Flashcards in Week 5 - Calcium and Renal stones Deck (18)
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1
How much of the Ca in the kidney is reabsorbed? Where does this occur?
-95-98%
-65% paracellular in PCT
-25% in ascending LoH
-10% in DCT under PTH
2
What is the connection between kidney and vitamin D?
-The kidney hydroxylates 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (active vit D) via 1a-hydroxylase
3
What are the functions of active Vit D3?
-Increase bone resorption
-Increase Ca uptake from gut
-Increase resorption in kidneys
4
What controls hydroxylation of active vitamin D?
-PTH which is under negative feedback by Ca and Pi
5
What are the functions of PTH?
-Increase 1a-hydroxylase
-Aids bone remodelling by stimulating osteoclastic activity and slowly osteoblastic activity (to release cytokines to stimulate osteoclasts)
-Increases Ca resorption in kidney
6
What is the function of calcitonin?
-Decrease Ca resorption
7
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
8
What is the main cause of hyperparathyroidism? How does it cause hypercalcaemia?
-Parathyroid adenoma
-Excess PTH secretion causes continual Ca resorption despite plasma concetration
9
What are the symptoms of hypercalcaemia?
-Stones -> real calculi
-Moans -> Depression and cognitive difficulty
-Groans-> constipation
10
Name a malignancy why commonly causes hypercalcaemia
-Squamous cell carcinoma of lung due to secretion of PTHrp
11
How do you treat hypercalcaemia?
-Hydration and loop diuretics
12
What are the symptoms of hypocalcaemia?
-Hyperexcitability of NMJ leading to tetany
-Paralysis, coma, death
13
Where can renal stoned lodge?
-Anywhere along UT but most common at pelviuretic junction, pelvic brim or ureteric orifice
14
Who are renal stones more common in?
-Men
15
What are the main types of renal stone?
-Calcium
-Magnesium ammonium phosphate
-Uric acid
16
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
17
What is the presentation of renal stones?
-Extreme colic
18
