Urinary tract calculi Flashcards
Define nephrolithiasis.
Nephrolithiasis refers to the presence of crystalline stones (calculi) within the urinary system (kidneys and ureter).
What is the epidemiology of kidney stones?
- Common condition with a 7% to 10% lifetime risk for women and men, respectively.
- More common in caucasian men
- More common in hot, arid, dry climates
How are kidney stones classified?
- Size: <5mm; 5-20mm; >20mm; staghorn
- Location: Renal (calyceal, pelvic, diverticular); Ureteric
- Xray Characteristics: radiolucent; radioopaque
- Stone composition: Calcium oxalate (80%), Calcium phosphate, Uric acid, Cysteine, Infection/Struvite stones
What is the aetiology of kidney stones?
- High levels of urinary solutes such as calcium, uric acid, oxalate and sodium
- Decreased levels of stone inhibitors such as citrate and magnesium
- Low urinary volume and very high/low pH of urine
Once crystals form they either pass out with urine or become retained in the kidney where they can grow and stones can form.
What are the risk factors for kidney stones?
- High protein intake - secondary to the increased prevalence of hyperuricosuria, hypocitraturia, and hypercalciuria associated with this diet.
- High salt intake
- White ethnicity
- Male sex
- Dehydration - low urine output can produce a higher concentration of urinary solutes, therefore leading to stone formation.
- Obesity
- Crystalluria
- Occupational exposure to dehydration e.g. those exposed to high temperatures
- Warm climate
- FH
- Precipitant medications
Why can high salt intake cause kidney stones?
Higher sodium intake → higher urinary sodium and calcium levels, and decreased urinary citrate→ promotes calcium salt crystallisation due to urinary saturation of monosodium urate and calcium oxalate/calcium phosphate being increased.
Salt excess can also can lead to bone loss → worsening hypercalciuria.
Which medications can be a risk factor for kidney stones?
- Calcium-containing antacids
- Carbonic anhydrase inhibitors
- Sodium and calcium containing medications
- Vitamin C
- Vitamin D
- These cause higher urinary levels of calcium, uric acid, oxalate and sodium, promoting kidney stone formation.*
- Poorly soluble medications with high urinary excretion, favouring direct crystallisation and stone formation in urine:*
- Protease inhibitors (e.g. indinavir, atazanavir)
- Ephedrine
- Guaifenesin
- Triamterene
- Sulfadiazine
- Antibiotic exposure e.g. sulfas, cephalosporins, fluoroquinolones, nitrofurantoin, broad-spectrum penicillins.
Which stones can you not see on X-Ray?
Uric acid stones
What is the composition of struvite kidney stones? Which type of stones are formed from this?
Struvite (magnesium ammonium phosphate) is a phosphate mineral.
Staghorn calculi
1st line treatment is PCNL (for stones in renal collecting system and renal pelvis) for staghorn calculi >3cm.
What are the signs and symptoms of nephrolithiasis?
- Acute, severe flank pain, that radiates to ipsilateral groin - some are asymptomatic and do not radiate.
- N&V - acute episode
- Urinary frequency/urgency - stones pass and get lodged in distal ureter/intramural tunnel which can cause bladder irritation causing these symptoms.
- Haematuria - microscopic present on urinalysis up to 85-90% cases, sometimes macroscopic
- Testicular pain - flank pain can radiate here as stones pass through the ureter
Uncommon:
- Groin pain - as stones pass through ureter
- Fever - in obstruction urgent decompression is needed (may also be a sign of struvite stones)
- Tachycardia, hypotension - ?urosepsis
- Costovertebral angle and ipsilateral flank tenderness - acute renal colic
What investigations should you do for kidney stones?
- Urinalysis - normal or WBC/RBC, nitrates. But up to a third can have a normal dip stick.
- FBC w/ differential - WCC raised if infection (UTI or pyelonephritis)
- **Serum electrolytes, urea and creatinine ** - check kidney function; other: hyper Ca may suggest hyperparathyroid; hyperuricaemia shows gout.
- Spot urine for cysteine - cystinuria
Imaging:
- **Non-contrast CT KUB (gold standard)** - shows calcification in renal collecting system of ureter; hydronephrosis; perinephric stranding (inflamm/infection)
- Stone analysis - post surgical or after passing.
- KUB (x ray) - calcification seen within urinary tract
- Renal US
- IV pyelogram - replaced by CT now
- 24hr urine monitoring - helps check underlying/metabolic cause once stone has passed
Other:
- Pregnancy test - in all females to exclude ectopic pregnancy
- NB. Immediate imaging if: (EAU Recommendation)*
- Fever
- solitary kidney
- diagnosis unclear
What general advice can you give to someone with kidney stones?
- High fluid intake – urine should be champagne colour
- Normal diet – do not cut out dairy products
Attend / return to A&E if
- Pain not controlled by analgesia
- PYREXIA
(If urine is darker than champagne colour then patient is probably not drinking enough)
What is the A&E protocol for ureteric colic?
- Crystalloids
- hydration
- Analgesia:
- Ketorolac (NSAID) 30mg IV initially - in normal renal function
- +/- morphine sulfate IV 1-5mg IV/4hrs
- Anti-emetic
- Ondansetron - 4mg IV /8hrs
Basic Investigations:
- FBC/U+E, Ca, Urate, Urine dipstick, ßHCG (♀)
Radiological Investigations:
- Plain both KUB and CT KUB
What medical treatment can be given for kidney stones?
Medical expulsive therapy (MET) only given for stones <10mm
Tamsulosin/alfuzosin/silodosin - alpha blockers which help increase stone passage rate and decrease time to stone passage. Given for 4-6weeks or until stone has passed. This is an “off-label” use of these medicines.
Ongoing kidney stone problems - therapy depends on urine composition:
- Hyperuricosuria/uric acid stones - xanthine oxidase inhibitor +/- alkalinisation therapy e.g. allopurinol +/- K citrate - helps in patients with gout; alkalinisation helpful if urine pH is 6.5-7.0
- Hypercalcuria - diuretics/alkalinisation e.g. chlortalidone/hydrochlorothiazide - thiazides help prevent hypokalaemia and hypocitraturia
- Hypocitraturia - alkalinisation e.g. K citrate
- Hyperoxaluria - oxalate chelator/alkalinisation e.g. calcium carbonate/K citrate
- Cystinuria - alkalinisation/thiol binding agent/cystine chelator e.g. K citrate/ tiopronin/penicillamine
- Struvite stones - urease inhibitor e.g. acetohydroxamic acid - reduces urine saturation or struvite but causes DVT, tremors, headaches.
What surgical treatment can be offered for kidney stones?
Non-septic patients:
Given if stones >10mm or failed medical therapy:
- Extracorporeal shock wave lithotripsy - ESWL
- Ureteroscopy - better stone-free rates than ESWL
- Percutaneous antegrade ureteroscopy - if >15mm and impacted in ureter or retrograde access not possible
- Percutaneous nephrostolithotomy - PCNL is min invasive and reserved for renal and proximal ureteric stones in north pole and those that are large >20mm or have complex renal anatomy
- Laparoscopic/open surgical removal - in rare cases where other methods fail.
What is a fibroid?
Fibroids are abnormal growths that develop in or on a woman’s uterus. Sometimes these tumors become quite large and cause severe abdominal pain and heavy periods
Calcified fibroid; PUJ & left renal stone not visible on KUB
This is a calcified fibroid.
What is shown?
PCNL
