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Acute pyelonephritis is caused by bacterial infection with organisms entering
the kidney by two routes:
• Ascending infection from the lower urinary tract (most common). Predisposing
factors that lead to
ascending urinary tract infection are pregnancy, diabetes mellitus, stasis of
urine, structural defects of the urinary
tract, and reflux of urine from bladder into ureters (vesicoureteric reflux).
• Bloodstream spread in bacteraemic or septicaemic states (unusual). Although
this seems to be the most likely cause in elderly patients who develop pyrexia
of unknown origin,
often with rigors, and acute renal failure.
Macroscopically the kidneys show variable numbers of small, yellowish white
cortical abcesses, which
are usually spherical, under 2 mm in diameter, and are sometimes surrounded by a
zone of hyperaemia;
the cortical abscesses are often most prominent on the sub-capsular surface,
after the capsule has been
stripped away. In the medulla the abscesses tend to be in the form of yellowish
white linear streaks that converge on the papilla.
The pelvicalyceal mucosa is hyperaemic or covered with a fibrinopurulent exudate.
kidney shows focal infiltration with neutrophils.
Chronic pyelonephritis is characterized by chronic interstitial inflammation
with large scars of the kidney
Chronic pyelonephritis is a common cause of end-stage chronic renal failure,
about 15% of all cases. The disease is characterized by interstitial chronic
inflammation and scarring,
which destroys nephrons. The areas of scarring are associated with distortion of
system of the kidney. Renal-induced hypertension may develop and
damage can increase renal damage.
There are two forms of chronic pyelonephritis:
reflux-associated and obstructive. In the most common form, reflux-associated
pyelonephritis, reflux of urine from the bladder up the ureters predisposes to
of inflammation, leading to scarring. This occurs in childhood, and disease
in early adult life.
In obstructive chronic pyelonephritis, recurrent episodes of infection occur in
in which there is obstruction to the pelvicalyceal drainage. The obstruction,
which can be at any
level in the lower urinary tract, may be due either to anatomical abnormality or
to renal tract stone.
Kidneys have irregular areas of scarring, seen as depressed areas, 1-2 cm in
size. The scars
are sited over a club-shaped distorted renal calyx and are associated with
fibrous scarring of the
renal papilla. The most common site for these areas of scarring is the renal
at the poles of the kidney.
Histologically the kidney has irregular areas of interstitial fibrosis with
cell infiltration. Tubules are atrophic or may be dilated and contain
Glomeruli show periglomerular fibrosis and many demonstrate complete
Tuberculous pyelonephritis may lead to destruction of the whole kidney
Tuberculous pyelonephritis is characterized by white caseous material filling
pelvicalyceal system, which may be unilaterally or bilaterally affected.
Infection is initially renal but, over a period of months or years, enlarges and
ruptures into the pelvicalyceal system, releasing tubercle bacilli into the
lower urinary tract.
This can lead to the development of tuberculous ureteritis, cystitis and, in the
prostatitis and epididymo-orchitis.
With time, extension of caseous granulomatous inflammation leads to destruction
and medulla, so that at the end-stage of the disease the kidneys are reduced to
of partially calcified caseous material; if both kidneys are affected,
chronic renal failure results.
This pattern of renal involvement in TB is distinct from renal involvement in
progressive miliary TB, in which the kidney is just one of many organs that
numbers of tubercle bacilli, spread from a fulminating lung infection. In
there are very large numbers of small tuberculous granulomas scattered
throughout both kidneys.
The patient usually dies before the individual granulomas can enlarge and show
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We give here simplified and accurate information about the disease
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