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renal tubular acidosis (RTA) type I (hyperchloremic acidosis, distal RTA)

Etiology: 1) defect in distal nephron acidification 2) *hypercalciuria may be the cause of RTA I - nephrocalcinosis 3) associated conditions: a) autoimmune disorders 1] Sjogren's syndrome 2] rheumatoid arthritis 3] primary biliary cirrhosis 4] systemic lupus erythematosus b) hypergammaglobulinemia/multiple myeloma c) genetic disorders 1] Ehlers-Danlos syndrome 2] Marfans syndrome 3] hereditary elliptocytosis 4] Fabry's disease [3] 5] Wilson's disease [3] d) disorders associated with nephrocalcinosis 1] primary hyperthyroidism 2] hypervitaminosis D 3] idiopathic hypercalcuria e) renal tubulointerstitial disease 1] obstructive uropathy 2] reflux nephropathy 3] medullary cystic kidney disease [3] 4] renal transplantation rejection f) volume depletion (marked) g) drugs 1] amphotericin B 2] lithium carbonate 3] ifosfamide 4] toluene sniffing 5] analgesic abuse h) hyperkalemic form associated with: 1] obstructive uropathy 2] sickle-cell nephropathy 3] systemic lupus erythematosus i) dysproteinemia 1] amyloidosis 2] cryoglobulinemia 3] hypergammaglobulinemia j) hepatic cirrhosis k) idiopathic Epidemiology: 1) more common than type II RTA 2) less common than type IV RTA Pathology: 1) papillary nephrocalcinosis 2) hypercalciuria may be the cause of RTA I 3) inability to lower urine pH normally; reduced renal H+ excretion 4) impaired distal tubule H+ excretion 5) citrate reabsorption 6) increases risk for nephrocalcinosis (urolithiasis) Genetics: 1) autosomal recessive form(s) 2) autosomal dominant form Clinical manifestations: 1) osteomalacia (rickets) most severe of all the RTA's 2) frequent musculoskeletal complaints (hypokalemia) 3) hypokalemia, hypokalemic paralysis 4) growth retardation Laboratory: 1) metabolic acidosis a) HCO3- 5-15 meq/L, ~ 10 meq/L [3] b) normal anion gap c) hypokalemia d) hyperchloremia e) positive urinary anion gap [3] 2) urine pH: a) inappropriately high b) > 5.5 (pH < 5.5 excludes RTA-1) c) inability to acidify urine below a pH of 6.0 [3] 3) serum aldosterone normal to high 4) low 24 hour urine citrate - citrate is an inhibitor of nephrocalcinosis (urolithiasis) 6) no aminoaciduria 7) hypercalciuria* 8) hyperphosphaturia *hypercalciuria may be the cause of RTA I. Radiology: - punctate renal calcifications may be seen on plain radiographs Differential diagnosis: - renal tubular acidosis type II (proximal RTA) - urine pH usually < 5.5 without alkali therapy - serum HCO3-: 14-20 meq/L, ~16-18 meq/L [3] Management: 1) correction of K+ deficit (hypokalemia) first [3] - potassium citrate 1 meq/kg/day may useful for treatment of nephrocalcinosis 2) bicarbonate replacement (1-2 meq/kg/day) - this may correct Ca+2-wasting & osteomalacia

Specific

distal renal tubular acidosis with deafness distal renal tubular acidosis with preserved hearing (RTADR)

General

renal tubular acidosis (RTA)

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995
  2. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 602-603, 616, 620
  3. Medical Knowledge Self Assessment Program (MKSAP) 11, 15, 16, 17, 18, 19. American College of Physicians, Philadelphia 1998, 2009, 2012, 2015, 2018, 2021. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  4. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 1324
  5. Comer DM, Droogan AG, Young IS, Maxwell AP. Hypokalaemic paralysis precipitated by distal renal tubular acidosis secondary to Sjogren's syndrome Ann Clin Biochem. 2008 Mar;45(Pt 2):221-5. PMID: 18325192
  6. Karet FE. Inherited distal renal tubular acidosis. J Am Soc Nephrol. 2002 Aug;13(8):2178-84. Review. PMID: 12138152 Free Article
  7. Valles PG, Batlle D. Hypokalemic distal renal tubular acidosis. Adv Chronic Kidney Dis. 2018;25:303-20. PMID: 30139458