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. It occurs
more on the right and is frequently bilateral.
Clinical
features
There may be prodromal symptoms of headache,
lassitude and nausea but the onset of pain is usually sudden, often with a rigor
and vomiting. There is acute pain in the flank and hypochondrium. In a few cases
the pain resembles renal colic. The temperature rises to 38.8 or 39.50C
and is remitting. The symptoms of cystitis set in soon after the onset with
urgency, frequency and scalding dysuria. On examination, there is tenderness in
the hypochondrium and in the loin. Rarely in cases of severe bilateral
pyelonephritis, especially when there is an associated obstruction, the damage
to renal function may be sufficient to cause uraemia.
Bacteriological examination of the urine
A
midstream urine should be collected into a sterile container; the urine is
centrifuged and the sediment examined microscopically. In early acute
pyelonephritis there are usually a few pus cells and many bacteria. The
macroscopic appearance of the urine may be misleadingly clear, until the
infection becomes established when the urine is cloudy and full of pus. 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 400C 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
be sure that the patient does not have pneumonia, acute appendicitis or
acute cholecystitis. 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 radiograph
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. In about 10 per
cent of cases the disease runs a severe and protracted course and 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. The possibility of urinary sepsis
should always be considered if a child 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 underlying
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. In some patients the reflux
is caused by high pressure in a neuropathic bladder. It may be intermittent and
is often more marked when there is active infection. Renal damage results from
the combination of reflux and urinary infection early in life and reflux
nephropathy is the most common cause of end stage renal failure in the UK. Once
the diagnosis has been confirmed by micturating cystography, the urine should be
cleared by means of an appropriate antibiotic. Long-term prophylactic antibiotic
treatment has become the favoured treatment for recurrent urinary infections
resulting from reflux. Surgical reimplantation of the ureters is reserved for
those in whom conservative measures fail. Reimplantation in these patients often
fails to cure reflux.
Acute
pyelonephritis associated with urinary retention
Acute pyelonephritis is a relatively uncommon
complication of chronic urinary retention. Often the organisms are introduced
during instrumentation and, in the days of unsterile catheterisation, the
condition was known as ‘surgical kidneys’. Patients who have significant
post-micturition urinary residue should be given prophylactic antibiotics to
cover transurethral procedures.
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.
The
patient will usually feel like lying in bed. While awaiting the
bacteriological report and the results of sensitivity tests, an antimicrobial
with a wide range of activity, such as amoxycillin or gentamicin, should be
administered, parenterally if necessary. If the urine is acid, as it is in the
common coliform infections, alkalinisation of the urine by potassium
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. Gentamicin
and carbenicillin are suitable for
combating infections with more resistant strains of Pseudomonas pyocyanea, Proteus sp. and Klebsiella sp. Ciprofloxacin is
particularly useful against Pseudomonas sp.
in patients who do not have septicaemia. Despite the efficacy of modern
antibacterial drugs, recurrent infection is likely if there is an untreated
underlying abnormality of the urinary tract such as a stone, vesicoureteric
reflux or retention of urine.