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Nephrotic Syndrome
See also:
Acute Renal Failure,
Chronic Renal Failure,
Acute Nephritis and Nephrosis,
Interstitial Nephritides and Nephrotoxins,
Glomerulonephritis.
Nephrotic syndrome is a pattern of presentation of renal disease, rather than a single pathological entity or diagnosis. It comprises the following elements:
Features of the nephrotic syndrome:
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Oedema is thought to occur due to the loss of plasma oncotic pressure secondary to hypoalbuminaemia, causing accumulation of fluid in the extracellular space; a decrease in intravascular volume is thought to cause renal hypoperfusion further enhancing salt and water retention. However, this model cannot fully explain all the pathophysiological and clinical features of the nephrotic syndrome and other, as yet unelucidated, intra- and extra-renal mechanisms may be responsible for the combination of biochemical and clinical features seen in nephrotic syndrome. Hypercholesterolaemia is thought to be caused by:
- Stimulation of the liver to increase synthesis of all plasma proteins (including the lipoproteins), due to their low level in the blood.
- Reduction of lipoprotein catabolism due to reduced levels of lipoprotein lipase in blood.
Other consequences of nephrotic syndrome:2
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In the US, its annual incidence among children is reported to be 2–7 cases per 100,000.2 Incidence varies among adults depending on the incidence of underlying causes for the condition, particularly diabetes mellitus.
Primary renal diseases
- Minimal-change nephrotic syndrome (~85% of childhood cases)
- Focal segmental glomerulosclerosis (~9% of childhood cases)
- Mesangial proliferative glomerulonephritis (~2% of childhood cases)
- Membranous nephropathy (~3% of childhood cases)
- Membranoproliferative glomerulonephritis
Secondary renal diseases
- Postinfectious causes, e.g. Group-A beta-haemolytic streptococci, TB, malaria, syphilis, viruses such as VZV, HBV, HIV, infectious mononucleosis.
- Collagen vascular diseases, e.g. SLE, rheumatoid arthritis, polyarteritis nodosa, Henoch-Schönlein purpura, vasculitides.
- Metabolic diseases, e.g. diabetes mellitus, amyloidosis.
- Inherited disease, e.g. Alport's syndrome, hereditary nephritis, sickle cell disease.
- Malignant disease, e.g. multiple myeloma, leukaemia, lymphoma, carcinoma of breast/lung/colon/stomach.
- Medications, e.g. NSAIDs, captopril, lithium, gold, diamorphine, interferon-alpha, penicillamine, probenecid and many others.
- Toxins, e.g. bee sting, snake bites, phytotoxins.
- Pregnancy, e.g. pre-eclampsia.
- Transplant rejection.
Symptoms
- In children facial swelling is a common presenting feature, with periorbital oedema often being the first evidence that something is wrong; oedema may progress to involve the whole body.
- Adults tend to present with peripheral oedema affecting the ankles and legs, which may progress to involve the whole body.
- Some patients may notice frothiness of their urine.
- Hypercoagulability may manifest as venous or arterial thrombosis, e.g. DVT, MI.
- Recurrent infections and/or general fatigue, lethargy, poor appetite, weakness or episodic abdominal pain may cause presentation to a doctor.
Signs
- Oedema of dependent parts or generalised oedema are the main clinical findings.
- Facial oedema may be found in children.
- Occasionally, severely hypoalbuminaemic cases may have pleural effusions or ascites.
- Urinalysis will reveal gross proteinuria.
- Hypertension and haematuria are not usually found but may affect a minority of cases.
- To find underlying cause of syndrome, direct future management and establish baseline of severity/monitor response to treatment
- Urinalysis and urine microscopy/culture and sensitivity
- Urinary protein:urinary creatinine ratio
- Light-chain urinary protein excretion (?myeloma)
- 24-hour urinary protein excretion
- U&E, creatinine
- Serum albumin
- Serum lipids
- FBC
- Hepatitis B and C serology
- Serology for other possible infective aetiologies including HIV if thought relevant
- Cryoglobulins/serum protein electrophoresis/autoantibody profile if relevant
- CXR to exclude malignancy and exclude other causes of oedema
- Renal tract ultrasound to assess size and structural condition of kidneys (obstructed or small kidneys may contraindicate renal biopsy).
Most cases will require renal biopsy to determine the exact underlying cause of the condition; children under 8 years old usually have minimal-change nephrotic syndrome and so may be spared this investigation, especially if they are steroid-responsive. Adults with an obvious cause (e.g. diabetes with evidence of other complications) may be spared a biopsy at the discretion of a renal specialist. Other investigations to diagnose less usual causes such as abdominal fat/gingival biopsy to detect amyloidosis may be needed in place of or in addition to a renal biopsy.
- Most cases do not require acute hospitalisation.
- Indications for acute admission include:
- Severe generalised oedema, particularly if pleural effusion/oedema causing respiratory compromise
- Tense scrotal/labial oedema
- Complications of the nephrotic state (e.g. sepsis, pneumonia, MI, DVT, growth failure)
- Inability to comply with therapy/inability to cope with condition in family/independently
- Any features of a possible nephritic syndrome such as haematuria, hypertension and impaired renal function parameters
- Reduce salt intake in diet (avoid processed foods and adding salt to food).
- Give diet with adequate calorific intake and sufficient protein content (1–2 g/kg daily).3
- Hyperlipidaemia – does not initially require therapy but may do so if prolonged.3
- Fluid restriction is not usually necessary (if severe enough to need this then may need admission).3
- Referral to a renal service for urgent outpatient assessment is advisable, to confirm the mode of presentation and direct any future investigations/therapy.
- Oedema is treated through diuretic therapy with furosemide (~1mg/kg/day) ± spironolactone (~2mg/kg/day).
- Check weight regularly to assess response to diuretics and ensure fluid retention is not worsening, or that patient is over-diuresed.
- Patients with very low albumin levels may not respond to diuretics and may require admission to receive intravenous albumin therapy.
- Some children with severe oedema may be prescribed antibiotic prophylaxis against infection and this should usually be on the advice of a renal specialist.
- Most children will have minimal-change nephrotic syndrome and usually respond to a trial of steroid therapy under the direction of a renal specialist.
- Other forms of nephrotic syndrome are less treatment responsive; ACE inhibitors are frequently used in adults to some effect.
- In children who do not respond to steroids, and in some adults, treatment may be with other immunomodulatory drugs such as cyclophosphamide, cyclosporin and levamisole.
- This is highly variable depending on the underlying cause.
- Congenital nephrotic syndrome usually carries a very poor prognosis.
- Outlook for the vast majority of children with minimal-change nephrotic syndrome is excellent; response to steroids is the norm, although there may be relapses and a need to use alternative immunomodulatory drugs.
- Adult prognosis is variable and largely related to the underlying cause, its severity, progression and response to any treatment used to modify it.
Document References
- Russo LM, Sandoval RM, McKee M, et al; The normal kidney filters nephrotic levels of albumin retrieved by proximal tubule cells: Retrieval is disrupted in nephrotic states. Kidney Int. 2007 Jan 17;. [abstract]
- Agraharkar M, Gala G, eMedicine, Nephrotic Syndrome, 2006.
- Travis L, eMedicine, Nephrotic Syndrome, 2005; Paediatric overview
Internet and Further Reading
- Medline Plus - Acute Nephritic Syndrome
- Acute nephritis (GPN)
- Medline Plus - Nephrotic syndrome.
- EdREN, website of renal unit of the Royal Infirmary of Edinburgh, information for patients on the nephrotic syndrome, 2006.
- Loghman-Adham M; Evaluating proteinuria in children. Am Fam Physician. 1998 Oct 1;58(5):1145-52, 1158-9. [abstract]
- Carroll MF, Temte JL; Proteinuria in adults: a diagnostic approach. Am Fam Physician. 2000 Sep 15;62(6):1333-40. [abstract]
- Travis L, eMedicine, Nephrotic Syndrome, 2005; Paediatric overview
- Hogg RJ, Portman RJ, Milliner D, et al; Evaluation and management of proteinuria and nephrotic syndrome in children: recommendations from a pediatric nephrology panel established at the National Kidney Foundation conference on proteinuria, albuminuria, risk, assessment, detection, and elimination (PARADE). Pediatrics. 2000 Jun;105(6):1242-9. [abstract]
- Carome MA, Moore J Jr; Nephrotic syndrome in adults. A diagnostic and management challenge. Postgrad Med. 1992 Aug;92(2):209-15, 218, 220. [abstract]
- Hogg RJ; Adolescents with proteinuria and/or the nephrotic syndrome. Adolesc Med Clin. 2005 Feb;16(1):163-72. [abstract]
DocID: 2505
Document Version: 21
DocRef: bgp676
Last Updated: 2 Feb 2007
Review Date: 1 Feb 2009
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