From the Guidelines
Pyelonephritis is a bacterial infection of the kidney and renal pelvis that occurs when bacteria ascend from the lower urinary tract or, less commonly, spread through the bloodstream to the kidneys, with the most common causative organism being Escherichia coli (E. coli), accounting for approximately 80% of cases 1.
Pathophysiology
The infection typically begins when uropathogens colonize the periurethral area and ascend through the urethra to the bladder, causing cystitis. From there, bacteria can travel up the ureters to the kidneys. These bacteria possess virulence factors such as adhesins (P fimbriae) that allow them to attach to uroepithelial cells, preventing bacterial washout during urination. Once in the kidney, bacteria trigger an inflammatory response with neutrophil infiltration, causing tissue damage, microabscess formation, and potential scarring. The infection can lead to tubular obstruction from inflammatory debris and edema, impairing renal function.
Risk Factors
Risk factors include urinary tract abnormalities, vesicoureteral reflux, urinary obstruction, pregnancy, diabetes, and immunosuppression. If left untreated, pyelonephritis can progress to renal abscess formation, sepsis, or chronic kidney disease due to permanent parenchymal damage and scarring 1.
Clinical Presentation
The clinical presentation of pyelonephritis can range from mild flank pain with low-grade or no fever to septic shock, and up to 20% of patients lack bladder symptoms. In patients with flank pain or tenderness, without or with voiding symptoms, without or with fever, and with a urinalysis showing pyuria and/or bacteriuria, pyelonephritis is an appropriate presumptive diagnosis 1.
Diagnosis
Urinalysis, including assessment of white and red blood cells and nitrite, is recommended for routine diagnosis 1. In addition, a urine culture and antimicrobial susceptibility testing should be performed in all cases of pyelonephritis. Evaluation of the upper urinary tract via ultrasound should be performed to rule out urinary tract obstruction or renal stone disease in patients with a history of urolithiasis, renal function disturbances or a high urine pH 1.
Treatment
The treatment of pyelonephritis should be based on local resistance patterns and the severity of illness at presentation, with fluoroquinolones and cephalosporins being the only antimicrobial agents that can be recommended for oral empiric treatment of uncomplicated pyelonephritis 1. Patients with uncomplicated pyelonephritis requiring hospitalization should be treated initially with an intravenous antimicrobial regimen, such as a fluoroquinolone, an aminoglycoside (with or without ampicillin), or an extended-spectrum cephalosporin or penicillin 1.
From the Research
Pathophysiology of Pyelonephritis
- Pyelonephritis is a bacterial infection of the renal parenchyma, commonly caused by Escherichia coli 2, 3, 4.
- The infection can lead to severe complications if left untreated, and empirical antibiotic therapy should be initiated promptly 2, 4.
- The choice of antibiotic therapy depends on various factors, including the severity of the infection, patient's medical history, and local resistance patterns 2, 3, 4, 5.
Risk Factors and Complications
- Certain factors can increase the risk of developing severe sepsis or septic shock in patients with acute complicated pyelonephritis, including age > 65 years, urinary instrumentation, lack of mictional syndrome, and bacteremia 6.
- The prevalence of severe sepsis and septic shock in patients with acute complicated pyelonephritis is high, with crude and attributable mortality rates of 17.7% and 11.7%, respectively 6.
- Patients with severe sepsis or septic shock require immediate treatment and admission to a hospital 6.
Treatment Options
- Oral fluoroquinolones, such as ciprofloxacin and levofloxacin, are effective in treating acute uncomplicated pyelonephritis, with symptoms resolving within 5-7 days in about 96% of patients 2.
- Injectable third-generation cephalosporins, such as ceftriaxone, are also effective in treating pyelonephritis, especially in patients with severe infections or those who are unable to take oral medications 2, 3, 4.
- The choice of antibiotic therapy should be guided by susceptibility testing results and local resistance patterns to minimize the risk of treatment failure and antibiotic resistance 2, 3, 4, 5.