2016 AJKD--Pathophysiology of Renal Tubular Acidosis: Core Curriculum 2016 -- Hyperkalemic RTA (type 4)

Topic: Pathophysiology of Renal Tubular Acidosis: Core  Curriculum 2016 -- Hyperkalemic RTA (type 4)
整理	內容 a defect in regeneration of HCO3 secondary to lack of adequate urinary NH4 => most common: hypo-aldosteronism w/ hyperkalemia => pesistent hyperkalemia without obvious cause (eg, kidney failure, use of K supplements, or K-sparing diuretics) hypo-aldosterone: hypo-reninism w/ kidney dz, Or a defect in RAA pathway Normal or high aldosterone in hyper-K RTA => the defect is in response to aldosteone: patients on ENaC blocker Hyper-K impair NH4 excretion: intracellular alkalosis (lumen K into PTC exchange for Na/H => inhibit ammoniagenesis 透過NKCC2抑制NH4在thick ascending limb of loop of Henle的reabsorption (K和NH4 compete for the same site on this transporter) => medullary NH4 absorption decrease Hereditary hyperkalemia RTA vs. Acquired hyperkalemic RTA Hereditary: Decrease in aldosterone synthesis (congenital isolated hypoaldosteronism or pseudohypoaldosteronism type 2), DCT NaCl absorption increase => 2nd hyperaldosteronism, Resistance to aldosterone action => type 1 pseudohypoaldosteronism Acquired: secondary to hyporeninism: CKD due to DKD or CIN Pirmary adrenal insufficiency can result from autoimmune adrenalitis, infectious adrenalitis (eg, HIV), and other disorders Severely ill patients due to unknown mechanisms Obstructive uropathy: impaired H and K secretion in CD (可能Urine pH > 5.5 when acidemia) Drugs: K-sparing diuretics, antibiotics (TPM and pentamidine), NSAID, CNi, Angiotensin inhibitors, Heparin/LMWH (附圖) Dx: document low NH4 + K excretion: UAG + UOG Urine pH < 5.5 (例外：obstr. uropathy, urine pH>5.5) Low urien K excetion: TTKG + Urine K/Cre ratio Drug screen serum Aldosterone + renin: hypo-aldo +/- hypo-renin Tx: Short-term: Normalize serum K => H+NH3 secretion增加改善metabolic acidosis + 增加PTC glutamine代謝，然後增加HCO3的產生 try to correct metabolic acidosis directly if failure to the 1st method Long-term: Hyper-K in P’t w/ Hyper-K RTA DC all drugs affecting K Restrict dietary K Control Hyperglycemia Tx metabolic acidosis Tx volume depletion Use loop diuretics (排酸？） Mineralocorticoids Kayexalate
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