Acute pyelonephritis

Pyelonephritis is an infection of the renal parenchyma, more common in women than in men.

The pathogens causing pyelonephritis are the same as those causing cystitis (see Acute cystitis, Chapter 9).

Pyelonephritis is potentially severe, especially in pregnant women, neonates and infants.

Management depends on the presence of signs of severity or complications or risk of complications.

Clinical features

Neonates and infant

• Symptoms are not specific: fever, irritability, vomiting, poor oral intake. Palpation of the lower abdomen may show abdominal tenderness. The absence of fever does not rule out the diagnosis. On the other hand, fever –with no obvious cause– may be the only manifestation.
• Neonates may present with fever or hypothermia, altered general condition, altered conscious state, pale/grey colour, shock.

In practice, a urinary tract infection should be suspected in children with unexplained fever or septic syndrome with no obvious focus of infection.

Older children and adults

• Signs of cystitis (burning pain on urination and urinary urgency and frequency, etc.)

AND

• Fever > 38 °C and unilateral flank pain or abdominal tenderness
• Nausea and/or vomiting are common.

Laboratory

See Acute cystitis, Chapter 9.

Treatment

• Criteria for hospital admission:
  • Patients at risk of complications: children, pregnant women, men a Citation a. Pyelonephritis is rare in men; bacterial prostatitis should be suspected in the event of febrile urinary tract infection. , functional or structural abnormality of the urinary tract (lithiasis, malformation, etc.), severe immunodeficiency; 
  • Patients with complicated pyelonephritis: urinary tract obstruction, renal abscess, emphysematous pyelonephritis in diabetic patients;
  • Patients with signs of severe infection: sepsis (infection with signs of organ dysfunction) and septic shock, dehydration or nausea/vomiting preventing hydration and oral treatment;
  • No clinical improvement 24 hours after the start of oral antibiotherapy in women treated as outpatients. 

• Antibiotherapy in children

• Children under one month 
  ampicillin slow IV (3 minutes) for 7 to 10 days
  Children 0 to 7 days (< 2 kg): 50 mg/kg every 12 hours
  Children 0 to 7 days (≥ 2 kg): 50 mg/kg every 8 hours
  Children 8 days to < 1 month: 50 mg/kg every 8 hours
  + gentamicin slow IV (3 minutes) for 5 days
  Children 0 to 7 days (< 2 kg): 3 mg/kg once daily
  Children 0 to 7 days (≥ 2 kg): 5 mg/kg once daily
  Children 8 days to < 1 month: 5 mg/kg once daily
  or
  cefotaxime slow IV (3 minutes) for 7 to 10 days
  Children 0 to 7 days (< 2 kg): 50 mg/kg every 12 hours
  Children 0 to 7 days (≥ 2 kg): 50 mg/kg every 8 hours
  Children 8 days to < 1 month: 50 mg/kg every 8 hours

• Children one month and over
  ceftriaxone IM or slow IV b Citation b. The solvent of ceftriaxone for IM injection contains lidocaine. Ceftriaxone reconstituted using this solvent must never be administered by IV route. For IV administration, water for injection must always be used.  (3 minutes): 50 mg/kg once daily until the child's condition improves (at least 3 days)
  then change to oral route to complete 10 days of treatment with:
  amoxicillin/clavulanic acid PO (dose expressed in amoxicillin)
  Children < 40 kg: 25 mg/kg 2 times daily 
  Children ≥ 40 kg:
  Ratio 8:1: 2000 mg daily (2 tablets of 500/62.5 mg 2 times daily)
  Ratio 7:1: 1750 mg daily (1 tablet of 875/125 mg 2 times daily) 

• Antibiotherapy in adults [1] Citation 1. Gupta K, Hooton TM, Naber KG, Wullt B, Colgan R, Miller LG, Moran GJ, Nicolle LE, Raz R, Schaeffer AJ, Soper DE, Infectious Diseases Society of America, European Society for Microbiology and Infectious Diseases. International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: A 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis. 2011;52(5):e103. 
  https://academic.oup.com/cid/article/52/5/e103/388285 [Accessed 17 December 2018]

• Uncomplicated pyelonephritis 
  ceftriaxone IM: 1 g single dose or gentamicin IM: 5 mg/kg single dose
  +
  ciprofloxacin PO: 500 mg 2 times daily for 7 days
  or
  amoxicillin/clavulanic acid PO (dose expressed in amoxicillin) for 10 to 14 days
  Ratio 8:1: 2000 mg daily (2 tablets of 500/62.5 mg 2 times daily)
  Ratio 7:1: 1750 mg daily (1 tablet of 875/125 mg 2 times daily) 
  or
  cefixime PO: 200 mg 2 times daily or 400 mg once daily for 10 to 14 days

• Pyelonephritis with criteria for hospital admission
  ampicillin slow IV (3 minutes): 2 g every 6 hours for at least 3 days + gentamicin IM: 5 mg/kg once daily for 3 days
  then change to amoxicillin/clavulanic acid PO (or another antibiotic depending on the antibiotic susceptibility test) to complete 10 to 14 days of treatment
  or
  ceftriaxone IV b Citation b. The solvent of ceftriaxone for IM injection contains lidocaine. Ceftriaxone reconstituted using this solvent must never be administered by IV route. For IV administration, water for injection must always be used.  : 1 g once daily for at least 3 days + gentamicin IM: 5 mg/kg once daily for 3 days in the event of sepsis then change to amoxicillin/clavulanic acid PO (or another antibiotic depending on the antibiotic susceptibility test) to complete 10 to 14 days of treatment

Preferably use the combination ampicillin + gentamicin to cover enterococci. 
Pyelonephritis with abscess formation or emphysematous pyelonephritis may require longer antibiotherapy.

• Treatment of fever and pain: do not administer NSAID (Fever, Chapter 1).
• Maintain proper hydration (1.5 litres daily in adults), especially in children (risk of dehydration); treat dehydration if present (see Dehydration, Chapter 1).
• Management of septic shock if needed.