The common causes of perinephric abscess are
shown in Fig.
Clinical
features
The classical symptoms and signs of
perinephric abscess are a high swinging pyrexia, abdominal tenderness and
fullness in the loin (Fig. 64.33). Local signs present early if the infection
starts in the lower part of the perinephric fat. Infection at the upper pole is
masked by the lower ribs and the signs in the loin are much less marked. The
white cell count is always markedly raised but there are characteristically no
pus cells or organisms in the urine.
Imaging
The psoas shadow is obscured on the plain
abdominal radiograph. There may be a reactionary scoliosis — with the concavity
toward the abscess — and elevation and immobility of the diaphragm on the
affected side. A calculus may be present. Ultrasonography and CT are
diagnostic.
Treatment
Open drainage may be necessary if the abscess
cannot be aspirated through a large percutaneous needle. A lumbar incision is
made under antibiotic cover. This should be large enough to allow the surgeon to
open pockets of pus and to explore for an unruptured cortical abscess which may
also be present. A specimen of pus is sent for culture and the wound is closed
over a tube drain.