Urinary17&18 - Urinary Tract Infections & Kidney Stones

Question 1

2 features of the pathophysiology of UTIs

Major Defences x5
Ascending Colonisation

Answer 1

1. ) Major Defences - keeps the urinary tract normally sterile and resistant to bacterial colonisation
   - bladder emptying, vesico-urethral valves, urine acidity, immunological factors and mucosal barriers
2. ) Ascending Colonisation - bacteria colonises at the urethra and works its way up the urinary tract
   - infection of the bladder is cystitis (lower UTI)
   - infection of the kidneys is pyelonephritis (upper UTI)

Question 2

6 risk factors for UTIs

Obstructive Causes x3
Gender
Neurological Conditions
Pregnancy x2
Abnormal Urinary Tract x2
Impaired Host Defence

Answer 2

1. ) Obstructive Causes
   - renal stones, enlarged prostate, retroperitoneal fibroids
2. ) Abnormal Renal Tract
   - vesico-ureteric reflux (retrograde urine flow) in children
   - insertion of urinary catheters

3.) Female - shorter urethra

4. ) Pregnancy
   - enlarged uterus
   - progesterone relaxes ureter and bladder smooth muscle leading to urinary stasis
5. ) Neurological Conditions - can affect bladder emptying
   - multiple sclerosis (MS) and stroke

6.) Impaired Host Defence - immunosuppressed and diabetes mellitus

Question 3

3 bacterias causing UTIs

Escherichia coli
Klebsiella pneumoniae
Staphylococcus saprophyticus

Answer 3

1.) Escherichia coli - g-ve bacilli (coliform)
- main cause of the majority of all UTIs
- converts endogenous nitrates into nitrites so the
urine dip-stick tests positive for nitrites

2. ) Klebsiella pneumoniae - g-ve bacilli
   - causes UTIs in older women and catherised patients
   - tests positive for nitrites
3. ) Staphylococcus saprophyticus - g+ve cocci
   - found in the normal flora of the female genital tract
   - honeymoon cystitis: sexual intercourse increases risk of UTIs as it is displaced from the vagina into the urethra
   - tests negative for nitrites in urine dipstick

Question 4

Symptoms of cystitis and pyelonephritis

Cystitis x7
Pyelonephritis x5

Answer 4

1. ) Cystitis
   - dysuria, nocturia, haematuria, cloudy urine, urgency
   - suprapubic tenderness, mild pyrexia
2. ) Pyelonephritis - may have symptoms of cystitis
   - high fever +/- rigors, nausea and vomiting
   - loin/flank pain and tenderness

Question 5

4 features of an uncomplicated UTI

Definition
Epidemiology
Investigations
Treatment

Answer 5

1.) Definition - infection by a usual organism in a patient with a normal urinary tract and normal urinary function

2. ) Epidemiology - can occur in any gender or age
   - however in practice, most cases in children, men and pregnant women are managed as a complicated UTI
   - pyelonephritis is often treated as complicated aswell
3. ) Investigations - no urine culture required
   - urine dipstick: test for nitrites, RBCs and leukocyte esterase (WBCs)
4. ) Treatment - fluids, analgesics, NSAIDs
   - 3 day course of nitrofurantoin (1st line) trimethoprim, or pivemcillinam
   - trimethoprim not suitable for patients with history of resistance or received it in the last 3 months

Question 6

5 features of a complicated UTI

Definition
Predisposing Factors
Investigations
Treatment 
Prevention

Answer 6

1.) Definition - one or more factors that predispose to persistent, recurrent infections or treatment failure

2. ) Predisposing Factors
   - abnormal urinary tract or impaired renal function,
   - virulent organism (e.g. S aureus),
   - impaired host defence (diabetes, immunosuppressed)
3. ) Investigations - urine culture is used
   - mid-stream urine (MSU) sample collected because you get false negatives if recently voided or dilute urine
   - urine dipstick is not useful in >65s or catherised patients
4. ) Treatment - fluids, analgesics, NSAIDs
   - 7 day course of nitrofurantoin (1st line), trimethoprim, or pivemcillinam
   - pyelonephrits/sepeticaemia: 10 day course of oral/IV co-amoxiclav or ciprofloxacin (if allergic to penicillin) or gentamycin (nephrotoxic)
5. ) Prevention - prophylaxis given if 3 or more episodes in one year or if pregnant
   - often trimethoprim or nitrofurantoin as a nightly dose
   - trimethoprim not given in first trimester because it inhibits folic acid synthesis –> neural tube defects

Question 7

5 features of renal stones

Composition x4
Location x5
Symptoms
Passing Stones
Imaging

Answer 7

1. ) Composition - calcium oxalate (CaOx) and calcium phosphate (CaP) account for 80% of renal stones
   - struvite (NH4MgPO4.6H2O) from infection by bacteria that posses the urease enzyme accounts for 10%
   - uric acid (UA) stones account for 9%
   - rest are: cystine and drug stones, ammonium acid urate
2. ) Location - pelvic stone, calyx stone, staghorn stone, mid-uretheral stone, bladder stones
   - pelvic stone blocks the renal pelvis
   - staghorn stones are branched stones, filling the renal pelvis and branching into the calyces

3.) Symptoms - dysuria, haematuria, loin/groin pain,

4. ) Passing Stones - depends on diameter
   - < 5mm = high chance, 5-7mm = 50% chance
   - >7mm = require surgical intervention

5.) Imaging - CT, X-Ray, USS, flouroscopy, ureteroscopy

Question 8

5 groups of causes of kidney stones

Metabolic
UTI
Diet
Medication
Genetic

Answer 8

1.) Metabolic - secondary hypercalcuria

2. ) Complicated UTIs - abnormal organisms
   - Proteus mirabilis, Pseudomonas, Klebsiella
3. ) Diet - obesity, high salt diet
4. ) Medication - furosemide
5. ) Genetic - primary hyperoxaluria, cystinuria

Question 9

3 surgical treatment options for renal stones

ESWL
PCNL
Open Surgery

Answer 9

1. ) Extracorporeal Shock-Wave Lithotripsy (ESWL)
   - non-invasive treatment to fragment calculi <2cm
   - uses shockwaves from a lithotripter
   - fragments pass out over several weeks
2. ) Pecutaneous Nephrolithotomy - PCNL
   - minimally invasive treament for calculi < 2cm
   - incision made in the skin and needle passed into the renal pelvis
3. ) Nephrectomy - open surgery to remove a kidney
   - done for very large stones