Urinary Caculus Disease

Question 1

Define a urinary calculus

Answer 1

• kidney stone
• solid conglomeration of mineral salts with or w/o associated urinary proteins
• form in the kidney

Question 2

Types of stone

Answer 2

• calcium oxalate
• urate
• magnesium ammonium phosphate
• cysteine
• others = xanthine, idinavir, matrix
• most mixed composition = urate and nidus common, calcium oxalate and calcium phosphate v. common

Question 3

Calcium oxalate Stones

Answer 3

• commonest type
• insoluble
• 2 types = dihydrate (softer) and monohydrate (extremely hard(
• show up on x-rays
• Randall’s plaques and duct of Bellini plugs

Question 4

Calcium Phosphate Stones

Answer 4

• associated with = hyperparathyroidism, distal renal tubular acidosis, medullary sponge kidney
• also associated with urinary stasis and infection
• show up reasonably well on x-ray
• quite hard

Question 5

Urate Stones

Answer 5

• bright yellow
• from uric acid which has entered urine
• formation related to urinary pH, 5.4 or 10.3 required for formation (free theory)
• soft and dissolvable
• associated with metabolic syndrome
• urate crystals -> stone formation (fixed theory)
• part of both theories
• treat by alkalinisation of urine (drink more liquid)

Question 6

Magnesium ammonium phosphate stones

Answer 6

• struvite
• infection related
• slightly shows up on x-ray
• relatively soft
• has some calcium phosphate
• associated with staghorn calculi

Question 7

Cysteine Stones

Answer 7

• associated with cysteinuria (genetic)
• poorly visible on x-ray
• hard
• produce white smoke/rotten egg smell when lasered = hydrogen sulphide
• treat with medical dissolution therapy in specialist centres

Question 8

Matrix Stones

Answer 8

• proteinaceous material

- chewing gum lik

Question 9

Idinavir Stones

Answer 9

• do not show up on CT

Question 10

Hounsfield Units

Answer 10

• CT scan
• semi quantitative
• hardness scale based on pixel brightness = x-ray attenuation
• can predict treatment success

Question 11

Free Theory

Answer 11

• explains stone formation
• stone constituents have appropriate amounts but without inhibitors = stones form
• affected by conc of solutes, urine acidity and presence of formation inhibitors
• drive the solute conc. down by increasing fluid intake

Question 12

Fixed Theory

Answer 12

• explains stone formation
• energy required to make a crystal lattice (enthalpy of formation) lower if surface to form on
• depends on surface to form lattice on, other crystals present, randall’s plaques (sub urothelial deposits then when urothelium denudes contacts urine so crystals form)

Question 13

Randall’s plaques

Answer 13

• calcium oxalate
• calcium phosphate forms in interstitium of kidney
• urothelium ulcerates exposing plaque to urinary surface

Question 14

Duct of Bellini plugs

Answer 14

• stones formed within tubules
• duct of bellini narrows (collecting duct)
• stones get stuck at papillary surface

Question 15

Causes of hypercalcaemia

Answer 15

• hyperparathyroidism
• sarcoidosis
• excessive vitamin D

Question 16

Oxalate

Answer 16

• in diet
• endogenous sources (liver)
• vitamin C -> oxalate
• absorbed by colon
• calcium binds in gut preventing it from being absorbed
• malabsorption = colitis, crohns, jejunoileal bypass surgery = enteric hyperoxaluria
• bile salts increase absorption

Question 17

Dietary sources of oxalate

Answer 17

• rhubarb
• spinach
• beetroot
• sweet potato
• nuts
• dark chocolate

Question 18

Stone Inhibitors

Answer 18

• THP = tamm Horsfall protein (uromodulin)
• osteopontin
• citrate
• nephrocalcin
  (prevent crystalline structures binding to renal epithelial cells and reduce free calcium on crystal for growth)

Question 19

What do THP mutations lead to?

Answer 19

• Familial Juvenile Hyperuremic Nephropathy
• Medullary Cystic Kidney disease 2
  (increased stone formation in both)

Question 20

THP role

Answer 20

• prevents some bacteria attaching to epithelium

Question 21

How does a ureteric colic present?

Answer 21

• sudden severe right loin pain
• radiates towards groin
• agony
• tender loin
• blood in urine

Question 22

Investigations

Answer 22

• rule out infection -> pyrexia?
• Urinalysis
• FBC
• U&E = elevated creatinine

Question 23

Differentials for ureteric colic

Answer 23

• biliary colic
• leaking AAA (older patient consider)
• ectopic pregnancy if female
• pneumonia
• MI
• pancreatitis
• pyelonephritis
• bleeding tumours = renal cell carcinoma

Question 24

Difference between ureteric colic and biliary colic

Answer 24

Ureteric = pain comes and goes with background of pain, radiates to groin
Biliary = pain comes and goes going away completely between bouts, also right upper quadrant radiating under ribs up to shoulder tip

Question 25

Significance of infection

Answer 25

• infection with stone kills!
• monitor temp!
• dip urine for nitrates and white cells
• CRP most sensitive blood marker for infection and ureteric colic inflammatory anyway

Question 26

Haematuria Significance

Answer 26

• only 20% colic has haematuria
• any inflammatory condition near urinary tract causes microscopic haematuria
• pneumonia can cause it

Question 27

Investigations

Answer 27

• urine dip (leucocytes, nitrates, urine pH)
• MSU
• Bloods (U&Es, FBC, CRP, calcium & urate)

Question 28

Radiology

Answer 28

CTKUB (ultra low dose no staining)
- position, size, hardness
- urate stones lucent, sensitivity and specificity = 50%
US
- if pregnant or children
- non irradiating
- 75% sensitivity = look for acoustic shadow/twinkle
MRI
- poor for stones
- if 2nd/3rd trimester of pregnancy

Question 29

What does management of stone depend on?

Answer 29

site
size
hardness

Question 30

Treatment

Answer 30

Should come out naturally
Analgesia
- NSAIDs (acute, can deteriorate renal function)
- opiates
Hydration
- IV fluids if patient vomiting
Medical Expulsive Therapy
- tamulosin relaxes lower ureter increasing passage for stone
Remove Stone

Question 31

Treatments to Remove

Answer 31

• semi rigid ureteroscopy
• flexible ureterorenoscopy (FURS)
• observe/medical expulsive therapy
• percutaneous nephrolithotomy (PCNL, through abdomen, anaesthetic)
• lithotripsy (ESWL)

Question 32

Metabolic Testing Indications

Answer 32

• multiple stone attacks
• bilateral stone disease
• solitary kidney (increased risk)
• urate, cysteine, calcium stones

Question 33

Metabolic Testing How?

Answer 33

• 2 x 24hr urine collections (calcium, oxalate, urate, volume, sodium & citrate)
• spot nitroprusside test for cysteine
• blood tests for calcium, urate, bicarb, U&Es

Question 34

Prevention Lifestyle

Answer 34

• increase urine flow >2L per day
• reduce sodium intake
• increase potassium intake
• restrict high oxalate foods
• reduce fatty foods (reduce oxalate absorption)
• calcium with high protein meals (do not restrict, reduces oxalate absorption)
• reduce animal protein intake (promote urate)
• not more than 1000% vitamin C per day (1 tablet)
• take vitamin D and calcium supplementation at meal times

Question 35

Prevention with drugs

Answer 35

• thiazides (reduce calcuria)
• potassium citrate (v. poorly tolerated)
• sodium bicarbonate
• allopurinol for urate stones
• penicillamine & thiola for cysteinuria

Question 36

Monitor treatment

Answer 36

• 24 urine (volume, sodium intake <5g/d, urate monitor therapy effectiveness)
• blood urate in users of allopurinol
• consider help from endocrinologist if metabolic syndrome, hyperparathyroidism and distal RTA

Question 37

Prognosis

Answer 37

• 50% chance of another stone within 10years if no dietary changes
• increase fluid intake 40% reduces risk
• consider 6 monthly/yearly KUB to follow known/asymptomatic stones
• in primary care