Renal Tubular Acidosis Explained

Kidney Tubules AnatomyI hate really hate studying this material but once you understand it, it becomes very easy to memorize.

Remember in renal tubular acidosis (RTA) there is normal anion gap.  [Na – (Cl – HCO3)] = 6-12.
Proximal part is the upper part of the renal tubules, while the distal part is the end part of the tubules.
Type II (Proximal)

  1. Pathophysiology: Decreased ability of the proximal kidney tubules to reabsorb most of the filtered bicarbonate because normally bicarbonate is filtered at the proximal tube.
  2. Urine pH: Variable: Urine pH is basic until bicarbonate is depleted, the it is acidic (less than 5.5)
  3. Blood K+ level: Low
  4. Kidney Stones: No
  5. Associations
    • Diagnosis: Infuse bicarbonate and evaluate the urine pH
    • Treatment: Thiazide because it causes volume depletion, which will enhance bicarbonate reabsorption.

    Type I (Distal)

    1. Pathophysiology: Distal tubule is damaged so it is unable to generate bicarbonate. Without bicarbonate, H+ cannot be secreted in the tubule to the urine, raising urine pH.
    2. Urine pH: Urine pH more than 5.5.
    3. Blood K+ Level: Low
    4. Kidney Stones: Yes
    5. Associations
      • Amphotericin use
      • Lithium Use
      • Sickle Cell Disease
      • Autoimmune Diseases (SLE, Sjorgen Syndrome, Rheumatoid Arthritis, etc)
    6. Diagnosis: Infuse acid
    7. Treatment: Bicarbonate to be absorbed in the proximal tubule, because majority of the bicarbonate is absorbed there.

    Type IV (Distal)

    1. Pathophysiology: Decreased or diminished effect of aldosterone at the kidney tubule. Loss of sodium and retention of potassium and hydrogen ions.
    2. Urine pH: Less than 5.5
    3. Blood K+ level: High
    4. Kidney Stones: No
    5. Associations
      • Diabetes
      • Addison’s Disease
      • NSAIDs
    6. Diagnosis: Urine salt loss, despite sodium restricted diet
    7. Treatment: Fludrocortisone

    Lung Volumes Definitions and Spirometry

    Total lung capacity (TLC): the volume in the lungs at maximal inflation, the sum of VC and RV.

    Residual volume (RV): the volume of air remaining in the lungs after a maximal exhalation

    Expiratory Reserve Volume (ERV): the maximal volume of air that can be exhaled from the end-expiratory position

    Inspiratory Reserve Volume (IRV): the maximal volume that can be inhaled from the end-inspiratory level

    Inspiratory Capacity (IC): the sum of IRV and TV

    Inspiratory Vital Capacity (IVC): the maximum volume of air inhaled from the point of maximum expiration

    Vital Capacity (VC): the volume of air breathed out after the deepest inhalation.

    Tidal Volume (VT): that volume of air moved into or out of the lungs during quiet breathing

    Functional Residual Capacity (FRC): the volume in the lungs at the end-expiratory position

    Forced Vital Capacity (FVC): the determination of the vital capacity from a maximally forced expiratory effort

    Forced Expiratory Volume (time) (FEVt): a generic term indicating the volume of air exhaled under forced conditions in the first (t) seconds
    FEV1 – Volume that has been exhaled at the end of the first second of forced expiration

    Peak Expiratory Flow (PEF): The highest forced expiratory flow measured with a peak flow meter

    Premature Ventricular Complex

    Premature Ventricular Complex, Ventricular Tachycardia, Ventricular FibrillationPremature ventricular complexes (PVC) usually occurs in post-myocardial infarction patients.  On ECG they have very wide QRS complex, (> 120 msec, which is 0.12 seconds). Remember one small box is 0.04 seconds and one large box is 0.20 seconds. QRS complexes should normally be 0.08-0.12 seconds.

    On ECG, PVC will also show a bizarre morphology, and a compensatory pause.  The prognosis is usually bad, but no treatment is necessary unless the patient is symptomatic.  With symptomatic patients DO NOT treat with antiarrythmic medications, because it will make worse.  Instead, treat patients with beta-blockers, which are the first like therapy for symptomatic patients.

    The picture on the side should help differentiate PVC from other abnormal ventricular contractions.  The video below explains PVC very well.

    Image Source: 5MinuteConsult