Urinary: Calcifications

Question 1

What are the most common kidney stones?

Answer 1

• Calcium oxalate (most common)
• Struvite stones
• Uric acid
• Cysteine
• Indinavir

Question 2

Cysteine kidney stones are associated with…

Answer 2

Congenital disorders of metabolism

Question 3

Indinavir kidney stones are are associated with…

Answer 3

HIV

Question 4

Which is the only kidney stone that is not seen on CT?

Answer 4

Indinavir stone

Question 5

Treatment for kidney stone

Answer 5

• Medical management (stones <5 mm)
• Intervention (stones >10 mm)

Note: Between 5-10 mm is variable. Uric acid stones can usually be treated medically regardless of size.

Question 6

Which type of kidney stone can usually be treated medically, even when very large?

Answer 6

Uric acid stones

Note: All you need is potassium citrate or sodium bicarbonate to increase the pH of the urine and “melt” the uric acid stones.

Question 7

Staghorn calculi are usually what type of stone?

Answer 7

Struvite

Note: These require alkaline urine to grow, usually in the setting of a Proteus or Klebsiella infection.

Question 8

How can you differentiate uric acid stones from other types of kidney stones on imaging?

Answer 8

• Uric acid stones have a lower attenuation (<500 HU)
• Uric acid stones have little if any change in HU on dual energy CT (due to the composition of lighter atoms)

Question 9

How do most kidney stones change on duel energy CT?

Answer 9

Most kidney stones will be have a higher HU at 80 kVp relative to 140 kVp

Note: The important exception are uric acid stones which have no to minimal change on duel energy (if any change it will be the opposite of other stones, having a lower HU on 80 kVp relative to 140 kVp).

Question 10

Answer 10

Cortical nephrocalcinosis (sequela of cortical necrosis)

Note: Cortical calcifications. Disseminated PCP and tuberculosis can look like this also.

Question 11

Differential for cortical nephrocalcinosis

Answer 11

Acute drop I blood pressure:

• Shock
• Postpartum
• Burn patients

Question 12

Answer 12

Medullary nephrocalcinosis

Note: Hyperechoic renal papilla/pyramids (may or may not shadow on ultrasound).

Question 13

Common causes of medullary nephrocalcinosis

Answer 13

• Hyperparathyroidism (most common)
• Medullary sponge kidney (second most common)
• Lasix use
• Renal tubular acidosis type 1

Note: Hyperparathyroidism and type 1 RTA tend to cause more dense calcification than medullary sponge.

Question 14

Answer 14

Medullary nephrocalcinosis

Question 15

Medullary sponge kidney

Answer 15

A congenital cause of medullary nephrocalcinosis (usually asymmetric) due to underlying cystic dilatation of the collecting tubules

Question 16

Medullary sponge kidney is associated with…

Answer 16

• Ehlers-danlos
• Caroli’s
• Beckwith-Wiedemann