Urinary tract calculi (URO) Flashcards
What is nephrolithiasis?
Presence of crystalline stones (calculi) within the urinary system (kidneys and ureter)
Describe the epidemiology of nephrolithiasis. (2)
- M>F
- 45-70y
What are the different types of stones (urinary tract calculi)? (4)
- calcium stones (80%) - calcium oxalate and calcium phosphate
- struvite (15%)
- uric acid (5%)
- cysteine (1%)
How do calcium stones appear on X-rays/CT (nephrolithiasis)?
Radiopaque = white
What are the differences between calcium oxalate and calcium phosphate stones?
- calcium oxalate - black/dark brown, acidify urine pH
- calcium phosphate - dirty white, alkaline
- (both radiopaque/white on scans)
What is a risk factor for calcium oxalate calculi?
Hypercalciuria
How do struvite stones (nephrolithiasis) appear on X-rays/CT scans?
White (radiopaque)
What do struvite stones (nephrolithiasis) do to urine pH?
Alkalises urine pH (alkaline)
What can struvite stones (nephrolithiasis) form into?
Staghorn calculi (big stones)
What do struvite stones (nephrolithiasis) contain?
Magnesium, ammonium and phosphate
What is a predisposing factor for struvite stones (nephrolithiasis)?
Recurrent UTIs (chronic Proteus/Pseudomonas/Klebsiella infection)
How do uric acid stones (nephrolithiasis) appear on X-rays/CT scans?
Radiolucent = black (not visible vs calcium oxalate/phosphate and struvite stones)
What condition may uric acid stones (nephrolithiasis) be associated with?
Gout/hyperuricaemia
What urinary pH is commonly associated with uric acid stones (nephrolithiasis)?
Urinary pH<5.5
What are cysteine stones (nephrolithiasis)?
Inborn error of abnormal renal tubular reabsorption of the amino acids cysteine, ornithine, lysine and arginine (yellow, light pink stones that are white on XR)
Where do kidney stones classically deposit? (3)
- pelviureteric junction (PUJ)
- pelvic brim
- vesicoureteric junction (VUJ)
What are some contributing factors to nephrolithiasis? (4)
- high urinary solutes - calcium, uric acid (by-product of purines), oxalate, sodium
- decreased stone inhibitors - citrate, magnesium
- low urinary volume e.g. dehydration
- low/high urinary pH
What foods are high in oxalate, potentially contributing to kidney stones? (6)
- chocolate
- tea
- rhubarb
- strawberries
- nuts
- spinach
When do urinary tract calculi become symptomatic?
Asymptomatic until they get stuck
What are the clinical features of urinary tract calculi? (5)
- renal colic - severe, acute flank pain that radiates to groin (loin –> groin) that may be colicky
- N&V
- urinary frequency/urgency (stone dislodged in distal ureter –> bladder irritation)
- haematuria
- testicular pain
What may be found on examination in urinary tract calculi?
Systemic signs of sepsis if urinary obstruction and infection above stone
What are some risk factors for urinary tract calculi? (10)
- chronic dehydration
- diet - chocolate, tea, rhubarb, strawberries, nuts, spinach (oxalate-rich)
- high salt intake
- white ancestry
- male
- obesity
- positive Fx
- crystalluria
- specific medicines
- various metabolic abnormalities
What are the first-line investigations for urinary tract calculi? (4)
- non-contrast CT KUB
- renal ultrasound (pregnant or child)
- urinalysis / urine dipstick
- FBC
What bedside test can we initially do in urinary tract calculi and what might it show?
Urine dipstick - may show microhaematuria
What is the gold standard investigation for urinary tract calculi?
Non-contrast CT KUB
(not in pregnant or children)
When should non-contrast CT KUB be done for urinary tract calculi?
Within 24 hours of presentation
What can non-contrast CT KUB show in urinary tract calculi? (3)
- calcification in renal collecting system / ureter
- hydronephrosis - dilatation of renal pelvis, calyces and/or proximal ureter due to distal obstruction to the outflow of urine
- perinephric stranding (indicative of inflammation or infection)
What may a patient with urinary tract calculi and hydronephrosis require?
Nephrostomy as decompression
(Hydronephrosis on non-contrast CT KUB = dilatation of renal pelvis, calyces and/or proximal ureter)
Who do we not do a non-contrast CT KUB on in urinary tract calculi?
Pregnant women or children - do renal USS
What investigation do we do for pregnant women or children with urinary tract calculi?
Renal ultrasound
Why is an X-ray important in urinary tract calculi?
Visible stone on XR is necessary for use of ESWL (extracorporeal shockwave lithotripsy)
What type of stones are radiopaque vs radiolucent?
- radiopaque: calcium (oxalate + phosphate), struvite, cysteine
- radiolucent: uric acid (associated with gout)
What other investigation for urinary tract calculi do we need to keep in mind?
Pregnancy test in all women of childbearing age to exclude ectopic pregnancy - urgent USS within 24h instead of CT
What are some differential diagnoses for urinary tract calculi? (8)
- ectopic pregnancy - RLQ/pelvic pain
- appendicitis - RLQ pain, fever, peritonitis
- ovarian cyst - low pelvic/abdominal discomfort and/or dyspareunia, palpable o/e
- diverticular disease - LLQ
- bowel obstruction - abdominal distension, vomiting and constipation
- acute pancreatitis - epigastric pain–>back
- PUD - abrupt, severe, related to meals
- iliopsoas abscess - fever and back/flank/hip pain
What does acute management of renal colic involve? (3)
- hydration
- analgesia (NSAIDs) - IM diclofenac
- anti-emetics
How do we manage urinary tract calculi with signs of obstruction or infection (AKI/sepsis/hydronephrosis)? (3)
- emergency
- surgical decompression (nephrostomy)
- IV Abx - empirical broad spectrum –> cefuroxime or gentamicin IV
What is the 1st line management for urinary tract calculi <5mm?
Watchful waiting - 95% pass spontaneously with increased fluid intake
Increased oral fluid intake, reduce calcium/vitamin D/oxalate-containing foods
What is the 1st line management for urinary tract calculi in distal ureter (<10mm)?
Tamsulosin (alpha1 blocker) - causes ureteric relaxation of smooth muscle and antispasmodic activity of ureter leading to stone passage (known as medical expulsive therapy)
If stone does not pass after 4-6 weeks –> surgery
How do we manage urinary tract calculi >10mm, or <10mm and fails to pass with conservative management?
- extracorporeal shockwave lithotripsy (ESWL) –> non-invasive method enabling stone fragmentation using an acoustic pulse
-
ureteroscopy if contraindicated - ureteroscope passed retrograde through ureter and into renal pelvis to visualise stones and remove (basket)/destroy (laser)
- preferred over ESWL in pregnant women
- percutaneous nephrolithotomy if above contraindicated (first-line for stones >20mm including staghorn stones) - minimally invasive keyhole surgery through back to retrieve stones
When is percutaneous nephrolithotomy done for urinary tract calculi? (2)
- staghorn calculi (struvite stones)
- stones >20mm
What is the management for calcium renal stones?
Thiazide diuretics - cause hypercalcaemia, meaning less calcium excreted into urine
How are uric acid stones treated?
Allopurinol (xanthine oxidase inhibitor)
Oral potassium citrate/sodium bicarbonate may help dissolve stones
What do we do in a patient with a long term suprapubic catheter that has a blockage (urinary tract calculi)?
Cystoscopy –> blockage may be due to blood clots or stones
Summarise the treatment for urinary tract calculi. (6)
- stone <5mm = expectant Rx
- distal ureteric stone = tamsulosin
- stone <2cm refractory / >10mm = lithotripsy (wave)
- stone <2cm refractory + pregnant = ureteroscopy
- stone >2cm/complex = percutaneous nephrolithotomy
- hydronephrosis/infection = nephrostomy
What are some complications of urinary tract calculi? (6)
- recurrent UTIs (risk of pyelonephritis or urosepsis)
- post-percutaneous nephrolithotomy bleeding
- post-shockwave lithotripsy haematoma, steinstrasse (fragments obstruct ureter)
- post-treatment sepsis
- pneumothorax
- ureteric syndrome
