URINARY TRACT CALCULI

Question 1

What is nephrocalcinosis?

Answer 1

Nephrocalcinosis refers to calcification within renal parenchyma from calcium deposition

Question 2

Types of stones?

Answer 2

Calcium oxalate & calcium phosphate
Magnesium ammonium phosphate
Uric acid
Cystine

Question 3

Types of stones and their appearance

Answer 3

(1)Calcium oxalate and calcium phosphate=irregular with sharp projections & radio opaque
(2)Magnesium ammonium phosphate=smooth and dirty white
(3) Uric acid = hard,smooth,often multiple & radio lucent
(4) Cystine= hexagonal,translucent,white crystals

Question 4

What is the other name of magnesium ammonium phosphate?

Answer 4

Struvite or staghorn calculi

Question 5

How is magnesium ammonium phosphate formed?

Answer 5

They are formed by urea splitting bacteria (proteus) which converts urea to ammonia

Question 6

Urine characteristics of all stones?

Answer 6

(1) calcium oxalate & phosphate
•inc calcium,oxalate,urate
•dec citrate & volume
•inc pH

(2)Magnesium ammonium phosphate
•inc ammonia
•inc pH > 7 (alkaline)

(3) Uric acid
•inc uric acid(e.g gout)
•dec pH(e.g from chronic diarrhea)

(4)cystine
•low urinary pH

Question 7

Diagnosis of renal stones?

Answer 7

Abdominal xray(90% of stones contain calcium and are seen on Xray)
Intravenous urography-> most commonly used investigation
Non-contrast spiral CT scan ->most accurate investigation
Other investigations-> urinalysis,urine culture,UCE,BUN:Cr,electrolytes,PO4,PTH,uric acid

Question 8

Causes of calcium oxalate & potassium stones?

Answer 8

They are caused by
•idiopathic hypercalciuria without hypercalcemia->50%
•hypercalciuria & hypercalcemia->10%
•hypocitraturia-> associated with acidosis and chronic diarrhoea
•hyperoxaluria