Ross M. Decter, MD, FRCS
Paul H. Smith III, MD
BASICS
DESCRIPTION
• Infectious process involving the renal parenchyma and collecting system
• Retrograde ascent of uropathogenic bacteria is most common cause
EPIDEMIOLOGY
Incidence
• 18,000–20,000 children per year hospitalized for diagnosis of pyelonephritis
• Risk of childhood UTI 2% for boys and 8% for girls
• UTI more common in males during 1st yr of life
– Gender predilection reversed thereafter
Prevalence
Low, given the acuity of illness and prompt treatment
RISK FACTORS
• Circumcision reduces risk of UTI during 1st yr of life
– 10× greater risk of UTI in uncircumcised boys
• Dysfunctional voiding
• Anatomic urinary tract anomalies
– Ureteropelvic junction obstruction
– Vesicoureteral reflux (VUR)
– Ureterocele/ectopic ureter
• Neurogenic bladder dysfunction
Genetics
P1 blood group antigen associated with recurrent pyelonephritis
PATHOPHYSIOLOGY
• Periurethral and fecal flora are the source of most uropathogens
– Escherichia coli is the most common organism
– Other common organisms are Klebsiella, Enterococcus, Pseudomonas, Staphylococcus saprophyticus, Enterobacter
• Bacterial virulence factors promote upper tract infection
– P fimbriae: E. coli virulence factor promotes adherence and subsequent invasion of bacteria into the urothelium (1)
• Inflammatory response initiated by interaction between bacterial endotoxin and toll-like receptor (TLR) 4 (1)
ASSOCIATED CONDITIONS
• Lobar nephronia: Pyelonephritis affecting only an isolated focus within the kidney
• Pyonephrosis: Purulent material within the collecting system
• Renal abscess
GENERAL PREVENTION
• Prophylactic antibiotics in patients with recurrent episodes of UTI or with VUR
• Surgical correction of anatomic urinary tract anomalies
• Optimization of bladder/bowel management in patients with neurogenic and nonneurogenic bladder dysfunction
• Antibiotic prophylaxis if major GU instrumentation
DIAGNOSIS
HISTORY
• Nonspecific symptoms or failure to thrive in young children
– High degree of suspicion required in young children
• Fever, nausea, vomiting
• Flank or abdominal pain
• Hematuria, dysuria, foul smelling urine, frequency, urgency
• History of UTIs
• Functional or anatomic urinary tract anomalies
PHYSICAL EXAM
• Fever
• Sepsis
• CVA tenderness
• Exam findings nonspecific in young children
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Urinalysis
– WBCs: >5 per HPF
– Presence of any bacteria
– Positive leukocyte esterase
– Positive nitrites: ∼4 hr of dwell time in the bladder required for nitrites to become positive
• Urine culture: Specimen collected by clean catch, catheterization or suprapubic aspiration (SPA)
– >50,000 C FU signifies positive culture (2)
• CBC: Leukocytosis with left shift
• Blood cultures
• Elevated CRP, ESR, procalcitonin
Imaging
• Renal and bladder ultrasonography (RBUS)
– Failure to improve clinically within 1st 2 days of antibiotic treatment should prompt evaluation with RBUS to evaluate for complications
Renal abscess
Pyonephrosis
– Used to identify structural abnormalities contributing to the development of pyelonephritis
• Voiding cystourethrogram (VCUG)
– Identifies VUR
– Requirement for VCUG after 1st febrile UTI controversial
– Invasive study (requires catheterization)
• Nuclear cystogram
– More sensitive for low-grade VUR than VCUG but less anatomic detail
• Nuclear renography (DMSA)
– Gold standard for diagnosis of pyelonephritis
Rarely necessary in acute setting
– Delayed study identifies renal scarring (3)
– Invasive study (IV injection of radionuclide)
– Radiation exposure
Diagnostic Procedures/Surgery
SPA for urine culture if clean catch or catheterization not feasible
Pathologic Findings
• Renal scarring
– Inflammatory reaction to renal parenchymal infection can cause irreversible renal scarring
DIFFERENTIAL DIAGNOSIS
• Renal abscess
• Pyonephrosis
• Other intra-abdominal process
TREATMENT
GENERAL MEASURES
• Prompt initiation of empiric antibiotics after acquisition of urine specimen suitable for culture (clean catch, catheterization, SPA)
• General supportive measures
– Volume resuscitation, antipyretics, analgesics
• Need for hospitalization based on severity of illness, however admission generally indicated for infants (<2–3 mo)
MEDICATION
First Line
• Empiric coverage
– Tailor to local antimicrobial resistance patterns (2)[A]
– Ampicillin (25–50 mg/kg/d) + gentamicin (2–2.5 mg/kg TID)
3rd-generation cephalosporin an alternative to ampicillin if low risk for enterococcus UTI
• Oral culture-directed antibiotics once clinically improving and tolerating oral intake
– Avoid nitrofurantoin due to minimal tissue penetration
– Parenteral antibiotics (daily ceftriaxone, IM) also an option for outpatient therapy
• 7–14 days total duration of therapy (2)[B]
Second Line
• Vancomycin if penicillin allergic
• Aztreonam an alternate to aminoglycoside if renal insufficiency
SURGERY/OTHER PROCEDURES
• Urethral catheter if critically ill or poor bladder emptying
• Surgery generally not indicated in acute treatment
• Ureteral stent or nephrostomy tube if obstruction
• Percutaneous aspiration/drainage if progression to renal abscess
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
N/A
Complementary & Alternative Therapies
Probiotics (experimental)
ONGOING CARE
PROGNOSIS
Related to degree of renal injury from pyelonephritic scarring
COMPLICATIONS
• Pyelonephritic scarring, especially with recurrent episodes and delayed treatment
• Pyonephrosis
• Renal abscess
• Xanthogranulomatous pyelonephritis
• Hypertension
FOLLOW-UP
Patient Monitoring
• Current American Academy of Pediatrics guidelines recommends RUS in children with febrile UTI
– Selective VCUG in patients with abnormal RUS or recurrent episodes (2)[C]
– Indications for radiographic imaging in children with 1st episode of febrile UTI remain controversial
• Delayed DMSA scan to detect renal scarring
Patient Resources
• National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC)
– http://kidney.niddk.nih.gov/kudiseases/pubs/pyelonephritis/index.aspx
– http://kidney.niddk.nih.gov/kudiseases/pubs/utichildren/
REFERENCES
1. Montini G, Tullus K, Hewitt I. Febrile urinary tract infections in children. N Engl J Med. 2011;365(3):239–250.
2. Roberts KB. Urinary tract infection: Clinical practice guidelines for the diagnosis and management of the initial UTI in febrile infants and children 2 to 24 months. Pediatrics. 2011;128:595–609.
3. Rushton HG, Majd M. Dimercaptosuccinic acid renal scintigraphy for the evaluation of pyelonephritis and scarring: A review of experimental and clinical studies. J Urol. 1992;148(5 pt 2):1726–1732.
ADDITIONAL READING
• Juliano TM, Stephany HA, Clayton DB, et al. Incidence of abnormal imaging and recurrent pyelonephritis after first febrile urinary tract infection in children 2 to 24 months. J Urol. 2013;190(4 suppl):1505–1510. doi: 10.1016/j.juro.2013.01.049.
• Shaikh N, Ewing AL, Bhatnagar S, et al. Risk of renal scarring in children with a first urinary tract infection: A systematic review. Pediatrics. 2010;126:1084–1091.
• Shortliffe LD. Infection and inflammation of the pediatric genitourinary tract. In: Wein AJ, Kavoussi LR, Novick AC, et al.Campbell-Walsh Urology. 10th ed. Philadelphia, PA: Elsevier Saunders; 2012.
See Also (Topic, Algorithm, Media)
• Pyelonephritis, Acute, Pediatric Image 
• Pyonephrosis
• Urinary Tract Infection (UTI), Complicated, Pediatric
• Urinary Tract Infection (UTI), Pediatric
• Vesicoureteral Reflux, Pediatric
CODES
ICD9
• 041.49 Other and unspecified Escherichia coli [E. coli]
• 590.10 Acute pyelonephritis without lesion of renal medullary necrosis
• 593.73 Other vesicoureteral reflux with reflux nephropathy NOS
ICD10
• B96.20 Unsp Escherichia coli as the cause of diseases classd elswhr
• N10 Acute tubulo-interstitial nephritis
• N13.729 Vesicoureter-reflux w reflux nephropathy w/o hydrourt, unsp
CLINICAL/SURGICAL PEARLS
• Signs and symptoms are often nonspecific in infants and young children with pyelonephritis.
• Culture of appropriately collected urine specimen mandatory in patients with suspected UTI and in infants with fever and no obvious source.
• Acute imaging (RUS) recommended if critically ill or failure to respond to treatment.