Flashcards in Week 5 - Calcium and Renal stones Deck (18)
How much of the Ca in the kidney is reabsorbed? Where does this occur?
-65% paracellular in PCT
-25% in ascending LoH
-10% in DCT under PTH
What is the connection between kidney and vitamin D?
-The kidney hydroxylates 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (active vit D) via 1a-hydroxylase
What are the functions of active Vit D3?
-Increase bone resorption
-Increase Ca uptake from gut
-Increase resorption in kidneys
What controls hydroxylation of active vitamin D?
-PTH which is under negative feedback by Ca and Pi
What are the functions of PTH?
-Aids bone remodelling by stimulating osteoclastic activity and slowly osteoblastic activity (to release cytokines to stimulate osteoclasts)
-Increases Ca resorption in kidney
What is the function of calcitonin?
-Decrease Ca resorption
How do Ca and Pi feedback on PTH?
-High levels of Ca or PTH bind to receptors on PT cells and inhibit/stimulate its release
What is the main cause of hyperparathyroidism? How does it cause hypercalcaemia?
-Excess PTH secretion causes continual Ca resorption despite plasma concetration
What are the symptoms of hypercalcaemia?
-Stones -> real calculi
-Moans -> Depression and cognitive difficulty
Name a malignancy why commonly causes hypercalcaemia
-Squamous cell carcinoma of lung due to secretion of PTHrp
How do you treat hypercalcaemia?
-Hydration and loop diuretics
What are the symptoms of hypocalcaemia?
-Hyperexcitability of NMJ leading to tetany
-Paralysis, coma, death
Where can renal stoned lodge?
-Anywhere along UT but most common at pelviuretic junction, pelvic brim or ureteric orifice
Who are renal stones more common in?
What are the main types of renal stone?
-Magnesium ammonium phosphate
What are the most common causes of renal stones?
-Supersaturation of urine with solute -> low urine volume with hypercalcuria
-Formation of crystals in filtrate cause retention
What is the presentation of renal stones?