Urinary: Renal Stones Flashcards Preview

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Flashcards in Urinary: Renal Stones Deck (17)
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1
Q

What is the most common site for stones to form?

A

The renal pelvis

however they can form anywhere in the urinary tract

2
Q

What are the causes of bladder stones?

A

Bladder outflow obstruction eg urethral stricture, prostate obstruction, neuropathic bladder (cant contract properly)
- gives time for the crystals to form

Presence of a foreign body eg catheter

Most are passed down from upper urinary tract

Drugs

Idiopathic

3
Q

Who do renal stones effect?

A

People aged over 30

2x more common in men (except struvite stones which are related to UTIs therefore more common in women)

4
Q

What are renal stones made of?

A

Calcium stones: (99%)

  • calcium oxalate with calcium phosphate
  • calcium phosphate alone
  • uric acid
  • struvite - triple phosphate stones

Others: (1-2%)

  • cysteine stones (occur in rare genetic disorder causing cystinuria)
  • drug stones
  • ammonium acid urate stones
5
Q

Why do urinary stones form?

A

If the urine is supersaturated with minerals - means there is more solute than can be held in solution, so they form solid crystals.

6
Q

How can the urine become supersaturated?

A
  • Decrease in water content eg dehydration (people with stones advised to drink a lot of water)
  • Increase in mineral content eg hypercalcaemia which is treatable
  • Decrease in solubility of a solute in urine eg a change in pH
7
Q

Hypercalciuria is a common abnormality in stone formers. What are the causes?

A
  • idiopathic
  • hypercalcaemia
  • excessive dietary intake
  • excessive resorption from skeleton eg prolonged immobilisation or weightlessness (astronauts)
8
Q

What are the causes of hypercalcaemia?

A

Hypersecretion of PTH -> increase bone resorption:

  • primary = hyperparathyroidism
  • secondary to renal failure which usually causes retention of phosphate so hypocalcaemia
  • ectopic secretion of PTH-related protein by malignant tumour eg squamous cell carcinoma of lung

Destruction of bone tissue by tumours, metastases, Pagets increased bone turnover, immobilisation

Others - excessive vit D, thiazide diuretics, sarcoidosis

9
Q

What are the signs of hypercalcaemia?

A

BONES - pian and fractures
STONES
GROANS in abdo - constipation, ulcers, pancreatitis
MOANS - depression, lethargy, seizures

10
Q

What are struvite stones?

A

They are ‘infection stones’ which form secondary to UTIs with organisms with the enzyme urease
Also the protduction of mucoprotein from infection provides a matrix for the stones to grow on.
They tend to form staghorn calculus - same shape as renal pelvis (they are very large)

11
Q

When do uric acid stones form?

A

Form when there is hyperuricaemia (also causes gout) which is often see in dehydration and tumour lysis syndrome
Also seen in people which have urine with pH <5.5

You cannot see them on xray.

12
Q

How do renal stones present?

A

Most are asymptomatic.

Can get renal colic - agonising, caused by spasm of ureter as it attempts to expel the stone 
Recurrent UTIs
Haematuria
Renal failure
Urinary tract obstruction
13
Q

What investigations are done when there is a suspected renal stone?

A

MSU - look for haematuria, urinary casts, culture
Serum - urea, creatinine, electrolytes, calcium
Abdo xray (uric acid stones cant be seen)
CT - can see all stone types

14
Q

What complications can occur from renal stones?

A

Acute pyelonephritis +/- gram negative septicaemia
Pressure necrosis of renal parenchyma
Hydronephrosis from urinary obsruction
Ulceration through the wall of collecting system

15
Q

How are urinary stones treated?

A
  • Analgesia with rest and warmth to the site of pain
  • Stones in the bladder or lower ureter can be grabbed in ureteroscopy
  • Extracorporeal shock wave lithotripsy (fragments stones so that they can be passed more easily)
16
Q

How can stones be prevented?

A

By decreasing urine supersaturation:

  • drink more water
  • decrease excretion of calcium (thiazide diuretics cause reab on calcium)
  • alkalinise urine
17
Q

What nerve root distribution is the pain of renal colic?

A

L1

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