A 43-year-old male presents to his primary care doctor with complaints of increasing abdominal girth. He has a long history of alcohol abuse and recently stopped drinking. Spironolactone is prescribed to aid the control of the patient's increasing ascites. Which of the following is the site of action of spironolactone?
(A) Ascending loop of Henle
(B) Collecting duct
(C) Descending loop of Henle
(D) Distal tubule
(E) Proximal tubule
The answer is "D".
You have to watch out for language. The people that said "B" probably didn't read as slowly as they should have. The Collecting DUCT is lower in the kidney, it regulates mannitol and ADH antagonsists.
The Collecting TUBULE/ Distal TUBULE is where Potassium sparing drugs work.
The best way to answer these questions is to draw out the kidney and mark where each drug works. Don't be fooled by language. The USMLE will trick you with these types of questions you just posted. Before you look at the answer, know in your head you should be looking for something with TUBULE. They can get you every time just by interchanging words on you.
1- Acetazolamide- Proximal
2- Mannitol- Proximal
3- Loops- Thick Ascending
4- Thiazides- Early Distal
5- Potassium Sparking- Late distal tubule / Collecting Tubule
6- ADH antagonists- Collecting DUCT