Njurbäckeninfektion

Njurbäckeninfektion, known in medical terms as pyelonephritis, is an infection of the kidney pelvis and renal parenchyma. It is an upper urinary tract infection that can be classified as uncomplicated or complicated by factors such as urinary tract obstruction, kidney stones, catheterization, pregnancy, diabetes, or compromised immune function. Most cases arise from ascending infection from the lower urinary tract.

The most common causative organism is Escherichia coli, but other bacteria such as Klebsiella, Proteus, Enterococcus, and, in healthcare-associated cases, Pseudomonas aeruginosa can also be responsible. Risk factors include female sex, pregnancy, urinary tract abnormalities, urinary retention, recurrent urinary tract infections, and recent instrumentation.

Typical symptoms include fever, chills, flank or abdominal pain, nausea and vomiting, and sometimes dysuria or urinary frequency. In older adults, presentations may be more vague with malaise or confusion. Diagnosis is based on clinical suspicion supported by urinalysis showing pyuria and bacteriuria, and urine culture to identify the organism and its sensitivities. Blood cultures may be obtained if fever is high or systemic infection is suspected. Imaging, usually ultrasound or computed tomography, is reserved for complicated cases, suspected obstruction, failure to respond to treatment, or in specific populations such as pregnant individuals.

Treatment depends on severity and context. Uncomplicated cases in healthy adults may be managed with oral antibiotics for about 5–7 days, using agents active against the identified organism (for example, trimethoprim-sulfamethoxazole or a fluoroquinolone, if susceptible). Nitrofurantoin is not appropriate for pyelonephritis. Complicated cases or severe illness require hospital admission and intravenous antibiotics (for example, ceftriaxone or piperacillin-tazobactam) followed by oral therapy. Adequate hydration and addressing underlying risk factors are important. Prognosis is generally good with timely treatment, though complications such as sepsis, renal abscess, or renal scarring can occur in some patients. Prevention focuses on prompt treatment of lower urinary tract infections and management of predisposing conditions.