Kidney stones (R1)

Question 1

Clinical anatomy
- Name the 3 sites of constriction within the ureter
- Which point is the narrowest?

Answer 1

Ureteropelvic junction
Pelvic inlet (where ureter enters the pelvis)
Ureterovesicular junction (narrowest)

Question 2

Aetiology
- Why do kidney stones form? (In terms of solutes/solvents)
- What 2 ions inhibit crystal formation?

Answer 2

Urine becomes too concentrated (↑ solutes, ↓solvent/water) –> supersaturation of urine –> solute precipitates out to form the stone.
Magnesium and citrate

Question 3

Aetiology
- Types of stones, from most to least common?

Answer 3

Calcium oxalate stones
Calcium phosphate stones
Uric acid stones
Struvite stones
Cystine stones
Xanthine stones

Question 4

Aetiology
- Calcium oxalate stones form in [acidic/basic] urine, while calcium phosphate stones from in [acidic/basic] urine
- Reasons why each can from?

Answer 4

Calcium oxalate: acidic (oxalate is an acid)
Calcium phosphate: basic (phosphate is a base)

Too much calcium
- Hyperparathyroidism
- Increased calcium absorption in GIT
- Decreased renal tubular calcium reabsorption

Too much oxalate
- Genetics
- Liver metabolism defect
- Diet: rhubarb, spinach, chocolate, nuts, beer (oxalate rich)

Question 5

Aetiology: uric acid stones
- Uric acid is formed from the breakdown of which substance?
- What foods are high in this substance –> promote uric acid stone formation?
- Seen in what condition?

Answer 5

Purines
Red meat, organ meat, anchovies, shellfish
Gout.

Question 6

Aetiology: struvite stones
- Produced by which bacteria? Hence, risk factor?
- What shape?

Answer 6

Urease producing bacteria (eg. proteus) - UTI’s
Staghorn

Question 7

Aetiology
- Cystine stones are produced in which condition?
- Xanthine stones: xanthine is a breakdown product of which substance, hence has similar properties to which stones?

Answer 7

• Cystinosis
• Purines: hence, uric acid stones

Question 8

Applied biomedical sciences
- Where in the nephron do stones tend to form?
- Where do the stones tend to lodge? Implications for the site of pain?
- Describe size of stones
- Is true urinary retention common with kidney stones?

Answer 8

Loop of Henle –> collecting duct
The three constriction sites - lon to groin pain.
Size
- 90 to 95% of stones are 5mm or less, and pass on their on
- 6-7 mm stones are borderline
- Stones 8mm and bigger will not pass on their own
Rare, can only happen if both ureters are blocked.

Question 9

3 complications?

Answer 9

Urinary obstruction –> hydronephrosis
Obstructive pyelonephritis
AKI

Question 10

Complications
- Describe how obstructive pyelonephritis occurs
- Do individuals with obstructive pyelonephritis get sick quickly?

Answer 10

Ureter is obstructed by a stone.
Leads to urinary stasis in the kidney –> bacteria multiply –> pyelonephritis.
Infection has nowhere to go but the kidney - BAD

Yes

Question 11

Risk factors for kidney stones?

Answer 11

• Personal and family history of kidney stones
• Demographics: obese, white, male
• Dehydration, high salt diet

Question 12

Prevention
- 3 ways?

Answer 12

Most important: hydration
Decrease sodium intake
Optimal BMI

Question 13

Clinical features
- History?

Answer 13

Question 14

Clinical features
- Exam?

Answer 14

Abdomen: while kidney tenderness may be present, it is more often absent (not -itis positive)

Question 15

Investigation
- Bedside?

Answer 15

Question 16

Investigation
- Labs?

Answer 16

Question 17

Investigation
- Imaging?

Answer 17

CT KUB (non contrast) is gold standard.
For pregnant individuals and young people: ultrasound

Question 18

Investigation
- Why is CT KUB non contrast?
- Jon’s 4 indications?

Answer 18

Non contrast means nothing else is bright except the stone.

• Impaired eGFR
• Signs of infection
• Reaching ceiling of analgesia
• Serious/equally likely diagnosis to rule out (eg. AAA)

Question 19

Treatment
- Principles of management?

Answer 19

Manage symptoms
Conservative treatment: medical expulsive therapy
OR interventional management

Question 20

Treatment
- Symptom management?

Answer 20

Analgesia: NSAIDs –> opioids
Antiemetics
Hydration: IV fluids

Question 21

Treatment
- When is conservative treatment vs interventional treatment indicated?

Answer 21

Conservative treatment for small stones <=5mm, interventional management for large stones >=8mm

Question 22

Treatment: conservative treatment/medical expulsive therapy
- How does it work?
- First and second line medications?

Answer 22

Helps relax the ureteral SMC to help the stones pass
First line: tamsulosin (alpha blocker)
Second line: nifedipine (CCB) - currently not routinely recommended

Question 23

Treatment: interventional management
- What are the 3 procedures?

Answer 23

Shockwave lithotripsy: shockwaves break up stones so they can pass.
Ureteroscopy (endoscopic removal of the stone) +- stent placement (allows urine drainage)
Large stones >=20mm: percutaneous nephrolithotomy: tube into kidney to remove the stone.

Question 24

Treatment
- Treating obstructive pyelonephritis

Answer 24

Question 25

Patient explanation
- What are kidney stones?
- What are the symptoms?

Answer 25

When stones form in your kidneys.
Stones leave the kidneys, go into the tubes.
Tubes contract on the stone, causing the tube to become irritated –> pain, blood in urine.
Can become generally unwell –> N&V