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Renal core conditions > Renal calculi and obstruction > Flashcards

Renal calculi and obstruction Flashcards

1
Q

What are nephrolithiasis (renal stones)?

A

Renal stones consist of crystal aggregates.

=> Stones form in collecting ducts and can deposit anywhere from the renal pelvis to the urethra

=> Most common place to deposit is:

  1. Pelviureteric junction
  2. Pelvic brim
  3. Vesicoureteric junction
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2
Q

How common is renal stones?

A

Very common

Life time prevalence = 15%

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3
Q

Who does it affect?

A

20-40 year olds

Male > Female [3:1]

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4
Q

What are the causes of urinary tract stones?

A
  1. Dehydration
  2. Hypercalcaemia
  3. Hypercalciuria
  4. Hyperoxaluria
  5. Hyperuricaemia & hyperuricosuria
  6. Infection
  7. Cystinuria
  8. Primary renal disease i.e. polycystic kidneys, medullary sponge kidneys, renal tubular acidosis
  9. Drugs
    => promoting calcium stones i.e. loop diuretics, antacids, glucocorticoids, theophylline, vitamins D and C, acetozolamide
    => promoting uric acid stones i.e. thiazides, salicylates
  10. Family Hx of stones or x-linked nephrolithiasis => increases risk 3x
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5
Q

How does a UTI lead to stone formation?

What is the composition of a mixed infective stone aka struvite stone?

What is the most common characteristic of a struvite stone?

A

UTI with proteus mirabilis hydrolyses urea with formation of ammonium hydroxide salts.

=> Ammonium salt and alkalinity of urine favour mixed infective stone formation

=> Mixed infective stone (aka Struvite stones) composed of magnesium ammonium phosphate and calcium

=> Struvite stones are large forming a stag horn calculus.

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6
Q

What causes uric stones?

A

Idiopathic gout = increased uric acid (hyperuricaemia)

Dehydration

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7
Q

What causes calcium stones?

A

Primary hyperparathyroidism

Vitamin D ingestion / synthesis

Sarcoidosis

High dietary calcium intake

Excessive resorption of calcium from skeleton due to immobilisation or weightlessness

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8
Q

What are the symptoms of urinary tract stones?

A

1) Pain => excruciating spasms of renal colic ‘loin to groin’ pain with Nausea & Vomiting

=> cannot lie still (differentiates it from peritonitis)

  1. Infection e.g. UTI / pyelonephritis (fever, riggers, loin pain, nausea & vomiting) ; pyelonephrosis (infected hydronephrosis)

=> increased risk of infection if voiding impaired

  1. Haematuria
  2. Proteinuria
  3. Sterile pyuria
  4. Anuria
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9
Q

What are the signs of urinary tract stones?

A

No tenderness on palpation

Renal angle tenderness on percussion if there is retroperitoneal inflammation

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10
Q

Describe the characteristic of the pain felt in obstructed

=> kidney

=> mid ureter

=> lower ureter

=> bladder or urethra

A

=> Obstructed kidney: pain in the loin, between rib 12 and lateral edge of lumbar muscle

=> Obstructed mid ureter: can mimic appendicitis / diverticulitis

=> Obstructed lower ureter: bladder irritability & pain in scrotum, penis tip and labia majora,

=> Obstruction in bladder or urethra: pelvic pain, dysuria, strangury (desire but inability to void) ± interrupted flow ; anuria, painful bladder distention => bladder outflow obstruction ; usually assoc. with bacteriuria

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11
Q

What are the types of urinary tract stones?

A
  1. Calcium oxalate
  2. Magnesium ammonium phosphahte (struvite stones)
  3. Urate stones
  4. Hydroxyapatite stones
  5. Brushite
  6. Cystine
  7. Mixed
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12
Q

What are the most common types of urinary stones?

A

Calcium oxalate (75%)

Magnesium ammonium phosphate / struvite stones (15%)

Urate stones (5%)

Hydroxyapatite (5%)

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13
Q

What are the initial tests to investigate urinary tract stones?

A
  1. Bloods: FBC, U&E, calcium, phosphate, glucose bicarbonate, urate
  2. Urine dipstick: +ve for blood (90%)
  3. Mid stream urine (MSU) microscopy, culture and sensitivity (MC&S)
  4. Urine pH
  5. 24h urine for calcium, oxalate, urate, citrate, sodium, creatinine
  6. Stone biochemistry (sieve urine and send stone)
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14
Q

What imaging is recommended in urinary tract stones?

A
  1. Non-contrast CT

=> Test of choice for imaging stones

=> 99% stones visible

=> Helps exclude differential causes of an acute abdomen i.e. ruptured abdominal aortic aneurysm (AAA) - presents similarly

  1. Kidney, ureters, bladder (KUB) X-ray
    => 80% of stones visible
  2. Ultrasound for hydronephrosis or hydroureter
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15
Q

What is the treatment for urinary tract stones?

=> What is the choice of treatment for stones<5mm?

=> What is the choice of treatment for stones>5mm?

=> What is the choice of treatment for stones <1cm?

=> What is the choice of treatment for large, multiple or complicated stones?

A
  1. Analgesia e.g. diclofenac (NSAID) 75mg IV/IM
  2. Antibiotics if infection
  3. Stones <5mm in lower ureter: ~95% pass spontaneously if hydration is maintained (drink 2.5L/day)
  4. Stones >5mm/pain not resolving: Medical expulsive therapy i.e. alpha blocker like Tamsulosin or nifedipine promote distal ureteral stones
    => alpha receptors predominantly present in distal ureter and detrusor
    => most stones pass within 48h
  5. If stone (<1cm) still present: Extracorporeal shockwave lithotripsy (EWSL)
  6. Percutaneous nephrolithotomy (key hole surgery) for large, multiple or complex stones
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16
Q

What is the indication for urgent intervention to prevent death of glomeruli?

A

Presence of infection and obstruction => percutaneous nephrostomy or ureteric stent to relieve sepsis

17
Q

What general prevention can patients with urinary tract stones take?

A

Drink plenty 2.5-5L/day

Normal dietary calcium intake (low calcium increases oxalate excretion)

18
Q

What specific prevention can you take for:

=> calcium stones
=> oxalate stones
=> struvite stones
=> urate stones
=> cystine stones
A
  1. Calcium stones: in hypercalciuria give thiazide diuretic to decrease calcium excretion
  2. Oxalate stones: decrease oxalate intake i.e. avoid nuts, spinach, chocolate, rhubarb
  3. Struvite stones (phosphate mineral): treat infection promptly
  4. Urate stones: allopurinol, urine alkalisation because urate dissolves in alkaline urine
  5. Cystine stones: hydration to keep urine output >3L/day and urinary alkalisation. Penicillamine to chelate cystine.
19
Q

What do the stones look like on X-ray?

i. Calcium oxalate
ii. Calcium phosphate
iii. Magnesium ammonium phosphate
iv. Urate
v. Cystine

A

Calcium oxalate: Spiky & radio-opaque

Calcium phosphate: Smooth, large & radio-opaque

Magnesium ammonium phosphate: Large, horny, staghorn & radio-opaque

Urate: Smooth, brown & radiolucent

Cystine: Yellow, crystalline & semi-opaque

Renal core conditions (9 decks)

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