Renal tubular acidosis


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Renal tubular acidosis

  1. 1. Dr.Anurag Fursule DNB Resident II yr JLNHRC,Bhilai
  2. 2.  Renal tubular acidosis (RTA) is a disease state characterized by a normal anion gap (hyperchloremic) metabolic acidosis in the setting of normal or near-normal glomerular filtration rate.
  3. 3.      Anion Gap = Serum(Na+ + K+ )-(Cl- + HCO3-) Purpose of using anion gap: metabolic acidosis resulting from bicarbonate loss can be differentiated from accumulation of non volatile acis Normal value : 14 – 18 mEq/L >20 is highly suggestive of presence of anion gap For every mEq of bicarb loss there is equal increase in serum chloride levels so anion gap remains within normal range
  4. 4.   Mostly reabsorped in PCT 80-85% Remainder in initial part of distal tubule
  5. 5.    Proximal (type II ) RTA is characterized by impairment of PCT reabsorption of bicarbonate. So at normal plasma HCO3 levels 15%(30% or mor in fanconi) or more HCO3 is excreted in urine and during sustained acidosis excessive HCO3 excretion is reduced and increased reabsorption of HCO3 from proximal tubule. Distal acidification mechanisms are intact.
  6. 6.     Primary isolated proximal RTA secondary to defective HCO3 reabsorption is rare,may occur as sporadic or inherited(AR). In children RTA II is usually part of global proximal tubular dysfunction i.e Fanconi syndrome. Proximal RTA is mc caused by sporadic Fanconi syndrome Among inherited conditions cystinosis is commonly identified
  7. 7. Hypophosphatemia,acidosis,lo w 1,25(OH)3 D3
  8. 8. A detailed history, with particular attention to  growth and development  recent or recurrent diarrheal illnesses  family history of mental retardation  failure to thrive  end-stage renal disease  infant deaths  miscarriages is essential Physical examination should determine  growth parameters  volume status  dysmorphic features suggesting an underlying syndrome
  9. 9. •Urine pH should be assesed during state of metabolic acidosis •Urine and blood pCO2 difference is more than 20mmHg
  10. 10.        Correction of acidosis: 5-20mEq/kg of alkali Prudent to give 5-8 mEq/kg bicarbonate (shohl solution,polycitra) Part of alkali is given in form of potassium citrate Dietary Na restriction Hydrochlorthiazide : contraction of ECF and increased proximal HCO3 reabsorption Supplements of phosphate (neutral phosphate , joulie solution)are necessary in Fanconi syndrome. Dose: 1-3gm/day Small doses of vit D may enable healing of rickets(though rare)
  11. 11. Mutation in CTNS gene(17p)--encodes novel protein:cystinosin(H+ driven cystine transporter) Defect in metabolism of cystine Accumulation of cystine crystals in major organs Kidney, brain ,liver,eye,others
  12. 12. 1.Infantile /Nephropathic cystinosis -1st 2 years of life -severe tubular dysfuntion -if no t/t then ESRD till first decade  2.Adoloscents -mild -slower progression to ESRD  3.Benign adult form with no kidney involvement 
  13. 13.         Diminished pigmentation: fair and blond Fanconi syndrome: polyuria, polydipsia Growth failure Rickets Fever: dehydration and decreased sweat production Ocular: photophobia, retinopathy, impaired visual acuity Hepatosplenomegaly, delayed sexual maturation, hypothyroidism Complications: CNS abnormalities, muscle weakness, swallowing dysfunction, pancreatic insufficiency.
  14. 14. Diagnosis: 1.Detection of cystine crystals in cornea 2.Increased leukocyte cystine content 3.Prenatal diag by CVS,amniocentesis       Early initiation of therapy is important. correcting the metabolic abnormalities associated with Fanconi syndrome or chronic renal failure. cysteamine,which binds to cystine and converts it to cysteine: facilitates lysosomal transport and decreases tissue cystine. cysteamine eyedrops is required growth hormone for growth failure
  15. 15. Mutation in OCRL1 of X chromosome(XLR) Encodes PIBPase in golgi network Accumulation of PIBP 1.Changes in protein trafficking 2.Defective actin cyctosleleton polymerization 3.Altered cell signalling for endocytosis
  16. 16. •Hypotonia with hyporeflexia •Severe psychomotor retardartion •Bilateral cong Cataract •Strabismus •Infantile onset Glaucoma •cheloids •Frontal bossing •Deep set eyes •Chubby cheeks •Fair complexion Rachitic rosary Fanconi syndrome
  17. 17. Diagnosis is clinical,molecular testing for OCLR gene is available.  Prenatal Dx: slit lamp examination of mother(punctate white opacities)  Treatment is symptomatic -cataract extraction -glaucoma control -physical and speech therapy -drugs to address behavioral problem 
  18. 18. Defects in one or more of following: -H+ ATPase -HCO3/Cl anion exchanger -Components of aldosterone pathway  Due to impaired H+ excretion urine pH cannot be reduced to <5.5  Inability to secrete H+ distally is compensated by secreting K+ leading to hypokalemia  Lack of NaHCO3 distally, owing to lack of H+ to bind to tubuLar lumen, leads to chloride absorption leading to hyperchloremia.  Chronic metabolic acidosis: impairs citrate excretion leading hypocitraturia  Hypercalciuria: -Increased calcium release from bone to buffer systemic acidosis -Acidosis induced downregulation of renal Calcium transport protein -Increased distal sodium delivery 
  19. 19. •Urine and blood pCO2 difference is <10mmHg provided urine pH >7.5 and bicarbonate >23mEq/L
  20. 20.      Base requirement for distal RTA is generally 2-4mEq/kg/24hr.(requirement decreases after age of 5 yrs) Patient should b monitored for development of hypercalciuria Some patients may require K+ replacement Symptomatic hypercalciuria: gross hematuria, nephrocalcinosis, nephrolithiasis — treated with thiazide diuretics Vit D should be used in case of severe rickets
  21. 21. aldosterone -direct effect on the H+/ATPase responsible for hydrogen secretion -potent stimulant for potassium secretion in the collecting tubule  Type IV RTA occurs as the result of -impaired aldosterone production (hypoaldosteronism) -impaired renal responsiveness to aldosterone (pseudohypoaldosteronism). 
  23. 23.     Growth failure Polyuria Dehydration with salt wasting Life threatning hyperkalemia
  24. 24. PHA I Salt loss Hypotension hyperkalemia  PHA II Hypertension Acidosis Hyperkalemia Hyporeninemic hypoaldosteronism 
  25. 25.        hyperkalemic non–anion gap metabolic acidosis Urine may be alkaline or acidic Elevated urinary sodium levels with inappropriately low urinary potassium levels reflect the absence of aldosterone effect. require chronic treatment for hyperkalemia with sodium-potassium exchange resin (Kayexalate). PHA I- Kayexelate PHA II-thiazides Addisons- fludrocortisone
  26. 26.    Nelson Textbook of Pediatrics 19th edition IAP Textbook of Pediatrics 5th edition Pediatric Nephrology by RN Srivastava,A Bagga 5th edition