Chronic pyelonephritis

Chronic pyelonephritis is so often associated with vesico ureteric reflux that some feel that it is better named ‘reflux nephropathy’. It is an important cause of renal damage and death from end-stage renal failure.

Pathology

There is interstitial inflammation and scarring of the renal parenchyma with a patchy distribution. The renal tubules bear the brunt of the destruction  they are atrophic and dilated. The glomeruli retain their normal structure until the final stages of the disease.

Clinical features

The condition is almost three times as common in women as it is in men. Two-thirds of affected females are under 40 years of age, whereas 60 per cent of the males are over 40.

It is possible, but unusual, for chronic pyelonephritis to remain clinically silent until the symptoms of advanced renal insufficiency appear. Lumbar pain, dull and nonspecific in character, is present in 60 per cent of cases. Increased urinary frequency and dysuria are common.

Hypertension is present in 40 per cent of cases and may be of the accelerated (‘malignant’) type. It develops slowly and is most in evidence in long-standing disease.

Constitutional symptoms of lassitude, malaise, anorexia, nausea and headache constitute the main complaint in 30 per cent of cases. The true cause of these nonspecific symptoms may elude diagnosis for years.

Pyrexia. Attacks of low-grade fever often prompt the urinary tract investigations which bring the condition to light.

Anaemia. Normochromic anaemia due to unsuspected renal impairment is an occasional presenting feature.

Investigations

As the glomeruli are relatively preserved, proteinuria is less marked than in glomerulonephritis (<3 g daily). Casts are not usually present but white cells are plentiful.

Bacteriological examination of the urine commonly reveals the presence of E. coli, S. faecalis, Proteus sp. or Pseudomonas sp.

Treatment

Treatment may be difficult and is aimed at eradicating predisposing contributory factors such as obstruction or stones and treating the infection with appropriate antibiotics, often as repeated courses of treatment. Unfortunately, once the parenchyma has been scarred it becomes vulnerable to blood-borne organisms and reinfection is likely, sometimes with a different and resistant organism. Consequently, antibiotics confer only temporary benefit and progressive renal damage is common.

Surgical treatment is only indicated when the disease is confined to one kidney. This is unusual but in such cases nephrectomy or partial nephrectomy may stop the symptoms of infection and make hypertension easier to control. Some patients with end-stage renal failure require renal transplantation.

Hypertension and a unilateral renal lesion

Ischaemia of the renal parenchyma leads to the release of pressor agents which cause arterial hypertension. Where a renal lesion is discovered during the investigation of hypertension, nephrectomy may not bring the pressure to normal but it may make the hypertension more amenable to drug treatment.