Urinary Tract Calculi

Question 1

What chemicals may calculi be formed from

Answer 1

Calcium oxalate (75%)
Uric acid (10%)
Struvite (5-10%)
Calcium phosphate (5%)
Cystine (2%)
Xanthine (<1%)

Question 2

Describe calcium oxalate stones

Answer 2

Associated with hypercalciuria (+ oxalate + citrate)
pH decreased (acidic)
Crystals - binconcave dumbells or bipyramidal envelopes
Radiopaque

Question 3

Describe uric acid calculi

Answer 3

Associated with gout (raised purine, uric acid)
pH decreased (acidic)
Crystals = rounded rhomboids/needle-shaped
Radiolucent

Question 4

Describe struvite calculi

Answer 4

Associated with UTIs with urease-producing bacteria
pH increased (alkali)
Crystals: stag-horn or rectangular prisms (Coffin-lid)
Radiopaque

Question 5

Describe calcium phosphate calculi

Answer 5

Associated with hyperparathyroidism and RTA T1/T3
pH increased (Alkaline)
Crystals: wedge-shaped prism
Radiopaque

Question 6

Describe cystine calculi

Answer 6

Associated with cystinuria and inherited errors of metabolism
pH decreased (acidic)
Crystals: hexagon shaped
Weakly radiopaque

Question 7

Describe xanthine calculi

Answer 7

Associated with xanthinuria
Crystals: amorphous
Radiolucent

Question 8

Risk factors for urinary tract calculi

Answer 8

Dehydration
High salt intake
White ancestry
Male sex
Obesity
Crystalluria
Occupation exposure to dehydration | Warm climate | family history of nephrolithiasis | Precipitant medications

Question 9

Symptoms of urinary tract calculi

Answer 9

Loin to groin pain
S - Loin
O – Sudden
C – Sharp, may be dull ache
R – Groin, scrotum, labium
A – Nausea and vomiting, voiding symptoms
T – Constant (kidney) or intermittent/colicky (ureteric)
E -
S – excruciating, 8-10/10
Bladder stone/UTI: Dysuria | Frequency | Strangury | Penile tip pain
Ureter stone :Urinary retention
Fever

Question 10

Signs of urinary tract calculi on examination

Answer 10

Patient is restless and writhing/rolling in pain
Flank or loin tenderness
Sepsis: tachycardia, hypotension

Distended bladder (ureteric stones)

Question 11

Investigations for urinary tract calculi

Answer 11

Urine dipstick + MC&S: + leukocytes/nitrates/blood OR normal
Urine pregnancy

Renal screen
Bone profile: ?hypercalcaemia
Uric acid: ?hyperuricaemia
FBC: ?infection
CRP: raised
Clotting screen: for planned surgery

Non-contrast CT KUB: calcification in the renal collecting system or ureter hydronephrosis | perinephric stranding
KUB X-ray: ?calcification
Renal US: for pregnant women or children
Stone analysis

Question 12

Management for urinary tract calculi

Answer 12

Symptomatic relief:
Analgesia: opiate, NSAID
Renal colic - PR diclofenac (CI in CVD)
Medical expulsive treatment: if <10mm calculi
- CCB (e.g. nifedipine) → ureteric spasm
- 𝝰 blocker (e.g. Tamsulosin) → ureteric spasm

Obstruction confirmed
Refer to uro
Renal decompression (percutaneous nephrostomy) and empirical antibiotics

No obstruction
Conservative, watchful waiting
Consider surgery if stone >10mm
1. External shockwave lithotripsy (ESWL)
2. Ureteroscopy if ESWL CI
3. Percutaneous nephrolithotomy (PCNL) if above fails - used for complex stones e.g. staghorn

Pregnant → Uteroscopy

Question 13

Long-term management for urinary tract calculi

Answer 13

For those with recurrent stones
Tailor towards the underlying factors

• Increased fluid intake (>3L/day)
• Reduce salt intake
• Reduce sugar intake
• Normal protein intake
• Diet modifications: avoid tea/strawberries/rhubarb/chocolate/nuts etc.
• Diet modifications: eat wholemeal/high fibre/potatoes/vegetables

Question 14

Complications of urinary tract calculi

Answer 14

Ureteric stricture: passage of stone or removal of stone.
→ Insert stent if necessary
Acute or chronic pyelonephritis: potential of sepsis
→ Sepsis 6
Renal failure: obstruction and back pressure causing hydronephrosis and kidney damage
→ Stone removal and close medical management
→ Renal monitoring
Intrarenal or perinephric abscess: complication of pyelonephritis, particularly if large “staghorn” stones are present. Pus discharges through the renal capsule into the perinephric fat
→ Drainage of abscess
Xanthogranulomatous pyelonephritis: chronic bacterial pyelonephritis with destruction of renal parenchymas and granuloma presence
→ Nephrectomy
Urine extravasation into the pelvic cavity
→ Drainage of extravasated urine and urine flow diverted so it does not continue
→ Fluid + antibiotics

Question 15

Prognosis for urinary tract calculi

Answer 15

20% of calculi will not pass spontaneously
50% have recurrence within 5 years, 80% recurrence within 10 years