Kidney Diseases Quiz

Glomerular Disease Principles

• Glomerular disease involves the breakdown of filtration barrier components.
• Key components in glomerular filtration that should not be filtered are red blood cells and protein, especially albumin.
• Proteinuria and hematuria are common indicators of glomerular pathology.

Glomerulus Functions

• The glomerulus allows an "ultrafiltrate" into Bowman's space, including water, electrolytes, glucose, and amino acids.
• It prevents the filtration of most proteins and red blood cells.
• Proteinuria and hematuria can result from glomerular pathology.

Glomerular Filtration Barrier

• The glomerular filtration barrier consists of capillary endothelium, basement membrane, and podocytes (epithelium).
• The capillary endothelium is fenestrated (with openings) and repels red blood cells, white blood cells and platelets.
• It's the first barrier to filtration.
• Damage to the capillary endothelium can result in red blood cells appearing in the urine (hematuria), and inflammation (nephritis).

Capillary Endothelium

• The capillary endothelium has openings (~40nm) that only allow small molecules to pass through.
• Red blood cells, white blood cells, and platelets are typically repelled.
• Damage leads to red blood cells in the urine (hematuria).
• Damage can also lead to inflammation and nephritis.

Basement Membrane

• The basement membrane contains negatively charged molecules (like heparan sulfate) that repel negatively charged molecules (like albumin).
• It acts as a size barrier, only small molecules (~4nm) can pass through.
• Type IV collagen is a component of the basement membrane.

Podocytes

• Podocytes are epithelial cells with "foot processes" that wrap around capillaries.
• Slits between the foot processes filter the blood.
• These slits act as a size barrier.
• Damage to podocytes results in protein loss.

Albumin

• Albumin is small (~3.6nm), able to pass through all size barriers, and negatively charged.
• It is repelled by the glomerular basement membrane's negative charge.
• Podocyte/GBM disease may cause albumin to be present in urine.

Glomerular Diseases

• Glomerular diseases occur due to a breakdown in the glomerular filtration barrier.
• Substances not normally present in urine, such as red blood cells and proteins (especially albumin), may be found.

Hematuria

• Urinalysis, using dipsticks, can detect heme (hemoglobin or myoglobin) in urine.
• Microscopy can confirm the presence of red blood cells.
• Hematuria has many causes, including kidney stones, bladder cancer, urinary tract infections (UTIs), and glomerular disease, with glomerular disease being a less common cause.

Glomerular Bleeding

• Red cell casts, dysmorphic red blood cells, and acanthocytes can all indicate glomerular bleeding.
• Proteinuria is also frequently seen.
• The urine may have a red, smoky brown or coca-cola appearance.
• Blood clots are generally not present.

Proteinuria

• Urine dipsticks measure protein, primarily albumin, in the urine.
• The color change indicates the amount of protein.
• A spot urine test, using a protein/creatinine ratio, is also beneficial for identifying proteinuria.
• Proteinuria is associated with the loss of the protein barrier, especially albumin.
• A 24-hour urine collection is a standard for assessing the amount of protein excreted in urine.

Nephritic Syndrome

• Filtration barrier loss to red blood cells (RBCs) and proteins are characteristic in this syndrome.
• Massive proteinuria, with a 4+ reading on dipsticks (greater than 3.5g/day), and/or inflammation are frequent indicators.
• The presence of RBC casts is observed in the urine, demonstrating various degrees of renal dysfunction, ranging from mild proteinuria to renal failure.

Nephrotic Syndrome

• In this syndrome, the glomerular filtration barrier is damaged, leading to significant protein loss (massive proteinuria), while the barrier to red blood cells remains intact.
• Proteinuria typically exceeds 3.5 g per day.
• A 4+ reading on routine dipsticks, and an abnormal degree of lipid in the urine (e.g., fatty casts, oval fat bodies) are indicative of nephritic syndrome.
• Signs and symptoms can include frothy urine, swelling in ankles and around the eyes, elevated serum cholesterol levels, and often a mistaken observation of an allergic reaction (due to swelling).

Microscopy

• These are essential tools for the diagnosis of renal diseases.
• Light microscopy examines kidney tissue at low magnification (up to ~2000x).
• Immunofluorescence microscopy analyzes the distribution of immune complexes (IgG, IgM, C3, C1q) within the kidney.
• Electron microscopy provides a detailed view of the glomerular structures at high magnification (up to ~10,000,000x).

Post-Streptococcal Glomerulonephritis

• Follows a group A beta-hemolytic streptococcal infection.
• Nephritogenic strains of bacteria carry specific M proteins associated with this disorder.
• Immune complexes deposit in the kidney, often following an infection.
• This causes inflammation, hypercellularity in the glomeruli, and subepithelial humps, as seen using electron microscopy.
• This disorder is generally less severe in children, and has a favorable prognosis, while adults tend to have worse outcomes.

IgA Nephropathy (Berger's Disease)

• This is the most common form of glomerulonephritis worldwide.
• Repeated episodes of hematuria (often seen in children) are a key characteristic.
• Immunologic factors (overactive immune system, IgA immune complexes) drive the development of this type of nephritis.
• Many patients eventually develop ESRD and HD.

Henoch-Schönlein Purpura

• This is a type of IgA nephropathy affecting extrarenal tissues.
• Palpable purpura commonly occurs on the buttocks and legs.
• Abdominal pain and melena (black, tarry stools) are common gastrointestinal manifestations.
• Inflammatory joint pain is another frequently observed presentation.
• IgA deposition in kidney tissues is a diagnostic indicator.

Diffuse Proliferative Glomerulonephritis (DPGN)

• Systemic Lupus Erythematosus (SLE) often causes this type of glomerulonephritis.
• Immune complexes deposit within the glomeruli, triggering a significant immune response.
• Thickening of capillary loops ("wire looping") is a classic finding, visible using electron microscopy.
• Granular IF, demonstrating an accumulation of immune complexes (IgG, IgA, IgM, C3, C1q), is confirmed using immunofluorescence analysis.
• Often characterized as a mixed clinical presentation, which includes proteinuria (sometimes nephrotic) and hematuria.
• Significant reduction in GFR, and can lead to end-stage renal disease (ESRD) and hemodialysis (HD), often causing patients to become critically ill.

Rapidly Progressive Glomerulonephritis (RPGN)

• Also called "crescentic" glomerulonephritis, frequently caused by a number of disorders. The different types are distinguished by immunofluorescence microscopy results.
• Inflammation, involving cells like monocytes/macrophages and fibrin, forms crescents in glomeruli.
• Symptoms (fatigue and anorexia) and signs (acute renal failure; nephritic urine) commonly appear abruptly, which is an important indicator.
• The pathogenesis of RPGN is diagnosed and differentiated based on immunofluorescence microscopy results showing positive or negative findings (e.g., type I - linear IF; type II - granular IF; type III - negative IF.

Goodpasture's Syndrome

• This is a type of RPGN. It is characterized by antibodies against the alpha-3 chain of type IV collagen within the glomerular basement membrane (GBM) and alveoli.
• Hemoptysis and evidence of nephritic syndrome are diagnostic indicators.
• The typical patient is a young adult male who experiences hemoptysis and hematuria.

Membranoproliferative Glomerulonephritis (MPGN)

• MPGN constitutes rare glomerular diseases.
• Significant basement membrane thickening and proliferation of mesangial cells frequently results in proteinuria and/or hematuria, and varying degrees of renal dysfunction.
• MPGN has two main types: type I, far more prevalent than type II (a.k.a "dense deposit disease".) Type II is mediated by complement activation and C3 deposits are frequently observed but IgG is usually absent

Tubulointerstitial Disorders

• Acute Tubular Necrosis (ATN) is caused by sudden damage to tubular epithelial cells.

• Ischemia (lack of blood flow) and toxins/drugs can be causative factors.

• Urine obstructed by sloughed cells and casts results in an increasing rise in BUN and Cr (blood urea nitrogen and creatinine).

• ATN commonly results in "muddy brown" urine and patchy necrosis of nephrons.

• Progression typically leads to kidney recovery.

• Acute Interstitial Nephritis (AIN) involves inflammation of the renal tubules and interstitium (the spaces between tubules).

• Hypersensitivity (allergic) reaction to certain drugs or infections are frequently the cause (but not exclusively.)

• This type of nephritis typically resolves by stopping the offending agent and resolves when the causal drug/infection is eliminated.

• Chronic Interstitial Nephritis (CIN) results from long-term exposure, most often to Nonsteroidal Anti-inflammatory Drugs (NSAIDs), and results in fibrosis and atrophy of tubules.

Papillary Necrosis

• Coagulative necrosis of the renal papillae (small structures at the end of the kidneys' collecting ducts) with sloughing of tissue, often causes painlessness and gross hematuria.
• Often caused by longstanding use/infection/congenital disorders, such as chronic use of phenacetin, diabetes, acute pyelonephritis, and sickle cell anemia.

Cortical Necrosis

• Due to ischemia of the renal cortex, this type of necrosis results in abrupt, severe renal failure, frequently seen in critically ill patients (septic shock; obstetric catastrophes.)
• It commonly develops abruptly and can progress to anuria due to lack of proper kidney filtration.

Renal Failure

• Decrease in glomerular filtration rate (GFR) over days/years can be either acute or chronic.
• Acute renal failure develops quickly and is often reversible (caused by poor perfusion), while chronic renal failure is slow and progressive, and leads to dialysis, and, eventually, end-stage renal disease (ESRD).
• Azotemia (abnormally high BUN and Cr in blood) and uremia (azotaemia + symptoms like: nausea, vomiting, pericarditis, asterixis, and encephalopathy) are observed in severe cases.

Cystic Kidney Disease

• Renal cysts are an abnormal accumulation of fluid-filled sacs within the kidney.
• Key types include multicystic dysplastic kidney diseases (MDK); autosomal recessive polycystic kidney disease (ARPKD); autosomal dominant polycystic kidney disease (ADPKD) and medullary cystic kidney disease (MCKD)

Other Relevant Information

• There are particular types and characteristics of glomerulonephritis, and each has different indicators and treatments.
• Determining which specific disease is occurring is essential for appropriate medical management.
• Determining the cause of renal failure often requires multiple tests and a thorough medical history.

Test your knowledge on various kidney diseases, including Multicystic Dysplastic Kidney and Polycystic Kidney Disease. This quiz covers abnormalities, symptoms, and consequences associated with these conditions. Gauge your understanding of these medical phenomena and their implications.