eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease
Pyelonephritis
Updated: Aug 6, 2009
Introduction
Background
Urinary tract infections (UTIs) are relatively common infections in children. Cystitis (lower-tract infection) is characterized by voiding-related symptoms with or without fever and often without other systemic signs. Findings on nuclear renal scans suggest that the vast majority of infants and young children with febrile UTIs have acute pyelonephritis (APN), which is an upper tract infection.
Early recognition and prompt treatment of UTIs is important to prevent late sequelae, such as renal scarring, hypertension, and renal failure. When assessing the pediatric patient with UTI, one may encounter few specific symptoms. Older children are most likely to have symptoms attributable to the urinary tract. Differentiating cystitis from pyelonephritis in the pediatric patient may be difficult and sometimes impossible. Febrile UTI should be assumed to be pyelonephritis and treated accordingly.
Pathophysiology
UTIs are generally ascending in origin and caused by perineal contaminants, usually bowel flora. However, in neonates, infection is assumed to be hematogenous in origin rather than ascending. This feature may explain the nonspecific symptoms associated with UTI in these patients. After the neonatal period, bacteremia is generally not the source of infection; rather, UTI or pyelonephritis is the cause of the bacteremia.
Bacterial colonization of the bladder is most likely to develop into infection if urinary stasis or low-flow conditions are present. Some causes of these conditions include infrequent voiding, incomplete voiding, obstruction or other urinary tract abnormalities. Vesicoureteral reflux (VUR) has been reported in as many as 33% of children with acute pyelonephritis. Even in the absence of urinary tract abnormalities, cystitis may result in VUR or worsen preexisting VUR and lead to pyelonephritis. Chronic or recurrent pyelonephritis results in renal damage, scarring, and, if severe, chronic renal failure.
Host genetic factors that promote inflammation contribute to renal scarring. Interleukin (IL)-8 and CXCR1 polymorphisms, ACE insertion/deletion (ACE I/D) gene polymorphism, and tumor necrosis factor-[alpha] polymorphism have been identified as potential mediators to tissue fibrosis and subsequent renal scarring following acute pyelonephritis.
Frequency
United States
The prevalence varies by age and sex. About 60-65% of children with febrile UTIs have acute pyelonephritis as defined by presence of abnormalities of the renal cortex on dimercaptosuccinic acid (DMSA) scan. In general, 2.7-4.1% of children younger than 2 years who have fever also have UTI, even if another source is identified. UTI is present in 17% of white girls younger than 2 years with fever (temperature >39°C).
Application of low-risk criteria and approach for the febrile infant: A reasonable approach for treating febrile infants younger than 3 months who have a temperature of greater than 38°C.
Mortality/Morbidity
Acute mortality is uncommon and is related to sepsis.
Generalized bacteremia or sepsis may develop from pyelonephritis. In patients younger than 2 years with acute pyelonephritis, 8-10% have bacteremia.
Acute renal parenchymal injury occurs in 20-90% of children with acute pyelonephritis. About 40% of these children have long-term renal scarring, which may lead to hypertension and renal insufficiency. Risk factors for renal scarring include young age, treatment delay, infection by P-fimbriated Escherichia coli and VUR. Treatment of pyelonephritis within the first 5-7 days after onset is necessary to prevent renal damage.
Impaired renal tubular function and secondary pseudohypoaldosteronism may develop in infants with pyelonephritis. Infants may develop hyperkalemia and hyponatremia.
Race
The prevalence of urinary infection is 5-fold greater in white children than in black children and 2-fold greater than in children of other races.
Sex
The prevalence of UTI in uncircumcised boys is 8 times greater than that of circumcised boys in the first year of life. In addition, the incidence of UTI is higher in uncircumcised male infants than in female infants. After age 12 months, UTIs are more frequent in girls than in boys.
Age
In neonates, infection is generally hematogenous in origin. Girls younger than 11 years have a 3-5% risk of infection. For boys younger than 11 years, the risk is 1%. Febrile infants are as likely to have UTI as a source of fever as they are to be bacteremic. Both are observed in about 6-8% of patients. Children aged 1-5 years have a 3-fold increased risk of acute pyelonephritis on DMSA scanning as infants, whereas children older than 5 years have a 4.5-fold greater risk of acute pyelonephritis when evaluated for febrile UTI.
Clinical
History
- Signs and symptoms of urinary tract infection (UTI) and pyelonephritis vary with the age of the patient.
- Neonates often present with nonspecific symptoms of jaundice, hypothermia or fever, poor feeding, vomiting, and failure to thrive. Neonates, especially male newborns, may develop hyponatremia and hyperkalemia as a result of secondary pseudohypoaldosteronism.
- Infants and young children aged 2 months to 2 years often present with nonspecific symptoms of fever lasting longer than 48 hours, poor feeding, vomiting, and diarrhea. Their urine may be malodorous; hematuria may be noted.
- Preschoolers and school age children present with fever for greater than 48 hours. They may complain of abdominal pain or flank pain. Vomiting, diarrhea, and anorexia may be present. Their urine is typically malodorous, and hematuria may be noted. Voiding-related symptoms including enuresis, dysuria, urgency, and frequency, may occur but need not be present.
- Adolescents are most likely to present with classic adult symptoms of fever, often with chills, rigors, and flank pain. They may have abdominal and suprapubic pain, along with voiding-related symptoms of frequency, dysuria, and hesitancy. Their urine is most often malodorous, although hematuria is variably present.
Physical
Because many symptoms of pyelonephritis are nonspecific, complete physical examination is necessary to exclude other causes of the patient's symptoms. Specific findings are as follows:
- General appearance
- Most infants and children are uncomfortable and appear ill.
- Older children and adolescents may be mildly to moderately ill.
- Vital signs
- Fever may be present, with body temperature of more than 38°C and often more than 39°C.
- Tachycardia may be present, secondary to fever and pain.
- Blood pressure is usually normal. Hypertension should raise concern for clinically significant obstruction or renal parenchymal disease. Hypotension may occur if sepsis and shock are present.
- Abdominal findings
- Abdominal pain may be present.
- A mass may indicate obstruction, hydronephrosis, or another anatomic abnormality.
- Suprapubic pain may be present, though this is more common with cystitis than with polynephritis.
- A palpable bladder indicates obstruction or functional difficulty in starting or completing voiding.
- Adolescent girls may have right upper quadrant pain similar to that observed in patients with cholecystitis.
- Back findings
- Tenderness in the costovertebral angle (CVA), back, or flank is likely to be present in older children and adolescents.
- Sacral dimple or birthmarks overlying the spine may be associated with an underlying anomaly of the spinal cord.
- Vertebral abnormalities may be evident.
- Genitourinary findings
- Assess for irritation, pinworms, vaginitis, trauma, or signs of sexual abuse.
- A bulging hymen suggests an imperforate hymen and urethral obstruction.
- Neurologic findings: Weak lower extremities or diminished reflexes may be signs of spinal-cord dysfunction, and they may be associated with a neurogenic bladder.
Causes
- Bacterial pathogens are the most common cause of pyelonephritis.
- E coli: This is by far the most common organism, causing more than 90% of all cases of acute pyelonephritis (APN).
- Klebsiella oxytoca and species
- Proteus species
- Enterococcus faecalis and species
- Gram-positive organisms, including staphylococcal species and group B Streptococcus: These are rare causes of acute pyelonephritis.
- Bacteremia is the leading cause of infection in neonates, whereas ascending infection from bacteriuria involving the lower urinary tract predominates in other age groups.
- High-grade vesicoureteral reflux (VUR) may increase the risk for pyelonephritis.
- Congenital or acquired anomalies, including dysplasia, hypoplasia, and obstruction, increase risk for UTI, VUR, and pyelonephritis.
- Delayed or incomplete voiding, as seen with neurogenic bladder or obstruction, increases the risk for urinary stasis and overgrowth of colonizing bacteria.
- Catheterization may increase the risk of introducing periurethral bacteria into the bladder. Clean intermittent catheterization leads to colonization of the bladder that might lead to pyelonephritis if stasis allows any infection to ascend.
- Constipation may impair bladder emptying, leading to stasis and ascending infection.
- Boys who are uncircumcised have a risk of UTI that is 2.2% higher than that of uncircumcised boys. The risk of acute pyelonephritis is not established.
- Sexual activity may cause urethral inflammation, lead to bladder colonization, and increase the risk for acute pyelonephritis.
- VUR increases the risk for and size of renal cortical lesions, although clinically significant lesions can develop in the absence of VUR.
- Familial inheritance of susceptibility to pyelonephritis may be related to chemokine receptor inheritance.
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| References |
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References
[Guideline] AAP. Practice parameter: the diagnosis, treatment, and evaluation of the initial urinary tract infection in febrile infants and young children. American Academy of Pediatrics. Committee on Quality Improvement. Subcommittee on Urinary Tract Infection. Pediatrics. Apr 1999;103(4 Pt 1):843-52. [Medline].
Faust WC, Diaz M, Pohl HG. Incidence of post-pyelonephritic renal scarring: a meta-analysis of the dimercapto-succinic acid literature. J Urol. Jan 2009;181(1):290-7; discussion 297-8. [Medline].
[Best Evidence] Hodson EM, Willis NS, Craig JC. Antibiotics for acute pyelonephritis in children. Cochrane Database Syst Rev. Oct 17 2007;CD003772. [Medline].
Montini G, Rigon L, Zucchetta P, et al. Prophylaxis after first febrile urinary tract infection in children? A multicenter, randomized, controlled, noninferiority trial. Pediatrics. Nov 2008;122(5):1064-71. [Medline].
Baker PC, Nelson DS, Schunk JE. The addition of ceftriaxone to oral therapy does not improve outcome in febrile children with urinary tract infections. Arch Pediatr Adolesc Med. Feb 2001;155(2):135-9. [Medline].
Benador D, Neuhaus TJ, Papazyan JP, et al. Randomised controlled trial of three day versus 10 day intravenous antibiotics in acute pyelonephritis: effect on renal scarring. Arch Dis Child. Mar 2001;84(3):241-6. [Medline].
Benador N, Siegrist CA, Gendrel D, et al. Procalcitonin is a marker of severity of renal lesions in pyelonephritis. Pediatrics. Dec 1998;102(6):1422-5. [Medline].
Bloomfield P, Hodson EM, Craig JC. Antibiotics for acute pyelonephritis in children. Cochrane Database Syst Rev. 2005;CD003772. [Medline].
Chiou YY, Wang ST, Tang MJ, et al. Renal fibrosis: prediction from acute pyelonephritis focus volume measured at 99mTc dimercaptosuccinic acid SPECT. Radiology. Nov 2001;221(2):366-70. [Medline].
Chong CY, Tan AS, Ng W, et al. Treatment of urinary tract infection with gentamicin once or three times daily. Acta Paediatr. 2003;92(3):291-6. [Medline].
Craig JC, Hodson EM. Treatment of acute pyelonephritis in children. BMJ. Jan 24 2004;328(7433):179-80. [Medline].
Ditchfield MR, Summerville D, Grimwood K, et al. Time course of transient cortical scintigraphic defects associated with acute pyelonephritis. Pediatr Radiol. Dec 2002;32(12):849-52. [Medline].
Garin EH, Olavarria F, Garcia Nieto V, et al. Clinical significance of primary vesicoureteral reflux and urinary antibiotic prophylaxis after acute pyelonephritis: a multicenter, randomized, controlled study. Pediatrics. Mar 2006;117(3):626-32. [Medline].
Grattan-Smith JD, Jones RA. MR urography in children. Pediatr Radiol. Nov 2006;36(11):1119-32; quiz 1228-9. [Medline].
Ha SK, Seo JK, Kim SJ, et al. Acute pyelonephritis focusing on perfusion defects on contrast enhanced computerized tomography(CT) scans and its clinical outcome. Korean J Intern Med. Jun 1997;12(2):122-7. [Medline].
Hoberman A, Charron M, Hickey RW, et al. Imaging studies after a first febrile urinary tract infection in young children. N Engl J Med. Jan 16 2003;348(3):195-202. [Medline].
Hoberman A, Wald ER. Treatment of urinary tract infections. Pediatr Infect Dis J. Nov 1999;18(11):1020-1. [Medline].
Hoberman A, Wald ER, Hickey RW, et al. Oral versus initial intravenous therapy for urinary tract infections in young febrile children. Pediatrics. Jul 1999;104(1 Pt 1):79-86. [Medline].
Jantunen ME, Siitonen A, Ala-Houhala M, et al. Predictive factors associated with significant urinary tract abnormalities in infants with pyelonephritis. Pediatr Infect Dis J. Jun 2001;20(6):597-601. [Medline].
Kao C, Hsieh J, Tsai S, et al. Using technetium-99M dimercaptosuccinic acid renal cortex scintigraphy to differentiate acute pyelonephritis from other causes of fever in patients with spinal cord injury. Urology. May 2000;55(5):658-62. [Medline].
Kavanagh EC, Ryan S, Awan A, et al. Can MRI replace DMSA in the detection of renal parenchymal defects in children with urinary tract infections?. Pediatr Radiol. Mar 2005;35(3):275-81. [Medline].
Kovanlikaya A, Okkay N, Cakmakci H, et al. Comparison of MRI and renal cortical scintigraphy findings in childhood acute pyelonephritis: preliminary experience. Eur J Radiol. Jan 2004;49(1):76-80. [Medline].
Levtchenko E, Lahy C, Levy J, et al. Treatment of children with acute pyelonephritis: a prospective randomized study. Pediatr Nephrol. Nov 2001;16(11):878-84. [Medline].
Lundstedt AC, Leijonhufvud I, Ragnarsdottir B, et al. Inherited susceptibility to acute pyelonephritis: a family study of urinary tract infection. J Infect Dis. Apr 15 2007;195(8):1227-34. [Medline].
Maruyama K, Watanabe H, Onigata K. Reversible secondary pseudohypoaldosteronism due to pyelonephritis. Pediatr Nephrol. Dec 2002;17(12):1069-70. [Medline].
Merrick MV, Notghi A, Chalmers N, et al. Long-term follow up to determine the prognostic value of imaging after urinary tract infections. Part 1: Reflux. Arch Dis Child. May 1995;72(5):388-92. [Medline].
Pecile P, Romanello C. Procalcitonin and pyelonephritis in children. Curr Opin Infect Dis. Feb 2007;20(1):83-7. [Medline].
Roilides E, Papachristou F, Gioulekas E, et al. Increased urine interleukin-6 concentrations correlate with pyelonephritic changes on 99mTc-dimercaptosuccinic acid scans in neonates with urinary tract infections. J Infect Dis. Sep 1999;180(3):904-7. [Medline].
Shaw KN, Gorelick M, McGowan KL, et al. Prevalence of urinary tract infection in febrile young children in the emergency department. Pediatrics. Aug 1998;102(2):e16. [Medline].
Sheu JN, Chen MC, Lue KH, et al. Serum and urine levels of interleukin-6 and interleukin-8 in children with acute pyelonephritis. Cytokine. Dec 2006;36(5-6):276-82. [Medline].
Smolkin V, Koren A, Raz R, et al. Procalcitonin as a marker of acute pyelonephritis in infants and children. Pediatr Nephrol. Jun 2002;17(6):409-12. [Medline].
Wang YT, Chiu NT, Chen MJ, et al. Correlation of renal ultrasonographic findings with inflammatory volume from dimercaptosuccinic acid renal scans in children with acute pyelonephritis. J Urol. Jan 2005;173(1):190-4; discussion 194. [Medline].
Weiser AC, Amukele SA, Leonidas JC, Palmer LS. The role of gadolinium enhanced magnetic resonance imaging for children with suspected acute pyelonephritis. J Urol. Jun 2003;169(6):2308-11. [Medline].
Williams GJ, Wei L, Lee A, Craig JC. Long-term antibiotics for preventing recurrent urinary tract infection in children. Cochrane Database Syst Rev. 2006;3:CD001534. [Medline].
Further Reading
Keywords
pyelonephritis, urinary tract infection, UTI, upper-tract infection, kidney infection, bladder infection, infected urine, acute pyelonephritis, APN, bacteremia, vesicoureteral reflux, VUR, sepsis, hypertension, Escherichia coli, hyperkalemia, pseudohypoaldosteronism, hyponatremia, abdominal pain, flank pain, vomiting, diarrhea, anorexia, constipation, treatment, diagnosis
