Acute Pyelonephritis (Kidney Infection)
This clinical presentation is highly consistent with acute pyelonephritis—a serious upper urinary tract infection requiring immediate antibiotic treatment to prevent complications including renal scarring and sepsis. 1, 2
Clinical Diagnosis
The combination of symptoms strongly indicates pyelonephritis rather than simple cystitis:
- Sharp, throbbing right flank/back pain (8/10 severity) represents the hallmark costovertebral angle pain that distinguishes upper from lower tract infection 1, 2
- Fever and chills indicate systemic infection extending to the kidney parenchyma, with fever typically >38°C (100.4°F) in pyelonephritis 1, 2
- Frequent urination and cloudy urine suggest concurrent bladder involvement (cystitis symptoms), though these can be absent in up to 20% of pyelonephritis cases 1
- Severe pain limiting movement reflects the inflammatory process affecting the kidney and surrounding tissues 3, 4
Immediate Diagnostic Steps
Urinalysis and urine culture with antimicrobial susceptibility testing should be obtained immediately before starting antibiotics: 1, 2
- Urinalysis will likely show pyuria (white blood cells) and/or bacteriuria, which confirms urinary tract infection 1, 5
- Urine culture is mandatory in all suspected pyelonephritis cases to guide targeted antibiotic therapy 3, 2
- The cloudy appearance suggests pyuria, though this must be confirmed by laboratory testing 6
Treatment Approach
Empirical antibiotic therapy must be initiated immediately based on clinical presentation, as delayed treatment can lead to renal scarring and serious complications: 1
For Outpatient Management (if patient is stable):
- Ciprofloxacin 500-750 mg twice daily for 7 days OR 2
- Levofloxacin 750 mg once daily for 5-7 days 2
- Alternative: Ceftriaxone 1-2 g once daily if fluoroquinolone resistance is suspected 2
Indications for Hospitalization and IV Antibiotics:
The patient should be hospitalized if: 3, 2
- Unable to tolerate oral medications (nausea/vomiting is severe)
- Hemodynamically unstable or showing signs of sepsis
- Severe pain requiring parenteral analgesia
- Failure to improve after 72 hours of oral antibiotics
Standard treatment duration is 7-14 days, with 14 days recommended when there is severe presentation or delayed response. 3, 2
Critical Follow-Up Considerations
If fever persists beyond 72 hours of appropriate antibiotic treatment, imaging with renal ultrasound is mandatory to rule out complications: 2
Complications requiring imaging evaluation include:
- Renal or perinephric abscess formation 3, 2
- Urinary tract obstruction from stones 2
- Pyonephrosis (pus-filled collecting system) 3
Important Differential Considerations
While pyelonephritis is most likely, the following should be briefly considered:
- Bacterial vaginosis does NOT cause fever, flank pain, or systemic symptoms 1
- Chlamydia presents with dysuria and discharge but NOT fever or flank pain 1
- Nephrolithiasis (kidney stones) can cause similar flank pain but typically presents with colicky pain and hematuria without fever/chills 3
Common Pitfalls to Avoid
- Do not delay antibiotic treatment while waiting for culture results—empirical therapy should begin immediately 1
- Do not treat based solely on urinalysis without considering clinical symptoms—pyuria alone does not confirm infection 3
- Do not use fluoroquinolones if the patient has used them in the last 6 months due to resistance concerns 3
- Do not assume improvement without follow-up—persistent fever after 72 hours requires imaging 2
Risk Factors Present
At age 25 and female, this patient has typical demographic risk factors for UTI, though the progression to pyelonephritis suggests: 4, 5