Renal Stones Flashcards
(37 cards)
What is urolithiasis/renal calculus?
Formation of stones in the urinary tract.
Where is the most common place for renal stones to form?
Most common place is within the renal pelvis but can form anywhere.
Are renal stones often recurrent?
Often recurrent especially when untreated especially when there is a predisposing factor.
What size are stones usually and how often are there more than one?
Can be single of multiple and 80% are unilateral. Can be minute like sand or staghorn calculi (gives a cast of pelvic and calyceal system) or large concretions in bladder.
Who is more likely to get stones and do stones form in the ureters?
Men get more renal stones than women apart from struvite stones. When in the ureter almost always they have formed further up and been passed down.
Can stones form in the ureter?
When in the ureter almost always they have formed further up and been passed down.
What are the most common reasons for bladder stone formation and why don’t they happen very often anymore?
Often they are seen with a low protein diet, chronic diarrhoea, dehydration, increased oxalate consumption, vitamins A, B1, B6 deficiencies and magnesium deficiencies.
What causes bladders stones to form?
- Bladder outflow obstruction – urethral stricture, neuropathic bladder and prostate obstruction.
- Presence of foreign body in the bladder – catheter, non-absorbable sutures
- Majority now days are passed down from upper urinary tract
If the stones block outflow what can this lead to?
Can lead to anuria and painful bladder distension.
What age is most common for stones?
30 years old
What chemical make up do most stones have?
Calcium makes up 99% of stones – 65% are formed from calcium oxalate with calcium phosphate otherwise known as apatite. Calcium phosphate alone forms 15% of stones and is often seen with hyperparathyroidism and renal tubular acidosis. Uric acid crytals make up only 3-5% of renal stones.
What are struvite stones?
Struvite’s are infection stones – urease stones, triple-phosphate stones (magnesium ammonium phosphate hexahydrate). These occur during or after infection by bacterial which have the urease enzyme.
What type of stones don’t contain calcium?
Other types of stones that don’t contain calcium include Cysteine stones which occur in rare genetic disorders such as cystinuria (cysteines transporter not present for reabsorption), stones occurring from drugs such as Indinavir for HIV, triamterene – a diuretic – and sulphonamide antibiotic.
Why do stones form?
Urine super saturation with minerals (more solute than can hold so crystallises out). Seed crystal forms by nucleation where first step formation results in a new structure that then self assembles. Physical not chemical reaction.
What reasons cause urine to become super saturated?
- Decrease in water content – dehydration.
- Increase in mineral content – hypercalcaemia and hypercalciuria, hyperoxaluria, hyperuricaemia, hyperuricosuria and cysteinuria.
- Decrease in solubility of solute in urine such as change in pH of urine.
How do changes in pH affect stone formation?
Acidic urine favours formation of calcium oxalate and uric acid stones, alkaline urine favours formation of calcium phosphate stones and they are dissolved by acid. Renal tubular acidosis results in persistently alkaline urine and decreased urinary citrate excretion.
Which stones are most commonly caused due to supersaturation?
Supersaturation is the likely cause of uric acid and cysteine stones, calcium bases stone formation may be more complex.
What is Randall’s Plaque and what are ducts of bellini?
Approximately 75% of calcium oxalate stones appear to grow like stalactites attached to exposed interstitial deposits of calcium phosphate, ‘Randall’s plaque’, on the tips of renal papillae. They are composed of a core of calcium phosphate surrounded by calcium oxalate.
Stones can form on plugs protruding from ducts of Bellini (excretory in the kidney) or free in solution.
Why might stones form?
Urine stasis due to low urine flow, obstruction and infection. Drugs can precipitate out of solution by themselves and cause stone formation. Genetic/congenital factors – primary metabolic disturbances e.g. cysteinuria, kidney abnormalities e.g. polycystitc kidneys medullary sponge kidneys.
What assoication do calcium oxalate stones have with metabolic disturbances?
5% are associated with hypercalcaemia and hypercalciuria such as in hyperparathyroidism, bone diseases and sarcoidosis.
55% have hypercalciuria without hypercalcaemia associated with hyperabsorption of calcium from gut or impairment in renal tubular absorption of calcium.
Finally 5% is associated with hyperoxaluria, this is hereditary or secondary to intestinal overabsorption in patients with enteric diseases.
What may cause hypercalciuria?
Can be secondary to Hypercalcaemia, excessive dietary intake of calcium and excessive resorption of calcium from skeleton due to prolonged immobilisation and weightlessness.
What causes are there for Hypercalcaemia relating to neoplasia?
- Hypersecretion of PTH resulting in increased bone resorption. Primary hypercalcaemia is caused by parathyroid hyperplasia of functional tumour, can be secondary to renal failures which causes retention of phosphate and hence hypocalcaemia. Ectopic – secretion of PTH related proteins by malignant tumour e.g. squamous cells carcinoma of lung.
- Destruction of bone tissue by primary tumours of bone marrow, skeleton metastases, Paget’s disease of bone and immobilisation (reduced bone formation whilst resorptions stays the same.
What causes other than neoplasia are there for hyercalcaemia?
- Excessive Vitamin D ingestion
- Thiazide diuretics
- Sarcoidosis – macrophages activate a vitamin D precursor
- Milk alkali syndrome (excessive calcium intake).
What clinical sings are there of hypercalcaemia?
Severe muscle weakness (opposite to hypocalcaemia where you get tetany), painful bones – fractures, renal stones, abdominal groans (constipation, peptic ulcers, pancreatitis and gallstones), psychic moans – (depression, lethargy and seizures).
Bones stones groans and moans.
