A perinephric abscess (infection around the kidney) and/or pyonephrosis may develop in severe cases of pyelonephritis. Xanthogranulomatous pyelonephritis
Xanthogranulomatous pyelonephritis is an unusual form of chronic pyelonephritis characterized by granulomatous abscess formation, severe kidney destruction, and a clinical picture that may resemble renal cell carcinoma and other inflammatory kidney parenchymal diseases. Most affected individuals present with recurrent fevers and urosepsis, anemia, and a painful kidney mass. Other common manifestations include kidney stones and loss of function of the affected kidney. Bacterial cultures of kidney tissue are almost always positive. Microscopically, there are granulomas and lipid-laden macrophages (hence the term xantho-, which means yellow in ancient Greek). It is found in roughly 20% of specimens from surgically managed cases of pyelonephritis. Prevention
In people who experience recurrent urinary tract infections, additional investigations may identify an underlying abnormality. Occasionally, surgical intervention is necessary to reduce the likelihood of recurrence. If no abnormality is identified, some studies suggest long-term preventive treatment with antibiotics, either daily or after sexual activity. In children at risk for recurrent urinary tract infections, not enough studies have been performed to conclude prescription of long-term antibiotics have a net positive benefit. Drinking cranberry juice does not appear to provide much if any benefit in decreasing urinary tract infections. Management
In people suspected of having pyelonephritis, a urine culture and antibiotic sensitivity test is performed, so therapy can eventually be tailored on the basis of the infecting organism. As most cases of pyelonephritis are due to bacterial infections, antibiotics are the mainstay of treatment.
Watchful waiting with serial imaging may be appropriate in rare circumstances. Follow-up
If no improvement is made in one to two days post therapy, inpatients should repeat an urine analysis and imaging. Outpatients should check again with their doctor. Epidemiology
There are roughly 12–13 cases annually per 10,000 population in women receiving outpatient treatment and 3–4 cases requiring admission. In men, 2–3 cases per 10,000 are treated as outpatients and 1– cases/10,000 require admission. Young women are most often affected. Infants and the elderly are also at increased risk, reflecting anatomical changes and hormonal status. Xanthogranulomatous pyelonephritis is most common in middle-aged women. It can present somewhat differently in children, in whom it may be mistaken for Wilms tumor. Research
According to a 2015 meta analysis, vitamin A has been shown to alleviate renal damage and/or prevent renal scarring. Terminology
The term is from Greek πύελο|ς pýelo|s, "basin" + νεφρ|ός nepʰrós, "kidney" + suffix -itis suggesting "inflammation".A similar term is "pyelitis", which means inflammation of the renal pelvis and calyces. In other words, pyelitis together with nephritis is collectively known as pyelonephritis. Etymology
The word pyelonephritis is formed by the Greek roots pyelo- from πύελος (púelos) renal pelvis and nephro- from νεφρός (nephrós) kidney together with the suffix -itis from -ῖτις (-itis) used in medicine to indicate diseases or inflammations. See also
Interstitial nephritis
Malakoplakia

References
External links

NIDDK
Atlas of Pathology