J de Zoysa: Renal Failure Flashcards
Vascular supply of the kidneys and describe/draw the nephron.
Blood supply: aorta
Venous supply: drains to IVC
Ureters to the bladder
The five key roles of the kidneys
- Elimination of waste products
- control of fluid balance: either conc or dilute urine
- regulate acid-base balance
- Produce hormones
- Regulation of electrolytes (minerals eg; salt, K+ and calcium)
The major role of the kidneys is to
Describe this.
- Major role; to remove waste products
- GFR: rate at which the blood is cleared of the waste products
- GFR > 120 ml/min usually
- if reduced = renal impairment
acute vs chronic kidney injury
AKI:
- Hours to days
- Potentially reversible
- ‘Acute renal failure’ had an inconsistent diagnosis and refeered to different set points.
CKD
- weeks/ months/years
- Progressive, irreversible
Rates of AKI, and what does it consist of?
- AKI is a syndrome with multiple aetiologies
- The incidence in the community is unclear
- Primary cause of admission in 5% of cases and affects 20% of acute admissions
- It is associated with ~50% of preventable hospital deaths
What are the KDIGO guidelines for staging?
Why is this important
- We measure serum creatinine and urine output?
- SC: 1.5-1.9 x baseline UO: <0.5ml/kg/hr for 6-12hr
- SC: 2 - 2.9x baseline UO: <0.5 ml/kg/hr for >12hr
- SC: 3x baseline UO: <0.3 ml/kg/hr for >24hr or anuria for >12 hours
- non elective mortality 3.3%
- AKI stage 1 mortality 16%
- AKI stage 2 mortality 16-33%
- AKI stage 3 mortality 33%
Types of AKI
- Pre-renal
- Renal
- Post-renal
What are the risk factors of AKI
- Chronic KD
- Age >75 (this can be variable)
- Diabetes
- Emergency surgery (sepsis and hypovolaemic)
- Intraabdominal surgery
- Congestive HF
- Liver failure
- Nephrotoxic medications (NSAIDs, dabigatrin, gentamicin, ACE inhibitors)
- past history of AKI
- Acute illness
- hypotension
- sepsis
- hypovolaemia
- High EWS
General approaches (1 and 2) to high-risk patients with/or suspected to have AKI
Approach 1: deal with symptoms
- Identify patient at high risk
- assess and optimise volume status
- Stop all nephrotoxic agents (NSAIDs, gentamicin, anti-hypertensive, and any meds that are renally excreted eg. hypoglycaemic agents)
- Review medications; dose adjust (or stop)
- Monitor creatinine and UO
Approach 2: target primary source
- Non-invasive diagnostic workup
- CT, xray, lab tests
- invasive diagnostic workup
- renal biopsy
- Daily weights
- Diet
- Targetted therapy
Assessment of volume status?
- JVP inspection
- Peripheral and sacral oedema
- Listen to heart sounds (3rd heart sound in overload)
- Listen to lungs for crackles
Chronic Kidney disease
“an abnormality of kidney structure or function, present for >3months, with implications for health”
- Slowly declining renal function over time*
- Based off cause, GFR and albuminuria
How to calculate the GFR
-
Clearance of artificially injected substances
- Inulin clearance: Sugar which is filtered by the glomerulus and neither reabsorbed nor secreted into the tubule
- GOLD STANDARD: inject inulin in blood and measure the clearance in urine
- Isotope clearance: inject radioactive substance (Cr-EDTA or I-IOT) and measure the clearance over time, very accurate measurement
- Inulin clearance: Sugar which is filtered by the glomerulus and neither reabsorbed nor secreted into the tubule
-
Creatinine clearance
- It’s produced by creatinine metabolism and freely filtered at the glomerulus and can be used to estimate the GFR. Be aware that is produced in muscles so varys between peoples muscle mass.
- Cr Clearance= (urine Ct x urine volume) / (plasma Cr x time period)
Potential issues with Creatinine clearance measures?
- As it’s also secreted in small amounts by the tubules, therefore Cr Cl tends to overestimate the GFR
- Serum Cr also reflects body size and muscle mass
- Presence of mod-severe CKI can confound CrCl
- As GF declines, extrarenal excretion of creatinine increases and there is decreased muscle mass → overestimation of GFR at end stage renal failure
Estimated GFR
most typically derived formula, using a single blood test of serum creatinine are used. (there’s over 80 formulas)
- CKD- EPI formula the most common: using age etc
STaging of GFR related to differing GFR levels
- ** we also measure albuminuria as a marker of renal disease
- A1 <30mg/mmol
- A2 30-300 mg/mmol
- A3 >300mg/mmol
- REMEMBER that renal function naturally declines with age so link their age to their levels accordingly
CKI Can be a marker of issues, such as heart disease etc.
How common is it?
What are the sociodemographic risk factors?
- Over 10% of the population is at risk of CKD
Sociodemographic Risk Factors
- age (M>F)
- sex (maori and pacific islanders > pakeha)
- ethnicity
- low income
- obesity
Many patients will also need drugs to control their BP
they will need multiple complementary drugs specifically combined to target these for systems
- **ACE inhibitors, angiotensin II receptor blockers, spirolactone: block the RAAS
- alpha blockers, B-blockers, calcium channel blockers: block the SNS
Uraemia
Symptomatics ESKD
- The manifestations of organ dysfunction seen in CKD G4 and G5
- the uraemic syndrome resembles a systemic intoxication
- Unfortunately, no singles compound has been found to produce the clinical picture of uraemia
Symptoms: faitgue/lethargy, headache, seizures, encephalopathy, peripheral neuropathy
