Signs and Symptoms of Pyelonephritis
Pyelonephritis typically presents with fever (>38°C), flank pain or costovertebral angle tenderness, and systemic symptoms such as chills, nausea, and vomiting, with or without lower urinary tract symptoms. 1, 2
Cardinal Features
Systemic Symptoms
- Fever is the hallmark, typically exceeding 38°C (or ≥38.5°C in some definitions), though it may be absent early in the illness 1, 3, 4
- Chills are common and indicate systemic inflammatory response 1, 5
- Malaise, fatigue, nausea, and vomiting frequently accompany the infection 2, 4
Localized Symptoms
- Flank pain is nearly universal and its absence should raise suspicion of an alternative diagnosis 2, 3
- Costovertebral angle tenderness on examination is a key physical finding 1, 2, 5
- The pain is typically unilateral 4
Lower Urinary Tract Symptoms
- Bladder symptoms including urgency, dysuria, and urinary frequency may be present but are absent in up to 20% of patients 2
- These cystitis symptoms are variably present and not required for diagnosis 5, 4
Laboratory Confirmation
- Urinalysis showing pyuria and/or bacteriuria is a key diagnostic finding that confirms the diagnosis in patients with compatible clinical presentation 2, 6
- White blood cells, red blood cells, and nitrites on urinalysis support the diagnosis 1, 5
- Urine culture yielding >10,000 colony-forming units per milliliter of a uropathogen is the fundamental confirmatory test 2
- Leukocytosis may be present on complete blood count 6
Atypical Presentations and Important Caveats
High-Risk Populations
- In diabetic patients, up to 50% lack typical flank tenderness, making clinical diagnosis more challenging 2, 5
- Diabetic patients are at higher risk for complications including renal abscesses and emphysematous pyelonephritis 2
- Elderly patients may present with atypical symptoms and are at higher risk for complications 2
- Immunocompromised patients may have blunted clinical presentations 7
Diagnostic Pitfalls
- A negative urine dipstick for nitrites and leukocyte esterase does not exclude the diagnosis and should prompt re-evaluation of clinical features 4
- The severity of symptoms ranges from mild pyrexial illness to life-threatening sepsis 4
- Flank pain with fever should be considered pyelonephritis until proven otherwise in the appropriate clinical context 3, 8