ARTICLE
Acute pyelonephritis
A
cute pyelonephritis (APN) is an infection involving the kidney and renal pelvis. It represents a more severe form of infection than acute cystitis. The main features that define this syndrome include the triad of high fever, flank pain and tenderness. 80 % of cases may present with storage lower urinary tract symptoms such as burning, frequency and urgency. The causative uropathogen is isolated by urinalysis and culture and the most common bacteria isolated is E. coli and other gram-negative bacilli. APN may be mild or severe resulting in sepsis and shock. The severity is dependent on host factors e.g. presence of comorbidities, immune status, presence of obstruction and elderly patients (> 65 years).
Epidemiology APN is a common disease. The estimated global annual incidence is 10.5 to 25.9 million cases. It is common among females. Percentage of hospitalized patients is higher among children and elderly than among healthy- young women. APN is a major cause of mortality. This is largely due to associated sepsis and septic shock. It is estimated that APN accounts for 10% of septicemia cases. The total estimated cost is very high, however, recent introduction of observation units and change in practice have resulted in significant drop in rates of admission.
DIAGNOSIS OF APN IS DEPENDENT ON CLINICAL EVALUATION, URINE CULTURE AND SUPPORTIVE IMAGING MODALITIES. IT DEPENDS LARGELY ON ISOLATION OF BACTERIA BY URINE CULTURE. IMAGING IS, INITIALLY, RECOMMENDED IN PATIENTS WITH SEPSIS OR SEPTIC SHOCK, KNOWN OR SUSPECTED UROLITHIASIS, OR A NEW DECREASE IN THE GLOMERULAR FILTRATION RATE.
or no improvement by 24 to 48 hours arouses concern for potential complications that may warrant urgent intervention. These complications may include obstruction (e.g. stones), abscess formation, severe gas-forming infection (especially in diabetics), acute kidney injury (usually transient), advanced renal failure and recurrent pyelonephritis (rate of < 10%).
Diagnosis Diagnosis of APN is dependent on clinical evaluation, urine culture and supportive imaging modalities. It depends largely on isolation of bacteria by urine culture. Imaging is, initially, recommended in patients with sepsis or septic shock, known or suspected urolithiasis, or a new decrease in the glomerular filtration rate. Subsequent imaging is indicated in patients whose condition worsens or does not improve after 24 to 48 hours of therapy. Differential diagnosis for flank pain or tenderness, with or without fever, include: 1. Acute cholecystitis, 2. Appendicitis, 3. Urolithiasis, 4. Paraspinous muscle disorders, 5. Renal-vein thrombosis 6. Pelvic inflammatory disease.
Pathogens •
Risk factors APN occurs in around 3% of cases of cystitis and asymptomatic bacteriuria. It also complicates cases of urinary tract obstruction e.g. pregnancy, stones. Others include genetic predisposition, high bacterial load and virulence and presence of comorbid conditions e.g. diabetes.
Natural history APN occurs when enteric bacteria enter the bladder and ascend to the kidneys. Rarely, organisms such as Staphylococcus aureus or candida seed the kidneys hematogenously. With appropriate care, clinical manifestations usually decrease progressively. However, resolution may require up to 5 days. Worsening
JULY.AUG 2021
106
Among young healthy women, E. coli
