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Nephrotic syndrome

Case

history

Pamela is 48 with a 20-year history of type I diabetes. You had seen her the previous day and arranged some urgent urine and blood tests. Her main complaint was ankle swelling extending up to her mid shin and, for the first few hours of the day, some swelling around her eyes. Examination had confirmed pitting ankle oedema. Blood tests reveal an albumin of 18g/L (normal 35-55g/L) and a cholesterol of 8.2mmol/L. Urine dipstick shows 3+ of protein.

Dr Tanvir Jamil discusses.

The results point to nephrotic syndrome. How does this differ from nephritic syndrome?

Nephrotic syndrome is defined by proteinuria (>3g/24 hours in adults and >0.05g/kg/L in children), hypoalbuminaemia, oedema (the periorbital pattern that Pamela has is classical) and hyperlipidemia. Urea and creatinine are usually normal. An interesting sign often seen is urine that froths (secondary to the proteinuria).

In nephritic syndrome the patient may have some degree of proteinuria but not in the nephrotic range. Patients also suffer from oliguria, hypertension, haematuria and rising U&Es and creatinine.

Pamela has diabetes, but what are the other causes of nephrotic syndrome?

Nephrotic syndrome can complicate any disease that perturbs the negative charge of the basement membrane or changes the architecture of the glomerular filtration system (ie pore size). Six conditions account for more than 90 per cent of cases in adults. As well as diabetes these include:

· minimal change glomerulonephritis

· focal and segmental glomerulosclerosis

· membranous glomerulonephritis

· membranoproliferative glomerulonephritis

· amyldosis.

Other causes include SLE, neoplasia, sickle-cell disease, malaria, medication (eg captopril, penicillamine, NSAIDs), metals (gold, mercury, cadmium), allergic reactions (eg insect stings, snake bites). In children nephrotic syndrome is usually due to minimal change disease (podocyes with 'missing feet' on electron microscopy) which often follows an infection.

Is there a logical way of investigating nephrotic syndrome?

There are three questions to ask yourself:

· How bad is the condition? ­ Measure Hb, PCV, 24-hour urine (for volume, protein measurement, sodium concentration and creatinine)

· How much has renal function been affected? ­ Measure plasma urea and creatinine and creatinine clearance

· What is causing the nephrotic syndrome? ­ Measure serum C3 & C4, differential protein clearance (IgG and albumin), serial urines for RBCs and casts, hep B status, autoantibody screen (ANF ­ SLE; ASO ­ post strep glomerulonephritis; ANCA ­ PAN and Wegener's granulomatosis)

Apart from referral, how else can I help Pamela?

Urgent referral to a specialist is essential. General management of nephrotic syndrome involves bed rest to stimulate diuresis, fluid restriction

(1-1.5L/day), daily U&E and weight (aim to lose 1kg/day), salt restriction (50mmol/day) + high protein and calorie diet (not clinically proven) and frusemide (40-80mg po). Patients are also often given penicillin prophylactically to prevent pneumococcal infection. Once Pamela is discharged you will need to monitor her renal function as well as keeping her diabetes under tight control.

Close monitoring of her blood pressure and rapid treatment of any potential infections are also paramount. If she is not already on an ACE inhibitor you may want to add this class of drug into her treatment plan as it can stabilise or even lower protein loss. You may also want to consider offering her pneumoccal vaccination.

The stress of an additional major illness to her diabetes may lead to depression. You may need to think about antidepressants and/or referral to a counsellor. Pamela may be fearful of impending kidney failure and an open and honest discussion may help her come to terms with her illness.

What complications do I need to watch for?

We've already mentioned infections and these occur due to the loss of IgG and alternative pathway complement components in the urine. If infection is suspected patients usually need immediate hospital admission for IV antibiotics. Hypovolaemic shock and acute renal failure leading to oliguria and uraemia is another well-known complication and a few of these patients may deteriorate further and require dialysis.

Other problems secondary to nephrotic syndrome include iron deficiency anaemia (loss of transferrin and iron), hypocalcemia and secondary hyperparathyroidism (vitamin D deficiency secondary to loss of cholecalciferol-binding protein), depressed thyroxine levels (due to urinary loss of thyroxine-binding globulin), muscle wasting, accelerated atherosclerosis, arterial thrombosis and renal vein thrombosis. The last occurs in some

1-2 per cent of patients with nephrotic syndrome.

Some patients exhibit no symptoms or just mild abdominal or back ache. Other patients may develop severe pain and loin tenderness, symmetrical leg oedema and haematuria. Renal vein thrombosis should be suspected in any nephrotic syndrome patient who has an unexpected decline in renal function and RBCs in the urine.

Diagnosis is usually made by doppler ultrasound, MRI or renal angiogram. Almost a third of patients also have a coincidental pulmonary embolus. Warfarin therapy for three-six months is usually undertaken. For an acute thrombosis streptokinase may be used to lyse the clot. Thrombosis can be such a problem in nephrotic syndrome that bed-bound patients are prophylatically anticoagulated with subcutaneous heparin.

What can I tell Pamela about prognosis?

The prognosis is variable often depending on the person's age, the causative factor and the degree of kidney damage. But diabetic nephropathy is the leading cause of end-stage renal disease in

Europe and North America and accounts for

30-35 per cent of patients on renal dialysis/ transplant therapy. With this in mind it's even more important that Pamela is regularly reviewed by you and the renal specialist for life.

Contacts:Diabetes UK www.diabetes.org.uk

Tanvir Jamil

is on a sabbatical in Canada

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