Pyonephrosis

The kidney is converted into a multilocular sac containing pus or purulent urine. Pyonephrosis can result from infection of a hydronephrosis, follow acute pyelonephritis or, most commonly, arise as a complication of renal calculus disease. Pyonephrosis is usually unilateral.

Clinical features

The classical triad of symptoms is anaemia, fever and a swelling in the loin. When the condition arises as an infected hydronephrosis, the swelling may be very large and the -pyrexia very high and associated with rigors. Symptoms of cystitis may be prominent.

Investigations

The plain radiograph may show a calculus and an ultrasonogram will demonstrate dilatation of the renal pelvis and calyces. The intravenous urogram will show poor function and the features of hydronephrosis on the affected side.

Treatment

Pyonephrosis is a surgical emergency because the patient is threatened with permanent renal damage and a potentially lethal septicaemia. Parenteral antibiotics should be given immediately and the kidney drained. If the pus is too thick to be aspirated through a large percutaneous nephrostomy, it may be necessary to consider open nephrostomy. In cases where there is a stone, the stone should be removed. Nephrectomy may be considered when long-standing obstruction is known to have destroyed the kidney, and func­tion on the other side is good.

Renal carbuncle

An abscess may form in the renal parenchyma as the result of blood-borne spread of organisms, especially coliforms or Staphylococcus aureus, from a focus elsewhere in the body. Occasionally the condition results from infection of a haematoma following a blow to the kidney. Renal carbuncle is most commonly seen in diabetic patients, intravenous drug abusers, those debilitated by chronic disease and patients with acquired immunodeficiency.

Pathology. The renal parenchyma contains an encapsulated necrotic mass.

Clinical features. There is an ill-defined tender swelling in the loin, persistent pyrexia and leucocytosis, signs that closely simulate those of perinephric abscess. In early cases there is no pus or bacteria in the urine but they appear after a day or so. Urography shows a space occupying lesion in the kidney which may be confused with a renal adenocarcinoma on ultrasonography and CT (Fig. 64.31).

Treatment. Resolution by antibiotic treatment alone is unusual. Formal open incision of the abscess may be necessary if the pus is too thick to be drained by percutaneous aspiration.