3. How well is protein conserved by Kidneys?
In 24-hour, approximately 930 L of plasma containing 7
gm/dL of protein passes through kidneys(~65 kg of
protein), but less than 100 mg appear in urine(0.00015%)
Filtration is dependent on adequate renal flow; maintained
by vasodilatation and vasoconstriction
4. Glomerular Membrane
Modified capillary wall comprising
endothelium (50-100 nm pores)
A cell-less basement membrane and
an outer specialized epithelial cell layer
(55 nm slit diaphragm)
The whole of the glomerular membrane carries
a fixed net negative charge:
Due to a Glycosialoprotein coat
Charge increases in density from the Lamina
Interna towards the Lamina rara Externa with
the greatest density at the slit diaphragm of
the epithelium
5. Glomerular Filter
Glomerular filter acts as a high capacity ultrafiltration
membrane
Made up of highly modified vascular endothelial cells, with
only a thin cytoplasm and large pores allowing almost direct
access of filtrate to the basement membrane
Thus the glomerular wall can be pictured as having two
filtration barriers in series:
An Inner, charge : dependent membrane; and
A more external, mainly size selective barrier in the
outer basement membrane
Glomerular filter acts via two phenomenon size
selectivity and charge selectivity
6. The Glomerular Membrane
Adapted from: Proteinuria: Tubular handling of albumin—degradation or salvation?
Erik I. Christensen & Henrik Birn
Nature Reviews Nephrology 9, 700-702 (December 2013)
8. Normal Urinary Protein Content
Normal Adult excretes < 140 mg/ 24 hour of protein
Plasma Proteins represent only 25 mg/24 hr of total urinary
protein; of which about half is albumin; remaining protein are
of renal origin, Uromodulin being the major contributor (70
mg/ 24 hour)
Low-level albuminuria (Microalbuminuria) has prognostic
value both for renal and non-renal diseases
Proteins of Renal Origin- Tamm- Horsfall Protein, Urokinase,
Secretory IgA
9. Proteinuria
Proteinuria means the presence of an excess of serum
proteins in the urine (> 500 mg/24 hour)
Normal protein in urine <150 mg/day
Approximately 30 mg is albumin
Rest is secreted by tubules: Tamm Horsfall, IgA,
Haptoglobin, Transferrin, β2 microglobulin
10. 1. “Leaky” Glomerular capillary barrier”
Allows albumin (and sometimes globulin) to
cross into Bowman’s space
Seen in Glomerulonephritis
Proteinuria – Mechanisms
11. Glomerular barrier
Tubule
Normally, the larger proteins are excluded
at the glomerular barrier
Smaller proteins can pass, but are mostly
reabsorbed
12. Tubule
Large proteins are able to pass by the
abnormal glomerular barrier
Leaky Glomerular barrier
13. 2. Malfunctioning tubular reabsorption of
smaller proteins
Albumin excluded at (normal) glomerular barrier
Sick tubules unable to reabsorb the normally-filtered
smaller proteins
“Tubular” proteinuria
eg:- Tubulointerstitial nephropathy
14. Tubule
Malfunctioning tubules unable to reabsorb the smaller
proteins filtered at the glomerulus
Tubular Reabsorption Malfunctioning
15. 3. “Overflow” proteinuria
Filtered load of proteins exceeds capacity of tubules
to reabsorb it all
“Filtered load” = plasma concentration X GFR
Increased plasma concentration: ie:- excess light
chains
Increased GFR: pregnancy, fever, hyperglycemia
17. Determinants of urine protein excretion
Age, Sex and Diurnal variation
In neonates, albumin excretion tends to be higher than in
older children and adults: this has been attributed to
greater permeability of the neonatal glomerulus;
Males
Protein excretion in day > night time
18.
19. Posture
Ambulatory urine protein excretion is higher than it is
overnight or during recumbency
Renal biopsies of patients with postural proteinuria
reveal that 8% have unequivocal evidence of well-defined
disease and 45% have subtle alterations in glomerular
structure
>50% of patients has been shown to have there is reduced
blood flow to the left renal vein during standing owing to
entrapment of the left renal vein
T/t: Conservative Management with annual assessment of
proteinuria and renal function
20. Exercise
Exercise-induced proteinuria was discovered over a century
ago in soldiers after marches or drills
Five –to 100-fold increases in the excretion of proteins such
albumin, transferrin and immunoglobulins have been
observed following 26-mile marathon runs
Glomerular Pattern, although mixed glomerular and tubular
proteinuria has also been described, which persists for over 3
hours after exercise
Reason: Some degree of Renal Ischemia owing to
redistribution of blood during exercise has been suggested
a possible mechanism
21. Pregnancy
Small increase in albumin excretion during the third trimester
(Increased Glomerular permeability)
Total urine protein excretion increases owing to decreased
renal tubular protein reabsorption
Detection of significant proteinuria in new-onset
hypertension distinguishes between those pregnancies
with pre-eclampsia and those with gestational hypertension
Reagent strip 1+ or greater, proteinuria should be
quantitated by a laboratory measure in a spot or 24 h urine
sample
Significant Proteinuria > 500 mg of Protein excretion
22. Proteinuria in Kidney Disease
Richard Bright (1836) Association between proteinuria
and kidney disease
Total urine protein excretion is <150 mg/24 h in adults and
<140 mg/m2/24 h in children, normal concentrations are
often undetectable by chemical methods
Albumin excretion rate < 20 µg/min
23. Type Pathophysiology Causes
Glomerular Increased glomerular capillary
permeability to protein
Primary and
Secondary
Glomerulo-nephritis
Tubular Decreased tubular reabsorption
of proteins in glomerular filtrate
Tubular or Interstitial
Disease
Nephrogenic
proteinuria
Increased excretion of protein
produced by the kidney (eg:-Tamm
Horsfall protein, N-Acetyl β-D
Glucosaminidase)
Acute Pyelonephritis
(Secretion of IgA)
Proteinuria of
Prerenal Origin
Increased production of low-
molecular-weight proteins
Light chain disease,
Myoglobinuria
Post-renal Proteinuria Obstruction of Urinary Tract or
Inflammation
UTI
24. Proteinuria in staging and prognosis of
chronic kidney disease
Association of proteinuria with poorer prognosis in people
in the general population and across all stages of chronic
kidney disease (CKD)
Quantitation of proteinuria (in the absence of a symptomatic
urinary tract infection and preferably using
the first morning urine) is an essential component of CKD
staging
The decision limit is an Albumin/Creatinine ratio (ACR) >30
mg/mmol(~300 mg/24 h) or urine protein/creatinine ratio
(PCR) >50 mg/mmol (~0.5 g/24 h)
25. Glomerular proteinuria and Nephrotic
syndrome
In the normal adult, the renal tubules reabsorb about
2–3 g of filtered albumin every 24 hour
Nephrotic syndrome can be defined as proteinuria severe
enough to cause hypo-albuminemia and edema
The degree of proteinuria varies but is generally >3.5 g/24
and is accompanied by a plasma albumin
<25 g/L
However, it should be remembered that the amount of
protein in the urine may decrease as the plasma protein
concentration or the GFR falls.
26. Nephrotic Syndrome
Massive Proteinuria (Loss of > 3.5 gm/day)
Hypoalbuminemia
Generalised Edema
Hyperlipidemia and Lipiduria
27.
28.
29.
30. Urine protein selectivity and classification of
glomerulonephritis
Selectivity: based on assumption that there may be differentia
filtration of large molecular weight proteins in glomerular dise
Protein selectivity is based on a comparison of the relative
clearance of IgG(150 000 Da) and transferrin (69 000 Da)
calculated as follows:
Clearance of IgG = [IgG]U x [Trans]P
Clearance of transferrin [IgG]P x [Trans]U
where:
[IgG ]u = Urine IgG concentration
[Trans]p = Plasma transferrin concentration
[IgG ]p = Plasma IgG concentration
[Trans]u = Urine transferrin concentration
31. Selectivity of proteinuria
Excretion of relatively low M.W. protein (Albumin or
transferrin) is known as Selective proteinuria while if
excretion is predominately high M.W. protein (IgG, IgM or
α2 macroglobulin) it is Non-selective proteinuria
Related to relative damage of Glomerular filter
If there is predominantly loss of charge selectivity
Selective proteinuria
If there is predominantly loss of size selectivity
Nonselective proteinuria
33. Patho-Physiological Consequences of
Glomerular Proteinuria
Hypoalbuminemia
Urinary Albumin Loss
Loss of Fixed Anionic charge on the glomerular
membrane
Edema; Salt and Water Retention
Hypoalbuminemia
Decrease in Colloid Osmotic Pressure
34. Abnormalities of Other Plasma Proteins
Urinary loss of Antithrombin III
Urinary Loss of Transferrin, Vitamin D binding
Protein
Hyperlipidemia
Increase in Total Cholesterol and TG ; Inverse
relationship with Albumin
Decrease in HDL: Urinary Loss
LCAT and LPL activity is decreased
35. Tubular Proteinuria
Protein Excretion in tubular proteinuria is generally
<1–2 g/24 h
Greater increase in proteins of <60 000 Da
Majority of filtered proteins and other solutes are
reabsorbed by the proximal tubule
In renal tubular disease, the reabsorption of protein
together with water, ions, glucose and amino acids is
impaired
In tubular disease, the increase in excretion of low
molecular weight proteins is far greater than that
found for larger proteins such as albumin
36. Renal disorders associated with tubular
proteinuria
Renal Interstitium and tubules are principally affected
Primary Tubular Proteinuria
Large amounts of plasma proteins if being presented to the
proximal renal tubules, absorption of it causes Inflammation
and Secondary tubular damage
Direct Tubular Toxic effects by Autoimmune or Infective
mechanisms, Drugs, Toxins, Metabolic disorders, pathology
leading to glomerular proteinuria
Tubular Dysfunction
39. Methods of assessing tubular damage
Tests of reabsorption of glucose, phosphate, bicarbonate
and amino acids
High molecular weight protein are commonly used
markers of renal tubular damage
N-Acetyl β-D Glucosaminidase (NAG) [1,50,000
Da]
Lactate Dehydrogenase
γ-glutamyl transferase
Alkaline phosphatase
40. Low molecular weight protein markers of renal
tubular disease
Characteristics:
It should have a constant plasma concentration
Be freely filtered by the glomerulus
Tubular reabsorption should be near saturation so that small
small reductions in tubular function result in significant
urinary excretion
Tubular reabsorption should be unaffected by coexisting
glomerular proteinuria
Should be stable in urine and easily measurable
41. Examples:
Lysozyme (Muramidase): first low molecular
weight marker of tubular function
β2- Microglobulin
Retinol Binding Protein
α1- Microglobulin
42. Proteinuria of Prerenal origin
Occurrence in the urine of abnormal amounts of protein
filtered by the glomeruli in the absence of any glomerular
or tubular abnormality
‘Overflow’ proteinuria such as Bence Jones proteinuria,
Hemoglobinuria and Myoglobinuria
Limitations: Abnormally high concentrations of protein at
the glomerulus and in the tubular lumen can cause
glomerular and tubular abnormalities
43. Bence Jones Proteinuria
Presence of Bence Jones Proteins (22 kDa)
Important indication of the presence of Myeloma
In approximately 20% of cases may occur in the absence of
a paraprotein band in the serum
Detection Methods: Classic Heat Test
Bradshaw Test
Electrophoresis supplemented by
Immunofixation
44. Myoglobinuria
Myoglobin (17.8 kDa)- Heme Containing protein catabolized
by endocytosis and proteolysis in proximal tubules following
glomerular filtration
Typically, only 0.01 to 5% of filtered protein appears in urine
Rhabdomyolysis: Causes rapid destruction of striated
muscle; release of Myoglobin to circulation
Myoglobin Directly Toxic to renal tubules, cause
acute tubular necrosis with acute renal failure
45. Microalbuminuria as a marker of risk
Microalbuminuria is defined as an albumin excretion rate of
20–200 µg/min (30–300 mg/24 hour or 3–30 mg/mmol
Creatinine)
Microalbuminuria was coined to describe an increase in
urine albumin that is detectable by sensitive immunoassays
but is below the detection limit of chemical urine protein
methods and dye-binding stick tests
Diabetic patients with microalbuminuria are at increased
risk of developing dipstick positive proteinuria and CKD
46. Early identification allows aggressive treatment to improve
glycemic control, blood pressure and plasma lipids and
been shown to improve outcome
Microalbuminuria in non-diabetic as well as diabetic
populations identifies patients at increased cardiovascular
risk
Furthermore, microalbuminuria has been found to be a
predictor of outcome in critically ill patients following insults
such as major surgery, trauma or sepsis
47.
48. Paraproteinemias
A monoclonal immunoglobulin or immunoglobulin light
chain in the blood or urine resulting from a clonal
proliferation of plasma cells or B-lymphocytes
Class of Ig produced by tumour gives clue to the site of B-
cell development where, malignant transformation has
occurred
eg:- Tumours of Early B-Cells secrete Monoclonal
IgM while tumours of end-differentiated B-cells
secrete IgG or IgA
Elderly > Young
50. Monoclonal Proteins
Appear as homogenous, compact bands on
electrophoretic separations
Detectable in serum are intact immunoglobulins; if
there is renal damage, leaks into Urine
Low Molecular weight fragments and monoclonal free
light chains [Bence Jones Proteins (BJPs)] can pass
through normal glomeruli and appear in urine [In the
absence of Renal Damage, may be detected in serum too]
53. Laboratory Investigations of Paraproteins
Serum Paraprotein and/or Bence Jones proteins (BJP)
Highly sensitive marker for B-Cell malignancies;
particularly for Myeloma > 95%;
Waldenstorm’s madroglobulinemia (> 10%)
Identification of Paraproteins
Serum Protein Electrophoresis (SPE) : Detection of
Monoclonal proteins is one of two clear indications for the
measurement of Serum IgG, IgA, IgM concentrations
54. Consensus Recommendation of the International
Myeloma Workshop Consensus Panel
Protein Electrophoresis Only reliable method for the
detection of Paraproteins in serum and urine
Abnormal bands in SPE- quantitated by Scanning
densitometry
Immunofixation should be used to type the monoclonal
band Confirms the Clonality and identify the
heavy and light chains
Paraproteins are seen in SPE If Concentration is
> 5gm/dl
May be missed if < 5gm/dl
55. Suspicion of B-Cell Malignancy with apparently
normal Electrophoresis Immunofixation
Raised concentration of IgG or IgA, but no clear
staining in βγ region indicates a Polyclonal Increase
IgD paraproteins and free heavy chains are susceptible to
post-synthetic degradation results in diffuse
paraprotein bands on electrophoresis, may be missed if
present at low concentrations
56. Mistaken Protein Variants for Paraproteins
Allotypic variants, e.g. α1-antitrypsin, may result in two
bands in a normally homogeneous region
Haptoglobin–haemoglobin complex as a result of invitro
haemolysis, causing splitting of the normally homogeneous
α2 zone
Acute phase proteins, e.g. C-reactive protein, increases,
which may result in additional bands being present
Fibrinogen in plasma or inadequately clotted samples
additional band in the γ region
Lipoproteins, which may give distinct bands in the β region
in agarose systems
57. Urine Examination
Urine should be examined in every patient suspected of B-Cell
Malignancy
Should be done even when there is no serum monoclonal
component detected
Also important to monitor the amount of BJP during a
patient’s follow-up, even when BJP is not detected at
presentation, it can appear later in the course of the disease
(BENCE JONES ESCAPE)
Presence of BJP Strong evidence of Malignancy
58. Several proteins can be mistaken for monoclonal proteins in
urine electrophoresis (Particularly in case of Tubular
Proteinuria:
α1- Macroglobulin
Lysozyme (γ region)
Degraded fragments of protein of glomerular origin
β2- Microglobulin
Combination of SPE and Free light chain measurement has
has been suggested as a suitable screening protocol for B-
Cell malignancy
59. Immunofixation
Helps to identify heavy and light chain components
Indications
Confirms Clonality of a band detected by Electrophoresis
Tests for ɑ, γ or µ heavy chains and ƙ and ƛ light chains
Tests for δ and ε heavy chains when a serum shows
monoclonal light chains without a corresponding ɑ, γ or µ
heavy chains
Presence of Amyloid: Where SPE shows no band
Investigate the possibility of an apparent paraprotein in
serum or urine caused by a high concentration of another
protein (eg:- Fibrinogen, Complement components, β2-
macroglobulin)
60. Detect Minimal Residual Disease or complete remission
following hematopoietic stem cell transplantation for
Myeloma when no monoclonal component is seen on
electrophoretic separation
Immunofixation techniques enhances the sensitivity of gel
electrophoresis both by removing background staining
selectively increasing the amount of protein (by adding
antibodies) in the band of interest
61.
62.
63.
64. Multiple Myeloma
Commonest of the malignant causes of
paraproteinemia
Plasma cell tumour; increased
Immunoglobulin production (IgG)
Disease of Elderly ; 70-80 years, Male>Female
Clinical Features:
Bone Pain (70%)
Hypercalcemia (30%)
Fever (15%)
Renal Insufficiency (10%)
Infection (10%)
65. Three Major diagnostic features
Identification of monoclonal protein in serum or urine
Presence of neoplastic cells in bone marrow
Destruction of Bone
Laboratory Parameters:
IgG, IgA and BJP: Account for majority of Paraproteins
in Myeloma
IgD paraproteins occur usually with ƛ Light Chains
Hyperviscosity Seen with IgA or IgG3 paraprotein, have
tendency to aggregate
Monoclonal protein concentration > 30g/L
66. Staging System for Multiple Myeloma
Durie Salmon Staging- previously used
International Staging System currently used;
Concentration of β2- Microglobulin and Albumin is
used for staging
67. β2-Microglobulin
Seen in Increased cell turnover, or example malignancy
(particularly lymphoid), acquired immune deficiency syndromes
and inflammatory conditions
Cleared from the plasma by glomerular filtration followed by
proximal tubular reabsorption and catabolism
Important prognostic indicator in Myeloma
68. Investigations in Myeloma
Diagnosis ( 2 out of 3 are required for Diagnosis)
1. Serum and Urine for presence of Paraprotein
2. Bone Marrow Biopsy
3. Skeletal X-ray Survey – Punched Out Lesions
69. Management and Prognosis
Serum Calcium
Serum Creatinine and Urea
Serum Albumin
Full Blood Count and Film
Erythrocyte Sedimentation Rate
Quantitative immunoglobulins
24 hour urine for UPEP, UIFE
Serum β2 Microglobulin
Serum Paraprotein Concentration
SPE, Serum Free Light Chains
Skeletal Survey, MRI Spine
Bone marrow biopsy: H+E, Flow Cytometry, Cytogenetics
Molecular Studies: FISH, Gene Expression Profiling (GEP), PCR
Optional: PET, bone
density examination
Future: Markers for
Apoptosis
70. Monoclonal Gammopathy of Undetermined
Significance
Benign
Monoclonal proteins < 30g/L
Clonal bone marrow plasma cells < 10%
No End organ damage (No Hypercalcemia, Renal Damage,
Anemia, Bone Lesions)
No Bence Jones Proteins
71. Waldenstrom’s Macroglobulinemia
IgM Myeloma is rare
Waldenstrom Macroglobulinemia is characterized by the
presence of an IgM paraprotein and pleiotropic lymphoid
proliferation in the bone marrow
Disease of elderly men
Investigations
Serum and Urine for presence of paraprotein
Bone marrow Biopsy
Lymph Node Biopsy
Hematologic Investigations
72.
73. The heavy chain diseases are rare lympho-plasmacytic
malignancies
Patients have absence of light chain and secrete a defective
heavy chain that usually has an intact Fc fragment and a
deletion in the Fd region
Gamma, alpha, and mu heavy chain diseases have been
described
Heavy Chain Disease
74. Gamma Heavy Chain Disease (Franklin's Disease)
Frequently associated with Autoimmune diseases, especially Rheumatoid
Arthritis
Diagnosis: Anomalous serum M component [Often <20 g/L (<2 g/dL)]
Alpha Heavy Chain Disease (Seligmann's Disease)
Most common of the heavy chain diseases
Closely related to a malignancy known as Mediterranean lymphoma
Alpha heavy chains assesment is difficult
Mu Heavy Chain Disease
Seen in patients with Chronic Lymphocytic Leukemia
Presence of vacuoles in the malignant lymphocytes and the excretion of
kappa light chains in the urine
75. Summary
Proteinuria is a potent risk marker for progression of renal
disease in both non-diabetic and diabetic kidney disease
Various type of proteinuria has been classified according to
the site of origin (Glomerular, Tubular) or incase of prerenal
origin (Overflow proteinuria)
Microalbuminuria has been attributed to the assessment of
cardiovascular risk, Diabetic Nephropathy
Paraproteinemias are most commonly diagnosed by
Electrophoresis scanned by Densitometry, Immunofixation
76. Acknowledgement
To my Moderator Mr. Binod
Kumar Lal Das Sir for his
support and guidance during
the preparation of the
presentation
Published reference ranges for total urinary protein excretion vary considerably with the analytical method used
Tamm-Horsfall Protein- Cast Formation
Urokinase- Fibrin Removal
Secretory IgA- Bactericidal
The excess protein in the urine often causes the urine to become foamy
Proteinuria of <1 g/24 h has been described in 0.6–9% of healthy young adults, in the absence of urinary red cells, white cells or casts, and can be divided into ‘Constant’ an d ‘Postural’ based on its persistence after recumbency
Biopsy is reserved for the rare patient who has evidence of progressive renal impairment
Large protein meal is associated with an increased urine albumin excretion, which appears to be secondary to an associated increase in GFR
In the UK, NICE guidelines for the routine antenatal care of healthy pregnant women recommend blood pressure and urine protein measurement at each antenatal visit; 660 000 women each year will have at least 7–10 such checks. Gestational hypertension is defined as new hypertension occurring after 20 weeks of pregnancy, but without significant proteinuria. In this group, routine urine protein measurement may be performed using an automated reagent-strip reading device (more reliable than a manual reading) or by a laboratory method.
NAG- from tubular damage
Any renal disease is more likely to progress, there is an increased risk of developing acute kidney injury, and both all-cause and cardiovascular mortality are increased
The presence of proteinuria in CKD is sufficient indication to initiate blockade of the renin–angiotensin–aldosterone system(RAS) with angiotensin- converting enzyme inhibitors (ACEI) or angiotensin-II receptor blockers(ARB)
Nephrotic syndrome, glomerular proteinuria is a feature of several other syndromes of nephron injury, and the severity of proteinuria taken together with other clinical findings can allow useful diagnostic classification
The enzyme most widely employed for monitoring tubular damage is N-acetyl β-d-glucosaminidase (NAG), a lysosomal enzyme of 150 000 Da, which is found in high
concentrations in the cells of the proximal tubule. Two isoenzymes of N AG are found in urine, one acidic and one basic: the acidic form is found in normal urine and both are excreted in patients with renal disease. Its lack of specificity limits its utility but NAG may be of value in monitoring inherited tubulopathies and in assessing tubular damage during cancer chemotherapy or treatment
Becoming apparent that non-renal conditions associated with proteinuria that disappears when the condition resolves
The link between microalbuminuria and outcome in such apparently diverse groups of patients appears to be that microalbuminuria reflects the systemic
microvascular endothelial dysfunction that, in various forms, is common to all these conditions.
Age> 50 yrs, 3.2% have a paraprotein
Age > 70 yrs, 5.3% with paraprotein
Plasma concentrations therefore reflect cell turnover and renal function
α-Interferon- Used in maintenance treatment of some β-Cell malignancies, induces marked increase in plasma β2-microglobulin concentration, and this should be taken into consideration when using β2-microglobulin or the assessment of tumour response during α-interferon therapy
Alpha heavy chain assessment is difficult : because the alpha chains tend to polymerize and appear as a smear instead of a sharp peak on electrophoretic profiles