Nephrolithiasis

Question 1

What are the features of a nephrolithiasis presentation?

Answer 1

Nephrolithiasis:
Flank pain
Acute onset of pain
Hematuria; isomorphic RBCs
Positive KUB (CT)

Question 2

How is the stone composition determined in nephrolithiasis?

Answer 2

Stone analysis is the definitive test. Radiology will narrow down radio-opaque vs. radio-lucent stones. Urinalysis and urine microscopy may reveal crystals that will infer the type of stone.

Question 3

Describe the urine microscopy appearance of calcium oxalate stones.

Answer 3

Envelopes

Question 4

Describe the urine microscopy appearance of uric acid stones.

Answer 4

Rhomboid shape and polarize on microscopy.

Question 5

Describe the urine microscopy appearance of struvite stones.

Answer 5

Coffin lids

Question 6

Describe the urine microscopy appearance of cysteine stones.

Answer 6

Hexagonal

Question 7

Describe the urine microscopy appearance of calcium phosphate stones.

Answer 7

Brushite crystals: long, thin rectangles

Question 8

What type of crystals form in the tubular lumen and why?

Answer 8

Struvite, uric acid, brushite and cystine stones form in the tubular lumen. This occurs because there is +++water removal here and so the concentration of the solute increases and the concentration of the solvent decreases leading to supersaturation.

Question 9

Where do calcium oxalate stones form?

Answer 9

Interstitium; LoH is hypertonic (there is little water hanging around) so addition of calcium can more easily lead to supersaturation and stone formation.

Question 10

When should nephrolithiasis patients be referred to urology?

Answer 10

5 Ps for when to refer to urology:

1. Pyrexia (fever)
2. Post-renal failure
3. Persistent symptoms
4. Previous problems (ex. difficulty passing stones)
5. Pretty big stone (>0.5cm)

Question 11

What is the work up and treatment for first time stone formers?

Answer 11

• Capture stone and do analysis
• Serum Cr, calcium and/or urate concentration
• Radiological fall up at 6-12 months
• Hydration
• Pain relief

Question 12

What are the indications for hospital admission in nephrolithiasis?

Answer 12

Indications for Admission:
Intractable pain
Intractable nausea/vomiting (dehydration/pre-renal failure)
Post-renal failure
Infection