What is the diagnosis for acute pyelonephritis?

From the Guidelines

To diagnose acute pyelonephritis, perform a urinalysis, urine culture, and blood tests, along with a thorough physical examination and patient history, as recommended by the most recent guidelines 1. Key diagnostic steps:

• Urinalysis: Look for pyuria (>10 white blood cells/hpf), bacteriuria, and positive nitrites.
• Urine culture: Identify the causative organism and antibiotic sensitivities.
• Blood tests: Check for elevated white blood cell count, C-reactive protein, and procalcitonin.
• Physical examination: Assess for costovertebral angle tenderness, fever, and flank pain.
• Patient history: Inquire about urinary symptoms, recent UTIs, and risk factors. In some cases, imaging studies like a renal ultrasound or CT scan may be necessary to rule out complications or anatomical abnormalities, as suggested by the European Association of Urology guidelines 1. Diagnosis is typically based on the presence of urinary tract infection symptoms (dysuria, frequency, urgency) along with systemic symptoms (fever, chills, flank pain) and positive laboratory findings, as outlined in the ACR Appropriateness Criteria 1. Early diagnosis is crucial for prompt treatment to prevent complications such as sepsis or renal scarring. If pyelonephritis is suspected, start empiric antibiotic therapy (e.g., fluoroquinolones or cephalosporins) while awaiting culture results, and adjust based on sensitivity testing, as recommended by the European Association of Urology guidelines 1.

From the Research

Diagnosis of Acute Pyelonephritis

The diagnosis of acute pyelonephritis is primarily based on clinical presentation, laboratory tests, and imaging studies. The key diagnostic features include:

• Fever, flank pain, and costovertebral angle tenderness 2, 3, 4
• Urinalysis showing positive results for leukocyte esterase and nitrite tests, although a negative result does not exclude the diagnosis 2, 4
• Urine culture with antimicrobial susceptibility testing to guide therapy 2, 5, 3, 6
• Blood cultures may be reserved for patients with uncertain diagnosis, immunocompromised, or suspected hematogenous infections 2

Diagnostic Criteria

The diagnostic criteria for acute pyelonephritis include:

• Clinical presentation of fever, flank pain, and nausea/vomiting 3, 4
• Laboratory evidence of urinary tract infection, such as positive urinalysis and urine culture 2, 5, 3, 6
• Imaging studies, such as computed tomography (CT) scan, may be necessary in complicated cases or when symptoms persist despite treatment 5, 3, 6

Laboratory Tests

Laboratory tests used in the diagnosis of acute pyelonephritis include:

• Urinalysis with leukocyte esterase and nitrite tests 2, 4
• Urine culture with antimicrobial susceptibility testing 2, 5, 3, 6
• Blood cultures may be performed in certain cases, such as uncertain diagnosis or immunocompromised patients 2
• Serum inflammatory markers may be measured, but are not routinely recommended in uncomplicated cases 6