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Nephrotic Syndrome
Essentials
- Suspect nephrotic syndrome as a rare cause of oedema. The most important symptom is oedema in the lower extremities and eyelids caused by accumulation of salt and fluid within the tissues.
- In addition to treatment directed at the primary disease, proteinuria, fat metabolism, hypertension (target blood pressure ≤ 120-130/80 mmHg) and oedema are treated.
Definition
- Nephrotic syndrome is caused by glomerular capillary wall damage. In nephrotic syndrome proteins are lost in the urine (in adults)> 3-3.5 g/day (urine albumin/creatinine ratio > 200 mg/mmol) and serum albumin concentration is decreased < 25 g/l.
- This will lead to decreased colloid osmotic pressure, accumulation of salt and water, and, in most cases, to oedema.
- The clinical picture also includes hyperlipidaemia, susceptibility to infections, and abnormal blood clotting predisposing the patient to thrombosis.
Signs and symptoms
- Symptoms emerge at the latest when the serum albumin concentration falls below 25 g/l due to excess proteinuria.
- The most important symptom is oedema of the lower limbs and the eyelids. It is caused by accumulation of fluid in the tissues as the serum protein concentration decreases and the capacity of the body to excrete sodium is reduced.
- The extent of oedema correlates fairly poorly with the blood albumin concentration.
Diagnosis
- The diagnosis is based on the clinical picture and on the results of laboratory investigations.
- Swellings, urinary albumin +++ ( 24-h urinary protein excretion > 3 g, urine albumin/creatinine ratio > 200 mg/mmol), serum albumin concentration low (< 25 g/l)
- Always also check plasma creatinine concentration (and eGFR; calculator Gfr Calculator) and possible haematuria.
- Renal ultrasonography
- To establish the aetiology, a renal biopsy is often required. Therefore, the patient should be admitted to hospital for investigations.
- Always consult specialized care. Refer as
- urgent if the symptoms have developed within a few days
- non-urgent if the symptoms have developed within weeks.
- Treatment of the underlying disease
- Reduction of proteinuria
- Optimal treatment of hypertension
- Target ≤ 120-130/80 mmHg
- Drug therapy consists of an angiotensin-receptor blockers (ARB) or an ACE inhibitor, and additionally, if needed, a calcium-channel blocker or other antihypertensive drug.
- Reduction of oedema
- Restricted salt intake (aim < 2 g of sodium, equivalent to < 5 g of sodium chloride / day)
- A diuretic
- Furosemide 20-80 mg two to four times daily orally. In severe oedema, treatment may be instigated with intravenous administration (the corresponding dose is 10-40 mg). Beware of hypovolaemia.
- The dose of furosemide is increased according to response.
- A thiazide diuretic enhances the effect of furosemide. The dose of hydrochlorothiazide is 25-50 mg/day (higher in renal failure).
- Avoid excessive weight loss; 0.5-1 kg/day is appropriate.
- An infusion of intravenous albumine and furosemide has been used in oedema resistant to other therapy, but its use remains controversial.
- Ultrafiltration may be required to remove excess fluid.
Complications
- Hypercoagulability; risk of venous thrombosis of the lower limbs, pulmonary embolism and renal vein thrombosis.
- Aspirin should be given routinely.
- During the stay on a hospital ward prophylactic low molecular weight heparin should be used, especially if the patient has prominent swellings.
- Prophylactic oral anticoagulation is usually not administered but it should be considered if the nephrotic syndrome is severe (serum albumin concentration < 20 g/l, 24-h urinary protein excretion > 10 g). It should always be instigated in patients with a history of a thromboembolic event and continued whilst the patient remains nephrotic.
- Susceptibility to infections. The loss of IgG in the urine predisposes the patient to infections.
- Gradual muscle wasting as a consequence of hypoproteinaemia
- The diet should include high quality protein, approximately 0.8-1 g/kg/day.
- Energy intake should be 35 kcal/kg/day.
- Atherosclerotic changes as a consequence of hyperlipidaemia
- Altered calcium metabolism
- Severe nephrotic syndrome may be associated with acute kidney injury (AKI) Acute Kidney Injury.
- Protein binding of drugs may be altered.
- With most drugs, it is not necessary to change the dosage.
- Warfarin dosage, for example, may have to be changed.