Acute pyelonephritis | Medical Science Optional Notes for UPSC PDF Download

Acute pyelonephritis-Etiology

Pyelonephritis is an infection of the renal pelvis and parenchyma.

Pathogens

• Most commonly Enterobacteriaceae (gram-negative rods)
• Escherichia coli (~ 75-90% of cases)
• Pseudomonas aeruginosa
• Klebsiella pneumoniae
• Proteus mirabilis
• Gram-positive bacteria (e.g., Enterococcus faecalis, Staphylococcus aureus)
• Candida infection (esp. in immunocompromised patients) is possible

Risk Factors

• Most common in women because they have shorter urethras
• Pregnancy (presents between 20-28 weeks, more commonly affects the right kidney because of dilated right ureter, might present with premature labor)
• Urinary tract obstruction
• Foreign bodies (e.g., catheters or other urologic instrumentation)
• Anatomical abnormalities (e.g., benign prostatic hyperplasia, vesicoureteral reflux, nephrolithiasis, ureteral strictures)
• Cystitis
• Recent administration of antibiotics (possible antibiotic resistance)
• Immunosuppression (e.g., HIV, diabetes)
• Acute kidney injury

Acute pyelonephritis-Presentation

Clinical Presentation

• Acute pyelonephritis is indicated by symptoms such as fever (temperature >38°C), rigors, flank pain, nausea and vomiting, and costovertebral angle tenderness.
• The severity of symptoms can range from a mild illness to a severe condition involving septic shock, renal failure, and a life-threatening situation.
• Pyuria, the presence of pus in the urine, is almost always observed.

Differentiation and Complications

• It is crucial to distinguish between complicated and uncomplicated pyelonephritis due to differing management approaches.
• Complicated pyelonephritis is characterized by the following factors:
  • Urinary tract abnormalities (e.g., obstruction, indwelling catheter)
  • Recent surgery on the urinary tract
  • Renal impairment
  • Immunosuppression and/or severe comorbidities
  • High-risk patients despite an uncomplicated clinical presentation (e.g., elderly)

Complications

• Urosepsis: Systemic infection originating from a urinary tract infection.
• Perinephric Abscess: Collection of pus in the tissue surrounding the kidney.
• Papillary Necrosis: Degeneration of renal papillae, often associated with severe pyelonephritis.
• Emphysematous Pyelonephritis: Severe infection causing the presence of gas within the renal parenchyma.
• Renal Abscess: Formation of a localized collection of pus within the kidney.
• Recurrent Bacterial Pyelonephritis:
  • If recurrence is due to the same organism despite adequate treatment, extend the antibiotic course for 6 weeks.
  • If a new pathogen is identified, adjust the antibiotic and treat for 2 weeks.
• Atrophic Kidneys: Reduction in the size of the kidneys.
• End-Stage Renal Disease (ESRD): Occurs if both kidneys are affected, the patient has a single kidney, or the other kidney has been damaged by a different pathology.

Acute pyelonephritis-Diagnosis

• Urinalysis: Examination of urine for pyuria, leucocyte casts, bacteriuria, and hematuria.
• Inflammatory Markers: Elevated levels of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR).
• Cultures: Collection of urine and blood samples for microbial cultures.
• Imaging:
  • Renal Ultrasound: Detects urinary obstruction, calculi, or abscess.
  • CT KUB (Kidneys, Ureters, Bladder): Identifies hemorrhage, renal, and bladder stones.
  • Retrograde Cystourethrogram: Useful for detecting vesicoureteral reflux (VUR).

Acute pyelonephritis-Management

Emphysematous pyelonephritis

• Life-Threatening Variant:
  • Description: Fulminant and necrotizing.
  • Causative Organisms: Gas-forming organisms such as E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis.
  • Risk Factors: Mainly associated with diabetes (90%) and urinary tract obstruction.
• Diagnosis:
  • Gas presence can be detected through imaging techniques such as X-ray, ultrasound (USG), or computed tomography (CT).
• Management:
  • Specific management strategies are not provided in the original text.

Chronic pyelonephritis

Xanthogranulomatous Pyelonephritis (Chronic Pyelonephritis)

• Etiology: Unknown.
• Severe chronic destructive granulomatous inflammation affects the renal parenchyma.
• Associated with urinary tract obstruction and infection.
• Predominantly observed in middle-aged women, displaying chronic symptoms such as flank pain, pyrexia, malaise, and a palpable mass.
• Differential diagnosis includes renal cell carcinoma.
• Diagnosis:
  • Culture typically reveals E. coli, Gram-negative bacilli, or S. aureus.
  • CT scans often indicate an enlarged, non-functioning kidney, the presence of calculi, low-density masses (xanthomatous tissue), and occasional involvement of adjacent structures.
• Histology:
  • Histological examination reveals lipid-laden foamy macrophages and multinucleated giant cells.
  • Gross examination displays large, irregular, yellow masses throughout the kidney.
• Treatment:
  • Nephrectomy is the recommended treatment.

Pyelonephritis (Acute/Chronic)

Q: What are the symptoms of acute pyelonephritis? Name the organisms that commonly cause acute pyelonephritis. List the antibiotics commonly used to treat severe pyelonephritis. (2012)