Urologic Stone Disease

Question 1

Remarks on struvite stones

Answer 1

• 10% of stones
• made up of magnesium - ammonium - phosphate
• more commonly in women with recurrent urinary tract infection
• most common cause of staghorn calculi

Question 2

Struvite stones are commonly associated with infection by these group of organisms

Answer 2

Urea-splitting bacteria (Proteus, Klebsiella, Staph, Providencia and Corynebacterium)

Question 3

Remarks on uric acid

Answer 3

• occurs more commonly in med
• are radiolucent, and urine is typically acidic

Question 4

Remarks on creatinine and acute obstruction due to stones

Answer 4

• Most patients have NO rise in serum creatinen because the unobstructed kidney function at up to 185% of its baseline capacity
• A rise in serum creatinine in acute obstruction suggests a solitary kidney or preexisting renal disease

Question 5

Most common sites of obstruction

Answer 5

1. Ureteropelvic junction (1cm pelvis constricts into the 2-3mm ureter)
2. Pelvic brim (where the ureter courses over both the pelvis and the iliac vessels)
3. Ureterovesical junction - most constricted site due to the muscilar coat of the bladder

Question 6

Two mimickers of nephrolithiasis that are very important to exlude

Answer 6

• abdominal aortic aneurysm
• renal artery infarction

Question 7

Disadvantage of US in detecting stones

Answer 7

1. Insensitive for mid-ureteral stones
2. May miss smaller (<5mm in diameter)

Question 8

ABSOLUTE indication for admission in patients with nephrolithiasis

Answer 8

• intractable pain or vomiting
• urosepsis (INDICATION FOR URGENT DECOMPRESSION)
• single or transplanted kidney with obstruction
• acute kidney injury
• hypercalcemic crisis
• severe medical comorbidities/ advanced age

Question 9

RELATIVE indications for admission

Answer 9

• fever
• solitary kidney or transplanted without obstruction
• obstructing stone with signs of urinary infection
• urinary extravasation
• significant medical comordities
• stone unlikely to pass - large stone above the pelvic brim

Question 10

Medication used for medical expulsion therapy

Answer 10

Tamsulosin (alpha-blockers) 0.4mg PO OD
Terazosin 5-10mg OD
Doxazosin 4mg OD