Материал: Oxford American Handbook of Urology ( PDFDrive )
152 CHAPTER 5 Infections and inflammatory conditions
Other forms of pyelonephritis
Emphysematous pyelonephritis
This is a rare, severe form of acute pyelonephritis caused by gas-forming organisms. It is characterized by high fever and abdominal pain, with radiographic evidence of gas within and around the kidney (on plain radiography or CT).
It usually occurs in diabetics and, in many cases, is precipitated by urinary obstruction by, for example, ureteral stones. The high glucose levels of the poorly controlled diabetic provide an ideal environment for fermentation by Enterobacteria, with carbon dioxide being produced during this process.
The presentation is usually as severe acute pyelonephritis (high fever and systemically very ill) that fails to respond within 2–3 days with conventional IV therapy. It is commonly caused by E. coli, less frequently by
Klebsiella and Proteus.
On KUB radiograph, crescentor kidney-shaped distribution of gas may been seen around the kidney. Renal ultrasonography often demonstrates strong focal echoes, indicating gas within the kidney. Intrarenal gas is seen on CT scan.
Patients with emphysematous pyelonephritis are usually very unwell and mortality is high. In selected cases, it can be managed conservatively, by IV antibiotics and fluids, percutaneous drainage, and careful control of diabetes. In those where sepsis is poorly controlled, emergency nephrectomy is sometimes required.
Xanthogranulomatous pyelonephritis
This is a severe renal infection usually, although not always, occurring in association with underlying renal calculi and renal obstruction. The severe infection results in destruction of renal tissue, leading to a non-functioning kidney. E. coli and Proteus are common causative organisms.
Macrophages full of fat become deposited around abscesses within the parenchyma of the kidney, hence the description xanthogranulomatous. The infection may be confined to the kidney or extend to the perinephric fat. The kidney becomes grossly enlarged and macroscopically contains yellowish nodules, pus, and areas of hemorrhagic necrosis.
It can be very difficult to distinguish the radiological findings from a renal cancer on imaging studies such as CT. Indeed, in many cases the diagnosis is made after nephrectomy for what was presumed to be a renal cell carcinoma.
Presentation is with acute flank pain, fever, and a tender flank mass. Bacteria (E. coli, Proteus) may be found on culture urine.
Renal ultrasonography shows an enlarged kidney containing echogenic material, and on CT, renal calcification is usually seen within the renal mass. Non-enhancing cavities are seen, containing pus and debris. On radioisotope scanning, there may be some or no function in the affected kidney.
OTHER FORMS OF PYELONEPHRITIS 153
On presentation these patients are usually started on IV fluids and antibiotics, as the constellation of symptoms and signs suggests infection. When imaging studies are done, the appearances often suggest the possibility of a renal cell carcinoma, and when signs of the acute infection have resolved, most patients undergo radical nephrectomy.
Only following pathological examination of the removed kidney will it become apparent that the diagnosis was one of infection (xanthogranulomatous pyelonephritis) rather than tumor.
Acute pyelonephritis, pyonephrosis, perinephric abscess, and emphysematous pyelonephritis—making the diagnosis
Maintaining a high degree of suspicion in all cases of presumed acute pyelonephritis is the single most important factor in allowing an early diagnosis of these complicated renal infections. If the patient is very ill, is diabetic, or has a history suggestive of stones, they may have something more than simple acute pyelonephritis.
Specifically ask about a history of sudden onset of severe flank pain a few days earlier, suggesting the possibility that a stone passed into the ureter, with later infection supervening. Renal imaging (KUB, ultrasound or CT urogram) should be done in all patients with suspected renal infection to rule out hydronephrosis, pyonephrosis, abscess or pus, or stones.
Clinical indicators suggesting a more complex form of renal infection are length of symptoms prior to treatment and time taken to respond to treatment. Most patients with uncomplicated acute pyelonephritis have been symptomatic for <5 days; often with a perinephric abscess patients are sick for >5 days prior to hospitalization.
Patients with acute pyelonephritis became afebrile within 2–3 days of treatment with an appropriate antibiotic, whereas those with perinephric abscesses remain febrile and systemically ill.
154 CHAPTER 5 Infections and inflammatory conditions
Chronic pyelonephritis
Chronic pyelonephritis is a confusing term. It can be a radiological or pathological diagnosis or a description. It is not a specifically clinically based diagnosis. The appearance, either pathologically or radiologically, is one of renal scarring. The scarring can be due to previous infection or it can occur from the long-term effects of reflux (with or without superimposed infection).
A child with reflux, particularly where there is reflux of infected urine, will develop reflux nephropathy (if bilateral, it may cause renal impairment or renal failure). If the child’s kidneys are examined radiologically (or pathologically if they are removed by nephrectomy), the radiologist or pathologist will describe the appearances as those of “chronic pyelonephritis.”
An adult may also develop radiological and pathological features of chronic pyelonephritis, due to the presence of reflux, or bladder outlet obstruction combined with high bladder pressures, again particularly when the urine is infected. This was a common occurrence in male patients with spinal cord injuries and detrusor-sphincter dyssynergia before the advent of effective treatments for this condition.
Essentially, chronic pyelonephritis is the end result of longstanding reflux (nonobstructive chronic pyelonephritis) or of obstruction (obstructive chronic pyelonephritis). These processes damage the kidneys, leading to scarring. The degree of damage and subsequent scarring is more marked if infection has supervened.
The scars are closely related to a deformed renal calyx. Distortion and dilatation of the calyces are due to scarring of the renal pyramids. These scars typically affect the upper and lower poles of the kidneys, because these sites are more prone to intrarenal reflux. The cortex and medulla in the region of a scar are thin. The kidney may be so scarred that it becomes small and atrophic. Scars can be seen radiologically on a renal ultrasound, an IVP, renal isotope scan, or a CT.
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156 CHAPTER 5 Infections and inflammatory conditions
Septicemia and urosepsis
Urosepsis is a form of sepsis that results from bacterial, fungal, or other infections originating from the genitourinary system Urosepsis accounts for approximately 25% of all sepsis cases and may develop from a community or nosocomial acquired urinary tract infection.
Bacteremia is the presence of pathogenic organisms in the blood stream. True rigors with fever and chills almost always indicate bacteremia and can lead to sepsis.
Septicemia or sepsis, the clinical syndrome caused by bacterial infection of the blood, is confirmed by positive blood cultures for a specific organism and accompanied by a systemic response to the infection known as the systemic inflammatory response syndrome (SIRS)1
SIRS is defined by at least two of the following:
•Fever (>38°C) or hypothermia (<36°C)
•Tachycardia (>90 beats/min in patients not on B-blockers)
•Tachypnea (respiratory >20/min or PaCO2 <4.3 kPa or a requirement for mechanical ventilation)
•White cell count >12,000cells/mm3, <4000cells/mm3 or 10% immature (band) forms
Severe sepsis is sepsis associated with organ dysfunction.
Septic shock is sepsis, plus hypotension despite adequate fluid resuscitation, plus hypoperfusion changes, such as lactic acidosis, oliguria, or alteration in mental status.
Septicemia is often accompanied by endotoxemia, the presence of circulating bacterial endotoxins. Hypotension in septic shock is defined as a sustained systolic BP <90 mmHg, or a drop in systolic pressure of >40 mmHg for >1 hour, when the patient is normovolemic and other causes have been excluded or treated.
It results from gram-positive bacterial toxins or gram-negative endotoxins that trigger release of cytokines (TNF, IL-1), vascular mediators, and platelets, resulting in vasodilatation (manifest as hypotension) and disseminated intravascular coagulation (DIC).
Causes of urosepsis
In the hospital setting, the most common causes are the presence or manipulation of indwelling urinary catheters, urinary tract surgery (particularly endoscopic procedures such as TURP, TURBT, ureteroscopy, PCNL), and urinary tract obstruction (particularly that due to stones obstructing the ureter).
Septicemia has been reported to occur in up to 1.5% of men undergoing TURP. Diabetic patients, patients in ICUs, and patients on chemotherapy and steroids are more prone to urosepsis.
Common causative organisms in urosepsis
•E. coli, enterococci (Streptococcus faecalis), staphylococci, Pseudomonas aeruginosa, Klebsiella, and Proteus mirabilis.
1 Bone R, Back RA, Cerra FB, et al. (1992). Definition for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. Chest 101(6):1644–1655.