Renal Stones Flashcards
Definition of Urolithiasis
-Urolithiasis: renal tract stone disease (stone at any point within the urinary tract)- kidney, PUJ, ureteric, bladder
-May be symptomatic or asymptomatic
-Can cause a range of clinical problems, including
=Pain
=Haematuria
=(Obstructive) urosepsis
=Loss of renal function
Urolithiasis incidence, age, sex/gender
-Urolithiasis is the common
-Peak onset 20-50y
-0% of Caucasian men will develop a renal stone by 70y
-30-50% of stone-formers will form recurrent stone within 3-5y
-25% have FH urolithiasis (familial RTA & Cystinuria are inherited)
-More common in men- M : F 3:1 (incr Cit in F is protective)
Urolithiasis Aetiology
-Intrinsic Factors
=Age (20-50y)
=Male gender
=FH Urolithiasis (RTA, Cystinuria)
=Abnormal Anatomy/Function that leads to Urinary Stasis: PUJO, HSK (Horseshoe kidney), VUR (Vesico-Ureteric Reflux), CD (calyceal Diverticulum), BOO
=Limited Mobility (leads to bone de-mineralisation)- CVA, MS, MND, paraplegia
-Extrinsic/Environmental Factors
=Hot Geographical Location & Summer
=Poor Water intake (<1.2L/d)
=Western Diet (excess protein- urinary acidification; high salt- causes hypercalciuria)
=Occupation- chef, steel-workers, bus/lorry/taxi drivers
Urolithiasis classification
-Radio-density: radio-opaque vs radiolucent
=CaOx, CaP vs Uric Acid, Cys, Indinavir
-Mineral Composition:
=CaOx 70-80%
=UA10-15%
=CaP 5-10%
=MAP (Mg-NH4-P)/Struvite 10%
=Cyst 1%
-Size, Shape & Locus:
=5mm circular mid-ureteric stone vs 6cm staghorn calculus-
Risk factors for urolithiasis classification
-CaOx (calcium oxalate) 85%
=Hyper Calcaemia/ Calciuria: Hyperparathyroidism, Bone resorption states (immobility), Type1 RTA, hyperuricosuria
=Hyper-Oxaluria: bowel resections, short bowel synd
=Stones are radio-opaque
-Calcium phosphate 10%
=RTA 1 and 3, high urinary pH increases supersaturation of urine with calcium and phosphate
=Radio opaque stones
-UA 5-10%
=Hyper-Uricaemia/-Uricosuria: Gout, Myeloproliferative states (malignancy as extensive tissue breakdown)
=Product of purine metabolism, precipitate when urinary pH low, more common in children with inborn errors of metabolism, radiolucent
-MAP (Mg-NH4-P)/ Struvite 2-20%
=Infection: Urease producing bact hydrolyse Urea > insol NH4 salts(MAP/Struvite stones) so associated with chronic infection
=Magnesium, ammonium, phosphate. Alkaline
-Cyst (cystine) 1%
=Cystinuria: Aut recessive inherited disorder= decreased absorption of cysteine from intestine and renal tubule
=Relatively radiodense as contain sulphur
Overall risk factors for renal stones
Risk factors
=dehydration
=hypercalciuria, hyperparathyroidism, =hypercalcaemia
=cystinuria
=high dietary oxalate
=renal tubular acidosis
=medullary sponge kidney, polycystic kidney disease
=beryllium or cadmium exposure
Risk factors for urate stones
=gout
=ileostomy: loss of bicarbonate and fluid results in acidic urine, causing the precipitation of uric acid
Drug causes
=drugs that promote calcium stones: loop diuretics, steroids, acetazolamide, theophylline
=thiazides can prevent calcium stones (increase distal tubular calcium resorption)
Presentation of Urolithiasis
-Asymptomatic:
=Found incidentally on XR or CT imaging
-Symptomatic:
=Pain (flank pain, typically sudden, colicky, radiation to groin/ scrotum/ urethra, N&V, haematuria, LUTS, paroxysmal timing, no comfortable position, 10/10)
=Haematuria
=Infections: rec UTIs (MAP/struvite),weakness, malaise
=Obstructive urosepsis, pylonephrosis
-DDx of Flank Pain:
=Thx- Lobar pneumonia, Rib fractures
=Renal- Ureteric/Renal stone, Acute pyelonephritis
=Abd- AAA, Acute pancreatitis/cholecystitis, Appendicitis
=Gynae- Ectopic pregnancy, Torsion/Rupture of Ovarian cyst
Clinical Assessment of urolithiasis
-General: ABC ? Relatively stable vs septic shock
T P R BP: ?distress, ?shock
-Abd: ?localised tenderness ?peritonism – abd pathology ?AAA
-MSU: Infection, Pregnancy Test
Clinical investigations of urolithiasis
-MSU:
=Infection- RBC, WCC, Nitrites > send for MC&S
-Pregnancy Test
-N.B. 24 Hour Urine Collections are indicated for Metabolic Screening in High Risk Stone-Formers (Paediatric patients, patients with single/solitary functioning kidneys, frequent stone-formers)
-Bloods:
=FBC, UE check renal function), LFT, Amylase, CRP
=Calcium, Urate (underlying cause)
=(PTH if Calcium is elevated)
=ABG if sig unwell
=Blood Cultures- if febrile/septic
-Dx:
=CTKUB is the gold standard: 95-97% sensitivity & specificity; quick, ULD (ultra-low dose protocols), unenhanced (no contrast given)
=non-contrast CT KUB should be performed on all patients, within 24 hours of admission NICE
if a patient has a fever, a solitary kidney or when the diagnosis is uncertain an immediate CT KUB should be performed. In the case of an uncertain diagnosis, this is to exclude other diagnoses such as ruptured abdominal aortic aneurysm
=IVU is largely historic/obsolete
=USS often used in young females/pregnant women, or in known lucent stone-formers (for monitoring renal stones)
=KUBXR- often used as an adjunct to CTKUB, to determine if stone is radio-opaque, and whether it can therefore be monitored clinically with further XR imaging (to determine the effects of treatment)
=MRI- does not show stones well, and therefore not typically used
Anatomic sites of narrowing where stones may impact/ obstruct
-Upper ureter: PUJ (pelvi-ureteric junction; (USA- UPJ) between renal pelvis and ureter)
-Mid Ureter: @ iliac crossing
-Lower Ureter: VUJ (vesico-ureteric junction, entrance of ureter into bladder)
Urolithiasis management
-Analgesia:
=NSAIDS: Diclofenac PR/IM
=If contraindicated or not giving sufficient pain relief, IV paracetamol
=Opiates (Morphine)
=Anti-emetics
=Alpha-blockers for distal ureteric stones less than 10mm in size
-Rehydration:
=IVF
-Antibiotics: if indicated
=Typically require both Gm +ve (Amoxicillin) + Gm –ve (Gentamicin) cover
=Local Abx protocols
=Liaise with Microbiology
-Clinical Observation vs Intervention:
=Further management is determine by the size and locus of stone, presence/absence of sepsis, patient factors (single vs dual kidneys, pre-existing renal function)
=Watchful Waiting: typically for ureteric stones <6mm when the patient is otherwise well (90% may pass)
=MET (Medical Expulsive Therapy): use of Tamsulosin to facilitate ureteric expulsion
=Active Rx of Ureteric Stone: ESWL, ureteroscopy + lasertripsy
=Active Drainage of Sepsis / Disobstruction: cystoscopy + insertion of Ureteric Stent, PCN (Percutaneous Nephrostomy)
=watchful waiting if < 5mm and asymptomatic
=5-10mm shockwave lithotripsy
=10-20 mm shockwave lithotripsy OR ureteroscopy
=> 20 mm percutaneous nephrolithotomy
-Uretic stones
=shockwave lithotripsy +/- alpha blockers>< 10mm shockwave lithotripsy +/- alpha blockers
=10-20 mm ureteroscopy
Indications for intervention for ureteric stones
-Uncontrolled/Refractory Pain- despite analgesia
-Fever/Sepsis
-Impaired Renal Function
-Large stone that is unlikely to naturally expel
-Small, persistent stone that has not been expelled over prolonged period (6 weeks)
-Occupation (pilot, lorry/bus/taxi driver, Royal Navy Scuba diver)
Active intervention for ureteric stones
1) ESWL (Extra-corporeal Shock-Wave Lithotripsy)
2) Cystoscopy + insertion of ureteric stent (carried out if ureteroscopy is not possible, for instance if ureter is too narrow then placement of a ureteric stent will subsequently dilate the ureter over a period of weeks and subsequently facilitate further attempt at ureteroscopy)
3) Primary Ureteroscopy + lasertripsy of stone / basket extraction of small stone
Management of obstructive urosepsis
-Obstructive Urosepsis is a true surgical emergency that must be recognised immediately and dealt with promptly
-Ureteric obstruction (stone) + proximal infection (infected, obstructed kidney / pus) + sepsis
-High mortality rate of Gm –ve urosepsis: 20-40%
-Resuscitate Patient
=ABC
=Wide-bore cannulae + IVF
=Urgent Bloods- FBC, UE, Coag
=Blood Cultures
=MSU – UA, Urine Culture
=IV Abx (to cover Gm +ve & Gm –ve eg Amoxicillin + Gentamicin)
=Urethral catheter
=Regular surgical obs
-Drain the infection
=PCN (Percutaneous Nephrostomy) or Ureteric Stent
=Choice of PCN vs stent may depend on whether patient is on anticoagulants, fitness for GA etc
-Deferred Rx of stone until the infection is resolved and patient well
=Ureteroscopy + lasertripsy of stone / basket extraction of small stone
=ESWL (Extra-corporeal Shock-Wave Lithotripsy)
Indications for intervention for renal stones
-Uncontrolled/Refractory Pain- despite analgesia
-Recurrent UTIs/pyelonephritis – due to infected stones (MAP/struvite)
-Impaired Renal Function/ renal cortical atrophy- due to stones
-Upper calyceal stones - likely to displace to ureter and become symptomatic
-Larger stones - more likely to progress in size and require intervention
-Occupation (pilot)
