Acute pyelonephritis is a serious upper urinary tract infection (UTI) involving the renal parenchyma and collecting system. It may be complicated or uncomplicated.
Unlike uncomplicated cystitis, pyelonephritis carries a risk of systemic illness, sepsis, and permanent kidney injury, making accurate diagnosis and timely treatment essential.
Acute pyelonephritis is a bacterial infection of the kidney, most commonly caused by ascending infection from the bladder. Bacteria invade the renal pelvis and interstitium, triggering inflammation that can impair kidney function temporarily or, in severe cases, permanently.
It is distinct from:
The majority of cases arise from ascending spread:
Less commonly, infection may occur via:
Risk factors include vesicoureteral reflux (reflux nephropathy), obstruction, urinary catheters, pregnancy, diabetes, and immunosuppression.
The causative organisms mirror those of lower UTIs, but with greater virulence.
Common pathogens:
In healthcare-associated or complicated infections:
Antibiotic resistance patterns are increasingly important in management decisions.
Classic features include:
Lower urinary tract symptoms (dysuria, frequency) may or may not be present.
Severe disease may present with:
Diagnosis is primarily clinical, supported by laboratory findings.
Key components:
Laboratory findings may include:
Imaging is not routine but is essential in selected cases (see below).
Imaging is indicated when there is concern for:
Ultrasound is the first imaging test to do. A CT scan with contrast may then be necessary.
Treatment requires prompt antibiotics, tailored to severity and resistance risk.
Uncomplicated cases:
Complicated or severe cases:
Antibiotic selection is refined once culture results are available.
Typical durations:
Overly prolonged therapy does not improve outcomes and increases harm.
Possible complications include:
Prompt recognition and treatment significantly reduce risk.
Rarely. Most otherwise healthy adults fully recover kidney function. However, risk of long-term damage increases with:
In vulnerable patients, pyelonephritis can contribute to progressive CKD.
Prevention focuses on addressing underlying risk factors:
For recurrent infections, further urologic evaluation may be necessary.
Acute pyelonephritis is a medical emergency of the kidney, not simply a ‘bad UTI.’
Diagnosis depends on clinical judgment, and management requires timely antibiotics, selective imaging, and attention to complications.
Informed patients play a crucial role in recognising symptoms early and engaging in shared decision-making.
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