Pyelonephritis: Diagnosis and Management

Definition and Clinical Presentation

Pyelonephritis is defined as inflammation of the renal parenchyma due to bacterial infection, affecting the kidney and renal pelvis, typically presenting with fever, flank pain, and urinary symptoms, as recommended by the European Association of Urology 1, 2
Typical symptoms include fever (>38°C), chills, flank pain, nausea, vomiting, and tenderness at the costovertebral angle, according to the European Urology guidelines 1
Patients may also present with symptoms of cystitis (frequency, urgency, dysuria), as noted by the American College of Radiology 2
In some populations (particularly diabetics), up to 50% may not exhibit typical flank tenderness, making diagnosis more challenging, as reported by the Journal of the American College of Radiology 3

Urinalysis showing white blood cells, red blood cells, and nitrite is recommended for routine diagnosis, as suggested by the European Urology guidelines 1
Urine culture with antimicrobial susceptibility testing should be performed in all cases of suspected pyelonephritis before initiating antibiotics, according to the European Urology guidelines 1
Ultrasound evaluation of the upper urinary tract should be performed to rule out urinary tract obstruction, renal stone disease, and structural abnormalities, as recommended by the Annals of Internal Medicine 5 and European Urology 6

Trimethoprim-sulfamethoxazole (TMP-SMX) for 14 days (based on susceptibility testing) is a recommended regimen for women with uncomplicated pyelonephritis, as suggested by the Annals of Internal Medicine 7, 5
Intravenous antibiotic options include extended-spectrum cephalosporins or penicillins, as recommended by the European Urology guidelines 1, 6
Carbapenems and novel broad-spectrum antimicrobials should be reserved for patients with multidrug-resistant organisms, according to the European Urology guidelines 1, 6

Potential complications include renal scarring (occurs in approximately 15% of patients after first episode), as reported by the Journal of the American College of Radiology 2
Renal or perinephric abscess is a potential complication, as noted by the Journal of the American College of Radiology 4
Long-term complications from renal scarring may include hypertension and chronic renal failure, though the risk is lower than previously thought, as suggested by the Journal of the American College of Radiology 2, 8

Addressing modifiable risk factors and prophylactic antibiotics if non-antimicrobial interventions have failed may be considered for patients with recurrent pyelonephritis, as recommended by the European Urology guidelines 9