Kidney infections:
2011-2010/ ‫ عبدالرزاق السلمان‬.‫د‬
Aetiology
Renal infections arise in the following ways.
• Haematogenous infection from a primary site in the tonsils or carious teeth,
or from cutaneous infections, particularly boils or a carbuncle. Renal
tuberculosis occurs by blood-borne spread from lymph nodes in the neck,
chest or abdomen.
• Ascending infection in the urinary tract is the most common route, and it is
most likely to occur when there is vesicoureteric reflux.
Predisposing factors are- Urinary stasis and the presence of calculi.
Bacteriology.
Escherichia coli and other Gram-negative organisms are commonly
responsible & Streptococcus faecalis , in which the urine is acid.
while Proteus sp. and staphylococci split urea, forming ammonia which makes
the urine alkaline and promotes the formation of calculi.
Acute pyelonephritis
Acute pyelonephritis is more common in females, especially during
childhood, at puberty, soon after marriage (as a complication of ‘honeymoon
cystitis’), during pregnancy and during menopause.
Clinical features
- Prodromal symptoms of headache, lassitude and nausea
- Acute pain in the flank and hypochondrium ,often with a rigor and
vomiting.
- The temperature rises to 38.8 or 39.5 Co and is remitting.
-The symptoms of cystitis set in soon after the onset with urgency, frequency
and scalding dysuria.
On examination,
Tenderness in the hypochondrium and in the loin.
Bacteriological examination of the urine
A midstream urine , In early acute pyelonephritis there are usually a few
pus cells and many bacteria. until the infection becomes established when the
urine is cloudy and full of pus.
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Culture and sensitivity testing of the causative organisms allows a rational
choice of antibiotic, but parenteral treatment with a broad-spectrum antibiotic
should be started before the results are available.
Severe cases.
There are repeated rigors and the temperature rises to 40Co or more, often
without a corresponding rise in pulse rate. There is vomiting, sweating and
thirst; the patient feels awful. The blood culture is usually positive, especially
if the specimen has been taken during a rigor.
Differential diagnosis
When the symptoms and signs are typical the diagnosis is straightforward.
In other circumstances it may be difficult to differentiated from
1- pneumonia,
2- acute cholecystitis.
3-acute appendicitis
The urgent need is to distinguish acute pyelonephritis from appendicitis,
and the site of pain and the presence of marked peritonism are usually helpful
in identifying the latter. A plain abdominal radio-graph may show the outline
of a swollen kidney and, if the infection is severe, a skilled ultrasonographer
may be able to detect the typical appearances of pyelonephritis.
Pyelonephritis of pregnancy
Pyelonephritis of pregnancy usually occurs between the fourth and sixth
month of gestation in women who have a past history of recurrent urinary
infection. occasionally leads to abortion or premature birth.
Urine infection in childhood
Urine infection in childhood is important to recognise because it may
endanger the function of the growing kidney.
In young children, there may be few symptoms but the child passes cloudy
or offensive urine, fails to thrive, fails to eat or suffers unexplained pyrexia.
Pain or screaming on micturition may occur.
The older child may complain of loin pain and may develop urinary
frequency and nocturnal incontinence.
Up to 50 per cent of children with urinary infection have an under-lying
anatomical abnormality.
Once the diagnosis has been confirmed by examination of a clean-catch
specimen or by a specimen obtained by suprapubic needle puncture, a full
urological investigation is essential.
Vesicoureteric reflux of urine is detectable in about 35 per cent of children
with recurrent urinary infection.
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Once the diagnosis has been confirmed by micturating cystography, the
urine should be cleared by means of an appropriate antibiotic.
Treatment of acute pyelonephritis
The treatment of acute pyelonephritis should be prompt, appropriate
and prolonged. A full investigation to exclude underlying abnormalities in the
urinary tract should be undertaken as soon as the attack is controlled.
Urine for culture & sensitivity tests,
Antimicrobial-an antimicrobial with a wide range of activity, such as
amoxycillin or gentamicin, should be administered, parenterally if necessary
Alkalinizing agents - If the urine is acid, as it is in the common coliform
infections, alkalinisation of the urine by potassium citrate may help by
inhibiting the growth of these organisms and relieving dysuria.
Analgesia
- Nonsteroidal anti-inflammatory agents
-Morphine-like analgesic drug may be necessary if severe pain.
The patient should be encouraged to drink copiously; if this is not possible
because of nausea and vomiting, an intravenous infusion should be set up.
Most urinary infections acquired outside hospital are sensitive to relatively
cheap agents such as trimethoprim and amoxycillin.
Hospital-acquired infections are much more likely to be resistant and more
expensive second-line antibiotics may be needed. Gentamycin and
carbenicillin are suitable for combating infections with more resistant strains
of Pseudomonas pyocyanea, Proteus sp. and Klebsiella sp.
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
women to men 3:1. Two-thirds of affected females are under 40 years of
age, whereas 60 per cent of the males are over 40.
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Lumbar pain, dull and nonspecific in character, is present in 60 per cent of
cases.Increased urinary frequency and dysuria are common.
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
Pyrexia. Attacks of low-grade fever.
Anaemia. Normochromic anaemia due to unsuspected renal impairment is an
occasional presenting feature.
Investigations
GUE/ 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.
Treatmen :Treatment may be difficult and is aimed at
- eradicating predisposing contributory factors such as obstruction or stones
- 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.
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