus abdominis muscles. And this side is posterior, so you can see the vertebral body here. You could see the kidney sitting right next to it and this little muscle sitting laterally on the vertebral bodies of psoas and you've got a little bit of the colon here.


I'm going to just spice this up a little bit with a bit of color. I've never mentioned before we've got three capsules of the kidney. Immediately surrounding the kidney, we've got the fibrous capsule which adheres to the surface of the kidney. And then we've got perinephric fat and then we've got the renal fascia, which is a continuation of the extraperitoneal fascia which wraps around the kidney.


In red, I'm just going to draw on the fibrous capsule which surrounds the kidney and adheres to its surface. And then outside the fibrous capsule, you've got the perinephric fat. This completely surrounds the kidney and it just sits outside the fibrous capsule.  This is the perinephric fat. I'll just draw it on roughly there.


And then outside the perinephric fat, we've got the extraperitoneal fascia, which his called the renal fascia as it surrounds the kidney.  This is in blue that I'm drawing on the renal fascia, which is a continuation of this extraperitoneal fascia, which lines the abdomen and sits between the peritoneum and the transversalis fascia.


Lateral to the kidney, the extraperitoneal fascia or the renal fascia fuses.


And then just another thing to mention, just outside the three capsules of the kidney, we've got some paranephric fat, which sits posteriorly and laterally. I don't know why I'm drawing it in blue, but it sits about here.


The perinephric fat immediately surrounds the kidney.  Peri- kind of like 'perimeter' means 'around', whereas 'paranephric', para- is kind of like 'paralympics', the paralympics running alongside the Olympics, the Olympic Games.  Peri- is immediately around the kidney and para- is outside the renal fascia, so alongside the renal fascia.