Perinephric abscess

 The common causes of perinephric abscess are shown in Fig. 64.32. Other causes are infection of a perirenal haematoma and perinephric discharge of an untreated pyonephrosis or renal carbuncle. A mycobacterial perinephric abscess may arise by extension from a nearby tuberculosis vertebra.

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.