Pyelonephritis laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Usama Talib, BSc, MD [2]


Pyelonephritis can be diagnosed with the help or urinalysis and urine culture. Urine culture should always be obtained before administration of antibiotics if pyelonephritis is suspected. A combination of leukocyte esterase test and nitrite test (with either of the two test being positive) is considered to be very effective with a sensitivity ranging from 75-84 and a specificity ranging from 82-98 percent. A blood culture is usually done but may not necessarily yield any findings.

Laboratory Findings

Laboratory tests are the initial investigations done when suspecting a case of pyelonephritis. Urine and blood samples must be drawn before the beginning of antibiotic therapy to avoid false negative results.[1][2][3]


  • Urinalysis is testing of a urine sample. The urine sample is collected in a special container in a health care provider’s office or commercial facility and can be tested in the same location or sent to a lab for analysis. The presence of white blood cells, nitrites and bacteria in the urine indicate infection and also indicate the need to start empirical treatment.
  • A combined leukocyte esterase test and nitrite test (with either of the two tests being positive) is known to be very sensitive (75-84%) and specific (82-98%).

Urine culture

  • A urine culture is performed by placing part of a urine sample in a tube or dish with a substance that encourages any bacteria present to grow. The urine sample is collected in a special container in a health care provider’s office or commercial facility and sent to a lab for culture. Once the bacteria have multiplied, which usually takes 1 to 3 days, they can be identified. The health care provider can then determine the best treatment.

Blood Culture

  • Blood cultures can sometime be positive in pyelonephritis. Since they are not always positive and may also be positive in many other conditions, they can help in making the diagnosis but are not exclusively sufficient to detect pyelonephritis in the absence of other tests.


  1. Ramakrishnan K, Scheid DC (2005). "Diagnosis and management of acute pyelonephritis in adults". Am Fam Physician. 71 (5): 933–42. PMID 15768623.
  2. Hoverman IV, Gentry LO, Jones DW, Guerriero WG (1980). "Intrarenal abscess. Report of 14 cases". Arch Intern Med. 140 (7): 914–6. PMID 6992728.
  3. Gupta K, Hooton TM, Naber KG, Wullt B, Colgan R, Miller LG; et al. (2011). "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. 52 (5): e103–20. doi:10.1093/cid/ciq257. PMID 21292654.

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