Kidneys

The kidneys are both important and difficult. Let's break the kidney down into fundamental blocks. 90% of the diseases covered on your test will fall into one of these blocks. The other 10% consists of some congenital problems and nephrotoxic medications. 

Here’s another big picture framework.

AFFERENT & EFFERENT ARTERIOLES

Regulators

The Afferent and Efferent Arterioles are the vessels connected to glomeruli. They play a critical role regulating our fluid levels. They lie at the intersection of the RAAS system, the natriuretic peptides, the sympathetic system and prostaglandins. I can’t emphasize enough how important they are. 

MALIGNANT HYPERTENSIVE & DIABETIC NEPHROPATHY

Onions yummy

Diabetes and hypertension will strangle your kidneys if given enough time. They achieve this by transforming the blood vessels that travel to the kidney. They narrow the lumens by thickening the arterial walls, and this chokes off the blood flow. There are a couple of different ways that they can fatten the walls, and the USMLE thinks it's important that we recognize these images, particularly the onion-skinning one. When the kidneys begin to notice that they’re receiving less blood than usual, they respond by turning on the RAAS system. This jacks up the blood pressure further. It’s a vicious cycle. You can stop this vicious cycle by blocking RAAS with ACE Inhibitors or ARBS. I think the point that the USMLE wants to convey is that we should know why diabetes and hypertension hurt our kidneys. 

I define Malignant Hypertension as “fucking awful blood pressure for decades.” I want you to think in the 170+ systolic range. Every day. For 20 years. These patients often refuse to take their hypertension drugs or haven’t seen a doctor in decades. 

ENDOCRINE KIDNEY 

The kidney makes a lot of interesting molecules