Week 7 Flashcards
What is urolithiasis
Formation of stones in the urinary tract
Most common location of urolithiasis
Renal pelvis
Where can uroliths be found
Renal pelvis and calyces
Ureter (usually from kidney)
Bladder
Causes of bladder stones
Bladder outflow obstruction - urethral structure, prostate obstruction, neurogenic bladder
Foreign body e.g catheter or non absorbable sutures
Passed down form upper tract
Symptoms of bladder stones
Anuria
Painful bladder distension (urinary retention)
What are nephroliths
Solid materials formed in kidneys from minerals and urine
Types of nephroliths
99% calcium stones - calcium oxolate, calcium phosphate, uric acid, struvite
1% other - drug, cysteine, ammonium acid urate
Causes of nephrolithiasis
Urine supersaturation
Urine stasis
Drugs
Congenital e.g polycystic kidney
What are Randall’s plaques
Calcium oxolate stones growing on interstitial deposits of calcium phosphate e.g renal papillae, ducts of Bellini, free in solution
What is urine supersaturation
Solvent contains more solute than it can hold so crystals form by nucleation
Broad cause of urine supersaturation
Low water content - dehydration
High mineral content
Low solubility of solute
What alters solubility of solute in urine
Urine pH
Consequences of acidic or alkaline urine
Acid - favours calcium oxolate and uric acid stone formation
Alkaline - favours calcium phosphate stone formation
What is renal tubular acidosis
Persistently alkaline urine and increased citrate excretion
Leads to calcium phosphate stone formation
What senses serum Ca
Parathyroid glands
Kidneys
Brain
Actions of PTH
Stimulates osteoclasts
Increases renal reabsorption of Ca
Increases phosphate excretion
Increases calcitriol synthesis
Actions of calcitriol
Stimulates osteoclasts
Increases renal reabsorption of Ca
Increases intestinal absorption of Ca
Actions of calcitonin
Inhibits osteoclasts
Increase excretion of Ca
Causes of hypercalciuria
Hypercalcaemia
Excessive dietary Ca
Excessive breakdown of bone e.g prolonged immobilisation
Increased gut absorption (idiopathic)
Causes of hypercalcaemia
Hyper secretion of PTH Increased bone destruction Excessive dietary Vitamin D and Ca Thiazides diuretics Sarcoidosis - macrophages activate vitamin D precursor
Causes of hyper secretion of PTH
Parathyroid hyperplasia/tumour
Secondary to renal failure - retention of phosphate reduces Ca in serum
Ectopic secretion of PTHrP by a malignant tumour
Reasons for increased bone destruction
Immobilisation
Bone marrow tumour
Diffuse skeletal metastases
Paget’s disease
Clinical signs of hypercalcaemia
Severe muscle weakness Fractures or bone pain Renal stones Gallstones Constipation Depression Seizures
Causes of hyperoxaluria
Type 1/2 primary hyperoxaluria - autosomal recessive disorder of oxolate synthesis
Increased intestinal absorption - secondary to GI disease e.g Chron’s
High dietary oxolate intake - tea, rhubarb, spinach, nuts
Low Ca intake - stimulates oxolate absorption in gut
What are struvite stones
Magnesium ammonium phosphate stones with variable amounts of Ca
What causes struvite stones
Secondary to infection by microorganisms that produce:
Urease enzyme - produce ammonium hydroxide
Mucoprotein - provides organic matrix for stone formation
What is the usual type of struvite stone
Staghorn calculi - cast of renal collecting system
Risk factors for struvite stones
Risk factors for UTIs: Spinal cord injury Neurogenic bladder Vesicoureteric reflux Urinary tract obstruction
Risk factors for uric acid stones
Hyperuricaemia
Urine pH <5.5
What is uric acid
Endpoint of purine metabolism
Causes of hyperuricaemia
Idiopathic gout
Increased cell turnover - lympho/myelo-proliferative disorders, following chemotherapy
Which renal stone is hardest to detect
Uric acid
It is radiolucent (need CT)
Symptoms of renal stones
Asymptomatic Renal colic Recurrent UTI Loin pain Haematuria Renal failure Urinary tract obstruction
Where is renal colic pain referred to
Flank to iliac fossa
Inner thigh
Labia/scrotum
How do you investigate renal stones
Mid stream urine sample - culture, detect RBCs and crystals
Serum sample - urea, electrolytes, creatinine, minerals
AXR
CT (ideally during pain)
Examine calculi
Complications of renal stones
Acute pyelonephritis
Pressure necrosis of renal parenchyma
Urinary obstruction
Ulceration through wall of collecting system
Treatment for renal stones
Analgesia
Ureteroscopy
Percutaneous nephrolithotomy - remove renal stones by cutting into back
Shock wave lithotripsy - focused ultrasonic energy to fragment stones so they can be passed spontaneously (<5mm)
Prevention of renal stones
Keep hydrated to reduce urine supersaturation
Increase Ca excretion (diuretics)
Potassium citrate to alkalinise urine - reduces risk of calcium oxolate, uric acid and cysteine stones
