Renal Colic

Question 1

Renal stone compositions and their radiolucency:

Answer 1

Calcium- 75%
- Calcium oxylate, Calcium phosphate
- Hyperexcretion of Ca into urine- hyperCa, hyperPT
- Radiopaque

All other rarely visible on XR (but will see on CT)

‘Struvite’ (Ca, Mg, PO4)15%
- UTI with urea-splitters (Klebsiella, Pseudomonas)
- Females
- Staghorn

Uric acid- 10%
- Hyperexcretion of uric acid- high purine diet (meat, shellfish), cancer
- Like “passing gravel”

Cysteine- 1%

Question 2

Demographic that get kidney stones:

Answer 2

Age 20 - 50
Males (3:1)

Question 3

What is the risk of recurrent renal colic after one episode?

Answer 3

50%

Question 4

Imaging modalities in renal colic:

Answer 4

Ultrasound
- Good initial option
- Look for unilateral hydroureter/hydronephrosis
- May see stone (not always)
- Unable to measure stone
- Will miss 30-40% of cases
–> Go on to further imaging if still suspicious.

CT KUB
- High sensitivity/ specificity (97%)
- Will see almost all stones regardless of composition
- Stone measurement
- Good look for alternative causes incl retroperitoneal
- Infective Cx

Xray
- Only sees calcium-based stones (75%)
- Confusion with calcified vessels/ nodes. May miss if overlying pelvic bones.
- Not diagnostic on own. Order WITH another modality for:
–> Tracking migration
–> Future episodes

IV Pyelogram
- As sensitive/ spec as CT
- Sees all stone types, can measure
- Can see functional obstruction (delayed contrast unilat)
- Retrograde rarely used

Question 5

Ultrasound findings suggestive of renal calculus:

Answer 5

Combined with symptoms

• May see stone
• Unilateral hydronephrosis
• Unilateral hydroureter
• Perinephric/ periureteric stranding
• Unilateral lost ureteric jet
  –> normal = 2 per min

Question 6

Diagnostic approach for first presentation renal colic:

Answer 6

If >50, other risk factors: definitely rule out aortic pathology –> CT.

Question 7

Common sites where renal calculi become obstructed:

Answer 7

• PUJ
• Crossing of iliac vessels/ pelvic brim
• VUJ –> narrowest

Question 8

Rate of spontaneous passage of renal calculi based on stone size/ location:

Answer 8

SIZE:
90% of stones <5mm will pass within a month
The more distal the stone, the more likely

Less likely to pass = >5mm, proximal.

Almost certainly won’t pass = 7mm (<5%)

Question 9

Management in renal colic:

Answer 9

WORK UP
Confirm diagnosis
–> Ultrasound in first instance (if neg, CT)
–> Xray if known radiopaque
Rule out DDx
–> >60, aorta imperative.
Look for complications:
–> AKI
–> Infection
–> Unlikely to pass (>5mm proximal, >7mm)

SUPPORTIVE
Analgesia
- NSAIDS first line (superior efficacy as pain is prostaglandin mediated)
–> Ketorolac IM, indomethacin 100mg PR
Antiemetics
No evidence that extra fluids help (avoid dehydration)

MEDICAL EXPULSIVE THERAPY
- Tamsulosin or nifedipine
–> Has little/ conflicting evidence

DISPOSITION
Most home if pain controlled, stone <5mm and no Cx
Urology FU for all
Admission criteria (see flashcard)
Intervention options:
–> Lithotripsy
–> Ureteroscopy +/- stent
–> Percut nephrostomy

Question 10

Admission criteria in renal colic:

Answer 10

Uncontrolled pain
Infection
AKI
7mm
Single or transplanted kidney

Consider: >5mm and proximal

Question 11

Antibiotics for infected renal calculus:

Answer 11

Amoxicillin 2g QID
+
Gentamicin 5mg/kg IV daily

If no pen: gent only
If no gent: ceftriaxone