The Urinary Tract, Kidney: Chronic Kidney Disease Flashcards
How is chronic kidney disease defined as?
Kidney damage or decreased GFR of less than 60mL/min/1.73m^2 for at least 3 months
What is ESKD a result of?
Progressive scarring from any type of kidney disease (glomeruli, tubules, interstitium, and vessels being sclerosed)
What are the most common causes of chronic kidney disease?
Diabetes (up to 50%)
Hypertension (up to 30%)
Glomerular diseases
Urinary tract obstruction
What is the treatment of chronic kidney disease?
Dialysis or transplantation
What is the criteria for chronic kidney disease? (7)
Either one of the following must be present for > 3 months:
1. Albuminuria
2. Hematuria
3. Electrolyte abnormalities due to renal tubular disorders
4. Abnormalities detected on histopathology
5. Structural abnormalities detected on imaging
6. History of kidney transplant
OR
Decreased GFR with or without kidney damage
How can hypertension lead to chronic kidney disease?
Glomerular and vascular changes
Interstitial nephritis
Chronic hypertension
What is the pathogenesis of glomerular and vascular changes in relation to CKD?
Elevated systemic BP causes a hypertrophic response, leading to intimal thickening of the large and small vasculature
The mechanism is compensatory at first but later on leads to glomerular damage:
- Global sclerosis
- Focal segmental sclerosis
What is global sclerosis?
Ischemic injury to the nephrons causes death
What is focal segmental sclerosis?
Glomerular enlargement for compensation of the loss of nephrons in other areas of the kidney
What is the pathogenesis of interstitial nephritis in relation to CKD?
The vascular and glomerular disease leads to tubular atrophy and intense chronic interstitial nephritis
What is the effect of chronic hypertension on the kidneys?
Chronically, these changes lead to tubular and glomerular loss, causing nephron loss
What is the effect of nephron death?
Fewer available nephrons to maintain GF –> gradual decline in the GFR is noticed as nephrons continue to die
What is considered as malignant hypertension?
BP > 200/120mmHg
What is the pathogenesis of malignant hypertension?
- Long-standing hypertension,
- Increased permeability of the vessels to fibrinogen and other plasma proteins, endothelial injury, and platelet deposition –> which can lead to the appearance of fibrinoid necrosis of arterioles and small arteries and intravascular thrombosis OR
Mitogenic factors from platelets and plasma cause intimal hyperplasia of vessels –> hyperplastic arteriosclerosis - Kidneys become markedly ischemic
- Further elevation of the blood pressure via the RAAS activation
What is the morphology of malignant hypertension?
Fibrinoid necrosis
Hyperplasticity’s artriolosclerosis
What is fibrinoid necrosis?
Formation of pink fibrin of small renal arteries
What is hyperplastic arteriosclerosis?
Homogenous, granular eosinophilic appearance
What causes hyperplastic arteriosclerosis?
Proliferation of intimal cells after acute injury, which produces an onion-skin appearance
What is the morphology of hyperplastic arteriosclerosis?
Marked narrowing of interlobular arteries and larger arterioles,
Necrosis may also involve glomeruli as well as arterioles
What are the clinical symptoms of malignant hypertesnion?
Papilledema, encephalopathy, cardiovascular abnormalities, and renal failure
What are the early symptoms of malignant hypertension?
Increased intracranial pressure –> headache, nausea, vomiting, and visual impairment (scotomas or spots)
What are the renal manifestations of malignant hypertension?
Marked proteinuria and hematuria but no significant alteration in renal function
Presents with severe acute kidney injury and renal failure
What is the pathogenesis of CKD in regard to diabetes? (8)
- Hyperglycemia starts sticking to proteins in the blood –> non-enzymatic glycation
- The glucose can get through the endothelium, a process of glycation that involves the basement membrane of small blood vessels, making it thicken
- The process of glycation particularly affects efferent arteriole, causing it to get stiff and more narrow –> hyaline arteriosclerosis
- Creates an obstruction, making it difficult for the blood to leave the glomerulus, increasing the pressure within. Afferent arteriole dilates, allowing more blood flow and increasing the pressure even more
- High pressure in the glomerulus –> increase in GFR
- In response to high-pressure rate, the mesangial cells secrete more and more structural matrix –> expand the size of the glomerulus
- Thickening of the basement membrane makes it more permeable –> allow proteins such as albumin to be filtered out
- Diabetic nephropathy and GFR decraeses
What is considered the first stage of diabetic nephropathy?
The increased pressure in the glomerulus causing an increase in the GFR –> known as hyperfiltration
What happens if half of the number of nephrons is lost?
CKD progresses similarly regardless of etiology, initial hyperfiltration activates RAAS and causes proteinuria.
Angiotensin II and protein uptake at the tubule cause inflammation and fibrosis of the glomerulus and tubules.
Progressive decline in GFR and systemic complications occur
What is the pathogenesis of CKD in regards to nephron loss? (7)
- Decrease in nephron number
- Adaptive hyperfiltration at glomerulus
- Increased glomerular activity OR RAAS activation
- Increased filtration of proteins and molecules OR Increased single nephron GFR (in the early course) and hypertension
- Nephrotoxic inflammation/remodeling
- Tubulointestinal fibrosis and 2o FSGS
- Decreased GFR, decreased urine output and systemic complications
What is the result of increased filtration of proteins and macromolecules?
Proteinuria –> Dyslipidemia
What are the different stages of CKD>?
Stages 1 to 5
What is stage 1 of CKD like? What is the GFR like?
Kidney damage with NORMAL kidney function, GFR: 90 or higher
What is stage 2 of CKD like? What is the GFR like?
Kidney damage with MILD LOSS of kidney function, GFR: 89 to 60
What is stage 3a of CKD like? What is the GFR like?
MILD to MODERATE loss of kidney function, GFR: 59 to 45
What is stage 3b of CKD like? What is the GFR like?
MODERATE to SEVERE loss of kidney function, GFR: 44 to 30
What is stage 4 of CKD like? What is the GFR like?
SEVERE loss of kidney function, GFR: 29 to 15
What is stage 5 of CKD like? What is the GFR like?
Kidney FAILURE, GFR: < 15
What are the gross features of CKD? (3)
- Kidneys are symmetrically contracted
- Damage in blood vessels or glomeruli
- Damage by chronic pyelonephritis
What is the appearance of the kidneys if there is damage in blood vessels or glomeruli in CKD?
Kidney surface: red-brown and diffusely grsnular
What is the appearance of the kidneys if there is damage by chronic pyelonephritis in CKD?
Uneven kidneys with deep scarring
What are the microscopical features of CKD? (5)
- Glomerular sclerosis
- Interstitial fibrosis with lymphocytic infiltrates
- Tubules atrophy
- Loss of portions of the peritubular capillary network
- Arteries (thick-walled, narrow lumina)
Which arteries are affected in CKD?
The small or medium sized ones
In chronic glomerulonephritis what is shown with a Masson trichrome stain?
Complete replacement of virtually all glomeruli by blue-staining collagen
In which stages of CKD are patients asymptomatic?
Stages 1 to 3, where the GFR > 30ml/min
In which cases of CKD are the patients symptomatic?
Stages 4 & 5, where the GFR < 30ml/min
What are the early signs of CKD?
Polyuria/oliguria (changes in urine output)
Hematuria
Edema
Because of the hyperfiltration compensatory mechanism
What are the late signs of CKD?
Hypertesnion
Signs of anemia (pallor)
Signs of uremia
What are the signs of uremia that affect the brain?
Uremic encephalopathy: low concentration –> confusion, lethargy, asterixis and coma
What are the signs of uremia that affect the heart?
Pericarditis
What are the GIT clinical presentations of CKD?
Nausea, vomiting, anorexia and diarrhea
What are the reproductive system clinical presentations of CKD?
Erectile dysfunction, decreased libido, amenorrhea
What are the blood system clinical manifestations of CKD?
Platelet dysfunction with a tendency to bleed, infections due to WBC dysfunction
What are the peripheral neuropathy clinical manifestations of CKD?
Numbness, paraesthesia, restless leg syndrome
What are the skin clinical manifestations of CKD?
Dry skin, pruritus, ecchymosis
What are other clinical manifestations of CKD?
Fatigue, hiccups and muscle cramps
What is the mechanism behind the generalized edema of CKD?
Water retention due to loss of GFR –> sodium and fluid retention –> fluid moves to extravascular space due to increased hydrostatic pressure –> pitting edema
What is the mechanism behind pulmonary crackles in CKD?
Fluid accumulation causes pulmonary edema and loss of air space –> ventilation-perfusion mismatch.
What is the mechanism behind anemia in CKD?
Renal failure –> loss of erythropoietin release
What is the mechanism behind weight loss in CKD?
Protein-energy malnutrition due to metabolic acidosis –> loss of kidney function results in impaired H+ secretion from the body
What is the mechanism behind hyperkalemia in CKD?
The inability of the kidneys to secrete potassium in the urine leads to life-threatening arrhythmias
What is the mechanism of hyperphosphatemia in renal osteodystrophy?
Damaged kidneys fail to excrete phosphate
Also secondary to high parathyroid hormone levels
What is the mechanism of hypocalcemia in renal osteodystrophy?
Secondary to low Vitamin D3, in early cases of CKD, low levels of calcitriol due to hyperphosphatemia. In later stages of CKD, low levels are hypothesized due to decreased synthesis of 1a-hydroxylase
What is the function of 1a-hydroxylase?
Converts calcifediol to calcitriol in the kidneys
What is the mechanism of secondary and tertiary hyperparathyroidism in renal osteodystrophy?
To compensate for low calcium because of low vitamin D levels
What is the effect of increased parathyroid hormone secretion?
High bone turnover, always attempting to normalize the low calcium levels in the blood –> maladaptive –> extraosseous calcification and parathyroid hyperplasia (tertiary hyperparathyroidism)
What is the mechanism behind the uremia complication: ecchymosis and GI bleeding?
Uremia-induced platelet dysfunction
What are the presenting symptoms of complications of uremia: ecchymosis and GI bleeding?
Increased tendency to bleed and ecchymosis
What is the mechanism behind the uremia complication: pericardial friction rub?
Uremic pericarditis
What is the mechanism behind the uremia complication involving the brain?
Uremic encephalopathy; adverse effects of urea of CNS (mechanism is unclear)
What are the presenting symptoms of pericardial friction rub?
Chest pain and malaise
What are the presenting symptoms of uremic encephalopathy?
Headaches, confusion and coma
What are thrombotic micronagiopathies?
Lesions that are seen in various clinical syndromes characterized by microvascular thrombosis accompanied by microangiopathic hemolytic anemia , thrombocytopenia and renal failure
What are the two types of thrombotic microangiopathies?
Primary TMA
Secondary TMA
What is Primary TMA?
Shiga-toxin mediated hemolytic uremic syndrome (HUS); atypical HUS and thrombotic thrombocytopenic purpura (TTP)
What is secondary TMA?
Malignant hypertension and scleroderma-associated TMA
What is the Shiga-toxin mediated HUS?
Intestinal infection with Shiga-toxin-producing E.coli and infections with Shigella dysenteriae type I
Where is E.coli usually found?
Contaminated ground meat
What is the pathogenesis of Shiga-toxin-mediated HUS? (low doses)
The toxin activates endothelial cells, leading to leukocyte adhesion, increased endothelin production, and decreased nitric oxide production, as well as other changes that may promote platelet adhesion and activation
What is the effect of increased endothelin production and decreased nitric oxide production?
Vasoconstriction
What is the pathogenesis of Shiga-toxin-mediated HUS? (high doses)
The toxin causes endothelial cell death
What is the result of all the alterations that take place in Shiga-toxin mediated HUS?
Formation of thrombi, which tend to be the most prominent in glomerular capillaries, afferent arterioles and interlobular arteries
What is atypical HUS?
Genetic abnormalities in complement regulatory proteins (mostly factor H but also factor I, and membrane cofactor protein)
What is the pathogenesis of atypical HUS?
Antibodies to complement regulatory proteins (anti-factor H or C5 to 9 MAC)
Excessive activation of complement, with ensuing microvascular injury and microvascular thrombosis
What is thrombotic thrombocytopenic purpura (TTP)?
Genetic or acquired deficiency of a protease, ADAMTS13
What is the function of ADAMTS13?
Cleaves multimers of von Willebrand factor (carrier for factor 8) on the surface of endothelial cells
What is the result of TTP ?
Abnormally large vWF multimers activate platelets spontaneously, leading to platelet aggregation and thrombosis in multiple organs, including the kidneys