Pyelonephritis Symptoms: Recognizing Kidney Infection - Symptoms & Causes

Pyelonephritis is a bacterial infection of the renal pelvis and parenchyma, usually ascending from the bladder. It is a serious condition requiring prompt antibiotic therapy to prevent sepsis and renal scarring.

Classic Symptom Triad

• Fever & Chills: Often high (39–40°C / 102–104°F), rigors.
• Flank Pain (CVA Tenderness): Unilateral or bilateral, dull to severe, costovertebral angle.
• Lower Urinary Symptoms: Dysuria, urgency, frequency, suprapubic discomfort (from concomitant cystitis).

Additional Symptoms

• Nausea, vomiting (common).
• Gross hematuria or cloudy/foul urine.
• Fatigue, malaise, anorexia.
• Confusion, delirium (especially elderly—may be sole presentation).
• Abdominal pain (can mimic surgical abdomen).

Atypical Presentations

• Elderly: Altered mental status, falls, anorexia, no fever.
• Children: Fever, vomiting, irritability, failure to thrive; dysuria less common.
• Pregnancy: Higher risk (ureteral dilation); asymptomatic bacteriuria → pyelo if untreated. Screen at 12–16 wks.
• Immunocompromised: May lack fever; consider fungal/TB.

Common Causative Organisms

• E. coli (70–90%).
• Klebsiella, Proteus, Enterobacter.
• Enterococcus faecalis.
• Resistant organisms: ESBL, CRE (healthcare-associated).

Red Flags for Complicated/Severe Infection

• Sepsis (qSOFA ≥2), hemodynamic instability.
• Obstruction (stone, stricture, tumor).
• Abscess, emphysematous pyelonephritis (gas-forming—diabetics).
• Renal failure (AKI).

Action

Suspected pyelonephritis = urgent medical evaluation. Delay risks sepsis, permanent renal damage. Outpatient oral antibiotics (fluoroquinolone or TMP-SMX if susceptible) for mild cases; IV antibiotics + hospitalization for severe, pregnant, elderly, comorbid, or unable to tolerate oral.