Renal tubular acidosis ppt

RENAL TUBULAR ACIDOSIS

Dr Hatem Eidunit c

Female patient 23years old ,single known to have IDDM for 13 years presented by history of bilateral lower limb swelling of 1 month durationO/E Hemodynamic stableChest ,heart and abdomen : NAD There is bilateral lower limb pitting oedema

Case presentationhistory and exam

CBC TLC : 9 , Platelet : 170 Hb : 9 (normochromic normocytic )

RBS :15 mmol Acetone in urine : -veVBG : Ph :7.24 HCO3 : 17.8Anion gap :Na – (Cl+HCO3) 134-(111+17.8)=6

NORMAL ANION GAPRFT : creatinine : 129 urea : 11.18Na :134 K : 6.3LFT: Albumin :29 Total proteins :61Urine Albumin –Creat Ratio :300 .

Labs

The patient was co-managed by medical and nephro team and diagnosed as a case of renal tubular acidosis type 4 based on her persistent normal anion gap metabolic acidosis and hyperkalemia with absence of other causes of normal anion gap metabolic acidosis (as diarrhea)

Renal tubular acidosis (RTA) syndromes are nonuremic defects of urinary acidification, which is characterized by a normal anion gap and hyperchloremic metabolic acidosis; plasma potassium may be normal, low, or high, depending on the type of RTA

Renal tubular acidosis

Renal acid-base homeostasis Renal acid-base homeostasis may be broadly divided into

2 processes

Proximal tubular absorption of HCO3- (Proximal

acidification)

Distal Urinary acidification.Reabsorption of remaining HCO3

- that escapes proximally.Excretion of fixed acids through buffering & Ammonia

recycling and excretion of NH4+.

Distal RTA (Type I): loss of hydrogen ion secretion into urine due to defect in distal tubule.

Proximal RTA (Type II): loss of bicarbonate reabsorption due to defect in the proximal tubule

Hypoaldosteronism or hyperkalemic (Type IV): aldosterone deficiency or distal tubule resistance to aldosterone leading to loss of potassium excretion. Ensuing hyperkalemia leads to suppression of ammonia excretion.

TYPES OF RTAs

Distal (type 1) RTADistal RTA (dRTA) is the classical form of RTA, being the first described

Distal RTA (dRTA) is a disorder secondary to impaired distal H+ secretion .

It is characterized by inability to lower urine ph maximally(<5.5) .

The serum HCO3- levels are very low <12 meq/l.It is often associated with hypercalciuria, hypocitraturia, nephrocalcinosis, and osteomalacia.

Distal RTA ..causes,,,The most common causes in adults are autoimmune

disorders ,chronic hyperglobulinemia

Drugs as analgesicsTubulointerstitial conditions as chronic pyelonephritis, obstructive uropathy

In children, type 1 RTA is most often a primary, hereditary condition .

Proximal RTA (pRTA) is a disorder secondary to impaired proximal reabsorption of filtered bicarbonate

fall of serum HCO3_ below 12 meq/l is unusual, as the distal acidification mechanisms are intact..

Proximal (type 2) RTA

Isolated defects in PCT function are rarely found. Most patients with a pRTA will have multiple defects in PCT function with subsequent Fanconi Syndrome.

Dysproteinemic states as Multiple myeloma and amyloidosis

Drug or toxic nephropathy as valproic acid , gentamycin

Hereditary disorders as Cystinosis, Wilson disease,

Proximal RTA…causes,,

Patients with pRTA rarely develop nehrosclerosis or nephrolithiasis. This is thought to be secondary to high citrate excretion.

In children, the hypocalcemia as well as the metabolic asacidosis will lead to growth retardation, rickets, osteomalacia and an abnormal vitamin D metabolism. In adults osteopenia is generally seen.

Proximal RTA…continue,,,

Type 4 RTA (Hyperkalemic RTA)This disorder is characterized by modest Hcmetabolic ascidosis with normal AG and association with hyperkalemia.

This condition occurs primarily due to decreased urinary ammonium excretion.Causes include:-Aldosterone deficiency (hypoaldosteronism): . Deficiency of aldosterone with glucocorticoid

deficiency is associated with Addison disease, bilateral adrenalectomy. Isolated aldosterone deficiency can be secondary to states of deficient renin secretion, including diabetic nephropathy, tubulointerstitial renal disease ,and NSAID

confirm the presence of metabolic acidosis.

Values of less than 12 demonstrate the absence of an anion gap.

-rule out other causes of normal anion gap metabolic acidosis, such as diarrhea ( which is

extremely common . )-

How to approach a suspected case of renal tubular acidosis,,

=[Na] – [Cl + Hco3]< 12 = normal or absence of anion gap

as in bicarbonate loss in {diarhea ,RTA,carbonic anhydrase inhibitor , ureterosigmoidostomy,, pancreatic fistula}

>20 =increased anion gap as in{ lactic acidosis, DKA, uremia, poisoning with (salicylate,methanol,ethanol)}

How to approach a suspected case of renal tubular acidosis…continue


-Identify electrolyte abnormalities (K,Na,Cl) -True hyperkalemic acidosis is consistent with type

IV RTA, whereas the finding of normal or low potassium suggests type I or II

Urine pH may help distinguish distal from proximal causes. A urine pH of less than 5.5 suggests proximal RTA, whereas patients with distal RTA typically have a urine pH of more than 6.0.

Assess renal function-


A urinalysis should also be obtained to determine the presence of glycosuria, proteinuria, or hematuria suggesting the possibility of more global tubular damage or dysfunction

24-hr urine calcium and creatinine measurements will identify hypercalciuria .

A renal ultrasound should be obtained to identify underlying structural abnormalities such as obstructive uropathies as well as to determine the presence of nephrocalcinosis


Ultrasound examination of a child with distal renal tubular acidosis demonstrating medullary nephrocalcinosis

The mainstay of therapy in all forms of RTA is bicarbonate replacement .

Patients with type IV RTA may require chronic treatment for hyperkalemia with sodium-potassium exchange resin.

Rickets may be present in primary renal tubular acidosis (RTA), particularly in type II or proximal RTA. Administration of sufficient bicarbonate to reverse acidosis stops bone dissolution and the hypercalciuria that is common in distal RTA. Proximal RTA is treated with both bicarbonate and oral phosphate supplements to heal bone disease.. Vitamin D is needed to offset the secondary hyperparathyroidism that complicates oral phosphate therapy

Treatment of RTA.

Patients with proximal RTA often require large quantities of bicarbonate, up to 20 mEq/kg/24 hr in the form of sodium bicarbonate or sodium citrate solution.

The base requirement for distal RTA is generally in the range of 2-4 mEq/kg/24 hr .

.

Treatment of RTA cont.

Depends on associated disease, otherwise good with therapy

Transient forms of all types of RTA may occur.

Prognosis,

Patient received anti hyperkalemic measure and NaHCO3 and last VBG showedPh:7.35 HCO3:23K : 4.6 And patient discharged to follow up nepherology OPD

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Renal tubular acidosis ppt