Acute Post-Streptococcal Glomerulonephritis
Acute glomerulonephritis results from immune-mediated damage to the glomerulus. The commonest type in childhood is due to immune complex formation following group A beta-haemolytic streptococcal infection. The presenting complaint is usually haematuria, which is cola coloured and typically occurs 1–2 weeks after a throat or 3–6 weeks after a skin infection. The child may have malaise, oedema, loin pain and headache or be asymptomatic. Urinalysis shows gross haematuria with granular and red cell casts and often proteinuria. In most children there is mild oliguria (reduced urine output) but in a minority there may be acute renal failure and hypertension. Useful investigations include a throat swab and antistreptolysin O (ASO) titre to look for evidence of streptococcal infection and there may be a low C3 complement level.
A 10-day course of penicillin is recommended to try to clear the nephritic strain of streptococcus, although there is no evidence that this alters the course of the disease. Acute renal failure is managed with careful monitoring of fluid balance and renal function. Salt and fluid restriction may be required and hypertension must be controlled. Rarely, acute glomerulonephritis leads to severe renal failure requiring renal dialysis.
Nephrotic syndrome is characterized by proteinuria, low albumin, oedema and high triglycerides. This is due to increased capillary wall permeability in the glomerulus which allows protein to leak into the urine. The commonest cause (85%) is ‘minimal change’ glomerulonephritis (MCGN), where the histological changes on renal biopsy are very mild. This type usually responds to steroid therapy. The presenting feature is oedema, which is usually most noticeable in the mornings around the eyelids and as pitting oedema on the legs. There may be history of a recent viral upper respiratory tract infection (URTI). Focal segmental glomerulosclerosis (FSGS) is the second most frequent form.
With time, weight gain, ascites and pleural effusions develop secondary to the hypoalbuminaemia. Hypertension is rare, but there may be anorexia, abdominal pain, diarrhoea and oliguria. There is an increased risk of infection due to leakage of immunoglobulins, and an increased risk of thrombosis. Urinalysis shows excessive protein and there is low serum albumin, high triglyceride and cholesterol levels and normal C3 complement.
Treatment of minimal change nephrotic syndrome involves fluid restriction, a low salt diet and corticosteroids (prednisolone). Prednisolone is continued until there is remission of proteinuria, continued at a weaning dose over 2–3 months. Parents should be warned about the immunosuppressive effects of nephrotic syndrome and steroids and should avoid live vaccines and chickenpox at this time. Prophylactic penicillin is given until the proteinuria has cleared.
Relapses are common, occurring in up to 75% of those who initially respond. Children who are steroid resistant need a renal biopsy to confirm the pathology and may need treatment with cyclophosphamide. Long-term prognosis is good although delayed relapses may occur. Other forms of nephrotic syndrome (e.g. following Henoch–Schönlein purpura) carry a worse prognosis and may progress to chronic renal failure requiring dialysis and eventually transplantation.
Other Renal Conditions
Acute Renal Failure
Acute renal failure is defined as a rapid onset of anuria or severe oliguria (<0.5 mL/kg per hour). Causes can be divided into prerenal (i.e. poor perfusion), renal or postrenal (due to urinary obstruction). The commonest prerenal cause is hypovolaemic shock. Prerenal failure can usually be managed with fluid replacement and inotropic support of the circulation.
Intrinsic renal causes include the following:
- Acute tubular necrosis (often secondary to shock)
- Haemolytic uraemic syndrome (HUS)
- Vasculitis and glomerulonephritis
- Renal vein thrombosis
- Nephrotoxic drugs (e.g. gentamicin, vancomycin).
Renal failure requires careful inpatient management. Hyperkalaemia, hypertension and fluid overload can be life-threatening complications. If conservative management is failing, there is severe electrolyte imbalance, progressive acidosis or fluid overload, and renal dialysis is then necessary, via peritoneal dialysis or haemodialysis.
Haemolytic Uraemic Syndrome
Haemolytic uraemic syndrome (HUS) is an important cause of renal failure associated with thrombocytopenia, renal failure and haemolytic anaemia due to fragmentation of red blood cells. It often follows an episode of bloody diarrhoea and is associated with a verotoxin producing E. coli O157:H7. The disease can also affect the brain, causing encephalopathy. Intensive care treatment may be needed for renal failure, encephalopathy and associated colitis. Chronic renal failure can result.
Chronic Renal Failure
Approximately 1000 children in the UK receive renal replacement therapy. The commonest cause is a congenital structural renal abnormality such as ‘cystic–dysplastic’ kidneys or severe obstructive nephropathy. Rarer causes include glomerulonephritis and renal disease as part of autoimmune systemic disease. Children with untreated chronic renal failure are at risk of anaemia, difficulty with exertion, poor appetite, poor growth, osteodystrophy and hypertension.
Management involves a high-calorie, low-protein diet that is low in phosphate. Growth hormone and vitamin D supplements are often required and anaemia may be treated with erythropoietin injections. When the renal disease becomes end stage, children require dialysis. Dialysis can either be haemodialysis (in hospital) or peritoneal dialysis (can be administered at home). The best long-term treatment is renal transplant from a cadaveric or living related donor.
- Careful urine analysis is essential.
- Haematuria is more likely to have serious underlying cause if associated with hypertension, proteinuria, impaired function.
- Nephrotic syndrome usually responds to steroid treatment but relapses may occur.
- Renal transplantation is the treatment of choice for end-stage renal disease.