Acute cystitis (lower urinary tract infection)

Acute cystitis is an infection of the lower urinary tract involving the urinary bladder and, in some cases, the urethra. It is the most common form of urinary tract infection (UTI) and occurs predominantly in women due to their shorter urethra and proximity of the urethral opening to the perineum. Acute cystitis may be classified as uncomplicated or complicated. Uncomplicated cystitis occurs in healthy, non-pregnant women of reproductive age with no structural or functional abnormalities of the urinary tract. Complicated cystitis occurs in all other patient groups, including men, pregnant women, children, elderly individuals, and patients with urinary tract abnormalities or immunocompromising conditions.

The most common causative organisms are Escherichia coli, followed by Klebsiella pneumoniae, Proteus species, and Staphylococcus aureus.

Epidemiology

Acute cystitis is one of the most common bacterial infections worldwide. Women are significantly more affected than men, with more than half of women experiencing at least one UTI during their lifetime. Recurrence is common, particularly among sexually active women and individuals with underlying urinary tract abnormalities.

Risk factors

General risk factors

• Female sex

• Sexual activity

• Previous urinary tract infection

• Pregnancy

• Diabetes mellitus

• Urinary tract obstruction

• Urinary stones

• Vesicoureteric reflux

• Neurogenic bladder

• Urinary catheterization

• Immunosuppression

• Poor perineal hygiene

• Incomplete bladder emptying

• Menopause

Pathophysiology

Acute cystitis usually results from ascending bacterial infection. Organisms colonize the periurethral area and ascend through the urethra into the bladder. Bacterial adherence to the urothelium triggers inflammation, leading to mucosal oedema, hyperaemia, and irritation of the bladder wall.

Inflammation of the bladder mucosa produces the characteristic symptoms of dysuria, frequency, urgency, and suprapubic discomfort. If left untreated, infection may ascend to involve the upper urinary tract, resulting in pyelonephritis.

Clinical presentation

Acute cystitis typically presents with localized lower urinary tract symptoms without significant systemic illness.

Symptoms

• Dysuria

• Urinary frequency

• Urinary urgency

• Suprapubic pain

• Suprapubic discomfort

• Burning sensation during micturition

• Nocturia

• Haematuria

• Cloudy urine

• Foul-smelling urine

Clinical signs

• Suprapubic tenderness

• Mild lower abdominal tenderness

• Pyuria

• Occasionally haematuria

• Temperature of 38°C or higher in some patients

Systemic features such as flank pain, severe fever, rigors, or vomiting should raise suspicion for upper urinary tract infection.

Diagnostic criteria

The diagnosis of acute cystitis is based on:

• Presence of urinary symptoms such as dysuria, frequency, and urgency

• Evidence of pyuria on urinalysis or urine microscopy

• Positive urine culture when available

Diagnosis is strongly supported by:

• Positive leukocyte esterase

• Positive nitrite test

• More than 8–10 white blood cells per high-power field on urine microscopy

• Significant bacterial growth on urine culture

Investigations

Urinalysis

• Leukocyte esterase

• Nitrite test

• Protein

• Glucose

• Urinary pH

Urine microscopy

• White blood cells

• Red blood cells

• Bacteria

Urine culture and antimicrobial susceptibility testing

Urine culture is recommended in:

• Recurrent infections

• Complicated infections

• Treatment failure

• Pregnancy

• Suspected antimicrobial resistance

Additional investigations

Where indicated:

• Full blood count

• Serum creatinine

• Blood glucose

• Renal ultrasound in recurrent or complicated infections

Management

The objectives of treatment are symptom relief, eradication of infection, prevention of recurrence, and prevention of complications such as pyelonephritis.

Non-pharmacological treatment

• Encourage adequate oral fluid intake

• Encourage regular bladder emptying

• Advise urination whenever the urge to void occurs

• Encourage urination after sexual intercourse

• Maintain good perineal hygiene

• Avoid unnecessary urinary catheterization

• Remove indwelling urinary catheters where appropriate

Pharmacological treatment

Analgesia for severe dysuria

Adults

• Paracetamol 500–1000 mg orally every 6–8 hours when required.

Children

• Paracetamol 15 mg/kg/dose orally every 4–6 hours when required, up to a maximum of 4 doses in 24 hours.

Uncomplicated cystitis

Adults

• Nitrofurantoin 100 mg orally every 12 hours for 5 days.

OR

• Flucloxacillin + amoxicillin (fixed-dose combination) 500 mg orally every 8 hours for 5 days.

Complicated cystitis

Adults

• Ciprofloxacin 500 mg orally every 12 hours for 7 days.

OR

• Amoxicillin + clavulanic acid (fixed-dose combination) 625 mg orally every 12 hours for 7 days.

Pregnant women and adolescents

• Nitrofurantoin 100 mg orally every 12 hours for 5 days.

OR

• Amoxicillin + clavulanic acid (fixed-dose combination) 625 mg orally every 12 hours for 7 days.

Children

• Nitrofurantoin 50 mg orally every 12 hours for 5 days.

Nitrofurantoin should not be used in children with glucose-6-phosphate dehydrogenase (G6PD) deficiency or porphyria.

OR

• Amoxicillin + clavulanic acid 40 mg/kg/day (calculated as the amoxicillin component) orally in three divided doses for 7 days, up to a maximum of 2000 mg amoxicillin daily.

Management according to underlying cause

Catheter-associated infection

• Remove or replace the catheter where appropriate.

• Treat according to urine culture and sensitivity results.

Urinary tract obstruction

• Treat infection promptly.

• Relieve obstruction and refer for definitive management.

Diabetes mellitus

• Optimize glycaemic control.

• Monitor for recurrent infection and complications.

Recurrent cystitis

• Investigate for urinary tract abnormalities.

• Consider specialist referral.

Referral

Refer the patient if:

• Symptoms persist despite appropriate treatment

• Recurrent urinary tract infections occur

• Urinary tract obstruction is suspected

• Urinary stones are suspected

• Significant haematuria is present

• Pregnancy is complicated by recurrent infection

• Renal impairment is present

• The diagnosis is uncertain

• There is suspicion of pyelonephritis or urosepsis

Complications

• Acute pyelonephritis

• Recurrent urinary tract infection

• Renal abscess

• Urosepsis

• Chronic urinary symptoms

• Renal scarring in recurrent infections

• Adverse pregnancy outcomes

Prognosis

The prognosis is excellent with prompt diagnosis and appropriate antimicrobial therapy. Most patients experience complete symptom resolution within a few days of treatment. Delayed treatment, antimicrobial resistance, or underlying urinary tract abnormalities increase the risk of recurrence and complications.

Prevention

• Adequate fluid intake

• Good personal hygiene

• Urination after sexual intercourse

• Avoid prolonged urinary retention

• Appropriate management of diabetes mellitus

• Prompt treatment of urinary symptoms

• Avoid unnecessary catheterization

• Early removal of urinary catheters

• Investigation and correction of structural urinary tract abnormalities where possible