Renal Tubular Acidosis (RTA) in Children: Type 4 and Review

by Brian Alverson, MD

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    00:01 Let’s move on though to a type you do have to know about, which is type 4 RTA.

    00:08 Okay.

    00:09 Type 4 RTA happens as a result of lack of responsiveness to aldosterone.

    00:17 So as we recall, aldosterone causes an activation of a counter exchange mechanism of sodium and potassium.

    00:27 The sodium is also getting out back into the blood through just a general channel and the potassium is balanced by going back into the urine through two channels.

    00:38 But it’s that pump that’s triggered by aldosterone that is responsible for both retaining sodium in the blood and spitting out potassium.

    00:49 Many people think of aldosterone as having a primary role of potassium homeostasis rather than sodium or hanging on to water, although it obviously has both roles.

    01:00 So in type 4 RTA, this counter exchange mechanism is not working correctly.

    01:09 Normally, this would hold on to sodium and spit out potassium.

    01:15 Now, patients are failing to hold on to sodium.

    01:18 They will lose their sodium and they are incapable of spitting out their potassium, so the potassium levels go up.

    01:27 So these patients get hyperkalemia which can be life-threatening and hyponatremia from loss of that.

    01:38 So the acidosis is actually not really our biggest concern.

    01:43 The acidosis is usually reasonably mild and these patients will only have a bicarbonate in the high teens or low 20s.

    01:54 There are many potential causes of a type 4 RTA.

    01:58 Examples include diabetic nephropathy, congenital adrenal hyperplasia and that’s certainly how we see it most often in young babies and children.

    02:08 HIV nephropathy can cause this or it can be from longstanding urinary obstruction.

    02:16 This condition can also be caused by drugs.

    02:20 Some drugs that can cause type 4 RTA include ACE inhibitors or ACE receptor antagonists.

    02:28 NSAIDs can do it.

    02:29 Spironolactone, the potassium sparing diuretic can cause it and it can be caused by cyclosporine.

    02:37 So our management of type 4 RTA is by necessity, a low potassium diet.

    02:45 We also will give children loop diuretics because those are potassium losing diuretics and thus, will essentially be encouraging the loss of potassium.

    02:55 Bicitra here is typically not needed because as I said before they’re not really all that acidotic.

    03:02 The primary issue is hyperkalemia.

    03:07 Okay, let’s review these three major types: Types 1, 2 and 4 together.

    03:14 Type 1 is a problem with proton secretion.

    03:17 It happens in the distal tubule.

    03:21 On labs, you will see a high urine pH, a low serum potassium and you will see high urine electrolytes particularly calcium and potassium.

    03:33 This is caused by primary autoimmune diseases, also sickle cell or lithium ingestion.

    03:42 Type 2 RTA is a problem with bicarbonate reabsorption.

    03:47 This occurs in the proximal tubule.

    03:49 Type 2 is closer than type 1.

    03:52 In these patients, they will have often an acidic or may be even normal urine pH depending on where things stand.

    04:01 The serum potassium will be low or normal and you may find many things abnormal in the urine, especially if they have Fanconi’s syndrome.

    04:10 This could include high glucose, uric acid, phosphate, protein, calcium or potassium.

    04:17 Again, this can be inherited.

    04:20 It could be as a part of Fanconi’s syndrome, which can be caused by a number of things including for example rickets or heavy metal toxicity.

    04:30 Lastly, we have type 4, which is really a problem of aldosterone insensitivity.

    04:36 The problem happens in the distal tubule.

    04:40 The urine pH is low, but the serum potassium is high and that’s key.

    04:47 This can come from a variety of different things such as congenital adrenal hyperplasia, longstanding urinary obstruction, spironolactone use or even NSAID use.

    04:59 So that’s a summary of the types of renal tubular acidosis.

    05:03 I hope that was helpful to you.

    05:05 Thanks for listening.

    About the Lecture

    The lecture Renal Tubular Acidosis (RTA) in Children: Type 4 and Review by Brian Alverson, MD is from the course Pediatric Nephrology and Urology. It contains the following chapters:

    • RTA Type 4
    • Reviewing the RTA's

    Included Quiz Questions

    1. Hyponatremia and hyperkalemia
    2. Hypernatremia and hypokalemia
    3. Hyponatremia and hypokalemia
    4. Severe acidosis
    5. Hypernatremia and hyperkalemia
    1. Aldosterone
    2. Cortisol
    3. Antidiuretic hormone
    4. Carbonic anhydrase
    5. Sodium-potassium-chloride cotransporter
    1. Sulfanamides
    2. Congenital adrenal hyperplasia
    3. Diabetic nephropathy
    4. Angiotensin converting enzyme inhibitors
    5. Spironolactone

    Author of lecture Renal Tubular Acidosis (RTA) in Children: Type 4 and Review

     Brian Alverson, MD

    Brian Alverson, MD

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    Excellent lecture
    By Jalil Z. on 09. March 2021 for Renal Tubular Acidosis (RTA) in Children: Type 4 and Review

    Excellent lecture: well explained, well summarised. All key points are discussed. Thanks