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ACUTE KIDNEY FAILURE
Interstitial nephritis as a cause of acute
kidney
failure
Leptospirosis
Acute
kidney
failure due to an interstitial nephritis may appear within a few
days of the onset of disease, but more commonly in the second
week. It occurs in about 10 per cent of cases of leptospirosis
and is frequently mild, but may be severe, with the plasma urea
level rising rapidly due to hypercatabolism. The diagnosis of
leptospirosis should be considered in any patient with
unexplained acute
kidney
failure who has myalgias/muscle tenderness, conjunctival
infection, and/or haemorrhage or jaundice. Direct enquiry must
be made as to whether any such patient has been exposed to rats.
Aside from
kidney
impairment, blood tests commonly reveal a dramatic conjugated
hyperbilirubinaemia (often >250 µmol/l) and thrombocytopenia
(seen in 40 per cent of cases). There may also be elevation of
serum creatine kinase and a slight increase in serum AST.
Anaemia may be severe due to intravascular haemolysis.
By contrast to most other causes of acute
kidney
failure, serum potassium is often normal or low in cases of
leptospirosis. Mild abnormalities of blood clotting tests can be
seen, but disseminated intravascular coagulation is not a
feature, which is an important point in its distinction from
bacterial septicaemia.
The
diagnosis is established by culture of Leptospira spp. (from
blood during the first phase or urine afterwards) or positive
serology. Doxycycline prophylaxis is effective at preventing
leptospirosis, but antibiotics are not of proven benefit in
treating disease. Mild cases are self-limiting; most physicians
treat patients who are symptomatic with a 7-day course of oral
doxycycline or intravenous benzylpenicillin, on the grounds that
this appears to shorten the duration of fever and leptospiruria.
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