Renal systems Flashcards
ILO 8.8a: be familiar with the underlying disease processes of the common medical disorders affecting the body
describe the location of the kidneys
- retroperitoneal
- superiorly - diaphragm
- inferiorly - abdominal wall muscles
- anteriorly - right liver: duodenum, ascending colon - left liver: stomach spleen, pancreas, jejunum, descending colon
- posteriorly - diaphragm, 11th and 12th rib, abdominal wall muscles
what are the main anatomical aspects of the kidney?
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- renal capsule
- renal cortex
- renal medulla
- renal pelvis
- ureter
describe the blood suppy path of the kidneys
- renal artery from abdominal aorta which divide in the kidneys into the
- segmental arteries which divide into the
- interlobar arteries which run between the renal pyramids and divide into
- arcuate arteries which arch along the border of the medulla and cortex
- interlobular arteries which are small branches extending into the cortex
- afferent arterioles which lead into the glomerulus
- efferent arterioles where the blood leaves the glomerulus
- peritubular capillaries and vasa recta which surround the nephron
- intralobular veins - arcuate veins - interlobar veins - renal vein - inferior vena cava
what is a nephron? where is it? what does it do?
- functional unit of the kidney consisting of the renal corpuscle (glomerulus and Bowman’s capsule) and tubules (PCT, LoH, DCT, CD)
- located in the renal cortex and medulla
- filters the blood, reabsorbs essential substances and excreting waste products
what does it mean that the renal system is autoregulated?
renal blood flow is independent between a mean pressure of 90-200mmHg
* both afferent and efferent arerioles can vasoconstrict to maintain constant blood flow
what is the function of the RAA system? what happens when blood pressure decreases?
maintains constant renal blood flow
1. renal blood flow and filtrate volume decrease
2. decreased soduim and chloride in the interstitial space
3. increased renin secretion from the kidney
4. angiotensin is a hormone secreted from the liver and renin stops it from being converted to angiotensin I
5. angiotensin I cannot be converted to angiotensin II by ACE from the lungs
6. angiotensin II increases blood pressure
how does angiotensin II increase blood pressure?
- it is a generalised vasoconstrictor: increased systemic vascular resistance (SVR) and blood pressure
- vasoconstriction of efferent arterioles greater than afferent arterioles: increased glomerular filtration rate (GFR)
- release of aldosterone from the adrenal gland: increased Na and water retention
- stimulates thirst by action on the hypothalamus
what is the role of the endothelial cells of the glomerulus?
have fenestrations which allow the passage of water and small molecules but retains blood
what is the role of the glomerulus? what does it consist of?
- filters the blood to create an ultrafiltrate
- consists of network of capillaries lined by fenestrated endothelial cells, a glomerular basement membrane and podocytes
- this arrangement creates the glomerular basement membrane
what is the role of the glomerular basement membrane?
acts as a primary barrier to macromolecules
what is the role of podocytes?
additional filtration layer after the fenestrations in the endothelium and basement membrane
what is the role of mesangial cells?
located at the capillary loops, they provide support and help regulate blood flow within the glomerulus
what is the glomerular filtration rate?
- a measure at how well your kidneys are filtering blood, indicating overall kidney function
- around 125ml/min
what is clearance?
the volume of plasma that is cleared of the substance in unit time
what are two ways of measuring GFR?
- insulin clearance as it is not reabsorbed, secreted, synthesised or metabolised by the kidney
- creatinine clearance is an alternate measurement and gives an estimate of GFR (eGFR)
what is the role of the PCT?
reabsorbs 60% of all solute including:
* 100% glucose and amino acids
* 90% bicorbonates
* 80-90% inorganic phosphates and water
* 40-50% urea
what is the role of the LoH?
concentrating urine (water reabsorption)
what is the role of the DCT?
fine tuning and reabsorption of ions
what is the role of the CD?
has a variable permeability to water due to aquaporins - ADH dependent
achieves final urine concentration
what are the functions of the kidney?
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- salt and water homeostasis
- acid-base homeostasis
- excretion of waste products, water soluble toxins and drugs
- calcium and phosphate homeostasis
- retention of vital substances - protein and glucose
- endocrine functions - production of erythropoietin
how do the kidneys control salt and water homeostasis?
- regulation of total body fluid volume mediated by osmoreceptors that affect ADH release
- ADH is released from the posterior pituitary gland and determines the permeability of the CD via aquaporins
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what is ADH released in response to?
3
- increased osmolarity in the hypothalamus
- decreased plasma volume
- angiotensin II
how do the kidneys control acid-base homeostasis?
- bicarbonate is the most important buffer system in the body
- it is absorbed mainly in the PCT, dependent on H+ secretion
- when H+ secretion is increased (acidosis) by the kidney, there is increased bicarbonate reabsorption and so, increased plasma bicarbonate
- when H+ secretion is decreased (alkalosis), there is decreased bicarbonate reabsorption and plasma bicarbonate
how does the kidneys regulate calcium and phosphate homeostasis?
calcium homeostasis
* PTH is released in response to low plasma calcium
* PTH acts on the kidneys to increase calcium reabsorption in the DCT
* kidney also converts 25-hydroxyvitamin D into activated 1,25-dihydroxyvitamin D
phosphate homeostasis
* PTH decreases phosphate reabsorption in the PCT
* fibroblast growth factor 23 (FBGF23) produced by osteocytes, further enhances phosphate excretion
what are the endocrine functions of the kidneys?
- erythropoietin (EPO) is produced by renal interstitial fibroblasts and stimulates erythopoiesis in the bone marrow (red blood cell production)
- renin is secreted by the juxtaglomerular cells which regulates blood pressure, electrolyte balance and fluid homeostasis
- calcitriol (1,25-dihydroxyvitamin D) is the activated form of 25-hydroxyvitamin D and is crucial for calcium and phosphate homeostasis
- klotho is produced in the kidneys (aKlothorotein) and is a co-receptor for FBGF23 which is important in phosphate metabolism and aging
how would you assess renal function?
- bloods
- urea and electrolytes (below)
- urea and creatinine secreted by kidney to measure GFR - renal function markers
what is estimated glomerular filtration rate (eGFR)?
- number derived from patient’s creatinine levels in conjunction with age, sex and race
- roughly equated to a **% of kidney function **
- used to stage chronic kidney disease
what is acute kidney injury? how is it identified? what happens in pre-renal, renal and post-renal AKI?
- a sudden decline in renal function
- identified by a rapid increase in serum creatinine levels and/or a decrease in urine output
- pre-renal - decreased perfusion of kidneys, hypovolaemia, hypotension
- renal - direct damage to renal parenchyma
- post-renal - obstruction
what is glomerulonephritis? how does it present? how is it diagnosed? how is it treated?
- **inflammation of the glomeruli **
- immune-mediated disorder (IgA neuropathy is most common)
- presents as clinical manifestations: hematuria (blood in urine), proteinurea, hypertension, renal dysfunction
- diagnosed via biopsy
- immunosuppressive and supportive treatment
what is acute tubular necrosis? what is a sign of this? how would you manage it?
- death of tubular epithelia cells
- can be ischaemic or nephrotoxic
- muddy brown casts in urine sediment
- management: avoid, supportive care (fluid management), renal replacement therapy
what is pyelonephritis? how is it treated?
- bacterial infection typically ascends from the lower urinary tract - usualy E.coli
- treated with antibiotics and **monitoring renal function **
what is post-renal acute kidney injury? what can it be caused by? how can it be treated?
- obstruction of urine flow from the renal pelvis to the ureter
- obstruction from - stones, tumours, strictures
- treatment - relief of obstruction - catheter, surgery
what are the causes of kidney stones (renal calculi)?
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- genetic factors
- dehydration
- diet
- metabolic disorders (obesity, diabetes, gout)
- medications (antacids, diuretics)
what kind of tumour is present with renal cancer? what are the risk factors? what is the treatment?
- renal cell carcinoma (originating from renal epithelium)
- risk factors: smoking, obesity, hypertension, certain hereditary conditions
- treatment: surgery, nephrectomy, ablation
how is chronic kidney disease discovered? what are the most common causes?
- discovered on routine screening
- causes: diabetes, hypertension, glomerulonephritis, polycystic kidney disease, chronic pyelonephritis
what causes diabetic nephropathy? what are the signs?
- prolonged hyperglycaemia causes cellular damage and inflammation
- overproduction of advanced glycation end products (AGEs) which activate protein kinase C which increases oxidative stress
- signs: glomerular hyperfiltration and microalbuminuria progressing to macroalbuminuria and a lower eGFR
what is hypertensive nephrosclerosis? what does it cause?
- structural changes in the kidneys due to sustained high blood pressure leading to progressive renal damage and renal dysfunction
causes:
* arteriosclerosis and arteriolohyalinosis - thickening and stiffening of small arterioles and
* glomerular hypertension and hyperfiltration - loss of autoregulation, increased glomerular capilary pressure, glomerular hypertrophy
* tubulointestinal fibrosis - ischaemia and glomerular damage leads to tubulointerstitial inflammation and fibrosis
* podocyte damage - reduced filtration and scarring
what is polycystic kidney disease? what are the difference between the two types?
- progressive formation of and enlargement of cysts leading to kidney enlargement, damage and chronic kidney disease
autosomal dominant polycystic kidney disease
* common
* presents in adulthood
* mutations in PKD1 or PKD2 gene
* associated with extrarenal manifestations
autosomal recessive polycystic kidney disease
* rarer and more severe
* presents in early childhood
* mutation in PKD1 gene
* numerous small cysts, congenital hepatic fibrosis
* high morbidity and mortality
what are the dental presentations of chronic renal disease?
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- white patch
- erythematous patch
- ulceration
- lichen planus
- oral hairy leukoplakia
- uremic stomatitis
- macules/nodules
- fibro-epithelial polyps
- geographic tongue
- papilloma
- pyogenic granuloma
what are the causes of kidney failure?
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- diabetes
- hypertension
- kidney inflammation
- polycystic
- urine drainage tubes blocked
- medicines
what are the symptoms of kidney failure?
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- energy loss
- urination problems
- dyspnea (SoB)
- swelling
- loss of appetite
- lower back pain
how do you prevent and treat kidney failure?
prevention:
* no smoking
* no alcohol
* healthy diet
* active lifestyle
treatment:
* haemodialysis
* peritoneal dialysis
what does dialysis do? what are the two different types? how does the machine work?
- removes metabolic waste products, excess body water and rebalancing electrolytes
- haemodialysis and peritoneal dialysis
- semi-permeable membrane that allows waste products and excess electrolytes to diffuse from the blood into the dialysate
how does dialysis affect dentistry?
- increased risk of oral diseases (PDD, caries, oral candida)
- management of bleeding risks - anticoagulant therapy
- timing of appointments - non-dialysis days
- infection control - compromised immune system
- OH and systemic complications - poor Oh linked with CVD, pneumonia
how do kidney transplants affect dentistry?
- post-transplant immunosuppressant therapy - susceptible to infections (PDD, oral candidiasis), immunosuppressants can cause gingival overgrowth and severe oral ulcerations
- dental caries risk increases post-transplant
- periodontal disease in transplant pts is associated with systemic health conditions
how is platelet function altered in patients with chronic kidney disease? what does this lead to?
- accumulation of uremic toxins impair platelet aggregation and adhesion
- leads to prolonged bleeding times and reduced platelet reactivity to agonists such as ADP and collagen
what are some drugs that you should not prescribe to a patient with renal failure?
- apirin
- ibuprofen
- tetracyclines
