From the Guidelines
Yes, it is possible to have pyelonephritis with a clear urinalysis (UA), although this is uncommon. Most cases of pyelonephritis show abnormalities in the UA such as white blood cells, bacteria, nitrites, or leukocyte esterase 1. However, in early infection, dehydration, urinary obstruction, or if antibiotics were recently taken, the UA may appear normal despite active infection. This phenomenon is sometimes called "sterile pyuria" when white blood cells are present without detectable bacteria.
Key Points to Consider
- If pyelonephritis is suspected despite a clear UA, additional testing such as urine culture, blood tests, or imaging studies like CT scan or ultrasound may be necessary 1.
- Symptoms like flank pain, fever, chills, nausea, and vomiting should not be dismissed even with a negative UA.
- Treatment typically involves antibiotics such as fluoroquinolones (ciprofloxacin 500mg twice daily for 7 days), trimethoprim-sulfamethoxazole (160/800mg twice daily for 14 days), or cephalosporins depending on local resistance patterns, with adjustment based on culture results when available 1.
Patient Risk Factors
- Patients with underlying diabetes are of particular concern as they are more vulnerable to complications from acute pyelonephritis, including renal abscesses and emphysematous pyelonephritis 1.
- Additional higher-risk populations may include those with an anatomic abnormality of the urinary tract, vesicoureteral reflux, renal obstruction, pregnancy, nosocomial infection, infections by treatment-resistant pathogens, transplant recipients, and immunosuppressed patients 1.
From the Research
Pyelonephritis and Urinalysis
- Pyelonephritis is a bacterial infection of the renal pelvis and kidney, and a positive urinalysis is often used to confirm the diagnosis 2, 3.
- However, it is possible for a patient to have pyelonephritis with a clear urinalysis, as the infection may not always cause significant changes in the urine 4.
- Urine culture is an important diagnostic tool in pyelonephritis, as it can help identify the causative pathogen and guide antibiotic therapy 2, 3, 5.
Diagnostic Considerations
- The diagnosis of pyelonephritis is typically based on a combination of clinical symptoms, such as flank pain and fever, and laboratory results, including urinalysis and urine culture 2, 3, 5.
- Imaging studies, such as computed tomography, may be necessary in some cases to confirm the diagnosis or to evaluate for complications 2, 3, 5.
- Blood cultures may also be useful in some cases, particularly in patients with severe or complicated pyelonephritis 4, 5.
Treatment and Management
- The treatment of pyelonephritis typically involves antibiotic therapy, with the choice of antibiotic depending on the causative pathogen and the patient's clinical condition 2, 3, 5.
- Outpatient management is often possible for patients with uncomplicated pyelonephritis, while hospitalization may be necessary for patients with severe or complicated disease 2, 3, 5.
- Urine cultures can provide important information for guiding antibiotic therapy and monitoring the patient's response to treatment 2, 3, 5, 6.