Urinary Tract Infection

Question 1

Pathophysiology and Definition of UTI

Answer 1

P: Occurs when bacteria gains access, overwhelms defences and ascends

D: An inflammation of the urinary epithelium usually caused by bacteria from gut flora. Can occur anywhere along the urinary tract; Urethra (Urethritis), Prostate (Prostatitis), Bladder (Cystitis), Ureter, Kidney (Pyelonephritis)

Question 2

Mechanisms of UTI

Answer 2

• Occur when bacteria access and ascends the urinary tract, typically overcoming the body’s natural defences

1. Entry of Bacteria: Enters through the UT through the Urethra, includes Gut Flora (e.g. Ecoli) or external contamination
2. Defence Mechanisms & Failure of Defence

Question 3

Defence Mechanism (+ Failure of Defence)

Answer 3

1. Urination: Flushing out bacteria from the urethra with Urine Flow
2. Low Urine pH: The acidic environment of urine inhibits bacterial growth
3. High Urea Concentration: Urea acts as natural defence by being toxic to bacteria
4. Tamm-Horsfall Protein: Secreted in the loop of Henle (The protein is bactericidal)
5. Vesico-Ureteric Junction Closure: Prevents backflow into the Kidneys
6. Male-specific Defence: Prostatic secretions are antimicrobial, and the longer urethra in males adds a physical barrier to bacterial ascent

Failure: When bacteria overcomes these defences, they ascend through the urinary tract, leading to infection

Question 4

Bacterial Factors

Answer 4

1. Capsular Antigens
   - Bacteria like E.Coli passes the capsular antigens that inhibit phagocytosis (Engulfment by immune cells), making it easier for bacteria to survive and multiply in UT
2. Hemolysin
   - This toxin, produced by certain bacteria, damages epithelial cells lining the UT, promoting infection
3. Fimbriae (Pili) on E.Coli
   - E.Coli has frimbrae (hair-like projections) that allow the bacteria to bind tightly to receptors
   - This attachment allows them to resist being flushed out by urination
4. Urease-Producing Bacteria
   - Proteus and Klebseilla species produce the enzyme Urease, which breaks down urea into ammonia (This raises the pH of the urine, creatinf an environment more favourable for bacteria growth and stone formation)

Question 5

Host Groups for UTI

Answer 5

1. Renal Stones
2. Diabetes
3. Immunosuppression
4. Pregnancy
5. Postmenopausal Women
6. Nuetrogenic Bladder
7. Cathetherization
8. Short Urethra in Women

Question 6

Types of UTI

Answer 6

1. Acute Cystitis (Bladder Infection)
2. Acute Pyelonephritis (Kidney Infection)
3. Chronic Pyelonephritis (Reflux Nephropathy)

Question 7

(Types) Acute Cystitis (Bladder Infection)

Answer 7

• Inflammation of Bladder

1. Casual Organisms
   - Escherichia Coli (E.Coli)
   - Staphylococcus Saprophyticus
   - Klebsiella, Proteus, Pseudomonas, Fungi, Viruses, and Parasites
2. Pathology Varients
   - Mild Inflammation: Characterised by hyperaemia (Increased blood flow) in the mucosa
   - Haemorrhage Cystitis: In advanced cases, different haemorrhage in the bladder mucosa occurs
   - Suppurative Cystitis: Presence of pus due to infection
   - Ulcerative Cystitis: Prolonged infection leads to sloughing of bladder mucosa and ulcer formation
   - Gangrenous Cystitis: Severe infections may cause necrosis of the bladder wall
3. Clinical Features
   - Increased urgency of Urination
   - Increased frequency of Urination
   - Dysuria (painful Urination)
   - Suprapubic Pain
   - Cloudy/Malodorous Urine
   - Occasional Hematuria (Blood in Urine)

Question 8

(Types) Acute Pyelonephritis (Kidney Infection)

Answer 8

• Infection of one or both upper UTs, including the Ureter, Renal Pelvis, and Renal Interstitium

1. Causes
   - Often results from UT procedures (e.g. Catheterisation, Surgery,)
   - Can occur from blood-borne spread
2. Casual Organisms
   - E.Coli, Proteins, Pseudomonas
3. Pathology
   - Progressive infection leads to inflammation, fibrosis (scarring), and formation of small abscess within the renal cortex
   - Visible streaks of pus can appear in the medulla
4. Clinical Features
   - Sudden onset Fever
   - Loin Pain
   - Tenderness over the Kidney
   - Increased Urinary Frequency
   - Dysuria

Question 9

(Types) Chronic Pyelonephritis (Reflux Nephropathy)

Answer 9

• Persistent or recurrent kidney infection that often leads to kidney scarring over time

1. Risk Factors
   - Renal Stones
   - Vesicoureteral Reflux (Backward flow of urine from the bladder to the kidney)
2. Pathology
   - Chronic infection leads to continuous damage and fibrosis in Kidney tissue, potentially resulting in chronic kidney disease
3. Clinical Features
   - Early stages may be asymptomatic
   - Tiredness
   - Hypertension
   - Proteinuria
   - Progressive Renal Impairment

Question 10

Treatment and Management

Answer 10

1. Antibiotics
   - First-line: Trimethoprim, Nitrofurantoin
   - Others: Ciprofloxacin, Norfloxacin, Co-amoxiclav
   - Duration: 3-7 days (Uncomplicated), 7-14 days (Complicated)
2. Symptom Management
   - Encourage fluid intake (2L/day)
   - Use of Urinary alkalinising agents (e.g. Potassium Citrate)

Question 11

Diagnostic Test

Answer 11

1. Urine Dipstick Test
2. Urine Microscopy and Culture
3. Imaging for Obstruction: X-ray, Ultrasound, CT Scan