Nephritic syndrome

Signs and symptoms

• Hematuria
• Proteinuria ranging from sub-nephrotic to >10 g/day, although it is rarely above nephrotic range proteinuria levels.
• Hypertension resting blood pressure is persistently at or above 130/80 or 140/90 mmHg.
• Blurred vision
• Azotemia
• Oliguria
• Red blood cell casts
• Pyuria

  Causes

Children/adolescents

• IgA nephropathy - Most commonly diagnosed in children who recently had an upper respiratory tract infection. Symptoms typically present within 1–2 days of a non-specific URI with severe flank/abdominal pain, gross hematuria, and edema of the hands, feet, and/or face.
• Post-streptococcal glomerulonephritis - Similar to IgA nephropathy, post-streptococcal glomerulonephritis most often occurs in children who have recently had an upper respiratory infection. In contrast with IgA nephropathy, however, PSGN typically presents 2–3 weeks after recovering from an URI that was caused specifically by a Streptococcus bacteria. The symptoms at onset are very similar to IgA nephropathy and include abdominal pain, hematuria, edema, and oliguria.
• Henoch–Schönlein purpura - Often considered a systemic form of IgA nephropathy, Henoch-Schönlein purpura is a systemic small-vessel vasculitis that is characterized by deposition of IgA antibody immune complexes in different key areas throughout the body. Most often, the condition presents in children with palpable purpura, abdominal pain, and arthritis. When the kidneys are affected, the IgA immune complexes deposit in the glomerulus very similarly to IgA nephropathy and will present in a similar way.
• Hemolytic uremic syndrome - Most cases occur immediately following infectious diarrhea caused by a specific type of E. coli. The bacteria produces a toxin that causes widespread inflammation and numerous blood clots in small blood vessels. When the inflammation reaches the kidney, or the by-products of systemic inflammation build up in the kidney, the patient will begin showing signs of nephritic syndrome or potentially acute kidney failure.

  Adults

• Goodpasture syndrome - This is a rare autoimmune disease where autoantibodies are produced that target the glomerular basement membrane in both the lungs and the kidneys. The damage to the basement membrane causes bleeding, and the disease often presents in patients as hematuria and hematemesis. If not treated promptly with plasmapharesis to remove the autoantibodies, it can lead to permanent damage in the lungs/kidneys.
• Systemic Lupus Erythematosus - Better known as simply "Lupus", this autoimmune disease can affect nearly every major system in the human body and the kidneys are no exception. Autoantibodies produced in SLE can form immune complexes that deposit along the glomerular basement membrane and cause glomerular inflammation which leads to a nephritic syndrome.
• Rapidly progressive glomerulonephritis - This is a syndrome of the kidney that is characterized by rapid loss of kidney function with glomerular crescent formation frequently seen on kidney biopsy. Without treatment, it will quickly lead to kidney failure and potentially death within months. This syndrome has numerous underlying causes that can also cause nephritic syndrome, so this may be more of an association than a cause.
• Infective endocarditis - Infection that affects the inner lining of the heart and can potentially cause a thrombus to form on one or more heart valves and, if left untreated, can cause septic emboli that can have many systemic effects, including deposition into the glomerulus, causing glomerulonephritis and nephritic syndrome.
• Cryoglobulinemia - Antibodies that are sensitive to the cold can become activated in cold conditions and cause an increase in blood viscosity as well as forming immune complexes that can deposit in the small blood vessels and can cause nephritic syndrome when this occurs in the kidneys.
• Membranoproliferative glomerulonephritis - Another type of glomerulonephritis that is caused primarily by immune complex deposition in the glomerular mesangium and glomerular basement membrane thickening, which activates the complement cascade and damages the glomerulus. This damage leads to inflammation in the glomerulus and can present with a nephritic syndrome.
• Other ANCA small-vessel vasculitides - The conditions included in this category are eosinophilic granulomatosis with polyangiitis, microscopic polyangiitis, and granulomatosis with polyangiitis.

  Pathophysiology

Diagnosis

Physical examination

• Edema - This could present as generalized edema or specific swelling of the hands, feet, and/or face.
• Other signs of fluid overload - Diffuse rales may be heard at bilateral lung bases or diffusely in all lung fields on auscultation with a stethoscope. Jugular venous distention may also be appreciated when visualizing the veins of the neck on physical exam.
• Elevated blood pressure - Measured at least two separate times with at least two minutes between measurements using a sphygmomanometer or equivalent method.
• Abnormal heart sounds - If the underlying cause is cardiac in nature, then you may appreciate abnormal heart sounds during auscultation of the heart.

  Laboratory testing

• Serum electrolytes - The kidney is one of the main regulators of electrolytes in the human body and measuring the different electrolyte levels using either a basic metabolic panel or comprehensive metabolic panel can be a useful indicator of the underlying pathology.
• Serum creatinine - Also measured using a BMP or CMP, creatinine is one of the most important indicators of current kidney function and is used to calculate the glomerular filtration rate. An elevated creatinine level is considered abnormal and may indicate decreased kidney function.
• Blood urea nitrogen - Also measured using a BMP or CMP, blood urea nitrogen is an indicator of how much nitrogen is in the blood at the time of the phlebotomy. The kidney is responsible for excreting nitrogenous substances in the urine, so an elevated BUN usually indicates that the kidney is not functioning appropriately.
• Urine Analysis - After the patient provides a urine specimen, it is sent to the lab for analysis using a variety of methods including urine dipstick testing and microscopic examination. Because the kidney is responsible for making urine, analyzing the urine directly can provide crucial data that can help the physician diagnose nephritic syndrome. Some findings on urinalysis that are consistent with nephritic syndrome include red blood cells, red blood cell casts, proteinuria, and possibly white blood cells.

• Blood culture - This is the process where a sample of the patient's blood is sent to the microbiology lab to attempt to isolate and grow any bacteria that may be circulating in the blood, in order to identify the pathogen. This is helpful if the physician suspects infection as the underlying cause of the nephritic syndrome.
• Antinuclear antibody titer - ANA is commonly positive in patients who have an underlying autoimmune disease, so this test is useful if the physician suspects an underlying autoimmune disease as the cause of the presenting nephritic syndrome. If positive, then the physician may order additional tests to determine which autoimmune condition is the cause and how best to treat it.
• Antiglomerular basement membrane antibody - If positive, this is highly indicative of Goodpasture's syndrome and can be used to guide treatment.
• Antineutrophil cytoplasmic antibody - If positive, this indicates that there is likely an underlying vasculitis that may be causing the acute nephritic syndrome.
• Serum complement - Complement factors bind to antibodies to form immune complexes and a decreased serum complement level could indicate that the complement is being consumed at a higher rate due to the formation of immune complexes leading to deposition in the glomerulus of the kidney. There are numerous underlying pathologies that cause consumption of complement factors.

• Invasive testing

Treatment

• Bed rest during the recovery process to ensure administration of optimal medical therapy with as low of a risk as possible for any exacerbating factors.
• Fluid restriction to minimize the risk of edema or to reduce any active edema that may be present.
• A special diet during the hospital stay that restricts sodium, potassium, and fluids in conjunction with the previously mentioned fluid restriction in an attempt to control symptoms of fluid overload.
• Administration of diuretics if patient is showing signs of fluid overload. This will cause excess fluids to be excreted in the urine and may lessen the workload placed on the kidney, allowing it to recover from the inflammatory damage.
• Administration of antihypertensives to alleviate hypertension and maintain a normal blood pressure during the recovery process.
• Administration of anti-inflammatory medications to reduce active inflammation in the kidney.
• If the patient is showing signs of kidney failure or end-organ damage, the treatment team may opt to utilize kidney dialysis temporarily to decrease stress on the kidneys and allow for optimal recovery.

Prognosis

Epidemiology

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