Session 7 Flashcards
What is the name given to the formation of stones in the urinary tract?
Urolithiasis
Where is the commonest site for renal stones?
Renal pelvis. More common in men
What are the causes of bladder stones?
Bladder outflow obstruction - neuropathic bladder/prostate obstruction
Presence of foreign body - catheter/suture
What are renal stones made of?
Calcium (99%) - oxalate (commonest)/phosphate/Uric acid)
Cysteine stones in cystinuria
Drug stones
What are the causes of renal stones?
Supersaturation due to:
Dehydration - decreased water content
Hypercalciuria, hyperoxaluria, cysteinuria -increased mineral content
Decreased solubility of solute in urine - acid urine favours calcium oxalate and Uric acid stones, alkaline urine favours calcium phosphate
How do the majority of calcium oxalate stones grow?
Like stalactites attached to exposed interstitial deposits of calcium phosphate on the tips of renal papilla (Randall’s plaque). They are composed of a core of calcium phosphate surrounded by calcium oxalate
What are other causative factors of renal stones other than supersaturation?
Urine stasis
Drugs
Genetic disorders (polycystic kidneys/cystinuria)
What are the actions of PTH?
Stimulates: Osteoclastic resorption of bone Intestinal absorption of calcium Synthesis of vit D Renal absorption of calcium and excretion of phosphate
What are the actions of Vit. D?
Stimulates:
Calcium resorption of bone
Calcium absorption in gut
What are the actions of calcitonin?
Decrease osteoclastic bone resorption
Increase renal excretion
What are the causes of hypercalciuria?
Idiopathic
Hypercalcaemia - hypersecretion of PTH, thiazide diuretics)
Excessive Ca2+ dietary intake
Excessive resorption from bone (immobilisation)
What are the causes of hyperoxalouria?
Rare genetic disorders of oxalate synthesis Increased intestinal oxalate absorption secondary to GI disease (crohns) Dietary habits (tea, nuts, spinach)
What stones are usually seen secondary to infection?
Struvite stones. More common in women (UTIs). Often form staghorn calculus
What causes uric acid stones?
Hyperuricaemia (gout) and in people with acidic urine
How do renal stones present?
Asymptomatic Renal colic due to peristaltic movement as it passes down the ureter. Pain in L1 Recurrent UTIs Dull ache in loins when in kidney Haematuria
What are the investigations performed when urinary stones are suspected?
Mid stream urine - RBCs, urinary crystals
Serum - urea,creatinine, electrolytes, calcium
Abdo. X ray (uric acid stones can’t be seen)
CT scan (best method)
Pass urine through sieve
What are the complications of urinary stones?
Acute pyelonephritis (infection)
Pressure necrosis of renal parenchyma
Urinary obstruction and hydronephrotis
Ulceration of wall of collecting system
What is the treatment for urinary stones?
Analgesia and warmth to side of pain
Ureteroscopy for stones in lower ureter
Percutaneous nephrolithotomy - cut through skin to renal pelvis
ESWL (shock wave) - for stones near renal pelvis, fragments stones
What are preventative measures for urinary stones?
Drink more water
Decrease excretion of calcium or oxalate
Potassium citrate to alkalise urine (but may promote calcium phosphate stones)
What are the defence mechanisms of the UT against infections?
Regular flushing during voiding
Antibacterial secretions into the urine and urethra
What host factors can increase the risk of developing UTIs?
Shorter urethra (females)
Obstruction - enlarged prostate, pregnancy, stones, tumours
Neurological problems - incomplete emptying, residual urine
Ureteric reflux
What bacterial factors can increase the risk of developing UTIs?
Fimbriae allow attachment to epithelium
Polysaccharide capsule resists host defences
Urease production creates favourable environment for growth
Haemolysins damage host membranes
What bacteria are the most common causes of UTIs?
Coliforms (e.g. E. coli) - gram negative rods
What are the clinical features of UTIs?
Cystitis (lower) - burning, increased frequency, dysuria and urgency
Acute/chronic pyelonephritis - systemically unwell, loin pain, fever, dysuria
Sepsis +/- shock
What is an uncomplicated UTI and how is the diagnosis made?
Infection by a usual organism in a patient with a normal UT and UT function
Diagnosis just based on history
What is a complicated UTI?
When factors are present that predispose patient to persistent/recurrent infection or treatment failure e.g. Abnormal UT, virulent organisms, impaired host defences. Most cases in men, children, pregnant women and pyelonephritis are managed as complicated UTI
How are specimens collected in a complicated UTI?
Mid stream urine
Collection bag (problem with contamination)
Catheter sample
Samples transported quickly to prevent multiplication and is preserved
How are urine samples tested for UTIs?
Near patient - turbidity (visual inspection), dipstick (useful to exclude UTI - tests leucocytes, nitrites, haematuria and proteinuria)
Laboratory - microscopy, urine culture
What is abacterial cystitis?
50% cystits do not have positive urine cultures
What is the treatment for UTI?
Increased fluid intake to increase flushing
3 day course of uncomplicated UTI
Treat underlying disorders (diabetes, enlarged prostate)
5-7 day course for complicated lower UTI
14 day course for pyelonephritis/sepsis
Prophylaxis if >2 episodes in 1 year
