Renal anatomy.


  • UTI = significant bacteriuria in presence of symptoms

Genitourinary infection

(1) Human urinary system: (2) kidney; (3) renal pelvis; (4) ureter; (5) urinary bladder (6) urethra.
Additional structures: (7) adrenal gland; (8) renal artery and vein; (9) inferior vena cava; (10) abdominal aorta; (11) common iliac artery and vein; (12) liver; (13) large intestine; (14) pelvis.

"UTI" frequently refers specifically to acute cystitis, but may also be used as a general term for all urinary infections; use location-specific diagnosis.

Clinical Features

Diagram showing the typical location of pain[1]
  • Pyelo = Cystitis symptoms AND fever/chills/nausea/vomiting
    • CVAT alone may be referred pain from cystitis
    • CVAT is only physical examination finding that increases likelihood of a UTI


  • Acute bacterial nephritis
    • CT shows ill-defined focal areas of decreased density
  • Renal/Perinephric abscesses
    • Sign/symptoms similar to pyelo (fever, CVAT, dysuria)
    • Occurs in setting of ascending infection with obstructed pyelo
    • Associated with DM and Renal Stones
    • Also occurs due to bacteremia with hematogenous seeding (Staph)
  • Emphysematous pyelonephritis
    • Rare gas-forming infection nearly always occurring in patients with DM and obstruction
      • Patients appear toxic and septic; nephrectomy may be required

Differential Diagnosis


Flank Pain



Urine with pyuria.
Renal ultrasound showing acute pyelonephritis with increased cortical echogenicity and blurred delineation of the upper pole.[2]
CT without contrast showing bilateral perirenal fat stranding (arrow heads).


Blood cultures are NOT indicated (organisms in blood culture matched those in urine culture 97% of time)




Treatment is targeted at E. coli, Enterococcus, Klebsiella, Proteus mirabilis, S. saprophyticus.


Consider one dose of Ceftriaxone 1g IV or Gentamycin 7mg/kg IV if the regional susceptibility of TMP/SMX or Fluoroquinolones is <80%

Adult Inpatient Options

Pediatric Inpatient Options



  • Consider if young, otherwise healthy, tolerating PO


Consider admission if:[8]

  • Elderly (>60)
  • Renal Calculi
  • Obstruction
  • Recent hospitalization/instrumentation
  • DM
  • Immunocompromised
  • Unable to tolerate PO
  • Pregnancy
  • Solitary kidney or other anatomic abnormality


  • Admit all second trimester pregnant patients with OBGYN consult
  • Urology consult during the inpatient admission for pediatric patients due to the risk for urologic scarring
  • Consider advanced imaging to rule out abscess of urolithiasis if patient has failed 3 days of therapy

Special Populations


  • Elderly patients with pyelonephritis: 20% present with primary respiratory or GI symptoms. Also 33% are afebrile.[9]

See Also


  1. Urinary Tract Infection Common Clinical and Laboratory Features of Acute Pyelonephritis". Retrieved 14 July 2019.
  2. Content initially copied from: Hansen, Kristoffer; Nielsen, Michael; Ewertsen, Caroline (2015). "Ultrasonography of the Kidney: A Pictorial Review". Diagnostics. 6 (1): 2. doi:10.3390/diagnostics6010002. ISSN 2075-4418. PMC 4808817. PMID 26838799. (CC-BY 4.0)
  3. Perirenal fat stranding is not a powerful diagnostic tool for acute pyelonephritis International Journal of General Medicine
  4. Gupta K, Hooton TM, Naber KG, et al. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women. Clinical Infectious Diseases. 2011;52(5):e103-e120. doi:10.1093/cid/ciq257
  5. Colgan R, Williams M. Diagnosis and treatment of acute uncomplicated cystitis. Am Fam Physician. 2011 Oct 1;84(7):771-6.
  6. Acute Pyelonephritis in Adults. Johnson, JR and Russo, TA. New England Journal of Medicine 2018; 378:48-59.
  7. Sandberg T. et al. Ciprofloxacin for 7 days versus 14 days in women with acute pyelonephritis: a randomised, open-label and double-blind, placebo-controlled, non-inferiority trial. Lancet. 2012 Aug 4;380(9840):484-90.
  8. Norris DL, Young JD. UTI. EM Clin N Am. 2008; 26:413-30.
  9. Norris DL, Young JD. UTI. EM Clin N Am. 2008; 26:413-30.