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 <30 g/l.
This will lead to decreased colloid osmotic pressure in the blood, accumulation of salt and water, and, usually, to oedema.
The clinical picture also includes hyperlipidaemia, susceptibility to infections, and abnormal blood clotting predisposing the patient to thrombosis.
Some genetic kidney diseases (e.g. congenital nephrosis, nail-patella syndrome)
Signs and symptoms
The main symptoms are oedema and weight gain due to fluid accumulation in the tissues as serum protein levels decrease and the capacity of the body to excrete sodium is impaired.
Weight gain can exceed ten kilograms and can be gradual or sudden, depending on the disease.
The oedema first appears in the ankles and, in the mornings, in the eyelids, but as the oedema increases it spreads to the whole body.
Fluid accumulates according to gravity; in bedridden patients, the accumulation may be most visible on the back.
In severe nephrosis, pleural fluid and ascites also accumulate.
Symptoms usually emerge at the latest when the serum albumin concentration falls below 25 g/l due to excess proteinuria.
The extent of oedema does not always correlate directly 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), plasma albumin concentration low (<30 g/l)
Always also check plasma creatinine concentration (and eGFR; calculator Gfr Calculator) and possible haematuria (chemical screening of urine).
Renal ultrasonography
To establish the aetiology, a renal biopsy is often required. Therefore, the patient should be referred to hospital for investigations.
Check plasma creatinine and potassium concentrations before starting medication with an ACE inhibitor or ATR blocker and 7-10 days after the start.
The goal is to reduce proteinuria to a level below 0.5-1 g/24 hours, if possible (urine albumin/creatinine ratio < 30-60 mg/mmol).
In chronic proteinuric diseases, SGLT2 inhibitors are also recommended if GFR > 25 ml/min (note: not in patients with type 1 diabetes).
Optimal treatment of hypertension
Target ≤ 120-130/80 mmHg
Drug therapy consists of an angiotensin-receptor blockers (ARB) or an ACE inhibitor, and additionally, as necessary, a diuretic, 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)
Fluid restriction
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.
During the stay on a hospital ward prophylactic low molecular weight heparin should be used, especially if the patient has prominent swellings. Sometimes it is still worth continuing treatment at home if the nephrosis is severe.
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) and bleeding risk is not considered too high.
Most experience is with warfarin. Research evidence on the use of direct oral anticoagulants (DOACs: dabigatran, rivaroxaban, apixaban and edoxaban) for thromboprophylaxis in patients with nephrosis is still scarce.
Anticoagulant therapy should always be instigated in patients with a history of deep venous thrombosis or pulmonary embolism and continued whilst the patient remains nephrotic.
Susceptibility to infections. The loss of IgG, for example, in the urine predisposes the patient to infections.