• Clinical science

Physician mode test card (Pyelonephritis)

Abstract

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 females 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 reveals leukocyturia and bacteriuria. Urine cultures should be obtained in all patients before initiating treatment to identify the pathogen and assess for possible antibiotic resistance. Treatment depends on the drug sensitivities of the offending pathogen and the patient's clinical profile (e.g., possible comorbidities). Early empiric antibiotic treatment is essential to avoid renal complications and urosepsis.

Etiology

References:[1][2]

Classification

Uncomplicated pyelonephritis

  • Typical pathogen in an immunocompetent patient with normal genitourinary anatomy and normal renal function [3]

Complicated pyelonephritis

  • Presence of one or more of the following [3]
    • Failure of outpatient therapy
    • Persistent nausea and vomiting
    • Sepsis
    • Age > 60 years
    • Urinary tract abnormalities (e.g., obstruction, indwelling catheter)
    • Recent surgery to the urinary tract
    • Renal impairment
    • Immunosuppression and/or severe comorbidities

Clinical features

  • High fever, chills
  • Flank pain, costovertebral angle tenderness (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

References:[4]

Diagnostics

Laboratory tests

Urine and blood cultures should be collected before empiric administration of antibiotics!

Imaging

References:[4]

Pathology

  • Destructive interstitial nephritis
    • Purulent inflammation of the interstitium with destruction of the parenchyma, the renal tubules, and in some cases the renal pelvis
    • Renal tubules infiltrated with neutrophils
  • Chronic pyelnohephritis
    • Chronic inflammatory changes such as rough scarring of at the junction of the cortex and medulla
    • Blunted calyces from recurrent urinary reflux
    • Eosinic (not eosinophilic!) casts in the tubules (so called “thyroidization of the kidney”)
  • Xanthogranulomatous pyelonephritis
    • Lipid laden foamy macrophages and multinucleated giant cells seen on histology
    • Large, irregular, yellow appear masses throughout the kidney on gross examination

Differential diagnoses

The differential diagnoses listed here are not exhaustive.

Treatment

Empiric therapy should be administered first, and antibiotics can later be adjusted according to the identified pathogen and drug sensitivities, comorbidities, and the current condition of the patient.

Uncomplicated pyelonephritis [5]

Complicated pyelonephritis[3]

In contrast to antibiotic treatment with most cephalosporins, empiric therapy with ciprofloxacin also covers infections with enterococci!
References:[1][8][4][2][5][6][3][7][9][10][11]

Criteria and management of primary treatment failure

Complications

References:[2]

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

Special patient groups

Pyelonephritis in pregnancy

During pregnancy, all asymptomatic cases of bacteriuria must be treated because pyelonephritis is the most common serious complication in pregnant women.

Do not use fluoroquinolones or trimethoprim-sulfamethoxazole in pregnant women!
References:[4]

Chronic pyelonephritis

References:[12][13][14]

Clinical practice guideline checklist

Uncomplicated pyelonephritis

Diagnostic checklist

  • Urinalysis and Gram stain
  • Urine culture: before administering 1 st dose of antibiotics
  • Complete blood count and basic metabolic panel

Outpatient treatment checklist

Complicated pyelonephritis

Diagnostic checklist

  • Urinalysis and Gram stain
  • Complete blood count
  • Basic metabolic panel
  • Urine culture: before administering 1 st dose of antibiotics
  • Blood cultures (2 sets): before administering 1 st dose of antibiotics

Treatment checklist

  • In-patient management
  • IV hydration
  • Start empiric IV antibiotics

Step-up management checklist

  • No symptomatic improvement on empirical IV antibiotics
  • Check urine and blood culture report
  • Change antibiotic according to the sensitivity report
  • CT scan of the abdomen and pelvis (with and without IV contrast)
  • Switch to step-down management once the patient is afebrile for at least 48 hours

Step-down management checklist

  • Symptomatic improvement: patient afebrile, tolerating oral liquids, pain-free?
  • Switch to oral antibiotics for a total of 14 days (including the IV antibiotic therapy)
  • Discharge from hospital
  • Follow-up after 72 hours or earlier if symptoms recur

Coding according to DSM V (2013)/ICD-10 (2018)

  • N10: Acute tubulo-interstitial nephritis
    • Includes: Acute:
      • infectious interstitial nephritis
      • pyelitis
      • pyelonephritis
      • Use additional code (B95-B98), if desired, to identify infectious agent
  • N11: Chronic tubulo-interstitial nephritis
  • N12: Tubulo-interstitial nephritis, not specified as acute or chronic
    • Applicable to:

Adapted from: ICD-10-CM Version 2018.