Pyelonephritis

Template:Short description Template:Use dmy dates Template:Cs1 config Template:Infobox medical condition (new) Pyelonephritis is inflammation of the kidney, typically due to a bacterial infection.<ref name=Lip2011>Template:Cite book</ref> Symptoms most often include fever and flank tenderness.<ref name=AFP2011/> Other symptoms may include nausea, burning with urination, and frequent urination.<ref name=AFP2011/> Complications may include pus around the kidney, sepsis, or kidney failure.<ref name=Lip2011/>

It is typically due to a bacterial infection, most commonly Escherichia coli.<ref name=AFP2011/> Risk factors include sexual intercourse, prior urinary tract infections, diabetes, structural problems of the urinary tract, and spermicide use.<ref name=AFP2011/><ref name=Lip2011/> The mechanism of infection is usually spread up the urinary tract.<ref name=AFP2011/> Less often infection occurs through the bloodstream.<ref name=NIH2017>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Diagnosis is typically based on symptoms and supported by urinalysis.<ref name=AFP2011/> If there is no improvement with treatment, medical imaging may be recommended.<ref name=AFP2011/>

Pyelonephritis may be preventable by urination after sex and drinking sufficient fluids.<ref name=NIH2017/> Once present it is generally treated with antibiotics, such as ciprofloxacin or ceftriaxone.<ref name=Pre2014>Template:Cite journal</ref><ref>Template:Cite journal</ref> Those with severe disease may require treatment in hospital.<ref name=AFP2011/> In those with certain structural problems of the urinary tract or kidney stones, surgery may be required.<ref name=NIH2017/><ref name=Lip2011/>

Pyelonephritis affects about 1 to 2 per 1,000 women each year and just under 0.5 per 1,000 males.<ref name=Fer2018>Template:Cite book</ref><ref>Template:Cite book</ref> Young adult females are most often affected, followed by the very young and old.<ref name=AFP2011>Template:Cite journal</ref> With treatment, outcomes are generally good in young adults.<ref name=Lip2011/><ref name=Fer2018/> Among people over the age of 65 the risk of death is about 40%, though this depends on the health of the elderly person, the precise organism involved, and how quickly they can get care through a provider or in hospital.<ref name=Fer2018/> Template:TOC limit

Signs and symptoms

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Signs and symptoms of acute pyelonephritis generally develop rapidly over a few hours or a day. It can cause high fever, pain on passing urine, and abdominal pain that radiates along the flank towards the back. There is often associated vomiting.<ref name=Ramakrishnan2005>Template:Cite journal</ref>

Chronic pyelonephritis causes persistent flank or abdominal pain, signs of infection (fever, unintentional weight loss, malaise, decreased appetite), lower urinary tract symptoms and blood in the urine.<ref name=Korkes2008>Template:Cite journal</ref> Chronic pyelonephritis can in addition cause fever of unknown origin. Furthermore, inflammation-related proteins can accumulate in organs and cause the condition AA amyloidosis.<ref name=Herrera2007>Template:Cite book</ref>

Physical examination may reveal fever and tenderness at the costovertebral angle on the affected side.<ref name=Weiss2007>Template:Cite book</ref>

Causes

Most cases of community-acquired pyelonephritis are due to bowel organisms that enter the urinary tract. Common organisms are E. coli (70-80%) and Enterococcus faecalis. Hospital-acquired infections may be due to coliform bacteria and enterococci, as well as other organisms uncommon in the community (e.g., Pseudomonas aeruginosa and various species of Klebsiella). Most cases of pyelonephritis start off as lower urinary tract infections, mainly cystitis and prostatitis.<ref name=Ramakrishnan2005/> E. coli can invade the superficial umbrella cells of the bladder to form intracellular bacterial communities (IBCs), which can mature into biofilms. These biofilm-producing E. coli are resistant to antibiotic therapy and immune system responses, and present a possible explanation for recurrent urinary tract infections, including pyelonephritis.<ref name=Hultgren2011>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Risk is increased in the following situations:<ref name=Ramakrishnan2005/><ref name=Scholes2005>Template:Cite journal</ref>

• Mechanical: any structural abnormalities in the urinary tract, vesicoureteral reflux (urine from the bladder flowing back into the ureter), kidney stones, urinary tract catheterization, ureteral stents or drainage procedures (e.g., nephrostomy), pregnancy, neurogenic bladder (e.g., due to spinal cord damage, spina bifida or multiple sclerosis) and prostate disease (e.g., benign prostatic hyperplasia) in men
• Constitutional: diabetes mellitus, immunocompromised states
• Behavioral: change in sexual partner within the last year, spermicide use
• Positive family history (close family members with frequent urinary tract infections)

Diagnosis

Laboratory examination

Analysis of the urine may show signs of urinary tract infection. Specifically, the presence of nitrite and white blood cells on a urine test strip in patients with typical symptoms are sufficient for the diagnosis of pyelonephritis, and are an indication for empirical treatment. Blood tests such as a complete blood count may show neutrophilia. Microbiological culture of the urine, with or without blood cultures and antibiotic sensitivity testing are useful for establishing a formal diagnosis,<ref name=Ramakrishnan2005/> and are considered mandatory.<ref name=Gupta2011>Template:Cite journal</ref>

Imaging studies

If a kidney stone is suspected (e.g. on the basis of characteristic colicky pain or the presence of a disproportionate amount of blood in the urine), a kidneys, ureters, and bladder x-ray (KUB film) may assist in identifying radioopaque stones.<ref name=Ramakrishnan2005/> Where available, a noncontrast helical CT scan with 5Template:Nbspmillimeter sections is the diagnostic modality of choice in the radiographic evaluation of suspected nephrolithiasis.<ref name=Pearle2007>Template:Cite book</ref><ref name=SmithCentennial2000>Template:Cite journal</ref><ref name=Fang2009>Template:Cite book</ref> All stones are detectable on CT scans except very rare stones composed of certain drug residues in the urine.<ref name=Pietrow2006>Template:Cite journal</ref> In patients with recurrent ascending urinary tract infections, it may be necessary to exclude an anatomical abnormality, such as vesicoureteral reflux or polycystic kidney disease. Investigations used in this setting include kidney ultrasonography or voiding cystourethrography.<ref name=Ramakrishnan2005/> CT scan or kidney ultrasonography is useful in the diagnosis of xanthogranulomatous pyelonephritis; serial imaging may be useful for differentiating this condition from kidney cancer.<ref name=Korkes2008/>

File:Ultrasonography of acute pyelonephritis.jpg

Acute pyelonephritis with increased cortical echogenicity and blurred delineation of the upper pole<ref name=Hansen2015>Content initially copied from: Template:Cite journalTemplate:Creative Commons text attribution notice</ref>

Ultrasound findings that indicate pyelonephritis are enlargement of the kidney, edema in the renal sinus or parenchyma, bleeding, loss of corticomedullary differentiation, abscess formation, or an areas of poor blood flow on doppler ultrasound.<ref name="CraigWagner2008">Template:Cite journal</ref> However, ultrasound findings are seen in only 20–24% of people with pyelonephritis.<ref name="CraigWagner2008"/>

A DMSA scan is a radionuclide scan that uses dimercaptosuccinic acid in assessing the kidney morphology. It is nowTemplate:When the most reliable test for the diagnosis of acute pyelonephritis.<ref>Template:Cite journal</ref>

Classification

Acute pyelonephritis

Acute pyelonephritis is an exudative purulent localized inflammation of the renal pelvis (collecting system) and kidney. The kidney parenchyma presents in the interstitium abscesses (suppurative necrosis), consisting in purulent exudate (pus): neutrophils, fibrin, cell debris and central germ colonies (hematoxylinophils). Tubules are damaged by exudate and may contain neutrophil casts. In the early stages, the glomerulus and vessels are normal. Gross pathology often reveals pathognomonic radiations of bleeding and suppuration through the renal pelvis to the renal cortex.Template:Citation needed

Chronic pyelonephritis

Chronic pyelonephritis implies recurrent kidney infections and can result in scarring of the renal parenchyma and impaired function, especially in the setting of obstruction. A perinephric abscess (infection around the kidney) and/or pyonephrosis may develop in severe cases of pyelonephritis.<ref name=Griebling2007>Template:Cite book</ref>

• UOTW 72 - Ultrasound of the Week 1.webm

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• UOTW 72 - Ultrasound of the Week 2.webm

  Abscess around both kidneys<ref name=UOTW72/>

• Ultrasonography of chronic pyelonephritis with reduced kidney size and focal cortical thinning.jpg

  Chronic pyelonephritis with reduced kidney size and focal cortical thinning. Measurement of kidney length on the US image is illustrated by ‘+’ and a dashed line.<ref name=Hansen2015/>

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.<ref name=Malek1978>Template:Cite journal</ref> 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.<ref name=Korkes2008/>

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.<ref name=Schooff2005>Template:Cite journal</ref> In children at risk for recurrent urinary tract infections, not enough studies have been performed to conclude prescription of long-term antibiotics has a net positive benefit.<ref>Template:Cite journal</ref> Cranberry products and drinking cranberry juice appears to provide a benefit in decreasing urinary tract infections for certain groups of individuals.<ref>Template:Cite journal</ref>

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.<ref name=Fer2018/> As most cases of pyelonephritis are due to bacterial infections, antibiotics are the mainstay of treatment.<ref name=Fer2018/> The choice of antibiotic depends on the species and antibiotic sensitivity profile of the infecting organism, and may include fluoroquinolones, cephalosporins, aminoglycosides, or trimethoprim/sulfamethoxazole, either alone or in combination.<ref name=Gupta2011/>

Simple

A 2018 systematic review recommended the use of norfloxacin as it has the lowest rate of side effects with a comparable efficacy to commonly used antibiotics.<ref name="Cattrall Robinson Kirby 2018 pp. 2285–2291">Template:Cite journal</ref>

In people who do not require hospitalization and live in an area where there is a low prevalence of antibiotic-resistant bacteria, a fluoroquinolone by mouth such as ciprofloxacin or levofloxacin is an appropriate initial choice for therapy.<ref name=Fer2018/> In areas where there is a higher prevalence of fluoroquinolone resistance, it is useful to initiate treatment with a single intravenous dose of a long-acting antibiotic such as ceftriaxone or an aminoglycoside, and then continuing treatment with a fluoroquinolone. Oral trimethoprim/sulfamethoxazole is an appropriate choice for therapy if the bacteria is known to be susceptible.<ref name=Fer2018/> If trimethoprim/sulfamethoxazole is used when the susceptibility is not known, it is useful to initiate treatment with a single intravenous dose of a long-acting antibiotic such as ceftriaxone or an aminoglycoside. Oral beta-lactam antibiotics are less effective than other available agents for treatment of pyelonephritis.<ref name=Gupta2011/> Improvement is expected in 48 to 72 hours.<ref name=Fer2018/>

Complicated

People with acute pyelonephritis that is accompanied by high fever and leukocytosis are typically admitted to the hospital for intravenous hydration and intravenous antibiotic treatment. Treatment is typically initiated with an intravenous fluoroquinolone, an aminoglycoside, an extended-spectrum penicillin or cephalosporin, or a carbapenem. Combination antibiotic therapy is often used in such situations. The treatment regimen is selected based on local resistance data and the susceptibility profile of the specific infecting organism(s).<ref name=Gupta2011/>

During the course of antibiotic treatment, serial white blood cell count and temperature are closely monitored. Typically, the intravenous antibiotics are continued until the person has no fever for at least 24 to 48Template:Nbsphours, then equivalent antibiotics by mouth can be given for a total of two-week duration of treatment.<ref name=Starlin2005>Template:Cite book</ref> Intravenous fluids may be administered to compensate for the reduced oral intake, insensible losses (due to the raised temperature) and vasodilation and to optimize urine output. Percutaneous nephrostomy or ureteral stent placement may be indicated to relieve obstruction caused by a stone. Children with acute pyelonephritis can be treated effectively with oral antibiotics (cefixime, ceftibuten and amoxicillin/clavulanic acid) or with short courses (2 to 4Template:Nbspdays) of intravenous therapy followed by oral therapy.<ref name=Strohmeier2014>Template:Cite journal</ref> If intravenous therapy is chosen, single daily dosing with aminoglycosides is safe and effective.<ref name=Strohmeier2014/>

Fosfomycin can be used as an efficacious treatment for both UTIs and complicated UTIs including acute pyelonephritis. The standard regimen for complicated UTIs is an oral 3g dose administered once every 48 or 72 hours for a total of 3 doses or a 6 grams every 8 hours for 7 days to 14 days when fosfomycin is given in IV form.<ref name="Zhanel Zhanel Karlowsky 2020 pp. 1–11">Template:Cite journal</ref>

Treatment of xanthogranulomatous pyelonephritis involves antibiotics as well as surgery. Removal of the kidney is the best surgical treatment in the overwhelming majority of cases, although polar resection (partial nephrectomy) has been effective for some people with localized disease.<ref name=Korkes2008/><ref name=Rosi1986>Template:Cite journal</ref> Watchful waiting with serial imaging may be appropriate in rare circumstances.<ref name=Lebret2007>Template:Cite journal</ref>

Follow-up

If no improvement is made in one to two days post therapy, inpatients should repeat a urine analysis and imaging. Outpatients should check again with their doctor.<ref name="Johnson Russo pp. 48–59">Template:Cite journal</ref>

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 1-2 cases/10,000 require admission.<ref name=Czaja2007>Template:Cite journal</ref> Young women are most often affected. Infants and the elderly are also at increased risk, reflecting anatomical changes and hormonal status.<ref name=Czaja2007/> Xanthogranulomatous pyelonephritis is most common in middle-aged women.<ref name=Malek1978/> It can present somewhat differently in children, in whom it may be mistaken for Wilms' tumor.<ref name=Goodman1998>Template:Cite journal</ref>

Research

According to a 2015 meta analysis, vitamin A has been shown to alleviate renal damage and/or prevent renal scarring.<ref name="Zhang Chen Zhao 2016 pp. 373–379">Template:Cite journal</ref>

Terminology

The term is from Greek πύελο|ς pýelo|s, "basin" + νεφρ|ός nepʰrós, "kidney" + suffix -itis suggesting "inflammation".Template:Citation needed

A similar term is "pyelitis", which means inflammation of the renal pelvis and calyces.<ref>medilexicon.com Template:Webarchive</ref><ref>Using Medical Terminology: A Practical Approach 2006 p.723</ref> In other words, pyelitis together with nephritis is collectively known as pyelonephritis.Template:Citation needed

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.Template:Cn

External links

• Kidney Infection (Pyelonephritis) at the US National Institute of Diabetes and Digestive and Kidney Diseases