Lecture 23 - Nephrourolithiasis Flashcards
What is the prevalence of kidney stones in the general population?
2-3%
In which gender is kidney stones more common?
M (x3)
Chance of stone recurrence is __% within 10 years
50%
What is the commonest cause of urological emergency admission?
‘colic’
What are the different types of kidney stones? (from most common to least)
Calcium oxalate (45%) Calcium oxalate + phosphate Triple phosphate (infective) Calcium phosphate Uric acid Cysteine
What kind of stones will show up on X-ray?
Those high in calcium
What are signs and symptoms of urolithasis?
Loin pain: typically severe, intermittent colic
NV
Ureteric colic (radiates to groin)
Dysuria/haematuria/testicular/vulval pain
UTI
Loin tenderness
Pyrexia
What are the major risk factor for calcium oxalate stones?
Hypercalciuria
Hyperoxaliuria
Hypocitraturia (as citrate forms complexes with calcium making it more soluble)
Are calcium oxalate stones radio-opague?
Yes (less so than calcium phosphate stones however)
What causes cystine stones?
Inherited recessive disorder of transmembrane cysteine transport leading to decreased absorption of cystine from intestinal + renal tubule
Are cystine stones radio-opague?
Yes
Uric acid is a product of metabolism of what substrates?
Purines
What things can cause uric acid stones?
Diseases with extensive tissue breakdown, e.g. malignancy
More common in kids with inborn errors of metabolism
Are uric acid stones radio-opague?
No
When might you get calcium phosphate stones?
In renal tubular acidosis, high urinary pH increases supersaturation of urine with calcium and phosphate (only types 1 and 3 increase risk of stone formation)
Are calcium phosphate stones radio-opague?
Yes - they are of a similar composition to bone
What are struvite stones formed of?
Magnesium, ammonium, phosphate
What do struvite stones result form?
Urease producing bacteria (+thus are associated with chronic infections) –> alkaline condition under which crystals can precipitate
Are struvite stones radio-opague?
Slightly
Which type of renal stone leads to alkaline urine?
Struvate
Can also be alkaline in calcium phosphate stones
What kind of stones tend to cause acidic urine?
Uric acid
What stones tend not to shift the pH of urine?
Calcium phosphate
Calcium oxalate
Cystine
What are staghorn calculi?
Calculi involving the renal pelvis and extending into at least 2 of the calyces
They develop in alkaline urine and are composed of strutive
What kinds of infections tend to predispose to struvite stones?
Ureaplasma urealyticum
Proteus infections
Which kinds of renal stones are radio-opague?
Calcium oxalate Calcium phosphate Triple phosphate stones (struvite) Mixed calcium oxalate/phosphate stones Cystine (semi opague)
Which renal stones are radio-lucent?
Urate stones
Xanthine stones
What investigations should you do in someone presenting with suspected kidney stones?
Bloods - FBC, UE, creatinine
Ca, albumin, urate
PTH (hyperparathyroidism may be an underlying aetiology)
Urine analysis + culture
24hr urine collections - excess Ca, uric acid?
What imaging can be done for suspected kidney stones?
KUB USS CT KUB (gold standard) IVU (intravenous urogram)
What does KUB stand for?
Kidneys ureter bladder
doesn’t involve contrast
What are indications for surgical treatment of kidney stones?
Obstruction of the urinary tract (painful, risk of infection, renal damage) Recurrent gross haematuria Recurrent pain + infection Progressive loss of kidney function Patient occupation
What are the different techniques that can be used for surgery for kidney stones?
Open (rare)
Endoscopic
ESWL
PCNL
What does ESWL stand for?
Extracorpeal shock wave lithotripsy
What are indications for open surgery for nephrourolithiasis?
Non-functioning infected kidney with a large stone necessitating nephrectomy
Cases which cannot be managed by PCNL or ESWL for technical reasons
What are indications for simple partial and total nephrectomy for nephrourolithiasis?
Non-functioning kidney with large staghorn stones or elderly frail patients with complex stones + normal contralateral kidney
What does PCNL stand for?
Percutaneous nephrolithotomy
What are indications for PCNL?
Large stone burden
Associated PUJ stenosis (obstruction to outflow of kidney)
Infundibular strictures
Calyceal diverticulum
Morbid obesity/skeletal deformity
ESWL resistant stones, e.g. cystine (v. hard)
What does PCNL involve?
Inserting a guidewire
Using a retrograde catheter or balloon and injecting contrast
Renal puncture guided by X-ray/USS to obtain access to collecting system
Remove pieces of stone with small scope
What are contraindications for PCNL?
Uncorrected coagulopathy
Active UTI
Obesity/unusual body habitus unsuitable for X-ray tables
What are relative CIs for PCNL?
Small kidneys
Severe perirenal fibrosis
What are complications of PCNL?
Pseudoaneurysm or AV fistula
Pelvic tear, ureteral tear, stricture of PUJ
Injury to adjacent organs, e.g. bowel, pneumothorax, liver, spleen
Sepsis, MI
What is ESWL used for?
For simple stones too large to pass through
Send shock waves to crush the stones and then the smaller fragments can pass in the urine
What kind of stones can ESWL not be used for?
Really big ones that may break off into fragments big enough to block the ureters - PCNL better for these
Don’t use for stones >2cm
Often doesn’t work for cystine stones
What tends to be the first line treatment for renal and ureteric stones?
ESWL
Do you require to be admitted to get ESWL?
No - can be done on day case basis with simple analgesia
What is the limit on the number of times you can have ESWL?
Can be repeated as often as req.
However, if not effective after 2 treatments, further treatment is not justified
Where do kidney stones usually get stuck?
At constrictions, e.g. PUJ, pelvic brim, VUJ
What are indications for open ureterolithotomy?
Not suitable for laparoscopic approach
Failed ESWL or ureteroscopy
What is a ureterolithotomy?
Surgical removal of a stone from the ureter
What are indications for ureteroscopy?
Severe unobstruction, uncontrollable pain, persistent haematuria, lack of progression, failed ESWL and patient occupation
What is the standard instrument used for treating lower ureteric stones?
Rigid ureteroscope (this is less successful for proximal ureteric stones)
What may be involved in surgery for ureteric or renal stones?
Flexible ureteroscopes
Flexible lithoclast
Holmium laser
What are minor complications of ureteroscopy?
Haematuria, fever, small ureteric perforation, minor VUR
What are major complications of ureteroscopy?
Major ureteric perforation, ureteric avulsion, ureteral necrosis + stricture formation
What are RFs for renal stones?
Dehydration Hypercalciuria, hyperparathyroidism, hypercalcaemia Cystinuria High dietary oxalate Renal tubular acisosi Medullary sponge kidney, PCKD Beryllium or cadmium exposure
What are RFs for urate stones?
Gout
Ileostomy
Why does ileostomy predipose to urate stones?
Loss of bicarbonate and fluid –> acidic uric –> precipitation of uric acid
What drugs can predipose to calcium renal stones?
Loop diuretics
Steroids
Acetazolamide
Theophylline
What drugs are known to prevent calcium stones?
Thiazides (they increase distal tubular calcium repsorption)
What is the analgesic of choice for renal colic?
NSAID
For patients who require admission with renal colic what analgesic should be considered?
A parenteral analgesic, e.g. IM diclofenac for rapid relief of severe pain
What initial investigations should be done when someone presents with suspected renal colic?
Urine dipstick and culture Serum creatinine + electrolytes - to check for renal function FBC/CRP - infection? Calcium/urate - underlying cause? Clotting if PCNL planned
What investigation should be performed on all individuals presenting with renal colic?
Non-contrast CT KUB within 14h admission
If solitary kidney, diagnosis uncertain, fever –> immediate CT KUB
What size of stone will tend to pass spontaneously?
<5mm
How long does it tend to take stones <5mm to pass?
4 weeks from symptom onset
When might a <5mm stone require more intensive/urgent treatment?
If there is ureteric obstruction, renal development abnormality, e.g. horseshoe kidney or prev. renal transplant
How should ureteric obstruction + infection be managed?
Surgical emergency - decompress (options - nephrostomy tube placement, insert ureteric catheter and ureteric stent placement
What minimally invasive treatment options for renal stones are preferred to open surgery?
ESWL
PCNL
Ureteroscopy
How does ESWL work?
Shockwave generated external to patient
Internally cavitation bubbles + mechanical stress –> stone fragmentation
Is ESWL painful?
Can be comfortable so analgesia is recommended
What are complications of ESWL?
Ureteric obstruction
Shock waves may cause solid organ injury
When is ureteroscopy indicated?
In patients where ESWL is CI (e.g. pregnancy)
In most cases of ureteroscopy what is left in situ and how long is it left for post-op?
Stent for 4 weeks
How should a stone burden of less than 2cm in aggregate be managed?
Lithotripsy
How should a stone burden of less than 2cm in a pregnant female be managed?
Ureteroscopy
How should a complex renal calculi or a staghorn calculus be managed?
PCNL
How should a ureteric calculi less than 5mm be managed?
Expectantly
How can calcium stones due to hypercalciuria be avoided?
High fluid intake
Low animal protein diet, low salt diet
Thiazide diuretics
How can risk of getting oxalate stones be reduced?
Cholestryamine (reduces urinary oxalate secretion)
Pyridoxine (does the same)
How can risk of uric acid stones be reduced?
Allopurinol Urinary alkalinization (e.g. oral bicarbonate)
How might bladder stones present?
Suprapubic/groin/penile pain
Dysuria, frequency, urgency
Persistent UTI
Sudden interruption of urinary stream
What usually is a bladder stone secondary to?
Outflow obstruction
How are bladder stones usually treated?
Mostly endoscopically
Larger stones can be treated with open excision
