I. General pathology information
A. Other Names
1. Urinary tract infection
2. Inflammatory disease of the kidney
B. Causes
1. Vesicoureteral reflux
2. Altered bladder function
3. Congenital urinary tract anomalies
4. Renal calculi
C. Incidence rates
1. In females, annual rates for outpatient treatment are 12-13 cases per 10,000.
2. In females, annual rates for inpatient treatments are 3-4 cases per 10,000.
3. Among males, outpatient annual rates are 2-3 cases per 10,000.
4. Among males, inpatient annual rates are 1-2 cases per 10,000.
5. Incidences are highest among young women, followed by infants and the
elderly.
D. Signs and symptoms
1. Unilateral or bilateral flank pain with costovertebral tenderness
2. Rapid onset of high fever, but may be absent early in the illness
3. Dysuria and urinary frequency and urgency
4. Possible abdominal pain, nausea, vomiting, and diarrhea
E. Pathologic affects
1. Bacteria adheres to the urothelium and inhibits peristalsis of the ureter by
blocking the α-adrenergic nerves within smooth muscle.
2. Infection passes into the collecting tubules, resulting in interstitial nephritis.
3. Renal filtration and blood flow is alterated in the affected area.
4. Ischemia develops locally secondary to inflammation
5. Necrosis and scarring may develop from ischemia.
F. Diagnostic tests
1. Urinalysis
a. White cells and bacteria present
1) Escherichia coli is the most common pathogen.
2. Blood tests
a. Increased white blood cells (leukocytosis with a neutrophilic shift)
b. increased C-reactive protein (CRP)
c. Possible increased erythrocyte sedimentation rate (ESR)
d. Occasionally positive blood cultures that grow the same organism as
cultured from the urine.
G. Treatment options
1. In the past decade, there has been an increasing rate of E. coli resistance to
extended-spectrum beta-lactam antibiotics
Outpatient treatment may start with fluoroquinolones by mouth if the resistance rate to floroquinolone is 10% or less.
If the rate of resistance is more than 10%, first an IV dose of gentamicin or ceftriaxone is administered followed by a regimen of fluoroquinolone by mouth.
Several antibiotic regimens can be used for inpatient treatment,
including fluoroquinolones, aminoglycosides, and cephalosporins.
2. It is not indicated to administer beta-lactam antibiotics and
trimethoprim/sulfamethoxazole (TMP/SMX) by mouth due to high levels of
resistance.
H. Prognosis
1. Majority of patients without complications respond quickly to antibiotics.
2. Imaging changes may take up to 5 months to resolve.
3. If an upper urinary tract infection is present with obstruction, the viability of
the kidney may be at risk and an emergency percutaneous nephrostomy may be indicated.
4. 95% of uncomplicated patient become afebrile with 48 hours of treatment with
antibiotics and almost 100% within 72 hours.
II. Imaging
Radiography
Intravenous urography
a. Today, it plays a minor role in diagnosis of pyelonephritis.
1) Is useful for determining the presence of an underlying anatomic
abnormality.
2) Determining the presence of an underlying process that may have
prevented a rapid therapeutic response such as obstruction or necrosis
3) Determining a renal or perinephric abscess
Voiding cystourethrography
Abdomen and pelvis (KUB)
a. Urinary renal calculi may be demonstrated
b. If gas is within the collecting system, a diagnosis of emphysematous
pyelonephritis may be made.
Antegrade pyelography
Ultrasound of the kidneys and bladder retroperitoneal
a. Most patients have a normal scan.
b. Abnormalities are only in about 25% of cases
1) Particulate matter in the collecting system
2) Reduced areas of cortical vascularity seen with power Doppler
3) Gas bubbles (emphysematous pyelonephritis
4) Renal parenchyma shows abnormal echogenicity
a) mass-like change
b) focal/segmental hypoechoic regions
a. Useful for patient who cannot tolerate contrast medium
CT of the abdomen and pelvis without and with contrast (see Appendix A)
a. Capable of evaluation of the renal tract for diagnostic purposes
1) renal calculi
2) gas
3) perfusion defects
4) collections
5) obstruction
Tc-99m DMSA scan of the kidney
a. Of particular interest for pediatric patients for differential diagnosis
between lower urinary tract infections and pyelonephritis
Tissue harmonic imaging
a. The parenchymal defects of pyelonephritis were commonly seen as focal or
segmental, patchy, hypoechoic lesions extending from the medulla to the
renal capsule.
Radiographic appearance (see Appendix A)
1. Renal enlargement
2. Striated or delayed nephrograms
3. Delayed caliceal appearance time
4. Dilatation or effacement of the collecting system
Appearance of pathology images
Diabetic patients display anatomic and severe functional abnormalities
ACR Appropriateness Criteria (see Appendix B)
References
Czaja, C., Scholes, D., Hooton, T., & Stamm, W. (2007). Population-Based Epidemiologic
Analysis of Acute Pyelonephritis. Clinical Infectious Diseases, 45(3), 273-280.
http://dx.doi.org/10.1086/519268
Colgan, R., Williams, M., & Johnson, J. (2011). Diagnosis and Treatment of Acute
Pyelonephritis in Women. American Family Physician, 84(5), 519-526. Retrieved from
http://www.aafp.org/afp/2011/0901/p519.html
Daffner, R. (2007). Clinical radiology. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins.
Nikolaidis, P et al. "ACR Appropriateness Criteria® Acute Pyelonephritis.". Agency for
Healthcare Research and Quality. N.p., 2012. Web. 2 May 2016.
Appendix A
Figure 1. Acute pyelonephritis seen in CT scan as the focal area of low attenuation in the posterolateral aspect of the lower pole of the right kidney (Radiopaedia.org, 2016)
Appendix B
Note: Abbreviations used in the tables are listed at the end of the "Major Recommendations" field.
Variant 2: Complicated patient (e.g., diabetes or immunocompromised or history of stones or prior renal surgery or not responding to therapy).
