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Year 3 > Urinary tract calculi (URO) > Flashcards

Urinary tract calculi (URO) Flashcards

1
Q

What is nephrolithiasis?

A

Presence of crystalline stones (calculi) within the urinary system (kidneys and ureter)

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2
Q

Describe the epidemiology of nephrolithiasis. (2)

A
  • M>F
  • 45-70y
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3
Q

What are the different types of stones (urinary tract calculi)? (4)

A
  • calcium stones (80%) - calcium oxalate and calcium phosphate
  • struvite (15%)
  • uric acid (5%)
  • cysteine (1%)
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4
Q

How do calcium stones appear on X-rays/CT (nephrolithiasis)?

A

Radiopaque = white

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5
Q

What are the differences between calcium oxalate and calcium phosphate stones?

A
  • calcium oxalate - black/dark brown, acidify urine pH
  • calcium phosphate - dirty white, alkaline
  • (both radiopaque/white on scans)
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6
Q

What is a risk factor for calcium oxalate calculi?

A

Hypercalciuria

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7
Q

How do struvite stones (nephrolithiasis) appear on X-rays/CT scans?

A

White (radiopaque)

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8
Q

What do struvite stones (nephrolithiasis) do to urine pH?

A

Alkalises urine pH (alkaline)

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9
Q

What can struvite stones (nephrolithiasis) form into?

A

Staghorn calculi (big stones)

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10
Q

What do struvite stones (nephrolithiasis) contain?

A

Magnesium, ammonium and phosphate

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11
Q

What is a predisposing factor for struvite stones (nephrolithiasis)?

A

Recurrent UTIs (chronic Proteus/Pseudomonas/Klebsiella infection)

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12
Q

How do uric acid stones (nephrolithiasis) appear on X-rays/CT scans?

A

Radiolucent = black (not visible vs calcium oxalate/phosphate and struvite stones)

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13
Q

What condition may uric acid stones (nephrolithiasis) be associated with?

A

Gout/hyperuricaemia

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14
Q

What urinary pH is commonly associated with uric acid stones (nephrolithiasis)?

A

Urinary pH<5.5

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15
Q

What are cysteine stones (nephrolithiasis)?

A

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)

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16
Q

Where do kidney stones classically deposit? (3)

A
  • pelviureteric junction (PUJ)
  • pelvic brim
  • vesicoureteric junction (VUJ)
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17
Q

What are some contributing factors to nephrolithiasis? (4)

A
  • 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
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18
Q

What foods are high in oxalate, potentially contributing to kidney stones? (6)

A
  • chocolate
  • tea
  • rhubarb
  • strawberries
  • nuts
  • spinach
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19
Q

When do urinary tract calculi become symptomatic?

A

Asymptomatic until they get stuck

20
Q

What are the clinical features of urinary tract calculi? (5)

A
  • 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
21
Q

What may be found on examination in urinary tract calculi?

A

Systemic signs of sepsis if urinary obstruction and infection above stone

22
Q

What are some risk factors for urinary tract calculi? (10)

A
  • 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
23
Q

What are the first-line investigations for urinary tract calculi? (4)

A
  • non-contrast CT KUB
  • renal ultrasound (pregnant or child)
  • urinalysis / urine dipstick
  • FBC
24
Q

What bedside test can we initially do in urinary tract calculi and what might it show>

A

Urine dipstick - may show microhaematuria

25
Q

What is the gold standard investigation for urinary tract calculi?

A

Non-contrast CT KUB

(not in pregnant or children)

26
Q

When should non-contrast CT KUB be done for urinary tract calculi?

A

Within 24 hours of presentation

27
Q

What can non-contrast CT KUB show in urinary tract calculi? (3)

A
  • 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)
28
Q

What may a patient with urinary tract calculi and hydronephrosis require?

A

Nephrostomy as decompression

(Hydronephrosis on non-contrast CT KUB = dilatation of renal pelvis, calyces and/or proximal ureter)

29
Q

Who do we not do a non-contrast CT KUB on in urinary tract calculi?

A

Pregnant women or children - do renal USS

30
Q

What investigation do we do for pregnant women or children with urinary tract calculi?

A

Renal ultrasound

31
Q

Why is an X-ray important in urinary tract calculi?

A

Visible stone on XR is necessary for use of ESWL (extracorporeal shockwave lithotripsy)

32
Q

What type of stones are radiopaque vs radiolucent?

A
  • radiopaque: calcium (oxalate + phosphate, struvite, cysteine)
  • radiolucent: uric acid (associated with gout)
33
Q

What other investigation for urinary tract calculi do we need to keep in mind?

A

Pregnancy test in all women of childbearing age to exclude ectopic pregnancy - urgent USS within 24h instead of CT

34
Q

What are some differential diagnoses for urinary tract calculi? (8)

A
  • 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
35
Q

What does acute management of renal colic involve? (3)

A
  • hydration
  • analgesia (NSAIDs) - IM diclofenac
  • anti-emetics
36
Q

How do we manage urinary tract calculi with signs of obstruction or infection (AKI/sepsis/hydronephrosis)? (3)

A
  • emergency
  • surgical decompression (nephrostomy)
  • IV Abx - empirical broad spectrum –> cefuroxime or gentamicin IV
37
Q

What is the 1st line management for urinary tract calculi <5mm?

A

Watchful waiting - 95% pass spontaneously with increased fluid intake

Increased oral fluid intake, reduce calcium/vitamin D/oxalate-containing foods

38
Q

What is the 1st line management for urinary tract calculi in distal ureter (<10mm)?

A

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

39
Q

How do we manage urinary tract calculi >10mm, or <10mm and fails to pass with conservative management?

A
  • 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
40
Q

When is percutaneous nephrolithotomy done for urinary tract calculi? (2)

A
  • staghorn calculi (struvite stones)
  • stones >20mm
41
Q

What is the management for calcium renal stones?

A

Thiazide diuretics - cause hypercalcaemia, meaning less calcium excreted into urine

42
Q

How are uric acid stones treated?

A

Allopurinol (xanthine oxidase inhibitor)

Oral potassium citrate/sodium bicarbonate may help dissolve stones

43
Q

What do we do in a patient with a long term suprapubic catheter that has a blockage (urinary tract calculi)?

A

Cystoscopy –> blockage may be due to blood clots or stones

44
Q

Summarise the treatment for urinary tract calculi. (6)

A
  • stone <5mm = expectant Rx
  • distal ureteric stone = tamsulosin
  • stone <2cm refractory / >10cm = lithotripsy (wave)
  • stone <2cm refractory + pregnant = ureteroscopy
  • stone >20mm/complex = percutaneous nephrolithotomy
  • hydronephrosis/infection = nephrostomy
45
Q

What are some complications of urinary tract calculi? (6)

A
  • 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

Year 3 (206 decks)

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