Session 7

Question 1

What is the name given to the formation of stones in the urinary tract?

Answer 1

Urolithiasis

Question 2

Where is the commonest site for renal stones?

Answer 2

Renal pelvis. More common in men

Question 3

What are the causes of bladder stones?

Answer 3

Bladder outflow obstruction - neuropathic bladder/prostate obstruction
Presence of foreign body - catheter/suture

Question 4

What are renal stones made of?

Answer 4

Calcium (99%) - oxalate (commonest)/phosphate/Uric acid)
Cysteine stones in cystinuria
Drug stones

Question 5

What are the causes of renal stones?

Answer 5

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

Question 6

How do the majority of calcium oxalate stones grow?

Answer 6

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

Question 7

What are other causative factors of renal stones other than supersaturation?

Answer 7

Urine stasis
Drugs
Genetic disorders (polycystic kidneys/cystinuria)

Question 8

What are the actions of PTH?

Answer 8

Stimulates: 
Osteoclastic resorption of bone
Intestinal absorption of calcium
Synthesis of vit D
Renal absorption of calcium and excretion of phosphate

Question 9

What are the actions of Vit. D?

Answer 9

Stimulates:
Calcium resorption of bone
Calcium absorption in gut

Question 10

What are the actions of calcitonin?

Answer 10

Decrease osteoclastic bone resorption

Increase renal excretion

Question 11

What are the causes of hypercalciuria?

Answer 11

Idiopathic
Hypercalcaemia - hypersecretion of PTH, thiazide diuretics)
Excessive Ca2+ dietary intake
Excessive resorption from bone (immobilisation)

Question 12

What are the causes of hyperoxalouria?

Answer 12

Rare genetic disorders of oxalate synthesis
Increased intestinal oxalate absorption secondary to GI disease (crohns)
Dietary habits (tea, nuts, spinach)

Question 13

What stones are usually seen secondary to infection?

Answer 13

Struvite stones. More common in women (UTIs). Often form staghorn calculus

Question 14

What causes uric acid stones?

Answer 14

Hyperuricaemia (gout) and in people with acidic urine

Question 15

How do renal stones present?

Answer 15

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

Question 16

What are the investigations performed when urinary stones are suspected?

Answer 16

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

Question 17

What are the complications of urinary stones?

Answer 17

Acute pyelonephritis (infection)
Pressure necrosis of renal parenchyma
Urinary obstruction and hydronephrotis
Ulceration of wall of collecting system

Question 18

What is the treatment for urinary stones?

Answer 18

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

Question 19

What are preventative measures for urinary stones?

Answer 19

Drink more water
Decrease excretion of calcium or oxalate
Potassium citrate to alkalise urine (but may promote calcium phosphate stones)

Question 20

What are the defence mechanisms of the UT against infections?

Answer 20

Regular flushing during voiding

Antibacterial secretions into the urine and urethra

Question 21

What host factors can increase the risk of developing UTIs?

Answer 21

Shorter urethra (females)
Obstruction - enlarged prostate, pregnancy, stones, tumours
Neurological problems - incomplete emptying, residual urine
Ureteric reflux

Question 22

What bacterial factors can increase the risk of developing UTIs?

Answer 22

Fimbriae allow attachment to epithelium
Polysaccharide capsule resists host defences
Urease production creates favourable environment for growth
Haemolysins damage host membranes

Question 23

What bacteria are the most common causes of UTIs?

Answer 23

Coliforms (e.g. E. coli) - gram negative rods

Question 24

What are the clinical features of UTIs?

Answer 24

Cystitis (lower) - burning, increased frequency, dysuria and urgency
Acute/chronic pyelonephritis - systemically unwell, loin pain, fever, dysuria
Sepsis +/- shock

Question 25

What is an uncomplicated UTI and how is the diagnosis made?

Answer 25

Infection by a usual organism in a patient with a normal UT and UT function
Diagnosis just based on history

Question 26

What is a complicated UTI?

Answer 26

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

Question 27

How are specimens collected in a complicated UTI?

Answer 27

Mid stream urine
Collection bag (problem with contamination)
Catheter sample
Samples transported quickly to prevent multiplication and is preserved

Question 28

How are urine samples tested for UTIs?

Answer 28

Near patient - turbidity (visual inspection), dipstick (useful to exclude UTI - tests leucocytes, nitrites, haematuria and proteinuria)
Laboratory - microscopy, urine culture

Question 29

What is abacterial cystitis?

Answer 29

50% cystits do not have positive urine cultures

Question 30

What is the treatment for UTI?

Answer 30

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