W17 64 renal physiology and chronic kidney disease Flashcards
How much of cardiac output do the kidneys receive?
25%
What is blood supply of a nephron?
From an afferent arteriole that opens onto the glomerular capillary bed
To an effect arteriole, supplying the peritubular capillaries and medullary vasa recta
What are the 2 main roles of kidneys?
Homeostasis
Metabolic/endocrine function
What homeostasis do the kidneys maintain?
Elimination of waste
Water homeostasis
Electrolyte homeostasis
Acid base homeostasis
Blood pressure control
How are kidneys affected by blood pressure?
Kidneys auto regulate their own blood flow when systolic BP is between 80-180.
In extreme hypotension or hypertension, this can lead to acute kidney injury and subsequently chronic kidney disease.
As part of the metabolic/endocrine function of kidneys, they synthesise hormones and excrete drugs and drug metabolites. What hormones do the kidneys synthesis?
Vitamin D
Erythropoietin
Renin
What does vitamin D do?
Promotes intestinal absorption of calcium and renal reabsorption of phosphate
When is erythropoietin release and what does it do?
Release in response to hypoxia
Stimulates the production of RBCs in bone marrow
What does renin do?
Regulates the angiotensin and aldosterone levels to control blood pressur
Pg610 don’t really get watch a YouTube vid. How ions are transported through the nephrons!
Read it and watch a YouTube vid pls. Need to understand.
What should the arterial blood pH be?
7.35-7.45
Hydrogen ion concentration in blood is maintained within narrow limits
What is the formula for the maintenance of acid-base balance in the blood?
H+ + HCO3- <-> H2CO3 <-> CO2 + H2O
The kidneys and lungs maintain acid-base homeostasis. What is the role of the kidneys?
Reabsorb and regenerate bicarbonate from urine
Excrete hydrogen ions and fixed acids (anions of acids) into urine
What is the RAAS system? SEE IMAGE PG611!
Angiotensinogen produced by the liver —> turned into angiotensin I (promoted by renin) —> ACE converts this to angiotensin II —> angiotensin II promotes alosterone secretion from kidneys
What does renin do?
Hydrolysed angiotensinogen to produce angiotensin I
What blood pressure effects do angiotensin II and aldosterone have?
Both increase the kidneys absorption of sodium chloride, thereby expanding the extracellular fluid compartment and raising blood pressure.
How does renin increase or decrease blood pressure?
When renin levels are raised, concentrations of angiotensin II and aldosterone increase, leading to increased sodium chloride reabsorption, expansion of the extracellular fluid compartment, and an increase in blood pressure
Conversely when renin levels are reduced, angiotensin II and aldosterone levels decrease, contracting the extracellular fluid compartment, and decreasing blood pressure.
What factors increase renin secretion?
Low blood pressure (causing reduced renal perfusion), low sodium level, synthetic nerve stimulation
What drugs affect renin secretion and lower blood pressure?
Beta blockers and NSAIDs (eg ibuprofen)
When is erythropoietin released?
In response to hypoxia in the renal circulation
Eg in anaemia, pt have a low RBC concentration, so have a low oxygen carrying capacity in the blood so tissues become hypoxic
What does erythropoietin do?
Stimulates erythropoiesis (production of RBCs) in the bone marrow, to help return the pt back to normal RBC concentration
What is measured in urea and electrolytes test (U&E)?
Sodium, potassium, urea, creatinine, eGFR
What is glomerular filtration rate (GFR) and how is it measured in practice?
Glomerular filtration rate (GFR) = (urine concentration (mmol/L) x urine volume) / plasma concentration (mmol/L)
Total volume of plasma per unit time leaving the capillaries and entering the Bowman’s capsule. In clinical practice creatinine is used because it is subjected to very little proximal tubular secretion.
What is estimated glomerular filtration rate (eGFR)?
Calculated from creatinine, age, gender, ethnicity
Good measure in stable renal function (but can be affected by the extremes of body mass)
What is renal clearance?
Renal clearance is the volume plasma from which a substance is removed per minute by the kidneys.
What is measured in drug clearance?
Glomerular filtration
Tubular secretion
Passive reabsorption
Urine excretion
What does reduced GFR do to drug effects on the body?
Reduced glomerular filtration rate will increase the accumulation of medications in the system and increase the effects and toxicity of drugs.
What factors affect drug clearance?
Renal disease
Age
Pathologies that impact renal blood flow or urine flow, eg - congestive heart failure, liver disease, and pathologies affecting antidiuretic hormone release.
How much of a substance is excreted, formula?
Excretion = filtration - reabsorption + secretion
What is chronic kidney disease/chronic renal failure?
Abnormalities of kidney structure or function, present for >=3 months, with implications for health. GFR <60mL/minutes/1.73m2
OR the presence of one of more markers of kidney damage
What are the markers of kidney damage?
Albuminuria/proteinuria, urine sediment abnormalities, electrolyte abnormalities due to tubular disorders, abnormalities detected by histology, structural abnormalities detected by imaging, or history of kidney transplantation
What are some causes of chronic kidney disease (CKD)?
Diabetes mellitus
Hypertension (cause and consequence of CKD)
Kidney disease - eg polycystic kidney disease, obstructive uropathy, glomerular nephrotic syndromes
What are the risk factors for CKD?
Aged over 50, male sex, black/Hispanic ethnicity, family history, smoking, obesity, long term analgesic use, diabetes, hypertension, autoimmune disorders
What are some common clinical findings/symptoms of CKD?
Fatigue - uraemia and anaemia
Oedema (periorbital and peripheral)
Nausea and vomiting (from toxin build up), metallic taste in mouth
Pruritis (itchy skin)
Abnormal renal function tests
What might renal function tests of someone with CKD show?
Reduced GFR, high creatinine and urea
Why might someone with CKD have anaemia?
Because anaemia is due to a lack of erythropoietin produced by the kidneys.
Why might someone with CKD suffer from oedema?
Due to salt and water retention as the glomerular filtration rate declines. Might be exacerbated by hypoalbuminaemia.
Briefly, what are the stages of CKD? (pg615 image)
Can be staged using glomerular filtration rate
G1 = normal or high GFR >90 … G5 = kidney failure <15
What are the 2 stages of management for CKD?
- Monitor disease progression and manage associated complications (progression is irreversible)
- Preventing progression (rate of progression is unpredictable)
What are the modifiable risk factors of CKD that can be treated to prevent progression?
Proteinuria - ACEi/ARB
Hypertension control
Smoking cessation
Control of underlying disease - diabetes/lupus
Caution with NSAID use eg ibuprofen
Refer to urology if outflow obstruction
How do you reduce the risk of cardiovascular disease in CKD?
Manage hypertension
Lipid management using statins
Anti-platelet agents for secondary prevention
What does fluid retention lead to and how do you treat it?
Hypertension and peripheral oedema
To treat, want to offload the fluid eg furosemide, and restrict oral intake of salt and water
What can hyperkalaemia cause?
Cardiac arrhythmia and worst case cardiac arrest
(happens when or has really reduced eGFR)A
What can metabolic acidosis cause?
Presents as shortness of breath due to increased respiratory drive
Pt might also have chest pain and confusion
In severe, pt will be in coma and this will lead to death
What can vitamin D deficiency cause?
Osteoporosis
When is renal replacement therapy indicated?
CKD stage 4 or 5
Rapidly deteriorating kidney function
Proteinuria
Poorly controlled hypertension
What are the types of renal replacement therapy.
Haemodialysis
Peritoneal dialysis
Haemofiltration
Transplantation (only if the pt is fit for surgery and for lifelong immunosuppression)
What is uraemia?
High level of urea in the blood - caused by excess in amino acid and protein metabolism end products, as a result of renal failure (AKI - acute kidney injury).
What are the causes of uraemia?
Prerenal - hypovolaemia, hypotension
Renal - infection of renal toxic medication
Postrenal - urinary outflow tracts obstruction
What are some oral manifestations of CKD?
Pallor or the oral mucosa (anaemia)
Pain and inflammation of the tongue and oral mucosa
Dry mouth
Uraemia breath
Sensations of metallic tastes in the mouth
Candida infection
What drugs do you have to be careful for prescribing for patients with CKD in dental practice?
Insulin - can cause hypoglycaemia
Opiates eg morphine - can cause overdose
Antibiotics eg Co-amoxiclav - can cause encephalopathy (reduce dose when eGFR is low)
Sedatives - can cause respiratory arrests (adjust dose)
What does the prostate do?
Produced and secretes fluid which nourishes sperm
Fluid contains proteolytic enzymes, prostatic acid and phosphatase, fibrinolysin, zinc, PSA (prostate-specific antigen).
Why is PSA important?
It is a tumour marker
If a pt >60yrs presents with urinary symptoms and haematuria, the GP might do a PSA test.
What is prostatitis?
Inflammation of the prostate gland
What is prostatitis caused by and treated with?
Caused by bacterial infection
Treated with antibiotics
Symptoms of benign prostate enlargement/benign prostate hyperplasia (BPH)
Increased frequency of micturition
Nocturia (waking up in night to pass urine)
Delay in initiation of micturition and postvoid dribbling
Urinary retention
What can urinary retention cause (in BPH)?
Leads to the back flow of urine into the kidney and leads to hydronephrosis. If left too long untreated can lead to permanent scarring of the kidney and chronic kidney disease.
What is hydronephrosis?
A condition where one or both kidneys become stretched and swollen as the result of a build-up of urine inside them
What are the symptoms of prostate cancer?
BPH symptoms + symptoms due to metastases (back pain, weight loss)
What is the treatment of prostate cancer?
Watchful waiting
Radical prostatectomy
Radiotherapy
What are the most common causes of urinary tract obstruction?
Prostatic obstruction eg BPH or prostate cancer
Gynaecological cancer eg ovarian or cervical cancer
Calculi (kidney stones)
What does urinary tract obstruction cause?
Backflpw or urine into the unilateral or bilateral of kidneys. Can cause hydronephrosis. Can be acute or chronic.
What are the clinical features of upper urinary tract obstruction?
Dull ache in the flank or loin area
Anuria (no urine at all) caused by complete obstruction
Polyuria caused by partial obstruction (leads to increased urinary frequency)
What are the clinical features of bladder outlet obstruction?
Hesitancy, poor stream, terminal dribbling, sense of incomplete emptying
Can lead to infection commonly
What investigations can be done for urinary tract obstructions?
US KUB (ultrasound kidney urethrobladder) - first line. Can see polycystic kidney disease. Can assess bladder emptying to see urinary tension.
Intravenous urogram - helpful for stricture or stone obstructing flow
CT KUB - if suspect renal stones. Can help assess other pathologies eg tumour or access in abdominal region.
What is the management of urinary tract obstructions?
Treat the cause of obstruction
Urinary diversion eg by catheters
What is polycystic kidney disease?
A genetic disorder that causes many fluid-filled cysts to grow in your kidneys. Unlike the usually harmless simple kidney cysts that can form in the kidneys later in life, PKD cysts can change the shape of your kidneys, including making them much larger.
