Acute Pyelonephritis

Symptoms

• Fever (often >38.5°C), chills, rigors
• Flank or back pain (unilateral or bilateral)
• Nausea and vomiting
• Lower UTI symptoms — dysuria, frequency, urgency — preceding or accompanying upper tract symptoms
• Malaise, fatigue, anorexia
• Elderly: may present atypically with confusion, falls, or simply nonspecific decline

Signs / physical exam

• Fever, tachycardia; hypotension in severe cases (urosepsis)
• Costovertebral angle (CVA) tenderness — classic finding on percussion
• Suprapubic tenderness if concurrent cystitis
• Signs of dehydration
• Hemodynamic instability suggests urosepsis — requires aggressive resuscitation

Classic findings

Fever + flank pain + CVA tenderness + pyuria = pyelonephritis. Add hypotension or organ dysfunction = urosepsis.

Diagnostic criteria

Clinical diagnosis: classic symptoms (fever, flank pain, CVA tenderness) + pyuria + bacteriuria. Urine culture confirms organism and susceptibility.

Labs

• Urinalysis with microscopy — pyuria, bacteriuria, WBC casts (specific for upper tract), nitrites, leukocyte esterase
• Urine culture and susceptibility — ALWAYS obtain (vs cystitis where culture is optional)
• Blood cultures × 2 if febrile, septic, hospitalized, immunocompromised, or pregnant
• CBC — leukocytosis with left shift
• BMP — assess renal function, electrolytes
• Lactate, procalcitonin if sepsis suspected
• Beta-hCG in reproductive-age women

Imaging

• Imaging not required in most uncomplicated pyelonephritis with prompt improvement
• CT abdomen/pelvis with contrast if: failure to improve after 48-72 h of appropriate antibiotics, sepsis, suspected obstruction or abscess, recurrent pyelonephritis, atypical course, history of stones, men
• Renal ultrasound — first-line in pregnancy and children, or if CT contrast contraindicated
• Findings: enlarged kidney, perinephric stranding, focal wedge-shaped hypoenhancement, abscess, hydronephrosis

First-line

• Outpatient (mild, hemodynamically stable, tolerating oral, no obstruction):
• Fluoroquinolone (pyelo) — ciprofloxacin 500 mg PO BID × 7 days or levofloxacin 750 mg PO daily × 5 days — first-line if local resistance <10%
• TMP-SMX DS PO BID × 14 days if susceptible (avoid empiric if resistance unknown)
• Consider initial single dose of long-acting IV antibiotic (ceftriaxone 1 g IV, ertapenem 1 g IV) followed by oral therapy
• Avoid nitrofurantoin and fosfomycin (do NOT achieve adequate parenchymal levels for pyelonephritis)
• Inpatient (severe illness, sepsis, pregnancy, inability to tolerate oral, obstruction, suspected resistant organism):
• Ceftriaxone 1-2 g IV daily, or piperacillin-tazobactam, or carbapenem (meropenem, imipenem, ertapenem) if ESBL risk
• Add ampicillin if Enterococcus suspected (or empiric if catheter-related)
• Aminoglycoside (gentamicin) addition in critically ill or if pseudomonal coverage needed
• Transition to oral once culture susceptibilities available and patient improving; total course 7-14 days

Second-line / adjunct

• Drain obstruction if present — percutaneous nephrostomy or ureteral stent — urgent if obstructed infected system
• Drain abscess if >3-5 cm — percutaneous drainage
• Aggressive IV fluid resuscitation, vasopressors as needed for septic shock
• Antipyretics and analgesics
• Pregnancy: hospitalize for IV antibiotics; ceftriaxone, ampicillin-gentamicin, or cefepime; total 10-14 days
• Reassess at 48-72 h — failure to improve warrants imaging to exclude obstruction or abscess