The types; it is associated with many many things, and I’ve listed a number of them here. Genetically transmitted disease, autoimmune diseases and disorders associated with nephrocalcinosis. If you hear nephrocalcinosis and acidosis, think type I RTA, and there are a couple of situations here. Drugs that have tubular toxicity; we talked about hypokalemia with cisplatin and amphotericin. Amphotericin will also give you a situation of RTA. Amphotericin also gives you renal failure in very sick patients, but in patients that are not so sick and we are using lower doses of amphotericin, there is a tubular toxicity, and that’s amphotericin-B I’m talking about. Others include pyelonephritis obstruction and kidney transplant.
Type II RTA is different than type I RTA. It’s not that you can’t excrete hydrogen ions. It’s that the kidneys leak bicarbonate. There is a low threshold in the blood for spilling bicarbonate in the urine. Normally you and I start to spill about 22 … or kids, actually, start to spill 22-24. In type II RTA they start to spill at 15-16, so they begin to lose their bicarbonate with relatively low serum bicarbonates. The clinical findings, again, hyperchloremia. I can’t stress enough, hyperchloremia – metabolic acidosis. With what in the potassium? Low potassiums, low or normal. That’s the way to recognize this. High chlorides, low or low normal potassium with an acidosis. The urine pH is greater than 5.5 when the bicarbonates, or the serum bicarbonates or the CO2 is normal. But it can decrease to less than 5.5 when you get very acidotic. Because then you get underneath the threshold and the body is able to reabsorb all the bicarbonate, and in this situation the distal tubule is working fine. It’s only the proximal tubule that is messed up and spilling all the bicarbonate. The K can be low or normal. Never high. This is seen usually with Fanconi’s syndrome, but it may be isolated.
Renal tubular acidosis
So what is the Fanconi’s syndrome? The Fanconi’s syndrome is a disease of the proximal tubule, that has all of the listed criteria, or many of the listed criteria; proximal RTA, they have amino aciduria, glucosuria, phosphaturia and hypophosphatemia and hypokalemia. They have uricosuria. They spill uric acid and decreased plasma uric acid. They have rickets, growth retardation, polyuria, dehydration, and sometimes low molecular weight globulin proteinuria.
Metabolic alkalosis
What are examples? This is the one they will ask you. Number one, cystinosis. Most frequent cause. Galactosemia, Wilson’s disease are others. Glycogen storage disease, Wilson’s disease, galactosemia, but cystinosis, nephropathic cystinosis, is the archetypal one. Here are some other selected causes. The full group is in your syllabus; heavy metal poisoning, cisplatin, biphosphamide, and then some other nephrologic ones, and glue-sniffing. Now if you have an isolate, those with Fanconi’s syndrome, I’ve listed some causes of isolated proximal RTA that are shown here. It is highly unlikely they will ask you any of these. And they are listed here: sporadic, genetic, carbonic anhydrase inhibition.
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