Urinary Calculus Disease Flashcards
1
Q
What is a urinary calculus
A
A kidney stone
- It is a solid conglomeration of mineral salts, with or without associated urinary proteins that form in the kidneys
2
Q
Name the types of urinary calculus
A
• Calcium Oxalate - calcium phosphate/hydroxyapatite • Urate • Magnesium Ammonium Phosphate • Cysteine
Others
• Xanthine
• Idinavir
• Matrix
3
Q
Most kidney stones have a…
A
most kidney stones have a mixed composition.
- Urate crystals forming a nidus are relatively common, and the most common composition is a 80% CaOX:20% CaPO4 mix
4
Q
What are the common types of urinary calculus
A
• Calcium Oxalate - Calcium phosphate/hydroxyapatite • Urate • Magnesium Ammonium Phosphate • Cysteine
5
Q
What are the most common combination of kidney stones
A
most common composition is a 80% CaOX:20% CaPO4 mix
6
Q
What is the commonest type of urinary calculus
A
Calcium oxalate (80%)
7
Q
describe calcium oxalate
A
- it is insoluble
- not forming this type of stone depends upon inhibitors
8
Q
What are the two types of calcium oxalate
A
- dihydrate which are softer (700HU)
- monohydrate which are extremely hard (1500 HU)
9
Q
Does calcium oxalate stone show up on X rays
A
yes
- spikes and radio-opaque
10
Q
What three conditions does calcium phosphate show up on
A
Classically associated with 3 conditions:
• Hyperparathyroidism
• Distal Renal Tubular Acidosis (Type 1)
• Medullary Sponge Kidney (MSK)
- also associated with urinary stasis and partly with infection
11
Q
Describe calcium phosphate
A
- Show up well on X ray - smooth and large
- usually quite hard 1200 HU
12
Q
What is urate stone formation related to
A
- Stone formation is related to urinary pH (acidic urine forms stones)
- associated with the metabolic syndrome and chemotherapy
13
Q
Describe urate stones
A
- Bright yellow stones formed from uric acid that has entered the urine
- Soft (400 HU)
- dissolvable - useful as you can dissolve them
- cannot see them on an x ray
14
Q
What stone is associated with metabolic syndrome
A
Urate stones
15
Q
What are magnesium ammonium phosphate stones often called
A
Struvite stones
16
Q
Describe magnesium ammonium phosphate stones
A
- Infection related- due to bacteria meeting a surface and producing a low acidic pH such that Mg salts precipitate out of the urine onto the surface
• Shows up slightly on X-rays - large
• Usually relatively soft (200-600HU)
• Often has associated Calcium Phosphate
• Classically associated with Staghorn Calculi
17
Q
What stone is often associated with calcium phosphate
A
Magnesium Ammonium phosphate
18
Q
What are cysteine stones associated with
A
associated with cystinuira a genetic disorder
19
Q
Describe cysteine stones
A
- Poorly visible on x-ray & are Hard (1400HU) - yellow and crystalline
- Produce white smoke and a rotten egg smell when they are lasered (Hydrogen sulphide)
- Treated with medical dissolution therapy in specialist centres
20
Q
describe matrix stones
A
proteinaceous material
21
Q
describe idinavir stones
A
Do not show up on CT
22
Q
Describe xanthine stones
A
almost anything with crystallise if the concentration is high enough
23
Q
What stones do not show up on X ray
A
Urate stones
24
Q
What does HU stand for
A
Hounsfield units
25
Describe the HU scale
- Air is -1000HU
- Water is 0HU
- Bone is +1000HU
- Soft tissue is +20HU
26
Name the two theories that are influencing stone formation
- Free theory
| - fixed theory
27
Describe free theory
- The presence of stone constituents in the appropriate amounts and without enough inhibitors will form stones
28
What is free theory affected by
- concentration of solutes
- urine acidity
- presence of formation inhibitors
29
What inhibits stone forming in free theory
inhibitors
30
Describe fixed theory
The energy required to make a crystal lance (enthalpy of formation) is lower if there is a surface to form them on e.g. Randall's plaques
31
What does fixed theory depend on
- depends upon a surface to form a lattice on
- crystals
- randall's plaques
32
Describe how free theory produces stones
- unsaturated urine
- as the concentration increases the solubility product is reached
- above the solubility product is the metastable region, there is saturated urine but crystals are prevented from forming by inhibitors
- then as the concentration increases you reach the formation product
- above the formation product is where crystals form spontaneously (spontaenous region)
33
in the free theory describe where non stone formers and stone formers sit
Non-stone formers
- these sit in the metastable region
Stone formers
- sit in both the metastable and spontaneous regions
34
Name some inhibitors in the free theory
These form soluble complexes with promoting ions
- Citrate - calcium citrate is soluble
- Magnesium - magnesium oxalate is soluble
35
What is the treatment for stones formed by free theory
decrease concentration by increasing the fluid intake
36
Describe the fixed theory
- there is high levels of energy needed to form a crystal lattice
- but much lower levels of energy is needed to form a crystal lattice on a rough surface
This rough surface can be due to
- other crystals such as urate
- can also be due to presence of sub urothelial deposits known as randall's plaques
example
- calcium phosphate crystals form at the base of the loop of hence which ulcerates the urothelium creating a rough surface for crystal formation
37
Why is urate stone formation different
- part of both free and fixed theory
- pH dependent (free theory)
- presence of urate crystals act as a nidus for stone formation (fixed theory)
38
When do urate crystals form
- When the urine pH is the same as the pKa value at 5.4, urate cyrstals can form which can be independent of the concentration
- there is a second pKa value at 10.3
39
fixed and free theories are not ...
mutually exclusive
| - e.g. urate and calcium oxalate crystals
40
What is the treatment of urate crystals
- the treatment of urate stone formation is therefore alkalisation of urine - including drinking more liquid
41
What are the two ways in which calcium oxalate stones form
- Randall's plaque
| - Duct of bellini "plugs"
42
Describe the two ways in which calcium oxalate stones form
Randall’s plaques:
• CaPhos forms in the intersFFum of the
kidney
• Urothelium “ulcerates” exposing plaque to urinary surface
Duct of Bellini “plugs” • Stones formed within the tubules
• Duct of Bellini narrows
• Stones gets “stuck” at papillary surface
43
Name some causes of hypercalaemia
* Hyperparathyroidism
* Sarcoidosis
* Excessive vitamin D
44
Where is oxalate found
- found in our diet from a host of sources
- oxalate is created from endogenous sources in the liver as part of glycolate metabolism
- Vitamin C is converted to oxalate
45
Where is oxalate absorbed
Primarily from the colon
46
what does calcium prevent oxalate from doing
- calcium binds oxalate in the gut and prevents it from being absorbed
47
What can cause enteric hyperoxaluria
Malabsorption from any cause, such as coliFs, especially crohns disease, or jejunoileal bypass surgery, can result in enteric hyperoxaluria
- free fatty acids bind to and precipitate calcium
- bile salts increase colonic absorption of oxalate and perhaps decrease bacteria that would otherwise breakdown oxalate
48
What are dietary sources of unopposed oxalate
- High levels
- Moderate levels
- Low levels
High
- Rhubarb
- Spinach
- Swiss chard
- Beetroot
Moderate
- Okra
- sweet potato
- dark chocolate
- Nuts
- Pak Choi
- Parsnips
Low
- carrots
- apples
- sprouts
- berry fruits
- leeks
- brocooli
- chives
- green beans
- cranberries
49
Name a stone inhibitor
Tamm Horsfall Protein (uromodulin)
50
How does Tamm Horsfall Protein work
- Prevents it binding to renal epithelial cells = potential nidus 'flushed away'
- reduces "free" calcium on crystal for group
51
What does mutation on Tamm Horsfall Protein do
- Leads to familial juvenile hyperuremic nephropathy
| - leads to medullary cystic kidney disease 2 (both have increased stone formation/nephrocalcinosis)
52
What does Tamm Horsfall Protein also do
- Prevents some bacterial to attach to epithelium (reduces UTI from E.coli
53
How does meat increase the risk of stones
- Meat contains huge levels of oxalate but also contains a lot of calcium
- meta increases the risk of stones via its high levels of urate
54
is tea a high level of oxalate
- tea is cited as asource of oxalate but added milk contains calcium and its associated volume makes it a risk reducer
55
What are the differential comapred to urinary colic
Abdominal Pathology
- abdominal aortic aneurism
- bowel colic
- biliary colic
- ectopic pregnancy in females
Medical causes
- pneumonia and MI
- pancreatitis
Other urinary tract causes
- pyelonephritis
- bleeding tumours such as renal cell carcinoma or transitional cell carcinoma of the renal pelvis
56
What is the difference between ureteric colic and bowel colic
Ureteric colic
- pain usually comes and goes with a background of pain
Bowel colic
- comes and goes, going away completely between bouts
57
describe what the infection signs are
- temperature
- dip the urine to look for nitrates and white cells
- presence of blood does not matter (20% of colic has no haematuria) and any inflammatory condition near the urinary tract will cause microscopic haematuria including pneumonia
- CRP is the most sensitive blood marker for infection as ureteric colic is inflammatory in nature
58
What investigations should you do if you suspect urinary colic
- Examination
- urine MSU
- Bloods - U%Es, FBC &CRP, Calcium, urate, phosphate, bicarbonate, glucose
- Imaging - spiral non contrast CT-KUB, KUB X RAY, USS, IV urogram, MRI
59
What is the main imaging that is used in renal colic
- Ultra low dose CTKUB is the mainstay of imaging
60
what does ultra low dose CTKUB tell you in imaging
* 99% of stones diagnosed
* Not operator dependant
* Position, size and hardness
61
What do you do if the CTKUB is positive
- Perform a KUB to look at the stone position
- scout film of the CTKUB is not good enough
- Dont try to diagnose a stone on a plain KUB - sensitivity and specificity is 50%
62
What is the alternative for imaging
Ultrasound used in:
- pregnancy
- children
63
What are the downside of using ultrasound
- 75% sensitivity
- misses very big and small stones
- overcalls renal sinus fat as stones
64
describe the use of IVU for imaging on stones
- dying out
- operator dependent
- 1:120,000 risk of death from contrast allergy
- multiple films give surrogate for obstruction
65
How can you tell the ultrasound is look at a stone
- need to look for an acoustic shadow or twinkle
66
describe the use of MRI for stones
- poor for stones
| - used in the 2nd and 3rd trimester of pregnancy
67
What does the management of stones depend on
- site
- size
- hardness of the stone
68
What is the treatment of stones
Analgesia
- NSAIDS - useful in acute situation but may deteriorate renal function
- Opiates - sometimes needed
Antibiotics if infection
- Hydration - IV if necessary as patient may be vomiting, but this will not push out the stone
Medical expulsive therapy
- tamsulosin is used to relax the lower ureter and increase stone passage
- there are few alpha receptor in the upper ureter so MET is not used here
- removal of stone if necessary
69
Name some ways to remove stones
- Semirigid urethroscopy (urs)
- flexible ureterorenoscopy (FURS)
- Percutaneous nephrolithotomy (PCNL)
- Lithotripsy
70
How does semirigid urethroscopy (urs) work?
- Involves passing a teloscope into the ureter through the penis into the bladder to break up the stone
71
How does flexible ureterorenoscopy (FURS) work
- involves using a similar scope but is more flexible, this allows full access to stones in the kidney
72
How does a Percutaneous nephrolithotomy (PCNL) work
- key hold surgery for large multiple or complex stones
73
What is the majority of treatment of stones
- observed/medicial expulsive therpay
74
How does Lithotripsy work
- involves using sound waves to break the stone up
75
How do you treat stones in the lower ureter
- 95% of these stones under 10mm will pass from this location with medical expulsive therapy
- patients have had lithotripsy but less effective
- usually end up having a semirigid urethroscopy (urs)
76
How do you treat middle ureter stones
- medial expulsive therapy
- semirigid urethroscoy
- Percutaneous nephrolithotomy
77
How do you treat stones in the upper ureter
- due to lack of alpha receptors watching them is poor choice
- lipthroscopy - stone has to be soft enough to work
- urethroscopy
- Percutaneous nephrolithotomy
78
How do you treat stones in the kidney
- Medical expulsive therapy and watching but anything over 4mm has a chance at causing damage
- lipthroscopy - stone has to be soft enough to work
- urethroscopy
- Percutaneous nephrolithotomy
79
What is metabolic testing indicated in
* Multiple stone attacks
* Bilateral stone disease
* Solitary kidney (increased risk)
* Urate / cysteine / calcium stones
80
How do you carry out metabolic testing
* 2 x 24 hour urine collections measuring: Calcium, Oxalate, Urate, Volume, Sodium & Citrate
* Spot Nitroprusside test for Cysteine
* Blood tests: Calcium, Urate, bicarbonate, U&Es
81
What is the biggest single win in metabolic testing
fluid volume increase
82
How do you prevent stones
- increase urine flow to greater than 2L per day
- reduce sodium intake
- increase potassium intake (citrus fruits)
- restrict high oxalate foods
- reduce fatty foods
- calcium with high protein meals ( do not restrict calcium this increases risk of net calcium loss and osteoporosis)
- reduce animal protein intake (urate promoter)
- not more than 1000% of vitamin C per day
- take vitamin D and calcium supplementation at meal times
83
What happens if you reduce calcium intake
- increases risk of net calcium loss
| - increases osteoporosis
84
What drugs can you take to prevent stones
• Thiazide = reduces calcuria (but no strong evidence that they are effective)
* Potassium citrate
* very poorly tolerated
• Sodium bicarbonate
- pyridoxine - oxalate stone prevention
* Allopurinol for urate stones prevention
* Penicillamine & Thiola for Cysteinuria
85
How do you monitor treatment
* 24hr urine
* esp. for urine Vol, Na intake (< 5g/d)
* Urate useful in urate stones
* Monitor if specific therapy working (eg citrate, oxalate restriction etc)
* Spot urine for Na/K as an alternative
* Blood urate in users of allopurinol
* Consider help from an endocrinologist in metabolic syndrome, hyperparathyiodsm and distal RTA
86
there is a 50% chance of...
50% chance of another stone within 10 years if no dietary changes happen
87
How much does a increase in fluid intake reduces risk of stone by
40%
88
when should you use a follow up ultrasound
* Consider a 6 monthly or yearly KUB to follow known, asymptomatic stones
* In stone free formers, a 6 monthly to yearly USSKUB is reasonable
* This can happen in primary car
89
What is the presentation of stones
- renal colic
- renal obstruction
- mid-ureter obstruction
- lower ureter obstruction
- bladder/uretra obstruction
- co-exisiting UTI
- haematuria
- proteinuria
- sterile pyuria
- anuria
90
What are the symptoms of renal colic
- loin to groin spasmodic pain with background level
- ipsilateral loin tenderness
- nausea and vomitting
- cannot stay still
91
What are the symptoms of renal obstruction
- pain in loin between rib 12 and lateral edge of lumbar muscles
92
What are the symptoms of lower ureter obstruction
- bladder irritability
| - pain in the scrotum/penile tip in males or labia major in females
93
What are the symptoms of bladder/urethra obstruction
- pelvic pain
- dysuria
- straining/inability to void and interrupted flow
94
What would you expect in a physical examination of someone with renal colic
- usually no tenderness on palpation
| - may be renal angle tenderness especially to percussion if there is retroperitoneal inflammation
95
What would you see on urine MSU in renal colic
- dipstick (usually and for blood 90%) - leucocytes and nitrites for infection
96
what would you normally see rise in bloods for renal colic
- rise in creatinine is normal but beware a stone in a solitary kidney
97
describe the size of the stone that usually pass spontaneously
- Stones <5mm in lower ureter - 90-95% pass spontaneously
| - increase in fluid intake to help them pass
98
What are the indications for urgent intervention
- glomerular death
- infection and obstruction
- urosepsis
- intractable pain or vomiting
- impending ARF
- obstruction in a solitary kidney
- bilateral stone obstruction
99
What is the first line investigation in stones
non contrast CT KUB
