Renal tubular disease Flashcards
What are the types of renal tubular disease?
1) Renal tubular acidosis RTA - types 1, 2, 4
2) Fanconi syndrom
3) Cystinosis
4) Hereditary hyperkalaemic tubulopathies
What is RTA?
Renal tubular acidosis - metabolic disorder, impaired acid secretion in the kidney.
- There is a hyperchloraemic acidosis with a normal anion gap
What is RTA type 1? Causes? Features? Tests? Treatment?
” Distal”
Due to an inability to excrete H+ and generate acidic urine in the distal tubule, even in states of metabolic acidosis.
- Inherited
- Acquired include SLE, Sjogren’s and drug (amphotericin)
Features include ricket’s or osteomalacia - due to buffering of H+ with Calcium from bone.
Nephrocalcinosis with renal calculi, recurrent UTIs (Both partly due to alkaline urine)
Test Urine pH - >5.5 despite metabolic acidosis
Treat oral sodium bicarbonate or citrate
Renal calculi biggest complication, can lead to ESRF
What is RTA type 2? Causes? Features? Tests? Treatment?
“Proximal”
Due to a bicarbonate “leak”, poor bicarbonate reabsorption in the proximal tubule. Excess bicarbonate in urine and a metabolic acidosis.
-Often associated with more general tubular defect (falcon) and rarer than type 1.
Hypokalaemia is common. Increased flow in distal tubule due to osmotic effect of HCO3- so less K reabsorbed
Test by loading with IV sodium bicarbonate, >15% excreted in urine.
Treat with high doses of bicarbonate, often intolerable
What is RTA type 4? Causes? Features? Tests? Treatment?
“Hyperkalaemic”
Due to hyporeninaemic hypoaldosteronism
Causes - Addison’s disease, diabetic nephropathy, interstitial nephritis (SLE, chronic obstruction) drugs (K sparing diuretics, B blockers, NSAIDs, cyslosporin)
Treat by removing cause, then fludrocortisone 0.1mg, furosemide or calcium resonium to control K
What is Fanconi syndrome?
A dysfunction of the proximal tubule leading to the loss of amino acids, glucose phosphate and bicarbonate.
Leads to dehydration, metabolic acidosis, osteomalacia/rickets, electrolyte abnormalities.
Congenital - Idiopathic, cystinosis, wilson’s disease, tyrosinaemia, lowe syndrome
Acquired - heavy metal poisoning, drugs, light chains, sjorgrens.
Treat by removing any cause and replace losses.
What is Cystinosis?
Autosomal recessive defect causes accumulation of cysteine in lysosomes. These cause fanconi syndrome in the kidney, but also affect vision, thyroid, muscles.
Treat as fanconi syndrome. Oral cysteamine delays ESRF.
Does not recur after transplant, though systemic disorder progresses.
What are the two hypokalaemic tubulopathies and what are their features?
1) Bartter syndrome - Inherited mutation in the co-transporter targeted by loop diuretics, so present with same symptoms. Usually presents in childhood. Replace K and consider indomethacin (a prostaglandin synthesis inhibitor) which can resolve abnormalities.
2) Gitelman syndrome - Inherited mutation in the co-transporter targeted by thiazide diuretics so similar patter of metabolic abnormalities. Usually presents later then Bartter with muscle cramps, weakness, low BP. Replace Mg, maybe K.
