Infection · Moderate
This case is fictional and exists for study. It describes no real patient.
34 years · female
A 34-year-old woman presents to the emergency department with a 2-day history of severe left-sided flank pain, chills, and high fever. She also reports dysuria, urinary frequency, and severe nausea. She has no significant past medical history and is not pregnant. On examination, she appears acutely unwell with marked left costovertebral angle tenderness on percussion. Urinalysis reveals positive nitrites, positive leukocyte esterase, and moderate protein. A urine pregnancy test is negative. Blood tests show an elevated white blood cell count and elevated C-reactive protein, with normal renal function.
Vital signs
- HR
- 108 bpm
- BP
- 112/70 mmHg
- RR
- 20/min
- Temp
- 38.9 °C
- SpO₂
- 98%
Examination findings
- Marked left costovertebral angle tenderness
- Mild lower abdominal tenderness without guarding
- Dry mucous membranes
Investigations
| White Blood Cells (WBC) | 16.5 10^9/L | reference: 4.0-11.0 |
| C-reactive Protein (CRP) | 115 mg/L | reference: <5 |
| Serum Creatinine | 82 µmol/L | reference: 45-84 |
Question 1 of 3
Which of the following is the most likely diagnosis?
The clinical presentation of fever, tachycardia, flank pain, and costovertebral angle tenderness combined with pyuria and nitrituria strongly points to acute pyelonephritis. Uncomplicated cystitis presents with lower urinary tract symptoms (dysuria, frequency) without systemic features or renal angle pain. Nephrolithiasis causes acute severe flank pain that often radiates to the groin, but without infection, it does not present with high fever and pyuria. Acute pelvic inflammatory disease presents with lower abdominal pain, cervical motion tenderness, and vaginal discharge rather than focal renal angle tenderness.
Teaching point: Fever, rigors, and costovertebral angle tenderness distinguish acute pyelonephritis from lower urinary tract infections.
Question 2 of 3
Which of the following is the most appropriate next investigation to perform before starting empirical antibiotic therapy?
A midstream urine (MSU) specimen for culture and susceptibility testing must be obtained in all suspected cases of acute pyelonephritis prior to starting antibiotics. This enables targeted antibiotic therapy based on organism sensitivities. Routine CT scanning or renal ultrasound is not routinely indicated for an initial uncomplicated presentation of pyelonephritis unless the patient fails to respond after 48-72 hours of treatment or has signs of urinary tract obstruction. Cystoscopy is an invasive procedure used for structural mucosal assessment and is contraindicated during an acute urinary tract infection.
Teaching point: A midstream urine culture should always be sent prior to initiating antimicrobial therapy in suspected acute pyelonephritis.
Question 3 of 3
Following specimen collection for culture, which of the following is the most appropriate empirical oral antibiotic regimen according to NICE guidelines for acute pyelonephritis?
NICE guidelines recommend oral cefalexin (or co-amoxiclav, ciprofloxacin) for 7 to 10 days as first-line empiric treatment for acute pyelonephritis in patients who can tolerate oral therapy and do not require admission. Nitrofurantoin is ineffective for pyelonephritis because it achieves poor tissue concentration in the renal parenchyma. Trimethoprim given for a 3-day course is reserved for uncomplicated lower UTIs. Amoxicillin has high resistance rates among common uropathogens like E. coli and is not recommended as empiric monotherapy.
Teaching point: Nitrofurantoin should never be used to treat pyelonephritis because it does not achieve therapeutic tissue concentrations in the renal parenchyma.
Key learning points
- Acute pyelonephritis is characterized by upper UTI symptoms, including fever, flank pain, rigors, and costovertebral angle tenderness.
- A midstream urine culture and sensitivity test should always be collected before initiating antibiotic therapy for upper or complicated UTIs.
- Nitrofurantoin is inappropriate for treating acute pyelonephritis due to inadequate renal tissue penetration; oral cefalexin or co-amoxiclav are preferred empirical options.
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