Acute Pyelonephritis- Management

Acute pyelonephritis is a bacterial infection involving the renal pelvis, calyces, and renal parenchyma. It represents an upper urinary tract infection (UTI) and is generally more severe than cystitis because of the risk of renal damage, bacteraemia, sepsis, and acute kidney injury. Acute pyelonephritis commonly occurs as a result of ascending infection from the lower urinary tract, although haematogenous spread may occasionally occur.

The condition requires prompt diagnosis and treatment to prevent complications. Unlike lower UTIs, acute pyelonephritis often presents with systemic symptoms and may require hospitalization and intravenous antimicrobial therapy.

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

Epidemiology

Acute pyelonephritis affects individuals of all age groups but is most common among women, pregnant women, young children, elderly individuals, and patients with urinary tract abnormalities. The incidence is higher in patients with diabetes mellitus, urinary obstruction, nephrolithiasis, vesicoureteric reflux, and urinary catheterization.

Pyelonephritis remains a major cause of hospitalization among patients with complicated urinary tract infections.

Risk factors

• Female sex

• Previous urinary tract infection

• Pregnancy

• Vesicoureteric reflux

• Urinary tract obstruction

• Urinary stones

• Benign prostatic hyperplasia

• Neurogenic bladder

• Diabetes mellitus

• Chronic kidney disease

• Urinary catheterization

• Congenital urinary tract abnormalities

• Immunosuppression

• Incomplete bladder emptying

• Recent urinary tract instrumentation

Pathophysiology

Most cases result from ascending infection originating in the bladder. Uropathogenic bacteria ascend through the ureters to the renal pelvis and renal parenchyma. Bacterial multiplication within the kidney triggers an inflammatory response characterized by neutrophil infiltration, oedema, and tissue injury.

If untreated, infection may spread into the bloodstream, causing bacteraemia, sepsis, septic shock, and permanent renal scarring. Recurrent episodes can lead to chronic pyelonephritis and progressive renal impairment.

Clinical presentation

Acute pyelonephritis typically presents with systemic symptoms in addition to urinary tract symptoms.

Important clinical note

Differentiation between upper and lower urinary tract infection in young children may not be possible on clinical grounds alone. Therefore, children with fever and suspected UTI should be carefully evaluated for possible upper urinary tract involvement.

Symptoms

• Fever

• Chills and rigors

• Flank pain

• Loin pain

• Dysuria

• Urinary frequency

• Urinary urgency

• Nausea

• Vomiting

• General malaise

• Weakness

• Loss of appetite

• Haematuria

Clinical signs

• Temperature of 38°C or higher

• Costovertebral angle tenderness

• Flank tenderness

• Tachycardia

• Dehydration

• Suprapubic tenderness

• Hypotension in severe cases

• Altered mental status in elderly patients

• Signs of sepsis in complicated disease

Diagnostic criteria

The diagnosis of acute pyelonephritis is based on:

• Fever of 38°C or higher

• Flank pain or costovertebral angle tenderness

• Evidence of urinary tract infection on urinalysis

• Pyuria on urine microscopy

• Positive urine culture where available

Diagnosis is strongly supported by:

• Positive leukocyte esterase

• Positive nitrite test

• Significant bacteriuria

• Elevated inflammatory markers

• Positive urine culture

Investigations

Urinalysis

• Leukocyte esterase

• Nitrite test

• Protein

• Blood

• Urinary pH

Urine microscopy

• White blood cells

• Red blood cells

• Bacteria

• White blood cell casts where present

Urine culture and antimicrobial susceptibility testing

Urine culture should be performed whenever possible before initiating antimicrobial therapy.

Blood investigations

• Full blood count

• Serum creatinine

• Blood urea nitrogen

• Serum electrolytes

• C-reactive protein

• Blood cultures in severe infection or suspected sepsis

Imaging studies

Imaging is indicated in patients with:

• Recurrent pyelonephritis

• Suspected urinary tract obstruction

• Nephrolithiasis

• Treatment failure

• Suspected renal abscess

• Severe or complicated infection

Investigations may include:

• Ultrasound of kidneys and pelvis

• CT urography where available

• MRI in selected cases

Management

Acute pyelonephritis is a potentially serious infection requiring prompt antimicrobial therapy and close monitoring.

Non-pharmacological treatment

• Ensure adequate hydration

• Encourage bed rest during acute illness

• Monitor fluid balance

• Monitor urine output

• Correct dehydration

• Identify and treat underlying urinary tract abnormalities

• Remove unnecessary urinary catheters

• Monitor vital signs regularly

Pharmacological treatment

Analgesia and fever control

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.

Outpatient treatment

Outpatient management should only be considered for women of reproductive age who have uncomplicated disease and do not have danger signs requiring admission.

Adults

• Ciprofloxacin 500 mg orally every 12 hours for 10 days.

Inpatient treatment

Patients requiring hospitalization should receive parenteral antimicrobial therapy.

Adults

• Ceftriaxone 1 g intravenously every 24 hours for 5 days.

Children

• Ceftriaxone 80 mg/kg intravenously or intramuscularly every 24 hours for 5 days.

Patients should be reassessed regularly, and antimicrobial therapy adjusted according to culture and sensitivity results where available.

Management according to underlying cause

Urinary tract obstruction

• Immediate drainage if obstruction is significant.

• Treat underlying cause.

• Refer for urological management.

Urinary stones

• Treat infection urgently.

• Manage stones after stabilization.

Vesicoureteric reflux

• Treat acute infection.

• Long-term urological follow-up.

Diabetes mellitus

• Optimize glycaemic control.

• Monitor for complications.

Urinary catheter-associated infection

• Remove or replace catheter where appropriate.

• Treat according to urine culture results.

Referral

Urgent referral or admission is indicated for:

• Children with suspected pyelonephritis

• Pregnant women

• Elderly patients with systemic illness

• Persistent vomiting

• Severe dehydration

• Hypotension

• Suspected sepsis

• Acute kidney injury

• Urinary tract obstruction

• Renal abscess

• Failure of outpatient treatment

• Immunocompromised patients

• Recurrent pyelonephritis

Complications

• Renal abscess

• Perinephric abscess

• Acute kidney injury

• Renal papillary necrosis

• Bacteraemia

• Urosepsis

• Septic shock

• Renal scarring

• Chronic pyelonephritis

• Chronic kidney disease

• Death in severe untreated cases

Prognosis

The prognosis is generally excellent when treatment is initiated early. Most patients recover completely without long-term sequelae. Delayed diagnosis, antimicrobial resistance, urinary tract obstruction, diabetes mellitus, or recurrent infection increase the risk of renal damage and systemic complications.

Prevention

• Prompt diagnosis and treatment of lower urinary tract infections

• Adequate hydration

• Good personal hygiene

• Appropriate catheter care

• Early removal of unnecessary urinary catheters

• Management of urinary tract obstruction

• Treatment of urinary stones

• Control of diabetes mellitus

• Investigation and management of recurrent UTIs

• Regular follow-up of patients with urinary tract abnormalities