Chronic pyelonephritis
Chronic pyelonephritis is so often associated
with vesico ureteric reflux that some feel that it is better named ‘reflux nephropathy’. It is an important cause of renal damage and death from
end-stage renal failure.
Pathology
There is interstitial inflammation and
scarring of the renal parenchyma with a patchy distribution. The renal tubules
bear the brunt of the destruction they are atrophic and dilated. The
glomeruli retain their normal structure until the final stages of the disease.
Clinical
features
The condition is almost three times as common
in women as it is in men. Two-thirds of affected females are under 40 years of
age, whereas 60 per cent of the males are over 40.
It
is possible, but unusual, for chronic pyelonephritis to remain clinically silent
until the symptoms of advanced renal insufficiency appear.
Hypertension
is present in 40 per cent of cases and may be of the accelerated
(‘malignant’) type. It develops slowly and is most in evidence in
long-standing disease.
Constitutional
symptoms of lassitude, malaise, anorexia, nausea and headache constitute the
main complaint in 30 per cent of cases. The true cause of these nonspecific
symptoms may elude diagnosis for years.
Pyrexia.
Attacks of low-grade fever often prompt the urinary tract investigations which
bring the condition to light.
Anaemia.
Normochromic anaemia due to unsuspected renal impairment is an occasional
presenting feature.
Investigations
As the glomeruli are relatively preserved,
proteinuria is less marked than in glomerulonephritis (<3 g daily). Casts are
not usually present but white cells are plentiful.
Bacteriological
examination of the urine commonly reveals the presence of E. coli, S. faecalis, Proteus sp. or Pseudomonas sp.
Treatment
Treatment may be difficult and is aimed at
eradicating predisposing contributory factors such as obstruction or stones
and treating the infection with appropriate antibiotics, often as repeated
courses of treatment. Unfortunately, once the parenchyma has been scarred it
becomes vulnerable to blood-borne organisms and reinfection is likely, sometimes
with a different and resistant organism. Consequently, antibiotics confer only
temporary benefit and progressive renal damage is common.
Surgical
treatment is only indicated when the disease is confined to one kidney. This is
unusual but in such cases nephrectomy or partial nephrectomy may stop the
symptoms of infection and make hypertension easier to control. Some patients
with end-stage renal failure require renal transplantation.
Hypertension
and a unilateral renal lesion
Ischaemia of the renal parenchyma leads to the
release of pressor agents which cause arterial hypertension. Where a renal
lesion is discovered during the investigation of hypertension, nephrectomy may
not bring the pressure to normal but it may make the hypertension more amenable
to drug treatment.