Week 7 - Renal Stones

Question 1

What is urolithiasis?

Answer 1

Formation of stones in the urinary tract

Question 2

Where is the commonest site of urolithiasis?

Answer 2

Renal pelvis

Question 3

What is a pelvis stone?

Answer 3

Formed in the renal pelvis

Question 4

What is a staghorn stone?

Answer 4

Is a cast of pelvic and calyceal part of kidneys

Question 5

What is lithotomy?

Answer 5

Surgical removal of a calculus from bladder, kidney or urinary tract

Question 6

What are the causes of bladder stones?

Answer 6

Bladder out flow obstruction e.g. Urethral stricture, neuropathic bladder, prostate obstruction
presence of foreign body e.g. Catheter or non absorbable sutures
Some are passed down from upper urinary tract

Question 7

What is the consequence of bladder stones?

Answer 7

Can cause bladder obstruction which causes anuria (difficulty urinating and painful bladder distention)

Question 8

What is a renal stone?

Answer 8

Solid material formed in the kidneys from minerals in the urine

Question 9

Are renal stones more common in men or woman?

Answer 9

Men are twice as likely to get them than women except for struvite stones

Question 10

What are renal stones made of?

Answer 10

Mainly calcium stones which are usually calcium oxalate with calcium phosphate
Can be calcium phosphate alone, uric acids, cysteine stones or from drugs

Question 11

What is a struvite stone?

Answer 11

Urease stones due to infection

Made of magnesium ammonium phosphate hexahydrate from bacteria which have urease

Question 12

How do cysteine stones form?

Answer 12

Occur in a rare genetic disorder called cystinuria

Cystine crystallises in the urinary tract

Question 13

Why do urinary stones form?

Answer 13

If there is urine superstation with minerals so solvent contains more solute than it van hold in solution
Seed crystals form by nucleation

Question 14

How can urine become supersaturated with minerals?

Answer 14

Decrease in water content
Increase in mineral content
Decrease in solubility of solute in urine

Question 15

What can cause decrease in water content in bladder?

Answer 15

Dehydration

Question 16

What can cause an increase in mineral content in bladder?

Answer 16

Hypercalcaemia and hypercalciuria
Hyperuricaemia and hyperuricosuria
Hyperoxaluria
Cysteinuria

Question 17

What can cause a decrease in solubility of solute in urine?

Answer 17

Change in pH
Acid urine favours formation of calcium oxalate and uric acid stones
Alkaline urine favours formation of calcium phosphate stones

Question 18

How do most calcium oxalate stones form?

Answer 18

Grow like stalactites attached to exposed interstitial deposits of calcium phosphate called Randall’s plaque on tips of renal papillae

Question 19

What other factors can cause renal stones?

Answer 19

Urine stasis - low urine flow
Obstruction
Infection
Drugs
Genetic/congenital factors (primary metabolic disturbances, kidney abnormalities like polycystic kidneys)