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Pyelonephritis

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Pyelonephritisis inflammation of thekidney,typically due to abacterial infection.[3]Symptoms most often includefeverandflank tenderness.[2]Other symptoms may includenausea,burning with urination,andfrequent urination.[2]Complications may includepus around the kidney,sepsis,orkidney failure.[3]

Pyelonephritis
Other namesKidney infection[1]
A color photomicrograph, demonstrating macrophages and giant cells in a case of xanthogranulomatous pyelonephritis.
CD68immunostainingon thisphotomicrographshowsmacrophagesandgiant cellsin a case of xanthogranulomatous pyelonephritis.
Pronunciation
SpecialtyInfectious disease,urology,nephrology
SymptomsFever,flank tenderness,nausea,burning with urination,frequent urination[2]
CausesBacterial infection[2]
Risk factorsSexual intercourse,priorurinary tract infections,diabetes,structural problems of theurinary tract,spermicideuse[2][3]
Diagnostic methodBased on symptoms and supported byurinalysis[2]
Differential diagnosisEndometriosis,pelvic inflammatory disease,kidney stones[2]
PreventionUrination after sex, drinking sufficient fluids[1]
MedicationAntibiotics (ciprofloxacin,ceftriaxone)[4]
FrequencyCommon[5]

It is typically due to a bacterial infection, most commonlyEscherichia coli.[2]Risk factors includesexual intercourse,priorurinary tract infections,diabetes,structural problems of theurinary tract,andspermicideuse.[2][3]The mechanism of infection is usually spread up theurinary tract.[2]Less often infection occurs through the bloodstream.[1]Diagnosis is typically based on symptoms and supported byurinalysis.[2]If there is no improvement with treatment,medical imagingmay be recommended.[2]

Pyelonephritis may be preventable by urination after sex and drinking sufficient fluids.[1]Once present it is generally treated withantibiotics,such asciprofloxacinorceftriaxone.[4][6]Those with severe disease may require treatment in hospital.[2]In those with certain structural problems of the urinary tract orkidney stones,surgery may be required.[1][3]

Pyelonephritis affects about 1 to 2 per 1,000 women each year and just under 0.5 per 1,000 males.[5][7]Young adult females are most often affected, followed by the very young and old.[2]With treatment, outcomes are generally good in young adults.[3][5]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.[5]

Signs and symptoms

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Diagram showing the typical location of pain[8]

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 associatedvomiting.[9]

Chronic pyelonephritis causes persistent flank or abdominal pain, signs of infection (fever,unintentional weight loss,malaise,decreased appetite),lower urinary tract symptomsandblood in the urine.[10]Chronic pyelonephritis can in addition causefever of unknown origin.Furthermore, inflammation-related proteins can accumulate in organs and cause the conditionAA amyloidosis.[11]

Physical examination may reveal fever and tenderness at the costovertebral angle on the affected side.[12]

Causes

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Most cases of community-acquired pyelonephritis are due to bowel organisms that enter the urinary tract. Common organisms areE. coli(70-80%) andEnterococcus faecalis.Hospital-acquired infectionsmay be due tocoliform bacteriaand enterococci, as well as other organisms uncommon in the community (e.g.,Pseudomonas aeruginosaand various species ofKlebsiella). Most cases of pyelonephritis start off as lower urinary tract infections, mainlycystitisandprostatitis.[9]E. colican invade thesuperficial umbrella cellsof the bladder to form intracellular bacterial communities (IBCs), which can mature intobiofilms.These biofilm-producingE. coliare resistant to antibiotic therapy and immune system responses, and present a possible explanation for recurrent urinary tract infections, including pyelonephritis.[13]Risk is increased in the following situations:[9][14]

Diagnosis

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Laboratory examination

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Analysis of the urinemay show signs of urinary tract infection. Specifically, the presence ofnitriteandwhite blood cellson aurine test stripin patients with typical symptoms are sufficient for the diagnosis of pyelonephritis, and are an indication forempirical treatment.Blood testssuch as acomplete blood countmay showneutrophilia.Microbiological cultureof the urine, with or withoutblood culturesandantibiotic sensitivity testingare useful for establishing a formal diagnosis,[9]and are considered mandatory.[15]

Imaging studies

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If a kidney stone is suspected (e.g. on the basis of characteristiccolicky painor the presence of a disproportionate amount of blood in the urine), akidneys, ureters, and bladder x-ray(KUB film) may assist in identifyingradioopaquestones.[9]Where available, a noncontrasthelical CT scanwith 5millimeter sections is the diagnostic modality of choice in the radiographic evaluation of suspected nephrolithiasis.[16][17][18]All stones are detectable on CT scans except very rare stones composed of certain drug residues in the urine.[19]In patients with recurrent ascending urinary tract infections, it may be necessary to exclude an anatomical abnormality, such as vesicoureteral reflux orpolycystic kidney disease.Investigations used in this setting includekidney ultrasonographyorvoiding cystourethrography.[9]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.[10]

Acute pyelonephritis with increased cortical echogenicity and blurred delineation of the upper pole[20]

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 ondoppler ultrasound.[21]However, ultrasound findings are seen in only 20–24% of people with pyelonephritis.[21]

ADMSA scanis a radionuclide scan that uses dimercaptosuccinic acid in assessing the kidney morphology. It is now[when?]the most reliable test for the diagnosis of acute pyelonephritis.[22]

Classification

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Acute pyelonephritis

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Acute pyelonephritis is anexudativepurulentlocalizedinflammationof therenal pelvis(collecting system) and kidney. Thekidney parenchymapresents in the interstitium abscesses (suppurativenecrosis), 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, theglomerulusand vessels are normal. Gross pathology often reveals pathognomonic radiations ofbleedingandsuppurationthrough the renal pelvis to therenal cortex.[citation needed]

Chronic pyelonephritis

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Chronic pyelonephritis implies recurrent kidney infections and can result inscarringof the renal parenchyma and impaired function, especially in the setting of obstruction. A perinephricabscess(infection around the kidney) and/orpyonephrosismay develop in severe cases of pyelonephritis.[23]

  • Abscess around both kidneys[24]
  • Abscess around both kidneys[24]
  • Chronic pyelonephritiswith reduced kidney size and focal cortical thinning. Measurement of kidney length on the US image is illustrated by ‘+’ and a dashed line.[20]
Xanthogranulomatous pyelonephritis
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Xanthogranulomatouspyelonephritis is an unusual form of chronic pyelonephritis characterized bygranulomatousabscessformation, severe kidney destruction, and a clinical picture that may resemblerenal cell carcinomaand other inflammatorykidney parenchymaldiseases. 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.[25]Microscopically,there are granulomas andlipid-ladenmacrophages(hence the termxantho-, which means yellow inancient Greek). It is found in roughly 20% of specimens from surgically managed cases of pyelonephritis.[10]

Prevention

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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-termpreventivetreatment with antibiotics, either daily or aftersexual activity.[26]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.[27]Cranberry products and drinkingcranberry juiceappears to provide a benefit in decreasing urinary tract infections for certain groups of individuals.[28]

Management

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In people suspected of having pyelonephritis, a urine culture andantibiotic sensitivitytest is performed, so therapy can eventually be tailored on the basis of the infecting organism.[5]As most cases of pyelonephritis are due to bacterial infections, antibiotics are the mainstay of treatment.[5]The choice of antibiotic depends on the species and antibiotic sensitivity profile of the infecting organism, and may includefluoroquinolones,cephalosporins,aminoglycosides,ortrimethoprim/sulfamethoxazole,either alone or in combination.[15]

Simple

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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.[29]

In people who do not require hospitalization and live in an area where there is a low prevalence ofantibiotic-resistantbacteria, a fluoroquinolone by mouth such asciprofloxacinorlevofloxacinis an appropriate initial choice for therapy.[5]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 asceftriaxoneor 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.[5]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. Oralbeta-lactam antibioticsare less effective than other available agents for treatment of pyelonephritis.[15]Improvement is expected in 48 to 72 hours.[5]

Complicated

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People with acute pyelonephritis that is accompanied by high fever andleukocytosisare typically admitted to the hospital for intravenous hydration and intravenous antibiotic treatment. Treatment is typically initiated with an intravenous fluoroquinolone, an aminoglycoside, anextended-spectrum penicillinor cephalosporin, or acarbapenem.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).[15]

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 48hours, then equivalent antibiotics by mouth can be given for a total of two-week duration of treatment.[30]Intravenous fluids may be administered to compensate for the reduced oral intake, insensible losses (due to the raised temperature) andvasodilationand to optimize urine output.Percutaneous nephrostomyor 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,ceftibutenandamoxicillin/clavulanic acid) or with short courses (2 to 4days) of intravenous therapy followed by oral therapy.[31]If intravenous therapy is chosen, single daily dosing with aminoglycosides is safe and effective.[31]

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.[32]

Treatment of xanthogranulomatous pyelonephritis involves antibiotics as well as surgery.Removal of the kidneyis the best surgical treatment in the overwhelming majority of cases, although polar resection (partial nephrectomy) has been effective for some people with localized disease.[10][33]Watchful waitingwith serial imaging may be appropriate in rare circumstances.[34]

Follow-up

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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.[35]

Epidemiology

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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.[36]Young women are most often affected. Infants and the elderly are also at increased risk, reflecting anatomical changes and hormonal status.[36]Xanthogranulomatous pyelonephritis is most common in middle-aged women.[25]It can present somewhat differently in children, in whom it may be mistaken forWilms' tumor.[37]

Research

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According to a 2015 meta analysis,vitamin Ahas been shown to alleviate renal damage and/or prevent renal scarring.[38]

Terminology

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The term is fromGreekπύελο|ςpýelo|s,"basin" + νεφρ|όςnepʰrós,"kidney"+ suffix-itissuggesting "inflammation".[citation needed]

A similar term is "pyelitis",which means inflammation of therenal pelvisandcalyces.[39][40]In other words, pyelitis together with nephritis is collectively known as pyelonephritis.[citation needed]

Etymology

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The wordpyelonephritisis formed by theGreekrootspyelo-fromπύελος(púelos)renal pelvisand nephro- fromνεφρός(nephrós)kidneytogether with the suffix -itis from -ῖτις(-itis) used inmedicineto indicatediseasesorinflammations.[citation needed]

References

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  39. ^medilexiconArchived6 January 2014 at theWayback Machine
  40. ^Using Medical Terminology: A Practical Approach 2006 p.723
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