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Last updated: June 11, 2021

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Pyelonephritis is an infection of the renal pelvis and parenchyma that is usually associated with an ascending bacterial infection of the bladder. It occurs more commonly in women and risk factors include pregnancy and urinary tract obstruction. Patients typically present with flank pain, costovertebral angle tenderness, fever, and other features of cystitis (e.g., dysuria, frequency). Urinalysis shows pyuria and bacteriuria. Urine cultures should be taken in all patients before initiating treatment to identify the pathogen and possible antibiotic resistance. Early empiric antibiotic treatment is essential to avoid renal complications and urosepsis. Definitive treatment depends on the drug sensitivities of the causative pathogen and the patient's clinical profile (e.g., possible comorbidities). See also urinary tract infections.


The terminology used for classifying pyelonephritis is somewhat controversial and serves primarily to estimate the risk of atypical or antibiotic-resistant pathogens.

  • Fever, chills
  • Flank pain
  • Costovertebral angle tenderness: pain upon percussion of the flank (usually unilateral, may be bilateral)
  • Dysuria as well as other symptoms of cystitis (e.g., frequency, urgency)
  • Weakness, nausea, vomiting (diarrhea may also be present)
  • Possible abdominal or pelvic pain


Laboratory tests

Collect urine and blood cultures before administering empiric antibiotic therapy.


CT abdomen with and without IV contrast [14]

Ultrasound of the kidneys and bladder [14]

MRI abdomen

  • Indications
    • Patients with contraindications to CT
    • Pregnancy [14]
  • Findings: similar to CT scan (see “CT abdomen with and without IV contrast” above) [14]

Additional imaging modalities

The following are rarely used, as CT and MRI are more widely available.

The differential diagnoses listed here are not exhaustive.

Antibiotic therapy, source control, and supportive care are the mainstays of treatment of pyelonephritis. The choice of empiric antibiotic regimen should be guided by the risk of infection with resistant organisms (i.e., complicated vs. uncomplicated pyelonephritis) and antibiotics should be tailored as soon as culture results become available. Consider specialist consultation in cases of complicated pyelonephritis, especially if urinary tract obstruction is suspected.

Uncomplicated pyelonephritis [4][6][20]

A single dose of a broad-spectrum parenteral antibiotic prior to the administration of oral antibiotics is recommended when local rates of E. coli resistance are > 10% (or unknown) or if trimethoprim-sulfamethoxazole is used empirically.

Complicated pyelonephritis [4][6][20]

Patients with complicated acute pyelonephritis should be admitted to the hospital and started on parenteral empiric antibiotic therapy as soon as possible. [12]

Empiric antibiotic therapy for complicated pyelonephritis [12][20][22]

Patient characteristics Antibiotic regimens to consider

Not severely ill and no risk factors for multidrug-resistant bacterial infection

Severely ill (i.e., septic) and/or with risk factor(s) for multidrug-resistant gram-negative bacterial infection

Enterococcus or MRSA suspected

Fluoroquinolone monotherapy should be avoided in severely ill patients with complicated pyelonephritis due to the high prevalence of fluoroquinolone-resistant pathogens!

Patients with concurrent urinary tract obstruction are at very high risk of clinical deterioration and require immediate intervention to remove the obstruction.

Admission criteria [12]

Consider inpatient management if any of the following are present:

Uncomplicated pyelonephritis [4][6][20][21]

Complicated pyelonephritis [4][6][20]

Rule out urosepsis in elderly patients with altered mental status!

We list the most important complications. The selection is not exhaustive.

Pyelonephritis in pregnancy [12][20]

All asymptomatic cases of bacteriuria during pregnancy must be treated to prevent the development of pyelonephritis!

Avoid fluoroquinolones, trimethoprim/sulfamethoxazole, and aminoglycosides in pregnant women!

  1. Colgan R, Williams M, Johnson JR. Diagnosis and treatment of acute pyelonephritis in women.. Am Fam Physician. 2011; 84 (5): p.519-526.
  2. Gupta K, Hooton TM, Naber KG, et al. 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. Clinical Infectious Diseases. 2011; 52 (5): p.e103-e120. doi: 10.1093/cid/ciq257 . | Open in Read by QxMD
  3. Murphy JE, Lee MW-L. PSAP 2018 Book 1: Infectious Diseases. American College of Clinical Pharmacy ; 2018
  4. Gupta K, Hooton TM, Naber KG, et al. Executive Summary: 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): p.561-564. doi: 10.1093/cid/cir102 . | Open in Read by QxMD
  5. Ferri FF. Ferri's Clinical Advisor 2018 E-Book: 5 Books in 1 (Ferri's Medical Solutions). Elsevier ; 2017 : p. 1779
  6. Agabegi SS, Agabegi ED. Step-Up To Medicine. Lippincott Williams & Wilkins ; 2013
  7. Hooton TM. Acute complicated cystitis and pyelonephritis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. updated: February 9, 2016. Accessed: February 15, 2017.
  8. Ramakrishnan K, Scheid DC. Diagnosis and management of acute pyelonephritis in adults.. Am Fam Physician. 2005; 71 (5): p.933-942.
  9. Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review.. Am Fam Physician. 2005; 71 (6): p.1153-62.
  10. Colgan R, Williams M. Diagnosis and Treatment of Acute Pyelonephritis in Women. Am Fam Physician. 2011 .
  11. Hesse, Albrecht. Urinary Stones. Karger Medical and Scientific Publishers ; 2009
  12. Van Nieuwkoop C, Hoppe BPC, Bonten TN, et al. Predicting the Need for Radiologic Imaging in Adults with Febrile Urinary Tract Infection. Clin Infect Dis. 2010; 51 (11): p.1266-1272. doi: 10.1086/657071 . | Open in Read by QxMD
  13. Johnson JR, Russo TA. Acute Pyelonephritis in Adults. N Engl J Med. 2018; 378 (1): p.48-59. doi: 10.1056/nejmcp1702758 . | Open in Read by QxMD
  14. Williams M. Comprehensive Hospital Medicine. Elsevier Health Sciences ; 2007
  15. Craig WD, Wagner BJ, Travis MD. Pyelonephritis: Radiologic-Pathologic Review. Radiographics. 2008; 28 (1): p.255-276. doi: 10.1148/rg.281075171 . | Open in Read by QxMD
  16. Ubee SS, McGlynn L, Fordham M. Emphysematous pyelonephritis.. BJU Int. 2011; 107 (9): p.1474-8. doi: 10.1111/j.1464-410X.2010.09660.x . | Open in Read by QxMD
  17. Das CJ. Multimodality imaging of renal inflammatory lesions. World Journal of Radiology. 2014; 6 (11): p.865. doi: 10.4329/wjr.v6.i11.865 . | Open in Read by QxMD
  18. Amery A, Fagard R, Lijnen P, Staessen J. Hypertensive Cardiovascular Disease: Pathophysiology and Treatment. Springer Science & Business Media ; 2012
  19. Lee J, Woo BW, Kim HS. Prognostic Factors of Renal Scarring on Follow-up DMSA Scan in Children with Acute Pyelonephritis. Child Kidney Dis. 2016; 20 (2): p.74-78. doi: 10.3339/jkspn.2016.20.2.74 . | Open in Read by QxMD
  20. Dunnick R, Sandler C, Newhouse J. Textbook of Uroradiology. Lippincott Williams & Wilkins ; 2012
  21. EAU Guidelines on Urological Infections- Limited update 2019. Updated: March 1, 2019. Accessed: April 27, 2020.
  22. Berger I, Wildhofen S, Lee A, et al. Emergency nephrectomy due to severe urosepsis: a retrospective, multicentre analysis of 65 cases. BJU Int. 2009; 104 (3): p.386-390. doi: 10.1111/j.1464-410X.2009.08414.x . | Open in Read by QxMD
  23. Kalra O, Raizada A. Approach to a Patient with Urosepsis.. J Glob Infect Dis. 2009; 1 (1): p.57-63. doi: 10.4103/0974-777x.52984 . | Open in Read by QxMD
  24. Matuszkiewicz-Rowińska J, Małyszko J, Wieliczko M. State of the art paper Urinary tract infections in pregnancy: old and new unresolved diagnostic and therapeutic problems. Arch Med Sci. 2015; 1 : p.67-77. doi: 10.5114/aoms.2013.39202 . | Open in Read by QxMD
  25. Abraham G, Reddy YNV, George G. Diagnosis of acute pyelonephritis with recent trends in management. Nephrol Dial Transplant. 2012; 27 (9): p.3391-3394. doi: 10.1093/ndt/gfs327 . | Open in Read by QxMD
  26. Cohen J, Powderly WG, Opal SM. Infectious Diseases. Elsevier Health Sciences ; 2016
  27. Chronic Pyelonephritis. Updated: May 1, 2016. Accessed: June 7, 2018.
  28. Le T, Bhushan V,‎ Sochat M, Chavda Y, Zureick A. First Aid for the USMLE Step 1 2018. McGraw-Hill Medical ; 2017
  29. Fulop T. Acute Pyelonephritis. Acute Pyelonephritis. New York, NY: WebMD. Updated: September 8, 2016. Accessed: February 15, 2017.
  30. Lohr JW. Chronic Pyelonephritis. In: Batuman B, Chronic Pyelonephritis. New York, NY: WebMD. Updated: December 6, 2015. Accessed: June 7, 2018.
  31. Colgan R, Williams M, Johnson JR. Diagnosis and treatment of acute pyelonephritis in women.. Am Fam Physician. 2011; 84 (5): p.519-526.
  32. Munar MY, Singh H. Drug dosing adjustments in patients with chronic kidney disease.. Am Fam Physician. 2007; 75 (10): p.1487-1496.
  33. American College of Radiology ACR Appropriateness Criteria® Acute Pyelonephritis. Updated: January 1, 2018. Accessed: September 30, 2018.