5. Structural Changes of Renal Vasculature and Glomerulonephritis

Causing Renal Failure

Lesions of the Main Renal Arteries

Lesions of the main renal arteries are a very rare cause of acute renal failure, but have been described in three situations.

Trauma

Severe trauma can cause rupture of the renal artery, either by direct damage to the intima of the artery with subsequent occlu­sion, or by avulsion as the result of violent deceleration. These injuries are usually fatal, but survival has been reported. An IVU will show an absent nephrogram, and arteriography shows taper­ing of the main renal artery. Surgical repair should be attempted if the patient's condition justifies the risk.

Renal Artery Embolus

Renal artery embolus is quite a common event, but seldom leads to renal failure. The patient complains of loin pain and may have frank haematuria. It is associated with the same radiological changes as those of direct trauma to the renal artery. Embolec­tomy may be successful even after a delay of 12 hours.

Dissection of Abdominal Aortic Aneurysm Involving Both Renal Arteries

Dissection of an abdominal aortic aneurysm is again rare, but surgical replacement of an abdominal aortic aneurysm by a pros­thesis commonly leads to renal failure. This is usually due to A TN unless the renal arteries are involved, in which case infarction may result and recovery is unusual.

M. Boulton-Jones, Acute and Chronic Renal Failure© MTP Press Limited 1981

42 Acute and Chronic Renal Failure

Lesions of the Renal Microvasculature

Accelerated Hypertension

Hypertension usually causes renal failure to develop insidiously, but occasionally patients with accelerated hypertension present with acute renal failure. The unfortunate patient often has a forceful left ventricular impulse and a loud aortic second sound. Papilloedema with exudates and haemorrhages is almost always present, and areas of purpura are sometimes found. The blood film reveals fragmented red cells and thrombocytopenia, although the coagulation screen may be nearly normal. Proteinuria (if urine is produced) is usual. An IVU performed as described above produces a very poor nephrogram, but the kidneys are smooth and of normal size. Renal biopsy can be performed once the blood pressure has been controlled and the platelet count has risen above 100 x 109/1. On biopsy, the glomeruli appear avascular with crinkling of the glomerular basement membrane. Arterioles show intimal proliferation with virtual occlusion of the lumen and fibrinoid material is present within the walls of some arteries and arterioles.

Treatment

Treatment involves radical control of hypertension aiming to keep the diastolic pressure below 95 mm Hg. Dialysis should be used to remove fluid and to control uraemia. Within two to four weeks there should be improvement in the fundal appearances, but return of some renal function is rare, perhaps occurring in only 10 per cent of patients. However, regular dialysis treatment with transplantation is often successful, although bilateral nephrec­tomy may be necessary to control the hypertension.

Haemolytic Uraemic Syndrome

Haemolytic uraemic syndrome (HUS) is a rare disease of unknown aetiology affecting children mainly below the age of 2 years of either sex. It usually occurs sporadically but small epidem­ics have been reported. It frequently presents with diarrhoea and

Structural Changes 43

fever lasting a few days, followed by acute renal failure, haemoly­tic anaemia and thrombocytopenia. The child becomes ill and irritable and focal neurological signs may appear. Hypertension may be absent at the onset but develops later. The prognosis is variable, being worse in older children. About 20 per cent die in the acute stage and a further 20 per cent progress more slowly to renal failure. Some have permanent neurological sequelae. Com­plete recovery occurs in 25 per cent and the remainder survive with a permanent reduction in renal function.

Diagnosis is based on the clinical presentation and the demon­stration of microangiopathic haemolytic anaemia on the blood film (fragmented red cells, microspherocytes and helmet cells) associated with thrombocytopenia and renal failure. Renal biopsy is only possible when the bleeding disorder has been corrected. The main abnormality is in the arteries and·arterioles which show necrosis, thrombosis and fibrin deposition. The glomeruli may be shrunken with areas of necrosis.

Treatment

Treatment centres on the management of renal failure and control of hypertension which frequently develops. Steroids and heparin have both been used extensively, but their efficacy remains unproven.

Thrombotic Thrombocytopenic Purpura (Moschowitz's Syndrome)

Moschowitz's syndrome is very similar to the haemolytic­uraemic syndrome, but it occurs in adults. The aetiology is also unknown, and the condition is even rarer than HUS. Clinically it comprises fever, signs of cerebral irritability, haemolytic anaemia, purpura due to increased platelet consumption and renal failure. The pathological changes in the blood and kidneys are similar to those described in HUS. The prognosis is bad, as few survivors have been described.

Treatment with large doses of steroids and heparin is usually given on an empirical basis, and recently recovery has been reported after exchange of large volumes of the patient's plasma with normal plasma.

44 Acute and Chronic Renal Failure

Postpartum Nephrosclerosis

Postpartum nephrosclerosis was first described in 1968. It is very rare. As its name implies, it follows pregnancy (which has usually been quite normal) by an interval of two to 12 weeks. Renal failure and haemolytic anaemia develop insidiously. Recovery is unusual, and steroids and heparin therapy are usually given. The disease appears to be self-limiting, the patient being left with severe renal failure and hypertension. Therefore regular dialysis treatment can be successful, although nephrectomy may be required to control hypertension.

Glomerulonephritis

Both acute exudative (or post-streptococcal) glomerulonephritis and rapidly progressive (or crescentic) glomerulonephritis are associated with ARF. The kidney may be the only organ involved, or it may be part of a more generalized illness such as occurs in systemic lupus erythematosus, polyarteritis nodosa, Wegener's granulomatosis, Henoch-Schonlein purpura or Goodpasture's syndrome. Early diagnosis is essential and rests on the clinical history, presence of proteinuria and cellular casts, and the demon­stration of a poor nephrogram on IVU. Both kidneys are either normal in size or enlarged; renal biopsy should be performed as soon as possible. A full description of these syndromes appears in another title in this series: Renal Glomerular Diseases (Sharp­stone 1980).

Renal Vein Thrombosis

Renal vein thrombosis is most commonly seen in infants who become dehydrated as a result of diarrhoea and vomiting; those born of diabetic mothers are particularly vulnerable. Renal vein thrombosis causes acute loin pain and large tender kidneys. One or both kidneys may be affected, but renal failure may develop even with unilateral disease. Recovery has been described after unilateral nephrectomy, which should be considered if severe coagulation defects are present. It is often followed by an

Structural Changes 45

improvement in the infant's general condition and a return of renal function. However, recovery also occurs with conservative measures including rehydration and anticoagulants, and this is the method of management most frequently employed.

Renal vein thrombosis rarely occurs in adults unless the kidney itself is abnormal. Classically it is associated with amyloid, mem­branous nephropathy or a transplanted kidney. Diagnosis is made by renal venography which can be difficult to interpret. Its effect on renal function is variable. Thrombectomy is occasionally suc­cessful, but should only be attempted if there has been a sudden and recent reduction in renal function. Anticoagulants have also been used, but since the natural history of the syndrome is unknown it is difficult to evaluate their effectiveness.