urolithiasis - stone disease in the urinary tract Flashcards
what are the commonest age group in which stones are seen?
30-50, unusual in children
males more than females
where are stones of the upper urinary tract?
renal stones
ureteric stones
where are stones of the lower urinary tract?
bladder
prostatic
urethral
why do people get stones?
anatomical factors - both congenital and acquired
urinary factors
infection
give some examples of anatomical factors that influence whether people get stones
congenital: spina bifid horseshoe kidney duplex kidney PUJO -Pelvi-ureteric junction obstruction
acquired:
- obstruction related to previous radiotherapy or previous surgery or stones from before
- trauma to the urinary tract can result in a changed anatomy
- reflux
give examples of urinary factors that can cause stones
- metastable urine ie a stage of saturation of the urine where crystals can form
- imbalance of stone promotors and inhibitors
- presence of high levels of calcium, oxalate, urate, cystine
- dehydration
what substances in the urine are stones made from?
oxalate
calcium
urate
cystine
explain the mechanism of stone formation with reference to a theory
nucleation theory - states that stones form from crystals in supersaturated urine
so dehydration plays a significant role
solubility point is where the solute and solvent are present in a metastable state as in you naturally have certain stone inhibitors which prevent solutes and solvents from making stones, but when you have supersaturated crystals in urine ie the formation point, this is when you make stones and crystals form due to pH and lack of inhibitors
Kfp - formation point
Ksp - solubility point
what are the most common types of crystals made from?
calcium based eg calcium oxalate and calcium phosphate
how do uric acid stones appear on KUB XR?
lucent ie not seen
what is another name for infection stones?
struvite stones
How do infection stones form?
these are potentiated by bacterial infection that hydrolyses urea to ammonium and raises urine pH to alkaline values (eg Proteus, Pseudomonas, Klebsiella, S. aureus and mycoplasma)
struvite crystals form in alkaline urine
what is the cause of cystinuria?
Cystinuria is an inherited autosomal recessive disease that is characterized by high concentrations of the amino acid cysteine in the urine, leading to the formation of cystine stones in the kidneys, ureter, and bladder.
Cystinuria is caused by gene mutations which prevent proper reabsorption of basic, or positively charged, amino acids: Cystine, lysine, ornithine, arginine. (COLA) Under normal circumstances, this protein allows certain amino acids, including cystine, to be reabsorbed into the blood from the filtered fluid that will become urine
how can we prevent the formation of stones?
overhydration - 3.5-3L per hour low ssalt diet normal dairy intake healthy protein intake reduce BMI
why is a low sodium diet needed to prevent the formation of stones?
a high sodium diet increases the amount of calcium in the urine
why is a normal amount of protein recommended?
eating too much protein increases the level of uric acid so causes uric acid crystals to develop
what happens if you eat too little calcium?
oxalate levels build up in the blood
why should a pt reduce their BMI to prevent stone formation?
as this reduces uric acid levels in the blood
what are the specific preventative measure for someone who keeps getting uric acid stones?
they only form in acid urine, so deacidify urine to pH 7-7.5
what are staghorn calculi?
upper urinary tract stones that involve the renal pelvis and extend into at least 2 calyces
how do we specifically treat cysteine stones?
overhydration
urine alkalinisation
cysteine binders
genetic counselling (as A. Recessive)
what are the symptoms of stones?
asymptomatic
loin pain (unilateral or bilateral)
renal colic - see card on the features of this
UTI symptoms - dysuria. strangury, urgency, frequency
recurrent UTIs
haematuria - visible or non-visible
what is renal colic?
pain from upper urinary tract obstruction
What are the symptoms caused by renal colic?
unilateral/bilateral loin pain
RAPID onset
unable to get comfortable - writhing from pain
radiates to groin and ipsilateral testis/labia
associated nausea and vomiting
colic/spasmodic pain that is worse with fluid loading
severe pain - worse than labour
how do we investigate ureteric colic?
ABC give analgesia/antiemetic focused history and examination- ask about risk factors and system review urinalysis - MSU - haematuria and leukocytes urine culture FBC U+E calcium uric acid NCCT-KUB as first line KUBXR for monitoring after NCCT-KUB
what is the ideal painkiller for kidney stones
NSAIDs
when may ultrasound be used
can be used for follow up of stones in the kidney ( not good for ureteric stones)
useful in pregnancy and younger recurrent stone formers as reduces radiation
describe the path of the ureters on KUBXR
along the transverse processes of the spine
in line with the sacroileac joint
cross the pelvic brim and enter the true pelvis into the bladder
what does NCCT KUB stand for?
non-contrast computerised tomography
what are the advantages of NCCT-KUB?
very rapid
very sensitive and specific
no contrast - so don’t have to worry about allergies and kidney function
what are the disadv of NCCT KUB?
no functional info as no contrast used
radiation
what are the disadv of NCCT KUB?
no functional info as no contrast used
radiation
may not be able to differentiate stones from artefacts caused by previous surgery
how should you interpret a NCCT KUB?
count the kidneys
look at the condition of the kidneys including the perinephric tissues, cortical thickness, hydronephrosis/hydroueter
stones
any other pathology
what is a scout image?
done before the NCCT-KUB to prescribe CT slices and to display slice locations
helps to determine the position of the stone
aids decisions for follow up imaging - ie check whether the stone is still there
how do we manage ureteric colic?
analgaesia - NSAIDs or opiates antiemetics may admit to hosp may give IV fluids observe for sepsis
what is infection of the kidney’s urinary collecting system called?
pyonephrosis
what are the complications of pyonephrosis?
can lose renal function in 24 hours
systemic sepsis leading to septic shock
infected obstructed kidney can kill - sometimes very quickly
how is pyonephrosis treated?
IV antibitoics
oxygen
escalate care
drain the infection
what are the two methods of drainage of kidneys in pyonephrosis
nephrostomy
ureteric stent
What does the method of drainage depend on?
position of stone, size and the symptoms caused and pt factors and local availability
what are the 4 treatment categories for stones?
conservative
medical
lithotripsy
surgical
what are the complications of kidney stones?
can migrate to the ureter if small
larger stones can occlude calyces and/or PUJ
can cause acute obstruction- renal or ureteric colic
chronci renal damage in infection stones causing abscess nad fistulae
xanthogranulomatous pylonephritis - unusual form of chronic pyelonephritis characterised by granulomatous abscess formation, severe kidney destruction
how many stones will progress?
1/3
How are renal stones managed?
conservative- if the stone is small and asymptomatic
ESWL - if the stone is up to 1-2 cm and have problems with passing fragments and clearance of the stone
ureteroscopic - lazer
PCNL - percutaneous nephrolithotomy - for stones > 2cm, or for several stones
nephrectomy if kidney function has declined
what is ESWL and what does it stand for?
Extracorporeal Shock Wave Lithotripsy - it is an external treatment, for stones that are 1-2 cm and we fragment them with X-rays
what is PCNL and what does it stand for?
Percutaneous nephrolithotomy - done through the skin and make a 1cm cut in the kidney to remove the stone
how do we treat ureteric stones?
conservative - if less than 5mm will pass by themselves
drainage if urosepsis
ESWL for small stones
ureteroscopy - with lazer
what is the gold standard for diagnosis of stones?
NCCT-KUB
what is the lifetime risk of stones?
10-15%
