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Renal & Urinary System

Acute Pyelonephritis

Infection and inflammation of the kidney parenchyma and renal pelvis (upper urinary tract), usually resulting from ascending bacterial infection from the bladder.

Also known as: Kidney Infection, Upper UTI

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Referral and warning signs

When to refer

Hospital admission (HC3/HC4/H) required for severe cases, sepsis, vomiting, pregnancy, significant co-morbidities, suspected obstruction/complication. Referral to Urology/Nephrology if: Obstructive cause identified. Recurrent pyelonephritis. Renal abscess requiring drainage. Failure to respond to appropriate antibiotics within 72 hours.

Red flags

  • Signs of sepsis (hypotension, tachycardia, altered mental status, high fever/hypothermia)
  • Severe flank pain, vomiting, inability to tolerate oral intake
  • Oliguria / Signs of AKI
  • Known urinary tract obstruction or stone
  • Pregnancy
  • Failure to improve after 48-72 hours of appropriate antibiotics

Signs and symptoms

  • Fever (often high, >38°C)
  • Chills / Rigors
  • Flank pain or tenderness (costovertebral angle - CVA tenderness).
  • Nausea, vomiting.
  • Malaise, fatigue.
  • May or may not have associated lower UTI symptoms (dysuria, frequency, urgency).
  • Symptoms may be atypical in infants (fever, poor feeding, vomiting) and elderly (confusion, falls, general decline).

Risk factors

  • Untreated or recurrent cystitis
  • Female gender
  • Pregnancy
  • Urinary tract obstruction (stones, BPH, strictures, tumours)
  • Vesicoureteral reflux (VUR) - especially in children
  • Urinary catheterization or instrumentation
  • Diabetes mellitus
  • Immunosuppression
  • Neurogenic bladder / Incomplete bladder emptying
  • Structural abnormalities of the urinary tract

Diagnosis

Clinical assessment

Diagnosis based on clinical presentation of fever, flank pain/CVA tenderness, +/- lower UTI symptoms. Assess for signs of sepsis/complicated infection. Differential diagnosis: Appendicitis, Cholecystitis, Pancreatitis, Diverticulitis, Pneumonia (lower lobe), Renal colic, Pelvic Inflammatory Disease.

Investigations

  • Urinalysis (MSU): Pyuria (WBCs), Bacteriuria, +/- Haematuria, Leucocyte esterase (+), Nitrites (+/-). White blood cell casts are suggestive but rarely seen.
  • Urine Culture & Sensitivity (MSU): Essential to confirm bacteriuria and guide antibiotic therapy.
  • Blood tests: CBC (leucocytosis), U&Es, Creatinine (assess renal function, dehydration), Blood cultures (obtain if systemic signs/sepsis suspected, or hospitalized).
  • Imaging (Not routine for uncomplicated cases, consider if severe, persistent fever >48-72h, recurrent, suspected obstruction/abscess):
  • - Kidney Ultrasound: Rule out obstruction (hydronephrosis), stones, abscess.
  • - CT Scan (Abdomen/Pelvis with contrast): More sensitive for detecting complications (abscess, emphysematous pyelonephritis), obstruction, anatomical abnormalities.

Diagnostic criteria

Clinical syndrome (fever, flank pain) + Evidence of UTI (positive urinalysis +/- positive urine culture).

Management

Non-pharmacological management

  • Adequate hydration (oral or IV).
  • Hospitalization often required for moderate/severe cases, inability to tolerate oral intake/meds, pregnancy, significant co-morbidities, suspected complications, or diagnostic uncertainty.
  • Monitor vital signs, urine output.

Pharmacological treatment

  • Antibiotics: Choice based on severity, local resistance patterns, and culture results when available. Longer duration than cystitis needed.
  • - Outpatient (Mild-moderate, able to tolerate oral, reliable follow-up): Fluoroquinolones (e.g., Ciprofloxacin 500mg PO BID or 750mg PO OD for 7-10 days) OR Trimethoprim-Sulfamethoxazole (if susceptible) OR Cephalosporins (e.g., Cefixime, Cefpodoxime). Initial IV dose (e.g., Ceftriaxone 1g) often given.
  • - Inpatient (Severe illness, sepsis, unable to take oral, pregnant, complicated): IV antibiotics initially.
  • - UCG Rec: IV Ceftriaxone 1g daily (Child 50-80mg/kg daily).
  • - UCG Alternative: IV Gentamicin 5-7mg/kg daily +/- IV Ampicillin 2g Q6H.
  • - Other options: Piperacillin/Tazobactam, Carbapenems (for resistant organisms/severe sepsis).
  • - Switch to appropriate oral antibiotic based on clinical improvement and culture results to complete total course (typically 10-14 days).
  • Analgesia/Antipyretics: Paracetamol.
  • Antiemetics if needed.

Monitoring

Monitor clinical response (fever, pain, vital signs) within 48-72 hours. Monitor renal function if impaired or using potentially nephrotoxic agents. Follow up urine culture usually not needed if clinically resolved, but consider in pregnancy or recurrent cases.

Complications

  • Sepsis / Septic shock
  • Acute Kidney Injury (AKI)
  • Renal abscess / Perinephric abscess
  • Papillary necrosis
  • Emphysematous pyelonephritis (gas formation - diabetic emergency)
  • Chronic pyelonephritis / Renal scarring -> CKD (esp. if recurrent/obstructed/VUR)
  • Pyonephrosis (pus in obstructed collecting system)

Prevention

  • Prompt treatment of cystitis.
  • Manage underlying risk factors (obstruction, reflux, diabetes control).
  • Adequate hydration.
  • Good hygiene practices.

Patient education

  • Explain kidney infection and importance of completing full antibiotic course.
  • Need for adequate hydration.
  • Pain/fever management.
  • Recognizing signs of worsening illness or complications requiring return.
  • Importance of follow-up if recommended.
  • Prevention strategies for future UTIs.

Uganda-specific notes

Common cause of fever and flank pain. Empirical treatment often necessary due to limited culture access. Ceftriaxone and Gentamicin +/- Ampicillin commonly used inpatient. Consider underlying TB or Schistosomiasis in relevant contexts. Rule out malaria.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 7, Section 7.2.2

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