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Questions and Answers
What is the earliest sign of kidney damage in a diabetic person?
Which test is primarily used to evaluate the extent of kidney damage?
What condition is characterized by thickening of the tubule basement membrane?
What is a significant factor that can trigger nephrosclerosis?
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How can a urinary tract infection be differentiated as pyelonephritis or cystitis?
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What is a common symptom of a kidney infection?
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What does the presence of casts in urine typically indicate?
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What does nephrosclerosis primarily result from?
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Which of the following is a potential consequence of nephrosclerosis?
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What typically indicates an infection when conducting a urine culture?
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What causes renal artery stenosis?
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Which condition can lead to the formation of atherosclerotic plaques in the kidneys?
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What is commonly observed in patients with pyuria?
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What is the main function of the kidneys related to metabolism?
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Which component of the kidney is primarily responsible for glomerular filtration?
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How does low glomerular filtration rate (GFR) affect tubular fluid chloride levels?
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Which of the following describes the selectivity of the glomerular filtration barrier?
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Which mechanism is NOT involved in the regulation of glomerular filtration rate (GFR)?
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What type of kidney disease is characterized by inflammation of the glomeruli?
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Which cells are responsible for the filtration process in the glomerulus?
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What key biochemical balance is maintained by kidney function?
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Which part of the kidney is typically affected by diabetic nephropathy?
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What is the primary laboratory test used to assess kidney function?
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Which substance is commonly elevated in the blood of patients with kidney disease?
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What are casts in the urine, and where are they formed?
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What happens to renal blood flow as the renal artery lumen narrows?
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What is a typical symptom of pyelonephritis?
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How do juxtaglomerular cells respond to reduced blood flow?
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What is a key factor contributing to diabetic nephropathy?
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How do bacteria typically reach the kidney in cases of infective pyelonephritis?
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Which feature is typical in the nephrons of patients with late-stage diabetic nephropathy?
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What structural change occurs in the glomerulus as a result of diabetic nephropathy?
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What is a key early pathology finding in diabetic nephropathy?
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What role do advanced glycation end products (AGEs) play in kidney damage?
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What is a potential consequence of renal atherosclerosis in patients with diabetes?
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What might occur as a result of prolonged hyperglycemia in relation to nephropathy?
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What is proteinuria a sign of in the context of kidney disease?
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Study Notes
Kidney Functions
- Excrete waste products of metabolism
- Regulate body water and electrolytes
- Maintain acid-base balance of plasma
- Secrete hormones
Kidney Mechanisms
- Glomerular Filtration
- Tubular Absorption
- Tubular Secretion
Glomerulus
- Network of capillaries covered by fenestrated endothelium and glomerular basement membrane
- Two layers of epithelial cells create the Bowmans space which collects filtrate
- Supportive mesangial cells
- Selectively permeable to water and small solutes
- Impermeable to albumin and larger molecules
Glomerular Filtration Rate (GFR)
- Regulated by:
- Autoregulation
- Tubuloglomerular feedback
- Neurohormonal influences
- Juxtaglomerular Apparatus (JGA) & Macula Densa (MD) involved in autoregulation and tubuloglomerular feedback.
- MD senses Cl- in tubular fluid. Low GFR means low tubular Cl-. Response is to dilate afferent arteriole & constrict efferent to up pressure and restore GFR.
Pyelonephritis
- Rare for bacteria to enter the kidneys via the bloodstream
- Symptoms:
- Sudden pain in the abdomen or back/flank
- Painful urination, frequency and urgency
- Fever
Diagnosis
- Haematuria: blood in the urine can often occur due to UTI. The presence of casts suggests pyelonephritis, as they are only formed in the tubules.
- Pyuria (leukocytes in urine). The presence of casts indicates pyelonephritis.
- Bacteriuria: a pure (single) culture indicates infection. Mixed culture suggests contamination.
- Diagnosis of infection is done by urine culture.
- Treatment decisions made using antibiotic sensitivity tests.
Nephrosclerosis
- Sclerosis (stiffening) of the renal arterioles and small arteries.
- One of the most common causes of end stage renal disease.
- Vessels have thickened walls and narrowed lumens resulting in reduced perfusion of underlying tissue.
- The initiating event appears to be vascular injury - generally due to hypertension.
- Injury leads to inflammation causing cell proliferation and deposition of extra cellular matrix.
- Consequent reduction in blood flow can lead to glomerular, tubular and interstitial injury resulting in atrophy, fibrosis (granulated surface) and reduction in organ size.
- Further vascular injury may lead to atherosclerotic plaque formation and/or thrombus formation which can result in severe ischemia.
- Any area of the kidney can be affected, making diagnosis difficult.
Renal Artery Stenosis
- Narrowing of the renal artery by an atheromatous plaque
- Vessel injury due to dyslipidemia, inflammation, smoking, diabetes or hypertension.
- Vascular permeability increases resulting in fat accumulation.
- Endothelial and smooth muscle cells proliferate.
- Macrophages enter and cause further inflammation.
- As the renal artery lumen narrows, renal blood flow decreases, eventually compromising renal function and structure.
- Juxtaglomerular cells sense the reduced blood flow and misinterpret it as low blood pressure, producing renin in response. This stimulates the production of angiotensin II and an increase in sodium and water retention to increase blood pressure.
- The ischemic kidney undergoes changes such as atrophy, fibrosis, glomerular changes.
- GFR will eventually decrease and proteinuria may be present.
Diabetic Nephropathy
- Nephropathy = kidney disease.
- Diabetic nephropathy = kidney damage due to diabetes.
- Approximately 40% of people with diabetes will develop kidney disease.
- Leading cause of chronic kidney failure in the USA.
- Due to damage of blood vessels by hyperglycemia.
Diabetic Nephropathy Mechanism
- Long term hyperglycemia has several effects thought to contribute to nephropathy:
- Glucose forms “advanced glycation end products” (AGEs) with amino acids of intracellular and extracellular proteins. High blood glucose levels greatly increases AGE formation.
- AGEs can:
- Stimulate the release of cytokines and growth factors that can cause inflammation and vascular changes (vascular endothelial growth factor - VEGF).
- Generate reactive oxygen species in endothelial cells, increasing the risk of vascular inflammation.
- Enhance proliferation of vascular smooth muscle and extracellular matrix.
- Cross link collagen fibres in blood vessels causing them to lose elasticity.
- Cause proteins to become trapped in blood vessels such as LDL and albumin.
- End result is inflammation in blood vessels leading to thickening, damage, plaque formation, and narrowing.
Diabetic Nephropathy Diagnosis
- Earliest sign is micro albuminuria.
- Two raised urine albumin tests 3-6 months apart in a diabetic person is generally diagnostic of diabetic nephropathy.
- Creatinine tests will be done to determine the extent of damage.
- No treatment for early kidney damage but attempts to control blood sugar and blood pressure are made, while urine albumin and serum creatinine are performed regularly.
- A kidney biopsy may be performed to confirm the diagnosis in later stage disease. This would show thickening of the tubule basement membrane and nodular sclerosis in the glomerulus due to inflammation.
Summary of Kidney Function Tests
- Creatinine
- eGFR
- Urinary protein, albumin
- Serum urea and electrolytes
- Cells in the urine
Glomerulonephritis
- Often immune mediated
- Diagnosis involves a combination of many investigations.
Differentiating UTIs
- UTIs can be differentiated as pyelonephritis or cystitis mainly on the basis of the presence/absence of casts in the urine.
Nephrosclerosis and Diabetic Nephropathy
- Nephrosclerosis can be triggered by vascular injury due to hypertension, smoking, diabetes.
- Kidney function tests will often be impaired but imaging is usually required for diagnosis.
- Diabetic nephropathy is the leading cause of chronic kidney failure in the USA.
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Description
Explore the essential functions and mechanisms of the kidneys in this quiz. Learn about glomerular filtration, tubular absorption, and secretion, as well as the regulatory mechanisms for glomerular filtration rate. Understand the structure of the glomerulus and the pathophysiology of conditions like pyelonephritis.
