Diseases » Pyelonephritis

Pyelonephritis

Pyelonephritis: Excerpt from The 5-Minute Pediatric Consult

Shamir Tuchman, MD

Kevin E. C. Meyers, MB, BCh

Pyelonephritis - BASICS

Pyelonephritis - description

Acute pyelonephritis (upper urinary tract infection) is defined clinically by fever and flank pain, and histologically by acute renal parenchymal (interstitial) inflammation secondary to bacterial invasion.

Pyelonephritis - epidemiology

• UTIs are more likely to involve the upper renal tracts in children <3 years of age.
• UTIs are more common in females, except in uncircumcised males <3 months of age.

Pyelonephritis - incidence

Cumulative incidence of UTIs (1st 6 years of life):

• 6.6% for girls, 1.8% for boys

Pyelonephritis - prevalence

• 5–7% of febrile infants <8 weeks of age
• 1% of all school-aged children
• 1–3% of girls between ages 1 and 5 years
• 0.03% in school-aged boys

Pyelonephritis - risk factors

• Previous history of UTI
• Sibling with a history of a UTI
• Female sex
• Indwelling urinary catheter
• Structural abnormalities of the kidneys and lower urinary tract
• Vesicoureteral reflux: Present in 20–40% of children with UTIs

Pyelonephritis - pathophysiology

Specific factors related to development of pyelonephritis:

• Host related:
  • Anatomic abnormalities (e.g., obstruction, fistula)
  • Functional abnormalities (e.g., dysfunctional voiding, vesicoureteral reflux)
• Pathogen related:
  • Adherence factors (P and type 1-fimbriae, adhesions)
  • Virulence factors (e.g., lipopolysaccharide, capsular antigen)
• Adhesion of bacteria to uroepithelium induces cytokine release and a subsequent inflammatory response.
• Patchy infiltration of the medullary parenchyma by polymorphonuclear leukocytes and lymphocytes leading to degradation of extracellular matrix, tubular disruption, and interstitial edema
• Parenchymal scarring may result as a consequence of the infection.

Pyelonephritis - etiology

• Enterobacteriaceae: Escherichia coli, most frequent cause (90% of initial infections and in up to 66% of recurrent infections); Proteus, Klebsiella, Enterobacter spp. are also implicated.
• Gram-positive organisms cause 10–15% of cases: Staphylococcus aureus, S. epidermidis, S saprophyticus, Enterococci spp.
• Other organisms: Pseudomonas, Haemophilus influenzae, Streptococcus group B

Pyelonephritis - associated conditions

• Struvite kidney stones: Associated with urease-producing bacteria (e.g. Proteus sp.)
• Anatomic or physiologic abnormality of the collecting system: Found in up to 50% of infants with pyelonephritis

Pyelonephritis - DIAGNOSIS

Pyelonephritis - signs & symptoms

• Fever
• Chills
• Flank pain
• Urination problems: Dysuria, frequency, urgency

Pyelonephritis - history

• A fever of 38.5°C may be the only presenting complaint.
• In the neonate, inquire of caregivers about vomiting, lethargy, poor feeding, irritability, fever, hypothermia, and jaundice.
• Older children are more likely to present with flank pain, dysuria, frequency, urgency, and incontinence.
• Important factors that predispose to the development of UTI that should be specifically inquired about:
  • Constipation
  • Bubble baths
  • Incorrect toilet training
  • Perineal skin irritation
  • Antibiotic exposure
  • Uncircumcised males
  • Previous UTIs
  • Investigations already performed
  • A family history of UTIs or reflux nephropathy
  • A history of structural abnormalities of the kidneys and/or lower urinary tract
  • Symptoms suggestive of dysfunctional voiding, such as that the bladder always feels full, infrequent use of the toilet, and urgency incontinence
  • Previous surgery or trauma to the lower back
  • Lower-motor milestones

Pyelonephritis - physical exam

• Findings may be nonspecific.
• Fever, irritability, rigors, lethargy
• Flank tenderness:
  • May be related to an underlying renal tract abnormality, such as flank mass due to obstruction with hydronephrosis or cystic kidney disease, spina bifida apparent or occult, as evidenced by a dimple, pilonidal sinus, or hemangioma
• Gentle posterior punch test will reveal tenderness at the costovertebral angle.
• Bimanual palpation of kidneys to assess tenderness and size
• Careful neuromuscular exam of lower limbs and back to evaluate for the presence of a neurogenic bladder
• Assess rectal tone.

Pyelonephritis - tests

• Imaging evaluation of the urinary tract after a urinary tract infection should be individualized based on the child’s clinical presentation and clinical judgment.
• All children ≤5 years of age should have an ultrasound and voiding cystourethrogram; in children >5 years of age, an ultrasound is recommended.
• After the urine is sterile, a voiding cystourethrogram can be performed; there is no need to wait 4 weeks.
• Administer antibiotic prophylaxis before the voiding cystourethrogram.

• False-positive test results:
  • May be due to nonsterile collection techniques (bagged urine specimen), allowing urine to stand unrefrigerated, or to precollection antibiotic exposure
• False-negative test results:
  • The rapid test for nitrites requires urine to stay in the bladder for several hours and is therefore not useful in infants who do not store urine in the bladder.

Pyelonephritis - lab

• Collect urine using sterile methods (e.g., midstream in toilet trained children, catheter or, suprapubic for infants).
• Urine dip for measurement of leukocyte esterase and nitrites as a rapid screen for infection.
• WBC casts on urine microscopy are usually diagnostic.
• As a screening test, an unspun clean-catch urine specimen with bacteria on stained microscopic examination correlates (80–90%) with culture results exceeding 100,000 colonies/mL in urine.
• Urine for culture and sensitivity: A positive culture result is defined by the growth of a single pathogenic organism of clean-catch 100,000 colonies/mL, catheter 1,000 colonies/mL, and by any growth in a suprapubic specimen.
• CBC with an elevated WBC count
• ESR and C-reactive protein (CRP) levels are often increased.

Pyelonephritis - imaging

• Renal ultrasound to rule out obstruction and assess renal size and parenchyma
• Voiding cystourethrogram (VCUG) to rule out anatomic anomalies including obstruction (e.g., posterior urethral valves) and vesicoureteric reflux
• ^99mTc-dimercaptosuccinic acid (DMSA) test can be done to confirm the presence of acute pyelonephritis and to look for renal scarring. This is a sensitive and specific test that some clinicians believe to be the imaging study of choice for diagnosing acute pyelonephritis and renal scarring.

Pyelonephritis - differencial diagnosis

• Cystitis
• Sterile pyuria:
  • Vulvovaginitis
  • Balanitis
  • Systemic viral illness
  • Postvaccination
  • Pregnancy
  • Appendicitis
  • Cystic renal disease
  • Tuberculosis
• Lower-lobe pneumonia
• Acute appendicitis

Pyelonephritis - TREATMENT

Pyelonephritis - medication

• Give IV antibiotics until afebrile for at least 24 hours, then change to an oral formulation.
• In total, 10–14 days of antibiotic therapy are required.
• Patients with 1st-time urinary infections should receive low-dose antibiotic prophylaxis until their workup is completed.
• Children with frequent symptomatic recurrences of urinary tract infection and those with vesicoureteric reflux require long-term antibiotic prophylaxis.
• Antibiotics such as co-trimoxazole, amoxicillin/clavulanate (Augmentin), and the 2nd-generation cephalosporins
• Familiarity with local antibiotic patterns of resistance is particularly important in treating hospital-acquired infections.
• Antipyretics (e.g., acetaminophen)

• Removing struvite calculi during active infection may precipitate bacteremia/urosepsis.
• High index of suspicion required for pyelonephritis associated with cystic renal disease as urine cultures may be negative when the infection is intracystic.

Pyelonephritis - iv fluids

• May be necessary when children are hospitalized with fever and vomiting to maintain hydration and urine output.
• Underlying anatomic or functional urinary collecting system abnormality should be evaluated/treated by a urologist.

Pyelonephritis - FOLLOW UP

Pyelonephritis - prognosis

• Fever usually resolves in 3–5 days.
• Ongoing fever or persistent flank pain requires further evaluation to exclude a drug-resistant organism, kidney stone, or another unrecognized urinary tract obstruction.
• Diagnosis and treatment of any underlying voiding dysfunction and constipation are required for successful management of urinary tract infections in children.
• Outcome of acute pyelonephritis is usually good but may result in parenchymal scarring.
• Pyelonephritis associated with struvite renal stones requires removal of the infectious stones after antibiotic treatment is completed.
• Risk factors for renal damage include obstruction, reflux with dilation, young age, delay in treatment, number of episodes of pyelonephritis, and bacterial virulence factors.

Pyelonephritis - complications

• Acute:
  • Reduced concentrating ability, hyperkalemic renal tubular acidosis
  • Bacteremia: Highest risk in young infants (23% of children younger than 2 months)
  • Perinephric abscess formation
• Chronic:
  • Focal renal scarring, hypertension, proteinuria, azotemia, xanthogranulomatous pyelonephritis

Pyelonephritis - patient monitoring

Requirements for testing: Educate caregivers in the use and interpretation of the dipstick, and about the symptoms and signs of UTI.

Pyelonephritis - bibliography

1. Agarwal S. Vesicoureteral reflux and urinary tract infections. Curr Opin Urol. 2000;10:587–592.
2. Bartkowski DP. Recognizing UTIs in infants and children. Early treatment prevents permanent damage. Postgrad Med. 2001;109:171–172, 177–181.
3. Bloomfield P, Hodson EM, Craig JC. Antibiotics for acute pyelonephritis in children. Cochrane Database System Rev. 2003;(3):CD003772.
4. Greenbaum LA, Mesrobian HO. Vesicoureteral reflux. Pediatr Clin North Am. 2006;53:413–427.
Jodal U, Hansson S. Urinary tract infection. In Holliday M, Barratt TM, Avner ED, eds. Pediatric Nephrology. 3rd ed. Baltimore: Williams & Wilkins; 1994:950.
5. Martinell J, Hansson S, Claesson I, et al. Detection of urographic scars in girls with pyelonephritis followed for 13–38 years. Pediatr Nephrol. 2000;14:1006–1010.
6. Raszka WV, Khan O. Pyelonephritis. Ped Rev. 2005;26:364–369.
7. Roberts JA. Infections in urology. Urol Clin North Am. 1999;26:753–763.
8. Rushton HG. Urinary tract infections in children. Epidemiology, evaluation and management. Pediatr Clin North Am. 1997;44:1133–1169.
9. Weir M, Brien J. Adolescent urinary tract infections. Adolesc Med State Art Rev. 2000;11:293–313.

Pyelonephritis - CODES

Pyelonephritis - icd9

590.10 Acute pyelonephritis

Pyelonephritis - FAQ

• Q: Should a DMSA scan be used to help diagnose acute pyelonephritis?
• A: Routine use of the DMSA scan to diagnose acute pyelonephritis is controversial because disagreement exists about the therapeutic implications of a positive test result and such routine testing is expensive. Children with hypertension and previous UTIs require a DMSA scan to look for renal cortical scarring.
• Q: Does renal parenchymal scarring occur without reflux?
• A: Yes. The causal relationships among reflux, acute pyelonephritis, and renal parenchymal scarring are complex.

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Book Source Details

• Book Title: The 5-Minute Pediatric Consult
• Author(s): M. William Schwartz MD; et al.
• Year of Publication: 2008
• Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.

More About Pyelonephritis

• Back to disease: Pyelonephritis: Introduction
• Next Book Extract About Pyelonephritis: Surveys relating to Pyelonephritis
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

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More About This Book: Title: The 5-Minute Pediatric Consult Authors: M. William Schwartz MD; et al. Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7577-9

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