renal tubular disorders

abnormalities of renal tubular function occur @ any point along length of nephron & affect any of substances handled by it
generalised proximal tubular dysfun (Fanconi syn)
1. prox tubule cells very metabolically active
  1. esp vulnerable to cellular damage
2. cardinal features: urinary loss of
  1. amino acids
  2. glucose
  3. phosphate
  4. bicarbonate
  5. Na+
  6. Ca2+
  7. K+
  8. urate
3. causes
  1. idiopathic
  2. secondary to inborn errors of metabolism
    1. cystinosis
      1. autosomal recessive disorder causing intracellular buildup of cystine
    2. glycogen storage disorders
    3. Lowe syn (oculocerebrorenal dystrophy)
    4. galactosaemia
    5. fructose intolerance
    6. tyrosinaemia
    7. Wilson disease
  3. acquired
    1. heavy metals
    2. drugs & toxins
    3. vit D def
4. consider in child presenting w/
  1. polydipsia & polyuria
  2. salt depletion & dehydration
  3. hyperchloraemic metabolic acidosis
  4. rickets
  5. failure to thrive/poor growth
specific disorders classifed accord to part of tubule affected
1. proximal tubule
  1. glycosuria
    1. asymptomatic
    2. reduced reabsorption of glucose
  2. cystinuria
    1. reduced reabsorption of cystine & dibasic amino acids
    2. renal calculi
  3. vit D resistant rickets
    1. reduced reabsorption of phosphate
    2. rickets
  4. pseudohypoparathyroidism
    1. increased reabsorption of phosphate
    2. obesity
    3. depressed nasal bridge
    4. short fingers (2nd, 4th & 5th)
  5. hyperuricosuria
    1. increased secretion or reduced reabsorption of uric acid
    2. renal calculi
  6. renal tubular acidosis type II
    1. reduced reabsorption of bicarbonate
    2. metabolic acidosis
    3. alkaline urine
    4. growth failure
  7. hypercalcuria
    1. reduced reabsorption of Ca2+
    2. nephrocalcinosis or renal stones
2. distal tubule & collecting duct
  1. nephrogenic diabetes insipidus
    1. decreased H2O reabsorption
    2. polydipsia & polyuria
    3. fever
    4. failure to thrive/poor growth
3. distal tubule
  1. Bartter syn
    1. reduced Cl- reabsorption
    2. hypokalaemic metabolic alkalosis
    3. hypercalciuria
    4. normal bp w/ raised renin
    5. polydipsia & polyuria
    6. growth failure
4. collecting duct
  1. renal tubular acidosis type I
    1. reduced secretion of H+
    2. metabolic acidosis
    3. alkaline urine
    4. growth failure
    5. nephrocalcinosis

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renal tubular disorders

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	Created by v.djabatey about 10 years ago