These recommendations are largely based on expert opinion and limited evidence of the risk factors for developing complications from acute pyelonephritis.

Absolute indications for hospital admission

• There is expert consensus to arrange admission for people with acute pyelonephritis who:
• Are unable to take fluid and medications [Neumann et al, 2008].
• Have signs of sepsis [Neumann et al, 2008].
• Fail to improve within 24 hours of starting antibiotics in primary care [HPA and Association of Medical Microbiologists, 2008].
• A number of experts recommend arranging admission for all pregnant women with acute pyelonephritis, for at least a short observation period, because of the risk of preterm labour and maternal renal complications [Ramakrishnan and Scheid, 2005].
• Experts from the Health Protection Agency recommend treatment with ertapenem, or other carbapenem, for frail elderly residents from care homes who have been recently hospitalized or who have recurrent urinary tract infection, because they are at increased risk of having a pathogen resistant to ciprofloxacin and cephalosporins [Livermore, Personal Communication, 2009]. Treatment requires hospital admission because this antibiotic is only available in an intravenous form and no other suitable oral alternative exists.

Relative indications for hospital admission

• Although experts recommend considering admission for people with a risk factor for developing a complication from acute pyelonephritis, CKS could find no specific criteria as to when to arrange admission for those with:
• Immunocompromise.
• A foreign body within the renal tract.
• Abnormalities of renal tract anatomy or function.
• Diabetes.
• Renal impairment.
• Advanced age.
• Serious complications from acute pyelonephritis can develop rapidly. It is therefore recommended that there should be a low threshold for arranging admission for people with risk factors.

Treatment in primary care

• People without signs of sepsis or risk factors for developing a complication of acute pyelonephritis have a good prognosis. Experts widely recommend treatment of these people in primary care [Ramakrishnan and Scheid, 2005].
• In the absence of any trial evidence, experts agree that people who are apyrexial and appear otherwise well can be considered to be at low risk for developing a serious complication from acute pyelonephritis, whether they have a risk factor or not [Solomon, Personal Communication, 2009; Wullt, Personal Communication, 2009].