Urinary tract calculi Flashcards
Define this.
What is another name for it?
Crystalline stone deposition within the urinary tract (which includes kidneys and ureter).
Also known as Nephrolithiasis
Name types of stone you find
Calcium stones;
- Calcium oxalate - 80% - MOST COMMON
- Calcium phosphate - 20%
Magnesium ammonium phosphate - usually stag horn ones - usually caused by reccurent UTIs - young women - proteus mirabalis
Other stones;
○ Uric acid - 10-20%
○ Struvite - up to 5%
○ Cysteine - 2%
What is the aetiology of calculi formation?
• Many cases are IDIOPATHIC
• Metabolic Causes; ○ Hypercalciuria ○ Hyperuricaemia ○ Hypercystinuria ○ Hyperoxaluria
• Infection;
○ Hyperuricaemia
• Drugs
○ Indinavir; antiretroviral
Risk factors of calculi formation
Acute: dehydration diurretics, nsaids, antacids, antiretrovirals Diet; Foreign bodies; catheter, stent
Chronic:
FH,
reccurent UTIs
metabolic - hypercalcaemia
RISK FACTORS:
- High protein intake
- High salt intake
- White ancestry
- Male sex
- Obesity
- Crystalluria -Increased urinary excretion of the stones is a risk factor for stone formation!
- Dehydration/ Low fluid intake
○ Structural urinary tract abnormalities (e.g. horseshoe kidney, VUR, stricture)
- precipitant medications
- Family history!
Which type of stone will be found in ;
- High urine pH - alkali
- Low urine pH - acidic
- High pH - alkali; Calcium phosphate stones
2. Low ph - acidic; Uric acid (thats why can be treated with alkali)
Which are the infection stones?
What shape are they?
Struvite stones: 1% to 5% of renal calculi, also known as infection stones;
composed of magnesium, ammonium, and phosphate.
They frequently present as staghorn calculi and may be associated with urea-splitting organisms such as Proteus , Pseudomonas, and Klebsiella species. E coli is not a urease-producing organism.
Which stones are casued by an inborn error of metabolism?
What is the genetic defect?
Cystine stones: 1% of renal calculi; caused by an inborn error of metabolism, cystinuria, an autosomal-recessive disorder that results in abnormal renal tubular re-absorption of the amino acids cystine, ornithine, lysine, and arginine
Recognise the presenting symptoms of urinary tract calculi
4 ways:
- Renal colic
- Infected, obstructed system - hydronephrosis -> emergency
- Anuria; 2 renal calculi/baldder stone, septic
Often ASYMPTOMATIC
• SEVERE loin to groin pain
- writhing around, moving constantly
• Nausea and vomiting (espech acute episodes)
• Urinary urgency, frequency or retention
• Haematuria
•often improves with NSAIDs
sometimes testicular pain
For abdo pain rule out AAA -> feel for the aorta
Recognise the signs of urinary tract calculi on physical examination
• Loin to lower abdominal tenderness
- tap the renal areas of back with a fist to assess if reproduction of pain; renal angle tenderness
• Signs of systemic sepsis - fever - if there is an obstruction and infection above the stone
- NO signs of peritonism
- Leaking AAA is the main differential to consider in older men
Identify appropriate investigations for urinary tract calculi
Urine;
○ Dipstick - microhaematuria is common (most patients) BUT may be normal; dipstick positive for leukocytes, nitrates, blood.
○ MC&S - positive for WBCs, RBCs, or bacteria
• Non contrast helical CT scan JUB(NCCT) - 1st line imaging! Gold.
○ Can also be used to image stones
• X-Ray KUB
○ 80% of kidney stones are radio-opaque
- also needed before lithotripsy
• Intravenous Urography (IVU)
○ Allows visualisation of the kidneys and ureters
• Ultrasound
○ May show hydronephrosis and hydroureter - di;lation basically
FBC - raised WBC may suggest infection (pyelonephritis or urinary tract infection).
Serum electrolytes inc urea and creatinine-
Bone profile - Hypercalcaemia may suggest hyperparathyroidism as an underlying aetiology; hyperuricaemia may indicate gout.
Stone analysis - after passing or surgical removal
• Isotope Radiography
○ Used to assess kidney function
Which stones are radiolucent?
Uric acid stones - cant be seen with xray KUB
When would x-ray KUB be used?
If stone cant be visualised with ncct
More detail about the NCCT Non contrast helical CT scan?
what dose to use, etc?
high sensitivity and specificity, and should be ordered as soon as nephrolithiasis is suspected.
A low-dose scan (<4 mSv) is preferred for patients with a body mass index (BMI) ≤30 kg/m²,
NCCT accurately determines presence, size, and location of stones; if negative, nephrolithiasis can be ruled out with high likelihood.
can be used as LAST LINE option for pregnant women with difficult diagnosis
If a woman is pregnant and nephrolithiasis is suspected, which modality to use?
which other group to use this modality for?
In pregnancy, renal ultrasound is the first-line imaging modality. It should also be the modality of choice when there is a desire to reduce or eliminate radiation exposure, such as for evaluation of children. Low-dose computed tomography (CT) can be considered in children if renal ultrasound is non-diagnostic.
What is the use of 24 hr urinary monitoring?
Helps in determining underlying metabolic cause or aetiology for nephrolithiasis. Should be ordered once the patient is stone free.
Basic measurements should include volume, pH, creatinine, sodium, calcium, oxalate, uric acid, and citrate.
Patients with recurrent renal stones should have subsequent periodic 24-hour urine monitoring.
