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.
How would you manage nephrolithiasis that presents with obstruction and infection
Patients with urinary calculi along with fever and other signs or symptoms of infection need emergency;
- Renal decompressiom/drainage and
- IV antibiotics.
Otherwise there will be urosepsis and death
Drainage can be accomplished in two ways.
- JJ stent/ Ureteric stent past the obstruction
- Percutaneous nephrostomy tube - Allows urine to drain
How to manage patient with stone but no signs or symptoms
If the patient has a stone present without signs or symptoms of infection, he or she can be managed conservatively with opioids and (NSAIDs).
note mx depends on location, size and presentation
How to manage patients with recurrent stones
secondary preventative measures should be tailored towards underlying metabolic factors that promote stone formation.
dietary modification with adequate hydration is an essential aspect of on-going management.
How to Manage of stones <10 mm and no complications
Acute medical treatment includes conservative therapy such as
hydration - fluid replacement
analgesia (intravenous pain relief with morphine or the NSAID ketorolac) - lecture: PR diclofenac
anti-emetics.
bed rest
Safetynet: if signs of infection or worsening pain come back.
medical expulsive therapy (MET), namely PO alpha-blockers - tamsulosin - may increase ureteral stone passage
Surgical intervention is indicated in the presence of persistent obstruction, failure of stone progression, sepsis, or persistent or increasing colic
How to Manage of stones >10 mm that dont pass with MET
Infected obstructed:
- IV ABx and fluid bolus
refer to surgeons, keep NBM - IR Nephrostomy OR Retrograde stent insertion
Relatively well patient:
Extracorporeal shock wave lithotripsy (ESWL) or
Ureteroscopy as first-line therapy.
Percutaneous nephrolithotomy (PCNL) for calculi between 10 mm and 20 mm achieves better stone-free rates for lower pole stones than ESWL
What does urethroscopy involve?
Ureteroscopy involves placing a small semi-rigid or flexible scope per urethra and into the ureter and/or kidney. Once the stone is visualised, it can be fragmented using a laser and/or grasped with a basket and removed.
Which is the least invasive method of removing stones?
Extracorporeal shock wave lithotripsy (ESWL)
What does PCNL
Percutaneous nephrostolithotomy (PCNL) is a minimally invasive form of treatment that is usually reserved for renal and proximal ureteric stones (i.e., in the lower pole) and those that are large (>20 mm), have failed therapy with ESWL and ureteroscopy, or are associated with complex renal anatomy. [77] Percutaneous access into the kidney is gained from the flank.
Requires hospital stay
How would you treat if;
If the underlying cause is hyperparathyroidism
if it is hyperuricaemia
parathyroidectomy if hypercalcaemia due to
hyperparathyroidism
allopurinol if hyperuricaemia
Identify possible complications of urinary tract calculi and its treatment
• Of Stones
○ Infection (PYELONEPHRITIS)
○ Septicaemia
○ Urinary retention
• Of Ureteroscopy
○ Perforation
○ False passage
• Of Lithotripsy
○ Pain
○ Haematuria
Prognosis?
Good
High chance of recurrence of stones
key areas of stone obstruction?
Pelvic brim
Pelvic ureteric junction PUJ
vesicoureteric junction VUJ
