Stones

Question 1

RFs for renal stones (20)

Answer 1

Male

caucasian>hispanic>black>asian

age 20-50

poor fluid intake

sedentary lifestyle

drugs: steroids, topiramate, chemo for myeloproliferative disorders

high protein diet

hot climate

reconstructed urinary tract

catheterisation

excess vit D>calcium

excess vit C>oxalate

obesity

imbalance of urinary pH

hyperparathyroidism

UTI

gout

genetic

previous stone=50% chance of recurrence

systemic disorders: RTA, sarcoid (hypercalcaemia), IBD, stoma bags

Question 2

Types of urinary stones (5)

Answer 2

calcium oxalate

calcium phosphate

struvite

uric acid

cystiene

Question 3

Features of calcium oxalate stones (3)

Answer 3

most common

caused by hypercalciuria, hyperuricosuria, hyperoxaluria

increased in Crohn’s

(oxalate often)

Question 4

Features of struvite stones (4)

Answer 4

magnesium ammonium phosphate

form staghorn calculi

assoc. w. infection (struvite strep)

when stones assoc. w. UTI, causative organism is usually proteus which raises urinary pH

Question 5

Features of uric acid stones (2)

Answer 5

radio-lucent

assoc. w. gout, high protein intake and high cell turnover e.g. tumour lysis, leukemias

Question 6

Features of cysteine stones (2)

Answer 6

only occur in cysteinuria-genetic defect w. impaired renal reabsorption of COAL amino acids.

faintly radio-opaque

Question 7

Presentation of urinary stones (3)

Answer 7

often found incidentally

renal colic

features of urinary obstruction

Question 8

Features of renal colic (6)

Answer 8

sudden onset, severe pain-unable to keep still

starts from flank, radiates to groin

visible haematuria

nausea/vomitting

chills/rigors

fever

(pain is due to dilatation and spasm of obstructed ureters)

Question 9

Ix for urinary stones (3)

Answer 9

urine:

• dip: haematuria, if -ve, consider: appendicitis, salpingitis, diverticulitis, ruptured AAA, ectopic pregnancy
• MC+S

Bloods: U+E for renal function

imaging:

• non-contrast CT KUB gold standard
• XR KUB
• USS to look for hydronephrosis/hydroureter: preferential in pregnant women

Question 10

Mx of urinary stones (6)

Answer 10

for colic:

• fluid resuscitation
• analgesia: diclofenac
• anti-emetics

if obstruction+infection, urosepsis, intractable pain/vomitting, impending acute renal failure, bilaterally obstructed/single kidney then urgent:

• percutaneous nephrostomy
• ureteric stent (viat ureter)

stones <5mm should pass spontaneously, if larger they made require intervention

Question 11

Options to aid stone expulsion (4)

Answer 11

medical expulsion

if not passing after 1mo, elective surgical Mx:

• ESWL
• flexible ureterorenoscopy
• PCNL

Question 12

Medical expulsion of stones (3)

Answer 12

analgesia: diclofenac

alpha blockers 1st line: tamsulocin, help relax tube

nifedipine 2nd line

Question 13

Features of ESWL, indications/CI and SEs (5)

Answer 13

uses USS/XR-guided shockwaves to shatter stones which are excreted in urine

works best with:

• stones <2cm
• stones in a favourable position for drainage e.g. not in lower pole of kidneys

not effective in obese pts.

SEs: can cause renal injury

Question 14

Indications for flexible ureterorenoscopy (4)

Answer 14

when ESWL has failed

stones <2cm

hard stones

anatomically challenging/trapped/lower pole stones

Question 15

Features and indications of PCNL (3)

Answer 15

USS/laser passed down nephroscope to shatter stone and remove the fragments

must do DMSA beforehand

useful for staghorn/large/complex

Question 16

Prevention of urinary stones (4)

Answer 16

thiazides to lower Ca

low Ca diet

fluid intake

treat UTIs

Question 17

Further evaluation after 1st stone (6)

Answer 17

serum creatinine

calcium

urate

urinary pH

urinary cysteine

stone analysis