Acute Pyelonephritis

Acute pyelonephritis is a suppurative inflammation of the kidney and the renal pelvis which is caused by bacterial infection.

Pathogenesis

Causative organisms

• Escherichia coli (most common)
• Proteus
• Klebsiella
• Enterobacter
• Staphylococci

Two pathways

Ascending infection

Ascending infection from the lower urinary tract is the most important and frequent route by which bacteria reach the kidney.

Hematogenous infection

Hematogenous infection through the bloodstream is often related with septicemia or infective endocarditis.

Risk factors

UTI most commonly happens in females. Following are important contributors -

• Short urethra- the distance between urethral opening and bladder is shorter in females as compared to males which increases chances of ascending infection from perineum and anus.
• Close proximity of urethra to anus- the anus and urethral opening are adjacent to each other in females, which can cause colonization by enteric bacteria.
• Trauma to the urethra during sexual intercourse is more common in females which facilitate the entry of bacteria into the urinary bladder and kidney.

Urinary stasis is another cause of bacterial colonization and proliferation in urinary bladder and kidney. Benign prostatic hyperplasia, stones and cancers may cause urinary outflow obstruction which leads to urinary stasis. It is perfect media for bacterial growth. In Pregnancy growing uterus pushes bladder and causes urinary stasis, hence UTI is very common in pregnant ladies.

Vesicoureteral reflux (VUR)

The reflux from bladder allows bacteria to ascend the ureter and, the renal pelvis. VUR results in residual urine and it favours bacterial overgrowth in ureter and renal pelvis.

It can be seen in-

• Congenital defect that results in incompetence of the ureterovesical valve.
• Acquired defect due to spinal cord injury or with bladder dysfunction secondary to diabetes.

Clinical features

• Flank pain
• Fever
• Chills
• Dysuria
• Urgency
• Frequency

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Acute pyelonephritis Complications - perinephric abscess, renal papillary necrosis, sepsis

Diagnosis

Clinical diagnosis and urine culture play central role.

• Urine analysis
• Neutrophils (Pyuria)
• Scattered RBC
• Bacteria and WBC cast
• Gold standard is clean catch urine culture with >100,000 bacteria/ml

Treatment

Oral (first-line treatment/ mild cases)

• Ciprofloxacin, levofloxacin
• Trimethoprim-Sulfamethoxazole

Parenteral (moderate cases)

• Ceftriaxone
• Ciprofloxacin, levofloxacin
• Aztreonam

Parenteral in severe cases

• Cefepime
• Piperacillin-tazobactam
• Meropenem

Revision today Hereditary Spherocytosis  

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