Hamzah's GU pathology Flashcards
(111 cards)
Where do renal stones form?
in the collecting duct
What is the lining of renal tubules?
cuboidal epithelium
Common sites of renal stones
- pelviureteric junction
- pelvic brim
- vesicoureteric junction
Types of renal stones
- calcium oxalate - 75%
- magnesium ammonium phosphate (triple phosphate) - 15%
- urate - 5%
- brushite, cysteine - 1%
- mixed - 1%
Aetiology of renal stones
- stone formation occurs when normally soluble material supersaturates the urine and begins to form crystals
Inhibitors of crystal formation
magnesium, citrate
Epidemiology of kidney stones
- common - lifetime incidence = 15%
- peak age = 20-40yrs
- M:F = 3:1
Risk factors for kidney stones
- high protein diet
- dehydration
- FH
Pathophysiology of calcium stones
- hypercalciuria - increased urinary calcium excretion
- hyperparathyroidism –> hypercalcaemia
- excessive dietary calcium
- excessive bone resorption
Pathophysiology of uric acid stones
- hyperuricemia
- people who have ileostomies are at risk because of the loss of bicarbonate from GI secretions –> acidic urine –> reduced solubility of uric acid
UTI and renal stones
- proteus produces urease
- urea –> NH3 (via urease) –> precipitation of triple phosphate stones
Clinical presentation of renal stones
- renal colic - excruciating pain in loin to groin, nausea and vomiting, cannot lie still
- renal obstruction = felt in loin between 12th rib and lateral edge of lumbar muscles
- obstruction of mid-ureter = mimics appendicitis/diverticulitis - iliac fossa pain, fever, nausea, pyrexia
- obstruction in bladder or urethra = pelvic pain, dysuria, interrupted flow, strangury
- UTI - pyelonephritis - loin to groin pain, fever, rigors, nausea and vomiting
- haematuria, proteinuria, pyuria, anuria (failure of kidneys to produce urine)
Differential diagnosis of renal stones
- bleeding in kidney (e.g. after renal biopsy) –> clots can obstruct ureter
- ectopic pregnancy
- leaking AAA
Diagnostic tests for renal stones
- FBC - U&Es, calcium, phosphate, glucose, bicarbonate, urate
- urine dipstick
- MSU - MC&S
- 24hr urine - calcium, oxalate, urate, citrate, sodium, creatinine, stone biochemistry
- imaging - non-contrast CT, KUB XR, IV urogram
Treatment of renal stones
- analgesics - diclofenac (NSAID)
- IV fluids
- abx if infection - cefuroxime/gentamicin
- stones <5mm - pass spontaneously –> increase fluid intake
Treatment of >5mm renal stones
- medical expulsion oral nifedipine (CCB) or alpha blockers (tamsulosin)
- extracorporeal shockwave lithotripsy (ESWL) - US waves shatter stone (SE=renal injury)
- Percutaneous nephrolithotomy (PCNL) - if stone is in kidney, keyhole surgery is done to remove large stones
- ureteroscopy with basket
Prevention of renal stones
- drink plenty of fluids
- normal dietary calcium intake - low calcium levels lead to oxalate excretion
- thiazide diuretics decrease calcium excretion
- allopurinol - decreases urate stones
What is acute kidney injury?
significant deterioration in renal function occurring over hours or days, measured by serum creatinine or urine output.
can be reversible
serum urea rises due to reduced renal excretion of nitrogenous waste products
Diagnostic criteria for AKI
- rise in creatinine >26micromol/litre in 48hrs
- rise in creatinine >1.5x baseline
- urine output <0.5ml/kg/hr for 6 continuous hours
Epidemiology of AKI
common - affects up to 18% of hospital patients and approximately 50% of ICU patients
Risk factors for AKI
> 75, male gender, pre-existing CKD, cardiac failure, sepsis, drugs, chronic liver disease, PVD
Common causes of kidney failure
- sepsis
- major surgery
- cardiogenic shock
- hypovolaemia
- diuretics, ACEi, lithium, methotrexate, gentamicin
Aetiology of AKI
divided according to site
- pre-renal
- renal
- post-renal
Pre-renal AKI causes
- hypovolaemia –> hypoperfusion of kidneys
- low cardiac output –> hypotension
- renal artery stenosis (atherosclerosis)
- renal vasoconstriction (NSAIDs, ARBs, ACEi)