Renal tract calculi Flashcards
Types of renal stones
- Calcium oxalate (35%)
- Calcium phosphate (10%)
- Mixed oxalate and phosphate (35%)
- Struvite - magnesium ammonium phosphate (PAM)
- Urate - radiolucent
- Cystine - familial disorders affecting cystine metabolism
PAM the staghorn deer, Struvite = Staghorn
Pathophys of renal calculi
- Oversaturation of urine
- Calcium and oxalate precipitate at lower saturation levels so most common
- Others have specific underlying pathology
Struvite stones - how do they form?
- Infection stones - form in alkaline urine in the presence of urease producing organisms
- Eg Proteus mirabilis and Klebsiella pneumoniae
- Urease catalyse urea to CO2 and ammonia which leads to magnesium ammonium phosphate crystals
Urate stones - how do they form?
- High levels of purines in the blood
- Either from diet eg red meat or haematological disorders eg myeloproliferative disease
- = increased urate formation and crystallisation in urine
Cystine stones - how do they form?
- Homocystinuria
- Inherited defect that affects the transport of cystine in the bowel and kidneys
- Citrate is a stone inhibitor - hypocitraturia can then predispose to stone
3 main narrowed points where stones are likely to impact
- Pelviureteric junction (PUJ) - renal pelvis becomes ureter
- Crossing pelvic brim - where iliac vessels travel under ureter in pelvis
- Vesicoureteric junction (VUJ) - where ureter enters bladder
Symptoms of renal calculi
- Pain - renal colic, from increased peristalsis around obstruction.
- Sudden onset pain, radiates from flank to pelvis (loin to groin)
- Nausea + vomitting
- Distal stones can cause urinary frequency
- Haematuria
Sometimes get no pain - if stone is non-obstructing
Symptoms if renal calculi become infected
- Rigors
- Fevers
- Lethargy
- Features of sepsis
Examination findings for renal calculi
- Unremarkable
- May be some tenderness in affected flank
- Signs of dehydration - reduced fluid secondary to vomitting
Differentials for flank pain
Pyelonephritis
Ruptured AAA
Biliary pathology
Bowel obstruction
Lower lobe pneumonia
MSK pain
Bedside and bloods for ?renal calculi
- Urine dip - haematuria, infection? –> send MC&S if signs
- FBC, CRP, U&E
- Urate and calcium levels
- If pass stone - retrieval and analysis
Imaging for renal calculi
- Non contrast CT KUB - kidney, ureter, bladder
- High sensitivity and specificity
- USS to assess for hydronephrosis (if known stone), can detect renal but not ureteric stones
- AXR - rarely used, not all stones radiopaque but if known stone that is visible, may be used for stone surveillance
Initial management renal calculi
- IV fluids
- Majority of cases - stones will pass spontaenously esp if distal ureter or less than 5mm
- Analgesia - NSAIDS PR
- IV abx if significant infection/sepsis and urgent urology referral
When is tamsulosin used?
- Not routinely used
- Limited evidence that their use may be beneficial in distal ureteric stones >8mm
Criteria for inpatient admission for renal stone
- Post obstructive AKI
- Uncontrollable pain from simple analgesics
- Evidence of infected stones
- Large stones - >5mm
What is the management if evidence of infection or AKI?
- Urgent decompression
- Stent insertion or nephrostomy
What is retrograde stent insertion?
- Placement of stent within ureter
- Approaching from distal to proximal via cystoscopy
- Allows ureter to be kept patent and temporarily relieve obstruction
What is nephrostomy?
- Tube placed directly into renal pelvis and collecting system
- Relieves obstruction proximally
- If needed, anterograde stent can be passed via same tract made
Management options if stone does not pass spontaneously
- Extracorporeal shock wave lithotripsy (ESWL)
- Percutaneous nephrolithotomy (PCNL)
- Flexible uretero-renoscopy (URS)
What is extracorporeal shock wave lithotripsy?
- Targeted sonic waves to break up stone - then will be passed
- Reserved for smaller stones - less than 2cm
- Done via radiological guidance - x-ray or USS
- Contraindications - pregnancy, anticoagulants or coagulopathy
What is percutaenous nephrolithotomy?
- Used for renal stones only
- Preferred for large renal stones - inc staghorn
- Percutaenous access to kidney with nephroscope passed into renal pelvis
- Stones can then be fragmented using lithotripsy
What is flexible uretero-renoscopy?
- Passing scope retrograde up into ureter
- Allowing stones to be fragmented through laser lithotripsy and then fragments removed
Complications of renal stones
- Infection
- Post renal AKI
- Recurrent renal stones –> scarring and loss of kidney function
Management of recurrent stone formers - ALL
- Specialised management
- Manage underlying cause
- Hydration
- Retrieve stones - if unable to, check calcium and urate levels
Recurrent oxalate stone formers management
- Avoid high purine foods and high oxalate foods
- eg nuts, rhubarb, sesame
Recurrent calcium stone formers management
- PTH levels checked
- Exclude primary hyperparathyroidism
- Avoid excess salt in diet
Recurrent urate stone formers management
- Avoid foods high in purine eg redmeat and shellfish
- May need urate lowering medication eg allopurinol
Management of recurrent cystine stone formers
Genetic testing for underlying familial disease
How do bladder stones form?
- Stasis of urine within bladder
- Commonly seen in cases of chronic urinary retention
- May also be secondary to infections eg schistosomiasis or passed as ureteric stones
What to consider if identify bladder stones in male patient?
- Bladder outflow surgery should be considered (eg TURP?)
Presentation and management of bladder stones
- Lower urinary tract symptoms
- Investigate for renal and ureteric stones - CT KUB
- Cystoscopy - allow stones to drain or fragment via lithotripsy
Complication of bladder stone
Chronic irritation of bladder epithelium by stone can predispose to SCC bladder cancer
