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=== Bacterial nephritis === * Although the classic symptoms of acute onset of fever, chills, and flank pain are usually indicative of renal infection, some patients with these symptoms do not have renal infection. Conversely, significant renal infection may be associated with an insidious onset of nonspecific local or systemic symptoms, or it may be entirely asymptomatic. * '''The relationship between laboratory findings and the presence of renal infection often is poor.''' ** '''The presence of bacteriuria and pyuria, the hallmarks of UTI, are not predictive of renal infection'''. ** Conversely, patients with significant renal infection may have sterile urine if the ureter draining the kidney is obstructed or the infection is outside of the collecting system. ** The pathologic and radiologic criteria for diagnosing renal infection may also be misleading. * '''The effect of renal infection on renal function is varied.''' ** '''Acute or chronic pyelonephritis may transiently or permanently alter renal function, but non-obstructive pyelonephritis is no longer recognized as a major cause of renal failure.''' *** However, pyelonephritis, when associated with urinary tract obstruction or granulomatous renal infection, may lead rapidly to significant inflammatory complications, renal failure, or even death. ==== Acute Pyelonephritis ==== ===== Pathogens ===== * '''E. coli (80% of cases)''' constitutes a unique subgroup that possesses special virulence factors * More resistant species, such as Proteus, Klebsiella, Pseudomonas, Serratia, Enterobacter, or Citrobacter, should be suspected in patients who have recurrent UTIs, are hospitalized, have indwelling catheters, or have had recent urinary tract instrumentation. * Except for E. faecalis, S. epidermidis, and S. aureus, gram-positive bacteria rarely cause pyelonephritis. ====== Differential Diagnoses ====== # '''<span style="color:#ff0000">Acute appendicitis''' # '''<span style="color:#ff0000">Diverticulitis''' # '''<span style="color:#ff0000">Pancreatitis''' * '''Can cause a similar degree of pain, but the location of the pain often is different''' ===== Diagnosis and Evaluation ===== ====== History and Physical Exam ====== * The clinical spectrum ranges from gram-negative sepsis to cystitis with mild flank pain. * '''<span style="color:#ff0000">History''' **'''<span style="color:#ff0000">Signs and Symptoms''' ***'''<span style="color:#ff0000">Upper tract signs (3):''' ***#'''<span style="color:#ff0000">Abrupt onset of chills''' ***#'''<span style="color:#ff0000">Fever''' ***#'''<span style="color:#ff0000">Unilateral or bilateral flank or costovertebral angle pain and/or tenderness''' ***'''<span style="color:#ff0000">Often accompanied by LUTS such as (3):''' ***#'''<span style="color:#ff0000">Dysuria''' ***#'''<span style="color:#ff0000">Increased urinary frequency''' ***#'''<span style="color:#ff0000">Urgency''' * '''<span style="color:#ff0000">Physical Exam''' ** '''<span style="color:#ff0000">Tenderness to deep palpation in the costovertebral angle''' ====== Labs ====== * '''<span style="color:#ff0000">CBC''' ** May have leukocytosis with a predominance of neutrophils. * '''<span style="color:#ff0000">Urinalysis''' ** Usually reveals numerous WBCs, often in clumps, and bacterial rods or chains of cocci. ** '''The presence of large amounts of granular or leukocyte casts in the urinary sediment is suggestive of acute pyelonephritis.''' * '''<span style="color:#ff0000">Urine cultures''' ** '''Usually positive''' *** '''≈20% of patients have''' urine cultures with < 105 cfu/mL and therefore '''negative results on Gram staining of the urine''' * '''<span style="color:#ff0000">Blood cultures''' ** '''<span style="color:#ff0000">Should not be routinely obtained for the evaluation of uncomplicated pyelonephritis in females.''' *** '''Positive in ≈25% of cases of uncomplicated pyelonephritis in females and the majority replicate the urine culture and do not influence decisions regarding therapy.''' ** '''Should be performed in males and females with systemic toxicity or in those requiring hospitalization or with risk factors such as pregnancy''' '''Imaging''' * '''In patients with presumed uncomplicated pyelonephritis who will be managed as outpatients, initial radiologic evaluation can usually be deferred.''' ** However, if there is any reason to suspect a problem or if the patient will not have reasonable access to imaging if there should be no change in condition, renal US can rule out stones or obstruction. * '''In patients with known or suspected complicated pyelonephritis, CT provides excellent assessment of the status of the urinary tract and the severity and extent of the infection.''' *'''Renal US and CT are commonly used to evaluate patients initially for complicated UTIs or factors or to reevaluate patients who do not respond after 72 hours of therapy''' ===== Management ===== * '''Any substantial obstruction must be relieved expediently by the safest and simplest means.''' **An obstructed kidney has difficulty concentrating and excreting antimicrobial agents. *'''Antibiotics''' **'''Oral''' ***'''Options[https://www.nice.org.uk/guidance/ng111/documents/draft-guideline-2 §]''' ****Amoxicillin / Clavulanic acid 625mg PO TID x 7 days *****If a gram-positive organism is suspected, amoxicillin or amoxicillin/clavulanic acid is recommended ****Ciprofloxacin 500mg PO BID x 7 days ****Levofloxacin 500mg PO daily x 7 days ***Many physicians administer a single parenteral dose of an antimicrobial agent (ceftriaxone, gentamicin, or a fluoroquinolone) before initiating oral therapy. **'''IV''' ***'''Options§''' ****Ceftriaxone 1-2g IV q24h ****Ciprofloxacin 400mg IV TID ****Gentamicin 5-7mg/kg q24h *** For patients sufficiently ill to require hospitalization (high fever, high WBC count, vomiting, dehydration, evidence of sepsis), has complicated pyelonephritis, or fails to improve during the initial outpatient treatment period *** If gram-positive cocci are causative, ampicillin/sulbactam with or without an aminoglycoside is recommended. *'''Follow-up''' **'''Repeat urine cultures should be performed after 5-7 days of therapy and 10-14 days after discontinuing antimicrobial therapy to ensure that the urinary tract remains free of infections.''' ***10-30% of individuals with acute pyelonephritis relapse after a 14-day course of therapy. ***Patients who relapse usually are cured by a second 14-day course of therapy, but occasionally a 6-week course is necessary ==== Acute focal and multifocal bacterial pyelonephritis ==== * '''Also known as lobar nephronia''' * '''An uncommon, severe form of acute renal infection in which a heavy leukocyte infiltrate is confined to a single renal lobe (focal) or multiple lobes (multifocal).''' * '''Represents a midpoint on the spectrum between pyelonephritis and renal abscess''' * '''Clinical presentation is similar to that of patients with acute pyelonephritis but usually is more severe''' * ≈50% of patients are diabetic, and sepsis is common * '''The diagnosis must be made by radiologic examination (US or CT)''' * '''Management''' ** '''Includes hydration and IV antimicrobial agents for at least 7 days, followed by 7 days of oral antimicrobial therapy''' *** Failure to respond to antimicrobial therapy is an indication for appropriate studies to rule out obstructive uropathy, renal or perirenal abscess, renal carcinoma, or acute renal vein thrombosis ==== Renal Abscess ==== * A collection of purulent material confined to the renal parenchyma ===== Pathogens ===== * '''Majority caused by gram-negative organisms''' ===== Pathogenesis ===== * '''Ascending infection associated with tubular obstruction from prior infections or calculi appears to be the primary pathway for the establishment of gram-negative abscesses.''' ===== Diagnosis and Evaluation ===== * '''May present with fever, chills, abdominal or flank pain, and occasionally weight loss and malaise. The patient typically has marked leukocytosis.''' * '''CT is the diagnostic procedure of choice''' because it provides excellent delineation of the tissue. * CT- or US-guided needle aspiration may be necessary to differentiate an abscess from a hypervascular tumor. ===== Management ===== * '''<span style="color:#ff0000">Size</span>''' **'''<span style="color:#ff0000"><3-5 cm: IV antibiotics are appropriate in clinically stable patient</span>''' *** Antibiotics, if begun early enough in the course of the process, may obviate surgical procedures. ** '''<span style="color:#ff0000">≥5 cm: percutaneous drainage</span>''' * '''Patients should have serial examinations with US or CT until the abscess resolves''' ==== Perinephric abscess ==== * '''Usually results from rupture of an acute cortical abscess into the perinephric space or from hematogenous seeding from sites of infection.''' * Diabetes mellitus is present in ≈1/3rd of patients ===== Diagnosis and Evaluation ===== * '''The onset of symptoms is typically insidious. Symptoms are present for > 5 days in most patients''' * Perinephric abscess should be suspected in a patient with UTI and abdominal or flank mass or persistent fever after 4 days of antimicrobial therapy. * '''Factors that differentiate perinephric abscess and acute pyelonephritis (2):''' *# '''Most patients with uncomplicated pyelonephritis are symptomatic for < 5 days before hospitalization, whereas most with perinephric abscesses are symptomatic for > 5 days''' *# No patient with acute pyelonephritis remained febrile for longer than 4 days once appropriate antimicrobial agents were started. All patients with perinephric abscesses had a fever for at least 5 days, with a median of 7 days. ===== Management ===== * Antimicrobial agents should be immediately started upon diagnosis of perinephric abscess. * '''<span style="color:#ff0000">For small perinephric abscesses (<3 cm), antibiotics alone can appropriately treat immune-competent patients''' * '''For larger collections or those not responsive to initial antibiotic therapy, intervention is the next step in treatment.''' ** '''<span style="color:#ff0000">Unlike in renal abscesses, early drainage of abscesses > 3 cm in diameter is recommended'''. ** Once the perinephric abscess has been drained, the underlying problem must be dealt with. ==== Chronic pyelonephritis ==== * '''In patients without underlying renal or urinary tract disease, chronic pyelonephritis secondary to UTI is a rare disease and an even more rare cause of chronic renal failure'''. In patients with underlying functional or structural urinary tract abnormalities, however, chronic renal infection can cause significant renal impairment. * '''Diagnosis and Evaluation''' ** '''There are no symptoms of chronic pyelonephritis until it produces renal insufficiency, and then the symptoms are similar to those of any other form of chronic renal failure''' ** Similarly, urinary findings and the presence of renal infection correlate poorly. Bacteriuria and pyuria, the hallmarks of UTI, are not predictive of renal infection ** '''Imaging findings:''' **# '''Asymmetry and irregularity of the kidney outlines''' **# '''Blunting and dilation of ≥1 calyces''' **# '''Cortical scars at the corresponding site''' * Management of radiographic evidence of pyelonephritis should be directed at treating infection if present, preventing future infections, and monitoring and preserving renal function ==== Infected Hydronephrosis and Pyonephrosis ==== * Infected hydronephrosis is bacterial infection in a hydronephrotic kidney. * Pyonephrosis is infected hydronephrosis associated with suppurative destruction of the parenchyma of the kidney, in which there is total or nearly total loss of renal function * The patient is usually very ill, with high fever, chills, flank pain, and tenderness. * A previous history of urinary tract calculi, infection, or surgery is common ==== Emphysematous pyelonephritis ==== * '''An acute necrotizing parenchymal and peri-renal infection caused by gas-forming uropathogens''' * '''Pathogens''' ** '''E. coli is the most common cause of emphysematous pyelonephritis and emphysematous cystitis''' * '''Usually occurs in diabetic patients''' * '''Diagnosis and Evaluation''' ** '''Almost all patients display the classic triad of fever, vomiting, and flank pain''' ** '''Imaging''' *** '''The diagnosis is established radiographically by the presence of gas in the parenchyma or collecting system.''' **** '''A crescentic collection of gas over the upper pole of the kidney is more distinctive.''' **** As the infection progresses, gas extends to the perinephric space and retroperitoneum. **** '''This distribution of gas should not be confused with cases of emphysematous pyelitis in which air is in the collecting system of the kidney. Emphysematous pyelitis is secondary to a gas-forming bacterial UTI, often occurs in non-diabetic patients, is less serious, and usually responds to antimicrobial therapy.''' * '''Management''' ** '''Requires urgent management'''. *** '''Most patients are septic, and fluid resuscitation and broad-spectrum antimicrobial therapy are essential.''' ** '''If a kidney is obstructed, urinary diversion (stent or nephrostomy) must be instituted''' ** '''If the kidney is functioning, medical therapy can be considered.''' ** '''Indications for nephrectomy (2):''' **# '''Affected kidney is non-functioning and not obstructed''' because medical treatment alone is usually lethal **# '''Failure to improve after a few days of therapy'''
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