ACUTE PYELONEPHRITIS

Clinical Definition

This is a clinical diagnosis, made on the basis of fever, flank pain, and tenderness, often with an elevated white count. It may affect one or both kidneys. There are usually accompanying symptoms suggestive of a lower urinary tract infection (frequency, urgency, suprapubic pain, urethral burning or pain on voiding) that led to the ascending infection, which resulted in the subsequent acute pyelonephritis. The infecting organisms are commonly -Escherichia coli, enterococci (Streptococcus faecalis), Klebsiella, -Proteus, and Pseudomonas.

Urine culture is positive for bacterial growth, but the bacterial count may not always be above the 100,000 colony-forming units (cfu)/mL of urine, which is the strict de.nition for urinary infection. Thus, if you suspect a diagnosis of acute pyelonephritis from the symptoms of fever and flank pain, but there are only 1000cfu/mL, manage the case as acute pyelonephritis.

Investigation and Treatment

For those patients who have a fever but are not systemically unwell, outpatient management is reasonable. Culture the urine and start oral antibiotics according to your local antibiotic policy (which will be based on the likely infecting organisms and their likely antibiotic sensitivity). We use oral ciprofloxacin, 500mg b.i.d. for 10 days.

If the patient is systemically unwell, admit them to hospital culture urine and blood, and start intravenous fluids and intravenous antibiotics, again selecting the antibiotic according to your local antibiotic policy. We use i.v. ampicillin 1 g t.i.d. and gentamicin, 3 mg/kg as a once daily dose.

Arrange for a kidney and urinary bladder (KUB) x-ray and renal ultrasound, to see if there is an underlying upper tract abnormality (such a ureteric stone), unexplained hydronephrosis, or (rarely) gas surrounding the kidney (suggesting emphysematous pyelonephritis).

If the patient does not respond within 3 days to this regimen of appropriate intravenous antibiotics (confirmed on sensitivities), arrange for a CTU. The lack of response to treatment indicates that you are dealing with a pyonephrosis (i.e., pus in the kidney, which like any abscess will respond only to drainage), a perinephric abscess (which again will respond only to drainage), or emphysematous pyelonephritis. The CTU may demonstrate an obstructing ureteric calculus that may have been missed on the KUB x-ray, and ultrasound and will show a perinephric abscess if present. A pyonephrosis should be drained by insertion of a percutaneous nephrostomy tube. A perinephric abscess should also be drained by insertion of a drain percutaneously.

If the patient responds to i.v. antibiotics, change to an oral antibiotic of appropriate sensitivity when they become apyrexial, and continue this for approximately 10 to 14 days.