Kidney infection: flank pain, fevers, leukocytosis as a complication of urinary tract infections.
It may be more protean than is usually recognized: "Incomplete presentations were frequent: fever was absent in 6.7%, pain in 17.8%, lower urinary tract symptoms in 52.9%. At CT or MR scan the lesions were bilateral in 12.6%, multiple in 79.8% (Ref)."
More common in diabetics, patients with structural abnormalities (especially obstruction and stones) and first UTI.
E. coli and other gram negative rods predominate.
Does not have to be IV, in high risk patients (DM, can't take po, etc,) should start with iv and change to po when stable.
Five days may be enough in uncomplicated disease (PubMed).
Pregnant patients should get iv therapy
Expect fevers for 3 to 5 days; if fevers persist look for a perinephric abscess. Air in the kidney with pyelonephritis is called emphysematous pyelonephritis, often due to E. coli and often in diabetics, although any organism that makes gas can cause this. It may require nephrectomy, but aggressive percutaneous drainage or open I&D may prevent the need to wack out a kidney (PubMed).
Who to image? Patients with sepsis or septic shock, known or suspected stones, a urine pH of 7.0 or higher, or a new decrease in the gfr to 40 ml per minute or lower. And anyone who is clinically declining (PubMed).
Duration of therapy? While 14 days is the tradition, it depends on the host and the bug, but 5 (levofloxacin) to 7 (ciprofloxacin) to 10 (ciprofloxacin) days may suffice (PubMed) or 14 days of TMP/sulfa or a beta-lactam.
They can be treated as outpatient if uncomplicated, no underlying problems and can take po (NEJM).
Relevant links to my Medscape blog