Renal Tubular Disorders

Posted by e-Medical PPT Thursday, August 2, 2012
Glomerulus produces an enormous volume of ultrafiltrate daily.
Tubules modify the UF by selective reabsorption and secretion of various solutes to maintain body homeostasis.

Classification  of renal tubular disorders – Primary or Secondary
CYSTIC DISEASES – PCKD (AR or AD), cortical cysts, nephronophthisis, medullary sponge kidney
DYSPLASTIC DISEASES – Renal aplasia, dysplasia, MCDK (uni or bilateral)
HEREDITARY DISEASES WITH TUBULAR TRANSPORT DEFECTS – Hartnup disease, Fanconi syn, Lowe’s syn, Cystinosis, Wilson’s dis, Galactosemia, RTA (many types), Vit D resistant rickets, Nephrogenic Diabetes Insipidus
HEREDITARY DISEASES WITH LITHIASIS – Hyperoxaluria, Xanthinuria, L- glyceris aciduria, Lesch- Nyhan syn, Cystinuria, Glycinuria
MISCELLANEOUS – Sickle cell anemia, Bartter’s syndrome, Total and partial lipodystrophy

Introduction to Renal Tubular Acidosis
RTA is a clinical syndrome  in which either an inherited or acquired renal tubular defect leads to failure to maintain a normal plasma bicarbonate conc in the presence of a normal rate of acid production from diet and metabolism
Clinically, it is characterized by a normal anion gap (AG), hyperchloremic metabolic acidosis (MA), bicarbonaturia, reduced urinary excretion of titrable acid and ammonia and an elevated urinary pH.

Types of Renal tubular acidosis (RTA)   
Type 1 RTA – Distal RTA – defect in hydrogen ion secretion by the distal tubule
Type 2 RTA – Proximal RTA – defect in bicarbonate reabsorption by the proximal tubule
Type 4 RTA – Hyperkalemic RTA – impaired distal nephron secretion of both H+ and K+ ions

Distal RTA
Distal renal tubular acidosis (dRTA) was recognized as a distinct entity by Albright et al in 1946. The clinical syndrome described consisted of hypokalemia, hyperchloremic metabolic acidosis, inability to lower urine pH below 5.5, nephrocalcinosis, and nephrolithiasis. Additional features included osteomalacia or rickets.

In infancy-
Failure to thrive, poor weight gain.
Recurrent vomiting.
 May have episodes of life threatening metabolic acidosis precipitated by minor infections.
In childhood- delayed physical milestones, short stature, rickets and bony deformities.
 Polyuria and polydipsia are constant features.
Older children- myalgia, fatigue and muscle weakness.
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