Renal: Nephrotic Syndrome & Nephritis Flashcards
What is nephrotic syndrome?
Note - this is a syndrome not a condition (i.e. other conditions cause it).
When the basement membrane in the glomerulus becomes highly permeable to protein, allowing proteins to leak from the blood into the urine.
What age is nephrotic syndrome most common?
Between 2-5 y/o
What classic triad is seen in nephrotic syndrome?
1) Hypoalbuminaemia (< 30g/L)
2) Proteinuria (>3+ protein on dipstick)
3) Oedema
What serum albumin level is seen in nephrotic syndrome?
Hypoalbuminaemia <30 g/L
What proteinuria level is seen in nephrotic syndrome?
≥3.5 g/day
What causes oedema that is seen in nephrotic syndrome?
Hypoalbuminaemia results in reduced oncotic pressure, causing oedema.
What 3 other features are seen in nephrotic syndrome?
1) Deranged lipid profile: high levels of cholesterol, triglycerides and low density lipoproteins (LDLs)
2) HTN
3) Hypercoagulability
Symptoms of nephrotic syndrome?
1) Peripheral oedema (more common in adults)
2) Facial oedema (more common in children)
3) Frothy urine
4) Fatigue
5) Poor appetite
6) Recurrent infection (due to immune dysfunction)
7) Venous or arterial thrombosis (e.g. MI, DVT) due to hypercoagulability
Clinical signs of nephrotic syndrome?
1) Oedema (e.g. peri-orbital, lower limb, ascites)
2) Xanthelasma and/or xanthoma
3) Leukonychia
4) SOB (with associated chest signs of pleural effusion – e.g. stony dullness in lung bases)
Typical urinalysis findings in nephrotic syndrome?
1) Proteinuria (protein ++++)
2) Frothy appearance
Pathophysiology of nephrotic syndrome?
1) Damage to the glomerular basement membrane and podocytes –> increased permeability to proteins (proteinuria).
2) Proteinuria then results in hypoalbuminaemia –> subsequent oedema due to reduced plasma oncotic pressure.
3) Loss of antithrombin-III, proteins C and S and an associated rise in fibrinogen levels predispose to thrombosis
4) Loss of thyroxine-binding globulin lowers the total, but not free, thyroxine levels.
What is the most common cause of nephrotic syndrome in children?
Minimal change disease.
This can occur in otherwise healthy children, without any clear risk factors or reason for developing the condition.
What will a renal biopsy and standard microscopy in minimal change disease?
Usually not able to detect any abnormality.
What will urinalysis show in minimal change disease?
1) Small molecular weight proteins
2) Hyaline casts
Management of minimal change disease?
Corticosteroids i.e. prednisolone.
Prognosis of minimal change disease?
The prognosis is good and most children make a full recovery, however it may reoccur.
What is the most common underlying cause in a 2 – 5 year old child with oedema, proteinuria and low albumin?
Nephrotic syndrome caused by minimal change disease.
What are 3 primary causes of nephrotic syndrome?
1) Minimal change disease
2) Focal segmental glomerulosclerosis (FSGS)
3) Membranous nephropathy
What are some 2ary causes of nephrotic syndrome?
1) Diabetes mellitus
2) SLE
3) Amyloidosis
4) Infections (HIV, Hep B and C)
5) Drugs (NSAIDs, gold therapy)
Investigations in nephrotic syndrome?
1) Urine dipstick: proteinuria and check for microscopic haematuria
2) MSU: exclude UTI
3) Quantify proteinuria –> use an early morning urinary protein:creatinine ratio or albumin:creatinine ratio.
4) FBC and coagulation screen
5) U&Es
What are 2 ways of quantifying proteinuria?
1) early morning urinary protein:creatinine ratio
2) albumin:creatinine ratio
What is the uribne albumin:creatinine ratio (ACR) in nephrotic syndrome?
High i.e. ≥250
General management of nephrotic syndrome?
1) High dose prednisolone
2) Low salt diet
3) Diuretics may be used to treat oedema
4) Albumin infusions may be required in severe hypoalbuminaemia
5) Antibiotic prophylaxis may be given in severe cases
How long are high dose steroids given for in nephrotic syndrome?
4 weeks, and then gradually weaned over the next 8 weeks.
In nephrotic syndrome, what dose ‘steroid sensitive’, ‘steroid dependent’, and ‘steroid resistant’ mean?
Steroid sensitive: 80% of children will respond to steroids
Steroid dependent: Patients that struggle to wean steroids due to relapses
Steroid resistant: Patients that do not respond to steroids
What are some complications of nephrotic syndrome?
1) Oedema
2) Hypotension
3) Thrombosis
4) Infection
5) AKI or CKD
6) Relapse
What % of patients will have a relapse in nephrotic syndrome?
80%
What causes hypotension in nephrotic syndrome?
Hypovolaemia occurs as fluid leaks from the intravascular space into the interstitial space, causing oedema and low BP.
What causes thrombosis in nephrotic syndrome?
1) Proteins that normally prevent blood clotting are lost in the kidneys
2) The liver responds to the low albumin by producing pro-thrombotic proteins
What causes a predisposition to infections in nephrotic syndrome?
The kidneys leak immunoglobulins, weakening the capacity of the immune system to respond.
This is exacerbated by treatment with medications that suppress the immune system, such as steroids.
What is nephritis?
Inflammation within the nephrons of the kidneys
What 5 classic signs are seen in nephritic syndrome?
1) Haematuria (either visible or detectable on urinalysis)
2) Mild to moderate proteinuria (typically <3.5 g/L) i.e. less than nephrotic syndrome
3) HTN
4) Oliguria (<300 mls/day)
5) Oedema
What 3 things are seen on urinalysis in nephritic syndrome/nephritis?
1) Haematuria (blood +++)
2) Proteinuria (mild - protein ++)
3) Red cell casts
What is the distinguishing feature of nephritic syndrome on urinalysis?
Red cell casts
What are the 2 most common causes of nephritis in children?
1) Post-strep glomerulonephritis
2) IgA nephropathy (Berger’s disease).
What is post-strep glomerulonephritis?
A glomerular condition mediated by an immunological response to a group A streptococci (GAS) infection.
What infection does post-strep glomerulonephritis follow?
Group A streptococci (GAS) i.e. Strep. pyogenes
E.g. tonsillitis caused by Streptococcus pyogenes
How soon after strep infection does post-strep glomerulonephritis typically occur?
Depends on the site of infection:
- 1-3 weeks for pharyngitis
- 3-6 weeks for skin infection
What is the most commonly affected age group for post-strep glomerulonephritis?
5-12 y/o
An increased risk also present for older adults >60years.
Are boys or girls more affected by post-strep glomerulonephritis?
Boys (2x)
Pathophysiology of post-strep glomerulonephritis?
Immune complexes made up of streptococcal antigens, antibodies & complement proteins get stuck in the glomeruli of the kidney and cause inflammation.
This inflammation leads to an acute deterioration in renal function, causing an AKI.
What is the most commonly recognised clinical presentation of post-strep glomerulonephritis?
Nephritic syndrome:
1) Generalised oedema
2) HTN
3) Haematuria
4) Oliguria (due to decline in renal function)
Note - Rarely, some cases can present, with rapidly progressive glomerulonephritis, with a rapid deterioration in kidney function towards kidney failure within weeks.
What causes HTN in nephritic syndrome?
Caused by water and salt retention due to renal insufficiency.
What causes oedema in nephritic syndrome?
Caused by water and salt retention due to renal insufficiency.
This can progress to severe complications of fluid overload, eg. respiratory distress due to pulmonary oedema.
What causes haematuria in nephritic syndrome?
Red blood cell components leak from glomerular capillaries through the damaged glomerular membrane into the urine.
What colour does urine typically appear in nephritic syndrome?
Urine looks tea or cola-coloured due to haematuria.
Key investigations in post-strep glomerulonephritis?
1) Urinalysis
2) U&Es: can show a variable degree of decline of eGFR and elevated creatinine
3) Culture (throat or skin swab to confirm the presence of GAS)
4) Serology
5) Renal biopsy
Purpose of urinalysis in post-strep glomerulonephritis?
1) Confirm haematuria
2) Quantify degree of proteinuria
Purpose of serology in post-strep glomerulonephritis?
Testing for antibodies against GAS can be helpful to confirm a recent infection using the Streptozyme test.
What is the Streptozyme test?
A combined test measuring the levels of the 5 antibodies that can be produced in response to a recent GAS infection e.g. Anti-streptolysin (ASO).
What investigation can provide a definitive diagnosis of post-strep glomerulonephritis?
renal biopsy - but due to the self-limiting clinical course of PSGN, a biopsy is rarely needed.
Management of post-strep glomerulonephritis?
Mainly supportive and focused on managing coomplications that arise from fluid overload.
1) Sslt & water restriction
2) Diuretics
3) Monitor BP
4) Monitor renal function
5) Abx if there is any evidence of a persistent streptococcal infection
What are some potential short-term complications of post-strep glomerulonephritis?
1) Pulmonary oedmea
2) Hypertensive encephalopathy
3) Severe AKI requiring dialysis
Prognosis of post-strep glomerulonephritis
Most cases in children resolve with no long-lasting effects.
What are some causes of transient or spurious non-visible haematuria?
1) UTI
2) Menstruation
3) Vigorous exercise (usually settles after 3 days)
4) Sexual intercourse
What are some causes of persistent non-visible haematuria?
1) Cancer (renal, bladder, prostate)
2) Stones
3) BPH
4) Prostatitis
5) Urethritis e.g. Chlamydia
6) Renal causes: IgA nephropathy, thin basement membrane disease
What are some spurious causes of haematuria (i.e. red/orange urine, where blood is not present on dipstick)
1) Foods: beetroot, rhubarb
2) Drugs: rifampicin, doxorubicin
What are 2 drugs that can cause discoloured urine?
1) Rifampicin
2) Doxorubicin
Who should be urgently referred under the 2 week wait in regard to haematuria?
Aged ≥45 y/o AND:
1) unexplained visible haematuria without UTI, or
2) visible haematuria that persists or recurs after successful treatment of UTI
Aged ≥60 y/o AND have unexplained nonvisible haematuria and either dysuria or a raised white cell count on a blood test.
Give some causes of haematuria
1) Trauma e.g. blunt injury
2) Infection (remember TB!!)
3) Malignancy
4) Renal disease e.g. Glomerulonephritis
5) Stones
6) Structural abnormalities e.g. BPH
7) Coagulopathy: causes bleeding of underlying lesions
8) Drugs
9) Benign: exercise
10) Gynaecological e.g. endometriosis
11) Iatrogenic e.g. catheterisation, radiotherapy
12) Pseudohaematuria
What infection is it important to consider in haematuria?
TB
What is the most common type of urothelial malignancy?
Transitional cell carcinoma –> painless haematuria.
What drugs can cause haematuria?
1) Cause tubular necrosis or interstitial nephritis –> aminoglycosides, chemotherapy
2) Cause interstitial nephritis –> penicillin, sulphonamides, and NSAIDs
3) Anticoagulants
Define glomerulonephritis
Inflammation of the glomeruli in the kidneys.
This damage allows protein (with or without blood) to leak into the urine.
Note - glomerulonephritis describes the pathology that occurs in various diseases rather than being a disease.
What is the glomerulus?
The first part of the nephron. It filters fluid out of the capillaries and into the renal tubule.
Give some ways the glomerulonephritis present
1) Isolated haematuria or proteinuria
2) Nephrotic syndrome
3) Nephritic syndrome
4) Acute renal failure
5) Chronic renal failure
What can glomerulonephritis be broadly categorised into?
Proliferative & non-proliferative
What is the definition of nephrotic syndrome?
Massive proteinuria (≥3.5 g/day) and hypoalbuminaemia (serum albumin ≤30 g/L).
What is non-proliferative glomerulonephritis characterised by?
A lack of glomerular cell proliferation.
How does non-proliferative glomerulonephritis typically present?
With nephrotic syndrome
What are the 3 types of non-proliferative glomerulonephritis?
1) Minimal change glomerulonephritis
2) Focal segmental glomerulosclerosis (FSGS)
3) Membranous glomerulonephritis
How does minimal change glomerulonephritis present?
With nephrotic syndrome.
Accounts for 80% of all nephrotic syndrome in children and 20% of nephrotic syndrome in adults.
What is the underlying cause of minimal change glomerulonephritis?
The underlying cause is unknown.
The name minimal change glomerulonephritis comes from the lack of changes seen on light microscopy.
What is the main histological finding in MCD?
Diffuse effacement of the podocyte foot processes (essential structures for maintaining the integrity of the glomerular filtration barrier).
This effacement occurs without significant immune complex deposition or thickening of the glomerular basement membrane.
What are the 3 key features of MCD?
Nephrotic syndrome:
1) Oedema
2) Proteinuria
3) Hypoalbuminaemia
How does oedema in MCD typically present?
- Periorbital puffiness
- Lower extremity swelling
- Ascites (severe cases)
What causes oedema in MCD?
1) Hypoalbuminaemia (decreases plasma oncotic pressure) –> due to proteinuria
2) Renal sodium retention (due to altered glomerular filtration)
What amount of protein is lost in the urine in MCD?
≥3.5 grams daily
What causes hypoalbuminaemia in MCD?
excessive urinary protein loss
What other possible features are seen in MCD?
1) Hyperlipidaemia
2) Haematuria
3) Renal insufficiency (AKI/CKD)
4) Infections
5) Thromboembolic events
What can cause hyperlipidaemia in MCD?
Due to increased hepatic synthesis of lipoproteins in response to hypoalbuminaemia.
Hyperlipidemia is also linked to a higher risk of atherosclerosis.
Describe haematuria in MCD
Microscopic haematuria may be present in a minority of MCD patients but is typically not a prominent feature.
If gross hematuria is observed, other diagnoses should be considered.
Why are patients with MCD at increased risk of infection?
Due to immunosuppressive treatment and the loss of immunoglobulins in the urine.
Infections include RTIs, cellulitis, and peritonitis.
Why are thromboembolic events more common in MCD
Due to hypercoagulable state induced by nephrotic syndrome.