Renal Tubular Disease Flashcards
What’s the main function of the Loop of Henle?
to reabsorb Na+
- approx 30% of the filtered Na+ is reabsorbed
- generates the medullary gradient
What’s the main function of the distal tubule and collecting tubule/duct?
- fine regulation of electrolytes (Na+, K+, Ca2+)
- acid/base regulation
- water resorption
Define cystinuria.
Inheritable genetic defect leading to failure of particular non-essential amino acid reabsorption
- cystine is insoluble in acidic urine –> forms calculi
What’s the clinical signs of cystinuria?
- calculi formation usually noted around 5y
- Lab and Newfies as young as 4-6m
- stranguria, pollakiuria, and hematuria
- urethral obstruction (male)
What’s the treatment for cystinuria?
- protein restricted diet
- alkalinization of urine (usually done with diet, can be done with thiol drugs, like 2-MPG)
What’s the significance of carnitinuria?
excessive loss will lead to deficiency –> cardiomyopathy
How does carnitinuria happen and how is it treated?
Can occur with dogs with cystinuria, but a high fat diet would exacerbate carnitine loss
What defect makes Dalmatian more prone to hyperuricosuria?
- defect in uric transport across the hepatic membrane –> limited uric metabolism
- also has less reabsorption in the proximal tubule
- a defective membrane transport –> active secretion in the distal tubule
- has normal uricase
How common is hyperuricosuria in Dalmatians?
25% of male Dalmatians will show clinical signs
- autosomal recessive
What’s another cause of hyperuricosuria, esp in non-Dalmatians/ cats?
primary liver disease
How is hyperuricosuria treated in Dalmatians?
allopurinol
What’s the MOA of allopurinol?
It’s a XO inhibitor –> blocs the metabolism of hypoxathine and xanthine to uric acid
- do NOT give allopurinol if not on purine restricted diet –> will lead to hyperxanthinuria
How is liver-related hyperuricosuria treated?
NOT with allopurinol (also don’t give to cats)
How is dilute urine accomplisehd?
protein restricted diet reduces renal medullary concentration ability
What’s the max transport capacity for glucose in the proximal tubules?
Dogs: 10-12.2 mmol/L
Cats: 14.4-17.2 mmol/L
Define Fanconi Syndrome.
- glucosuria with euglycemia
- also have amino acid in urine, and bicarbonate loss leading to systemic acidosis
What are some causes of Fanconi Syndrome?
- Inherited: Basenji! 10-30% of them
- Acquired: toxins, hypoparathyroidism, cancer, gentamicin, toxins that cause proximal tubular necrosis
What’s the MOA of Fanconi Syndrome?
- abnormal glucose absorption –> glucosuria –> osmotic diuresis
- amino acid resorptive abnormalities
- abnormal absorption of bicarbonate, Na+, K+ and urate
What are some clinical signs of Fanconi Syndrome?
- PU/PD
- weight loss
- poor haircoat
- weakness
- dehydration
- weakness from hypokalemia
What’s the treatment for Fanconi Syndrome?
Inherited = supportive therapy only
Acquired = resole underlying cause
What’s the prognosis for Fanconi Syndrome?
with intensive supportive therapy = approx 5y
How does the renal tubules maintain acid/base balance?
Proximal tubule: reabsorption of bicarbonate
Distal tubule: excretion of H+
What’s the abnormalities noted with a proximal tubule renal tubular acidosis?
- hyperchloremic
- metabolic acidosis is self-limiting as the distal tubule can excrete H+
- acid urine pH
- normal GFR
What’s the abnormalities noted with a distal tubule renal tubular acidosis?
- hyperchloremic
- metabolic acidosis, more severe than proximal tubule RTA
What is nephrogenic diabetes insipidus?
Congenital (rare): deficiency of ADH receptors
Acquired: receptor interference - drugs, toxins (E coli), metabolic conditions (hypokalemia, hypercalcemia), tubular injury/ loss
How is nephrogenic diabetes insipidus treated?
- Na+ and protein restricted diet –> less solutes to the kidneys, less urine produced
- diuretics! induce mild dehydration will promote proximal tubule water reabsorption –> reduces urine output by 20-50%
