9b.) Stones Flashcards
When do stones form in kidneys?
When the stone forming substance reaches high enough concentration to cyrstallise out of solution. But note, that other debris and crystals can promote crystal growth at lower concentrations
What are urinary calculi most commonly formed from?
Calcium (80% of all stones)
If someone frequently gets urinary calculi, what 2 things must you investigate/analyse?
- Urine
- Stone
What 3 places can stones be located?
- Kidneys
- Ureters
- Bladder
Describe how we cataegorise kidneys stones based on where they are
- Staghorn: filling numerous major and minor calices
- Non-staghorn:
- Calyceal: in minor calyx
- Pelvic: in renal pelvis
- Ureteral:
- Proximal
- Middle
- Distal
State the chances of the following kidney stones being passed:
- <5mm
- 5-7mm
- >7mm
- <5mm = high chance
- 5-7mm= 50% chance
- >7mm= almost always require urological intervention
Renal colic (flank pain) developas as the stone does what?
Begins to pass down urinary tract
Approx 90% of stones are sucessfully passed out of urinary tract; but some have to be removed. State, and briefly desribe, 3 surgical methods to remove urinary calculi
- Ureteroscopy: uteroscope up urethra, through bladder and to ureter. Try to move stone or break up with laser. General anaesthetic
- Percutaneous nephrolithotomy: small cut in back (between T11 and T12) and stone is either pulled out or broken into smaller pieces using a laser. General anaesthetic
- Shock wave lithotripsy: locate stone with USS. Ultrasound shock waves targeted at kidney stone to break it up- fragments passed out over severeal weeks. Give analgesia before. Often need multiple sessions
State 2 types of calcium stones
- Calcium oxalate
- Calcium phosphate
Calcium stones make up 80% of all stones; state some other types of stones
- Uric acid (9%)
- Struvite-from inffection by bacteria that have enzyme urease (10%)
- Others (1%) e.g. drug stones, cystine etc…
What does the stone type tell us about the supersaturation of urine at the time the stone was formed?
Stone type represents/correlates to the supersaturation present in urine when stone formed
e.g. If urine was supersaturated with calcium, a calcium stone would form
What is the ‘proper’ term for formation of stones in urinary tract?
Urolithiasis
Kidney stones have a high recurrence rate; true or false?
True
How long does it take for most stones to pass?
1-2 months
State some potential causes/risk factors for urolithiasis
- Metabolic: secondary to hypercalcuria
- Urinary infection with proteus, pseudomonas, klebsiella
- Diet: high salt, obese
- Medication: furosemide
- Genetic: primary hyperoxaluria, cystinuria
How do we confirm if someone has a kidney stone?
CT scan
Discuss criteria that determine whether someone with a kidney stone is suitable for treatmetn with shock wave lithotripsy
Define nephrocalcinosis
Diffuse renal calcium deposition
Why is first voided morning urine often the best for analysis?
It is the most concentrated
What does specific gravity measure/tell us about urine?
Specific gravity used to measure osmolality of urine; consequently, it can tell us about the concentrating ability of the kidneys.
*NOTE: after a period of dehydration urine osmolality should be 3-4 tiems that of plasma
Describe the typical clinical presentation of someone with kidney stones
- Haematuria
- Loin-groin pain
- Dysuria
- Nausea/vomitting
- Abdo discomfort
State some medical conditions associated with stone formation
- Hypercalcaemia
- Hyperparathyroidism: increase calcium
- IBD: excessive water loss in diarrhoea, excessive absorption oxalate in GI tract
- Hyperthyroidism: increase calcium loss from bone
- Malignancy: bone mestases increse calcium loss from bone
State some risk factors for devloping kidney stones
- Dehydration
- Reduced urinary volume
- Low calcium diet (usally oxalate binds to calcium in gut, if your diet is low in calcium oxalate will bind to calcium in kidneys forming stones)
- Obesity
- High salt diet
- Excessive laxative use (dirsupt mineral and nutrient balance and dehydrate you)
State some medications associated with kidney stone formation
- Asprin
- Antacids
- Certain anti-epiletpic medications
- Certain anti-retroviral drugs
