Imaging and renal stones

what is an x ray used to detect in kidneys

radio opaque stones

what is an ultrasound useful for imaging a kidney for

• Kidney size

• Shape

• Location and number

• Structure

• Drainage/obstruction

• Renal blood flow

how will a normal kidney appear on ultrasound

liver is brighter than the kidney

how will an abnormal kidney appear on an ultrasound

the kidney is more bright than the liver - pathological change

what is a CT used to visualise in the kidney

Useful for trauma, stone, tumour, infection

Accurate detection of structure - more precise

what are the two types of CT

non contrast and contrast

what does non contrast CT provide information on

• Information on renal stones - location +/- type

what does contrast CT use

IV iodinated contrast

what is a contrast CT used to give information on

arteries/veins/perfusion/neighbouring structure/excretion of contrast

what is the potential risk of contrast CT in those with eGFR <30ml/min

nephrotoxicity

what are risk factors which must be taken into account when deciding on a contrast CT

• AKI

• CKD With eGFR (usually </=30-40ml/min)

• Diabetes

• Transplant

• Heart failure

• >75 years

• Arterial imaging/venous imaging/contrast volume

what are benefits which are taken into account when deciding on a contrast CT

• Emergency

• Non emergency

• Pathology being considered

what is an MRI used for in the kidneys

what may Gd contrast agent cause

nephrogenic systemic fibrosis

what does radioisotope scanning allow us to visualise in kidney

• Structure

• Perfusion

• Excretion

• Differential renal function

renal stones are cause by too much…

calcium

oxalate

urate

cysteine

renal stones are cause by too little…

urine/filtrate

what is a renal stone formed from

Formed from the combination of excreted/secreted ions within the glomerular filtrate

% of men and women affected by renal stoned over age of 70

12% men

5% women

what are the location classifications of stones

• Kidney/ nephrolithiasis

• Ureter/ ureterolithiasis

• Bladder/ cystolithiasis

what are the composition classifications of stones

• Calcium-phosphate / calcium oxalate

• Urate/cysteine/struvate etc

what is genetic risk factors for stones

50% have a genetic component

Positive family history = 2.5 RR

what are environmental factors associated with stones

BMI >27 (RR 2.0)/ immobile or sedentary/ dehydration/ UTI

what factors may decrease risk of stones

Vegetarian (RR 0.5)

High fruit (RR 0.6)

High fibre (RR 0.6)

what has cause an increase in uric acid stones

rise in obesity and metabolic syndrome (DM/HBP)

% of stones which are calcium containing

80%

% of stones which are struvite containing

5-10%

% of stones which are uric acid containing

5-10%

% of stones which are cystine containing

1-2%

what are the different composition of renal stones

Calcium containing (80%)

• Calcium oxalate

• Calcium phosphate

Magnesium ammonium phosphate (struvite) (5-10%)

Uric acid (5-10%)

Cystine (1-2%)

Mixed stones

what are the two different types of calcium stones

• Calcium oxalate

• Calcium phosphate

what is the history of renal stone evaluation

• Renal colic/passage of stones/haematuria/infection

• Family history

• Diet

what happens in the examination for renal stones

• Flank tenderness/signs of infection on urinalysis

• Obesity/hypertension/gout/diabetes

what happens in the investigation of renal stones

Imaging

Serum and urine biochemistry

what is medullary sponge kidney

• A congenital disorder of the kidneys characterised by cystic dilation of the collecting tubules, predisposing to stone formation

 

what is the density of cystine

low

what is the density of struvite

low

what is the density of calcium stones

high

what is calcium stones associated with

nephrocalcinosis (normally CaPO)

where does calcification usually occur

corticomedullary junction - medullary sponge kidney - either CaOx or CaPO

what is associated with high calcium

Primary hyperparathyroidism

Hypercalcaemia

Idiopathic hypercalciuria

what is associated with high oxalate/urate/cysteine

Primary/secondary hyperoxaluria

Hyperuricaemia

Cystinuri

what is a pro-calculus urinary enviroment associated with

Hypocitraturia

Renal tubular acidosis (type 1 - distal)

what does serum biochemistry test

Serum calcium

Serum phosphate

Serum PTH

Serum urate

Serum bicarbonate

what does urine biochemistry test

Urine volume

Urinary pH

• Urinary calcium

• Urinary sodium

• Urinary oxalate

• Urinary citrate

• Urinary creatinine

• Urinary uric acid

• Urinary cystine

 

what is the treatment for small ureteric stones

With good chance of passage (<7mm)

• allow time to pass (2-4 weeks)

• Lower ureter: ureteroscopic stone removal

• Mid upper ureter eswl

what is the treatment of a large ureteral stones

• Eswl

• Ureteriscopic stone fragmentation

• Open surgery

what are urethral stones used to accomplish

• Drain obstructed kidney thereby alleviating pain

• Dilate ureter perhaps facilitating passage of stone

• Facilitate performance of eswl and ureteroscopic procedure

how to treat calcium phosphate

• Increase fluid

• If HPTH/sarcoid/RTA type 1 then treat the cause

• Consider citrate and is hypercalciuric consider a thiazide

• No good evidence for low Ca diet - promotes Ox absorption + osteoporosis

what is the treatment of calcium oxalate

• Increase fluid

• Treat the cause (low oxalate diet)

• Consider citrate and if hypercalciuric consider a thiazide

what is the treatment of uric acid stones

• Increase fluid

• Treat the cause (hyperuricaemia) with xanthine oxidase inhibitors (allopurinol/rasburicase)

• If polycythaemic/tumour then treat the cause

• Alkalinity the urine to target pH >6 (bicarbonate or citrate)

what is the treatment of cystine stones

• Increased fluid intake - 3-4L per 24 hr

• Treat the cause (cystinuria - reduce protein/sodium diet)

• alkali use urine to target pH >7 (bicarbonate or citrate)

what is the treatment of struvite stones

• Debunk where possible

• Treat the cause (aggressive treatment of UTI)