#5goodminutes Type IV RTA

For a number of years I have advised students and residents to keep a notebook of topics that arise on rounds.  Pick 2 topics that we discussed, then read about them for 5 minutes.  Everyone has 5 minutes to read about a topic. The idea here is that cognitive science has shown that we remember better if we both hear about a topic and read about the same topic. Since I have embarked on this project of one medical tweet each day, I have embraced the 5 good minutes philosophy.  So I will use the hashtag #5goodminutes each day, along with other tags. Today I want to increase understanding of Type IV RTA as many students, residents and practicing physicians find this topic confusing. Type IV RTA has other names – hyperkalemic normal gap metabolic acidosis and hyporenin/hypoaldo.  Generally the pathophysiology comes starts with decreased renin production which leads to decreased aldosterone production.  With decreased aldosterone production, the tubule retains potassium.  The key here is hyperkalemia.  That comes first and results in a normal gap acidosis.  Hyperkalemia inhibits ammonia production.  There are apparently several mechanisms here, but the one I understand best is that high potassium inhibits glutaminase.  Ammonia production includes glutaminase acting on glutamine + H2O to produce glutamate + NH3 (ammonia). Short aside – hypokalemia stimulates this enzyme and that explains why hypokalemia increases hyperammonemia. The lack of ammonia means that t...
Source: DB's Medical Rants - Category: Internal Medicine Authors: Tags: Medical Rants Source Type: blogs