Nephrology Flashcards
how is the anion gap calculated?
(Sodium and potassium - positive cations) - (chlorine and bicarbonate - negative anions)
what is the anion gap?
the blood serum should have a neutral charge. the number of cations (positive) should equal the number of anions (negative). the reason we have an anion gap is because we don’t calculate all the anions present in the blood stream. we only look at chlorine and bicarbonate.
there are other anions e.g. sulphate, phosphate and organic acids. when there is a big anion gap - these anions are making up a bigger proportion of the anion molecules e.g. raised lactic acid (lactate anion)
how does lactic acidosis widen the anion gap?
lactic acid dissociates to form a lactate anion and hydrogen ion. the hydrogen is buffered by the bicarbonate, lowering its numbers.
less bicarbonate and more lactate anions leads to a bigger anion gap
what are causes for a raised anion gap?
lactic acid
ketoacids
urate - renal failure
acid poisoning - methanol (formic acid) and salicylate
what happens in a normal anion gap acidosis?
the bicarbonate falls and kidney compensates for the decrease in anions by increasing the production of chlorine anions.
therefore, can also be known as a hyperchloraemic acidosis
what are causes of normal anion metabolic acidosis?
loss of bicarbonate in the GI tract = e.g. diarrhoea
renal tubular acidosis (RTA) e.g. decreased bicarb re-absorption in DCT
addissons disease
what causes metabolic alkalosis?
caused by a loss of hydrogen ions or gain of bicarb
mainly due to problems in the kidneys or GI tract
- diuretics
- vomiting/aspiration
- cushings syndrome
- primary hyperaldosteronism
- hypokalaemia
what is diabetes insipidus?
characterised by raised plasma osmolarity and low urinary osmolarity
due to a deficiency of ADH (cranial DI) or decreased sensitivity to ADH (nephrogenic DI)
what are causes of cranial DI?
idiopathic
head injury
pituitary surgery
craniopharyngomas
what are causes of nephrogenic DI?
genetic - mutations affection vasopressin receptor / aquaporin channel
electrolytes- hypercalcaemia, hypokalaemia
tubulo-interstital disease (pyelonephritis, sickle-cell, obstruction)
what are features of diabetes insipidus?
polyurea
polydipsia
high plasma osmolarity
low urine osmolarity (<700 )
what is rhabdomyolosis?
break down of muscle fibres and the release of their content into the blood stream - can cause serious complications such as renal failure
due to direct or indirect muscle injury
what is myoglobinuria?
the presence of myoglobin in the urine
usually associated with rhabdomyolosis or muscle destruction
what can cause renal tubular apoptosis?
aminoglycosides and radio contrast medium
what can cause renal tubular necrosis? ATN
myoglobinuria and haemolysis
how is an AKI defined?
an AKI is a syndrome of reduced renal function, measured by creatinine or urine output. There are a number of different aetiologies
clinically defined as:
how is AKi clinically defined?
1) creatinine rise >26 in 48 hours
2) Creatinine rise in adults by 50% + in 7 days
3) eGFR fall in children by 25% + in 7 days
3) urine output < 0.5ml/kg/h for >6 consecutive hours
what are the clinical parameters for the severity staging of AKIs?
Stage 1 = Creatining rise 1.5x baseline or Urine output <0.5 for > 6 hours
Stage 2 = Creatinine rise 2-2.9 x baseline or Urine output <0.5 for >12 hours
Stage 3 = creatinine rise >3 x baseline or urine output <0.3 for >24 hours
how are causes for AKI classified?
Pre-renal 85%
Renal 10%
Post renal 5%
what are pre-renal causes for an AKI?
anything causing decreased renal perfusion
- sepsis, shock
- haemorrhage, burns, pancreatitis, D and V
- cardiogenic shock, severe HF, MI (decreased cardiac output)
- drugs - vasodilation
- hypotension
- ACE-I, ARBs, hepatorenal syndrome, NSAIDs ( renal vasoconstriction)
- dehydration
what are renal causes for AKI?
anything damaging the actual kidney
glomerular = glomerularnephritis, acute tubular necrosis
interstitial = drug reaction, infection, infiltration
vessels = vasculitis, DIC (disseminated intravascular coagulation), TTP (Thrombotic thrombocytopenic purpura), HUS (haemolytic ureamic syndrome)
drugs - NSAIDs, ARBs, ACEi, gentamycin, radio contrast,
rhabdomyelosis
what are post-renal causes of AKI?
anything obstructing the output
- within renal tract: stone, renal tract malignancy, clot, stricture
- extrinsic pressure: retroperitoneal fibrosis, pelvic malignancy, prostatic hypertrophy
what are the most common causes of AKI?
- sepsis
- major surgery
- cardiogenic shock
- other hypovolaemias
- drugs
- hepatorenal syndrome
how does a patient with an AKI present?
dizzy, nausea, vomiting, fluid overload (orthopnea, pulmonary oedema etc), hypotension, tachycardia,
how is an AKI managed?
need to treat underlying cause
almost all AKI patients will need to have the following addressed: (regardless of aetiology): fluid balance (overload or dehydration), acidosis and hyperkalaemia.
how is fluid resuscitation in hypovolaemic AKI patients carried out?
500mL crystalloid bolus given over 15 mins and then reassessed. continue giving boluses of 250-500mL and then reassessing. stop when euvolaemic
if 2L given and no change - seek advice
Buffered solutions e.g. Hartmanns/ Ringers contain Potassium - be cautious if patient hyperkalaemic
non-buffered solutions e.g. 0.9% saline = contains chlorine. be wary of hyperchloraemic acidosis
Blood components should be used in haemorrhage (colloid)
how is fluid overload managed in AKI patients?
- oxygen if patient has pulmonary oedema
- fluid restriction
- venous vasodilator e.g. diamorphine (with antiemetic)
- diuretics can be used in symptomatic overload. not useful if the cause is oliguria
a patient with persistent fluid overload and oliguria/anuria needs urgent referral to critical care
what are causes of fluid overload?
sepsis - increased capillary permeability
aggressive fluid resuscitation
oliguria
Heart failure
how is hyperkalaemia treated in AKI?
1) calcium gluconate/calcium chloride (calcium chloride best given via central line) - stabilises heart cell membrane potentials
2) IV insulin - encourages cell take up of K+
3) salbutamol (nebuliser) - also shifts K+ into cells, at high doses
when is renal replacement therapy indicated?
- persistent fluid overload despite medication
- persistent hyperkalaemia
- severe/prolonged acidosis
- uraemic symptoms e.g. encephalopathy, pericarditis
what does the SALFORD pneumonic for AKI checklist stand for?
Sepsis? ACEi/ARBs/NSAIDs? - suspend! Labs - repeat creatinine levels Fluid resuscitation Obstruction - US for non- resolving AKI Renal replacement therapy? Dip the urine
how does the RAAS counteract hypovolaemia?
it attempts to increase circulating volume by
1) increasing reabsorption of Sodium and water
2) causing vasoconstriction of efferent arteriols to maintain GFR
(ACEi, ARBs and NSAIDs prevent this protective mechanism)
what is Acute Tubular Necrosis?
a condition involving the death of tubular epithelial cells that make up the renal tubules.
ATN presents with AKI and is one of the most common causes of AKI
what are common causes of ATN?
sepsis and nephrotoxic drugs
what are the 3 phases of ATN?
1) oligoruic phase
- patient produces <500ml urine /day
- at risk of fluid overload and electrolyte imbalance
- creatinine levels shoot up
2) maintenance phase
- creatinine levels stabilise/ rise slowly
- normal urine quantities produced
- fluid and electrolyte balance maintained
3) polyuric recovery phase
- large amounts off dilute urine produced
- patients can become hypovolaemic and unwell, hypokalaemic (electrolyte loss)
- DCT and collecting ducts recover last so water not reabsorbed by aquaporins
- creatinine levels drop
what is sepsis?
overwhelming and damaging systemic inflammatory response to infection.
can cause organ dysfunction
recognised by worsening vital signs
what is the pathophysiology of sepsis?
pathogen gains access to patient - risk increased with surgery, foreign bodies e.g. catheter and poor immunity
widespread inflammation leads to the systemic release of inflammatory molecules. NO causes vasodilation, other molecules activate endothelins - causing increase capillary permeability. fluid leaks out into tissue - causing oedema and hypovolaemia.
increased coagulapathy causes formation of microthrombi
the above compounds organ hypo-perfusion and dysfunction.
lactic acidosis and multi organ failure results
what are the SIRS criteria for sepsis?
need 2 or more of the below criteria tachycardia >90bpm RR> 22 acutely altered mental state temp >38.3 or <36 leukocytosis or leukopenia hyperglycaemia >7.7
what is the SOFA score for sepsis?
Sequential Organ Failure Assessment if a patient with infection scores 2 or more, suspect sepsis Resp; PaO2 liver: bilirubin Coagulation: platelets renal; urine output CV; catecholamine doses CNS; GCS score
what is the risk stratification approach to sepsis and how are moderate and high risk patients classified?
identifying infective patients who are high risk for sepsis
looking at
1) history
2) respiratory, >20 in moderate, >25 in severe
3) blood pressure, high in moderate, low in severe
4) circulation and hydration - raised HR, prolonged anuria
5) skin - cyansis, non-blanching skin rash
what investigations should be performed in suspected sepsis?
examination and culture of potential sites of infection blood culture FBC, LFTs, U and E, renal profile ABGs - hypoxia and Lactate? coagulation screening CRP, procalcitonin - raised in inflammation/sepsis glucose ECGs, CXR, CT - source of infection?
what is the sepsis six?
must be completed within the first hour mnemonic -O2 FLUID 1. Oxygen therapy - high flow 2. Fluid challenge - bolus 3. Lactate levels checked 4. Urine output - hourly measurement 5. Infection, blood culture 6. Drugs - ASAP antibiotics - broad spec at max dose
what electrolyte imbalance can omeprazole and furosemide cause?
hyponatraemia
what is chronic kidney disease?
impaired renal function or structure for >3 months with implication for health
or markers of kidney damage and GFR <60 (on 2 separate occasions) for over 3 months
what are the 5 stages of CKD?
1) >90
2) 60-89
3a) 45-59
3b) 30-44
4) 15-29
5) <15
at what GFR do symptoms of renal failure become apparent?
usually <30 GFR
what are causes of CKD?
1) hypertension and diabetes are responsible for majority of cases
2) glomerulonephritis - mainly IgA nephropathy
3) renovascular disease
5) pyelonephritis / reflux nephropathy
others = following AKI, ATN, adult polycystic kidney disease, interstitial nephritis, obstructive uropathy, lupus
what are symptoms of CKD??
often vague - requiring lab evidence
begins with fatigue, nausea, possible oedema
then as renal function worsens = uraemic symptoms such as pruritis, bone pains, restless legs, vomiting, fatigue, weakness, yellowish tinge to skin
signs of fluid overload
signs of hyperkalaemia - seizures, encephalopathy, coma, arrhythmias
what investigations should be performed in suspected CKD?
- Renal profile; GFR and creatinine levels
- Urine dipstick and analysis - haematuria, proteinuria, Pyuria?
- renal ultrasound
- diabetes revision/screen - glucose levels etc
how is proteinuria defined?
ACR - albumin: Creatinine ratio > 30 mg/mmol
Albumin >200mg/L
PCR: urine protein: creatinine ration > 45mg /mmol
ACR is more conclusive than PCR
how is STAGE 1-4 CKD treated?
- aim to slow down renal damage and prevent RRT
1) ACEi or ARBs = decreases the pressure in the kidneys (ramipiril or losarton)
2) Statins
3) additional hyptertensive medication - beta blockers, thiazide diuretics
2nd line = non -dilhydropyridine CCB e.g. diltiazam or verpamil
how is STAGE 5 CKD treated?
1st line = dialysis
2nd line = kidney transplant
what is the pathophysiological mechanisms behind diabetic nephropathy?
1) Raised glomerular pressure - due to HTN and RAAS activation by hyperglycaemia
2) barotrauma of mesangial cells
3) nephron ischaemia (microvascular damage, efferent arteriole vasoconstriction)
what are side effects of ACEi/ ARBs?
dry cough hyperkalaemia hypotension angio oedema AKIs - must be stopped in this case ( they prevent body's protective mechanism against pre-renal AKI)
how do ACEi and ARBs work in CKD?
they prevent salt retention and vasoconstriction
this reduced bllood volume and pressure in the kidneys
relaxes the efferent arteriole
- prevents the viscous cycle HTN causing hypoperfusion of kidney, which then activates the RAAS, raising BP
can you take ACEi/ARBs in pregnancy?
NO
what are the metabolic complications of CKD?
1) anaemia - decreased erythropoietin produced
2) Acidosis - failure to excrete various anions
3) CKD mineral bone disease - bone pain and muscle cramps
how is metabolic acidosis treated in CKD?
oral sodium bicarbonate
How is anaemia treated in CKD?
EPO stimulating agents e.g.
epoetin-alfa
darbepoetin-alfa
how does CKD lead to mineral bone disease?
hypocalcaemia is caused by kidneys inability to activate Vit D, and inability to excrete adequate phosphate.
Hypocalcaemia leads to secondary hyperparathyroidism - excess PTH causes excess phosphate
how is mineral bone disease in CKD treated?
alfacalcidol - vitamin D supplement / calcitriol
phosphate binding medication
when should a CKD patient be referred to a renal specialist?
Stage 5 - immediate referral
Stage 4 - urgent referral, or routine if stable
Stage 3 - routine referral if any of the following: uncontrolled BP, PCR>45, GFR fall by 15% after ACEi, unexplained anaemia, abnormal K, Ca, Phosphate, microscopic haematuria, systemic illness e.g. SLE
Stage 1 and 2 - referral not required
proteinuria w/ oedema and decreased serum albumin (nephrotic syndrome)
hyperkalaemia
malignant hypertension
which diabetic medication is contraindicated if eGFR < 30 ?
metformin
what is the target BP in all stages of CKD?
130/80
what are the features of hemodialysis?
- AV fistula created (better flow, less complications for needle insertion)
- dialysis carried out 3 times a week for 4 hours
- diet and fluid is restricted
- difficult to go abroad, unless dialysis clinics arranged
- lots of time travelling to/from hospital, spent in hospital
what are features of peritoneal dialysis ?
- tenckhoff catheter is fitted
- usual requirement = 4-6 exchanges per day with 4-6 hours of dwell time per exchange
- absolute CIs : IBD, ischaemic bowel, abdo abscess, pregnancy 3rd trimester, diverticulitis
- carried out at home, less bulky, portable equipment
- there are 2 forms: CAPD (continuous ambulatory PD) or APD (assisted PD).
- CAPD doesn’t require a machine - the patient fills the stomach with dialysate, leaving it to dwell whilst carrying out normal daily activities and then drains it with gravity
- APD uses a machine that automatically does exchanges whilst you sleep. the dwells are shorter. in the morning you fill with dialysate and leave it to dwell all day.
- risk of peritonitis, malnutrition
what is the average waiting time for a kidney transplant in manchester?
3 years
what is the annual cost of dialysis per patient?
£30800
how is the new kidney plumbed into the patient?
the renal artery is anatomised onto the iliac artery
the renal vein onto the iliac vein
and the ureter onto the bladder
the old kidney is left where it was
what immunosuppressant drugs can be used for kidney transplant patients?
calcineurin inhibitors: cyclosporine or tacrolimus
antiproliferative agents: mycophenolate mofitil, mycophenolate sodium or azathioprine
prednisolone
mTOR inhibitor: sirolimus
what are the complications of a kidney transplant?
1) Rejection
2) Infection- most commonly UTI then Chest. Diverticulitis = ~100% mortality in transplant patients
3) Malignancy
4) CV disease
5) Immunosuppressant drug interacts.
6)
how is transplant rejection diagnosed?
via US guided transplant biopsy
biopsy shows lymphocyte infiltration of tubularinterstitium and tubules.
Can be treated with steroids
if lymphocytes have infiltrated vasculature - under endothelium - this is very serious.
risk of which malignancy is increased most in transplant patients?
squamous cell carcinoma of the skin
which immunosuppressant drug has numerous interactions?
tacrolimus
give examples of phosphate binders used in CKD?
lanthanum, sevelamer, calcium carbonate/acetate
what is tertiary hyperparathyroidism?
after a long period of secondary hyperparathyroidism, the regulation of PTH hormone can become autonomous and dysregulated.
excessive PTH can be secreted leading to hypercalcaemia
treated with cinacalcet
what are side effects of erythropoietin treatment?
accelerated hypertension (leading to encephalopathy or seizures)
increased risk of thrombosis (b/c increased PCV)
iron deficiency
bone aches
flu-like symptoms
skin rashes
red cell aplasia (due to autoimmune antibodies)
how much protein and albumin is excreted daily in the urine?
<150 mg protein
<30 mg albumin
30-300 mg albumin = moderately increased albuminurea
what is glomerulonephritis?
- A group of diseases which cause injury to the glomeruli
- present with proteinuria and/or haematuria
- covering a spectrum from nephrotic syndrome to nephritis
- can cause CKD
- diagnosed on biopsy
what is nephrotic syndrome? (triad)
1) Proteinuria (hyperalbuminuria) >3.5g/24hr, PCR>300, ACR>250
2) Hypoalbuminaemia
3) Oedema
ALSO
hyperlipidaemia (serum proteins suppress lipid production usually)
lipiduria
what is the pathophysiology of Nephrotic syndrome?
damage to the filtration barrier of the glomeruli leads to proteins entering the urine. (>3.5g/24hr)
decreased protein in the serum leads to decreased oncotic and osmotic pressures. Fluid leaves the blood causing Oedema.
(?)lack of proteins/albumin in blood causes a rise in lipids. this results in hyperlipidaemia and lipiduria
which diseases fall under the umbrella of nephrotic glomerulonephritis?
Minimal Change disease
Focal Segmental Glomerulosclerosis
Membranous nephropathy
mebranoproliferative GN
which diseases fall under the umbrella of nephritic GN?
IgA nephropathy
Post-streptococcal GN
Anti GBM disease (Good Pastures)
What causes Minimal change disease?
most cases are idiopathic 10-20% have cause - drugs: NSAIDs, rifampicin - Hodgkin's lymphoma, thymoma - infectious mononucleosis
what are features of minimal change disease?
- nephrotic syndrome
- normotensive
- highly selective proteinuria (only intermediate sized proteins leek through)
- change only visible on electron microscopy - shows effacement of podocytes.
- responsible for 75% cases of GN in children
- and 25% cases in adults