Genitourinary tract Flashcards
what are the functions of the kidney?
- filter or secrete waste/excess substances
- maintains acid-base balance
- retains albumin and circulating cells
- reabsorbs glucose, amino acids and bicarbonates
- controls BP, fluid status and electrolytes
- activates 25-hydroxy vitamin D (by hydroxylating it to form 1,25 dihydroxy vitamin D)
- synthesises erythropoietin
what is the GFR?
glomerular filtration rate
- the volume of fluid filtered from the glomeruli into Bowman’s space per unit time (minutes)
- 120ml/min = 7.2L/h = 170L/day
what is the creatinine clearance rate?
- volume of blood plasma that is cleared of creatinine per unit time
- useful measure for approximating the GFR
- creatinine clearance exceeds GFR due to creatinine secretion, which can be blocked by cimetidine
what is reabsorbed in the proximal tubule?
- 2/3rds of salt and water (via Na/K ATPase pump)
- 100% of organic solutes (glucose, amino acids, inorganic phosphate)
- 65% of potassium
- 50% of urea
- 80% of phosphate
- 70-90% of citrate
what is Fanconi syndrome? what does it lead to?
- syndrome of inadequate reabsorption in the proximal renal tubules
- affects the PCT and proximal straight tubule
- glycosuria
- acidosis with failure of urine acidification
- phosphate wasting resulting in rickets/osteomalacia
- aminoaciduria
what are some causes of Fanconi syndrome?
- cytinosis
- Wilson’s
- tenofovir
- congenital or acquired diseases
- toxicity
- ADRs
what is reabsorbed in the loop of Henle?
- thin descending limb has low permeability to ions and urea, and is highly permeable to water
- thin ascending limb is impermeable to water but permeable to ions
- ascending limb reabsorbs sodium, potassium and chloride via NKCC2, and magnesium and calcium
- cortical thick ascending limb drains urine into the DCT
what is reabsorbed in the DCT?
- regulates pH by absorbing bicarbonate and secreting protons, or by absorbing protons and secreting bicarbonate
- secretes potassium and absorbs sodium (mediated by aldosterone and WNK kinases)
- reabsorbs calcium (mediated by PTH)
- expresses arginine vasopressin receptor 2
what is the function of the collecting duct?
- does salt handling; by this point, most of the salt has been reabsorbed
- tightly regulated by aldosterone (aldosterone increases the transcription of eNac channels which absorb Na+ in exchange for K+)
- secrete K+ and H+ into the urine
- water handling is also done here and water is absorbed via aquaporin 2 channels (regulated by vasopressin)
what are features of renal potassium control?
- K+ is freely filtered and mostly reabsorbed in the proximal tubule/loop of Henle
- distal tubule secretion determines renal excretion
- insulin and catecholamines drive cellular K+ uptake, buffering acute changes
what renal medication causes hypokalaemia?
- loop diuretics
- thiazide diuretics
what renal medication causes hyperkalaemia?
- spironolactone (aldosterone antagonist)
- amiloride (acts on eNac channels)
- ACE inhibitors
- angiotensin receptor blockers (ARB)
- trimethoprim (acts on eNac channels but milder)
how can diuretics affect kidney disease?
- diuretics are not nephrotoxic but hypovolaemia is (which they can cause)
- in advanced kidney disease you require huge amounts of diuretics to do the work
- thiazide and loop diuretics are extremely powerful and effective together resulting in profound diuresis
what happens if plasma is too concentrated?
if things are too concentrated then ADH is released resulting in increased aquaporins in the collecting duct and thus more water is absorbed, thereby diluting plasma
what are features of erythropoietin in the kidney? when is anaemia seen?
- the renal cortex acts as an oxygen sensor; blood flow and oxygen requirement (GFR) are matched
- anaemia is mainly seen after eGFR < 30
- erythropoietin is hormone that produces haemoglobin, it is produced in response to tissue hypoxia
- in advanced kidney disease and anaemia, erythropoietin will be given to help increase O2 transport
what is the process of vitamin D hydroxylation in the kidneys?
it takes 25-hydroxy vitamin D and hydroxylates it to form 1,25-dihydroxy vitamin D (calcitriol) by the enzyme 1alpha hydroxylase - this is the active form of vitamin D
what are the actions of calcitriol?
- increases Ca2+ and phosphate absorption from the gut
- increases phosphate absorption to a lesser extent
- suppresses parathyroid hormone (PTH)
- deficiency results in secondary hyperparathyroidism
how does deficiency of calcitriol result in secondary hyperparathyroidism?
- low vitamin D results in low Ca2+ and phosphate resulting in increased PTH which causes Ca2+ and phosphate leeching out of the bones
- PTH also acts on osteoclasts by increasing their activity and thus increasing their turnover resulting in reduced bone quality
what is the function of the lower urinary tract?
to convert the continuous process of excretion (urine production) to an intermittent, controlled volitional process (micturition)
what are the essential features of the lower urinary tract?
- low pressure and insensible storage of urine of adequate capacity
- prevents leakage of the urine stored
- allows rapid, low-pressure voiding at an appropriate time and place
what is the pressure like in the kidney?
- mean arterial pressure 60-70mmHg drives filtration in the Bowman’s capsule
- there is progressive reduction in pressure along the nephron due to reabsorption, until at the collecting system pressure is 3-10mmHg
what is the neural control of voiding?
- pontine micturition centre stimulates excitatory control to detrusor nucleus and inhibits Onuf’s nucleus
- signal is transmitted from spinal root S3,4,5 via the parasympathetic nervous system and this results in contraction of detrusor muscles and relaxation of the urethra
what is the neural control of storage?
- pontine storage centre stimulates and sends inhibitory signals to detrusor muscles and excitatory signals to Onuf’s nucleus
- signal is transmitted from spinal root T10, L1 and L2 via the sympathetic nervous system and this results in the relaxation of the bladder and contraction of the urethral sphincter
what is the function of the sacral micturition centre?
at the sacral micturition centre there is a reflex that, when bladder is full it initiates voiding - this is inhibited by conscious parts of the brain:
• if the cord is cut above S2,3,4 then will only urinate when the bladder is full, but the descending pathway will not be able to inhibit this with the brain as descending pathway will be destroyed
what occurs in voiding? is it parasympathetic or sympathetic?
- detrusor muscle contraction of bladder
- parasympathetic (cholinergic) - S3, S4, S5
what occurs in storage? is it parasympathetic or sympathetic?
- urethral contraction
- inhibition of detrusor muscle contraction of bladder
- sympathetic (noradrenergic) - T10, L1, L2
what is the histology of the bladder?
has urothelium (transitional epithelium):
• highly specialised stratified, 3-7 cells thick
• umbrella structure that is completely impermeable so cannot resorb urine
• able to fold and unfold to increase volume
what is the difference between women and men in urethras? what does this mean?
- men have a greater voiding pressure due to them having a longer urethra; more likely to develop retention
- women have a shorter urethra with lower resistance and thus higher flow rates; more likely to develop incontinence
what are renal stones?
- nephrolithiasis/urolithiasis
- renal stones (calculi) consist of crystal aggregates; stones form in collecting ducts and may be deposited anywhere from the renal pelvis to the urethra
where do renal stones classically occur?
occur classically at these 3 narrowings:
- pelviureteric junction
- pelvic brim
- vesicoureteric junction
what is the epidemiology of renal stones?
- incidence is increasing
- 10-15% lifetime risk
- peak age is between 20-40 yrs
- more common in males than females
- unusual in children
- more than 50% lifetime risk of recurrence once you’ve had them
- most stones are composed of calcium oxalate and phosphate
what are risk factors and aetiology of renal stones?
- anatomical abnormalities that predispose to stone formation e.g. obstruction or trauma
- chemical composition of urine that favours stone crystallisation
- dehydration resulting in a concentrated urine
- infection
- hypercalcaemia, hyperoxaluria, hypercalciuria, hyperuricaemia
- primary renal disease e.g. polycystic kidneys or renal tubular acidosis
- drugs e.g. diuretics, antacids, acetazolamide, corticosteroids, aspirin, allopurinol, vitamin C and D
- diet e.g. chocolate, tea, strawberries, rhubarb all increase oxalate levels
- gout
- family history
what are types of renal stones?
renal stone/calculi form from crystals in supersaturated urine:
• calcium oxalate are the most common stones (60-65%)
• calcium phosphate stones are uncommon (10%)
what are causes of hypercalcuria?
- hyperparathyroidism resulting in hypercalcaemia
- excessive dietary intake of Ca2+
- idiopathic hypercalciuria - increased absorption in gut
- primary renal disease such as polycystic kidneys or medullary sponge kidney
what are causes of hyperoxaluria?
- high dietary intake of oxalate rich food e.g. spinach, rhubarb, chocolate and tea
- low dietary Ca2+ resulting in decreased binding of oxalate (by Ca2+) so increased oxalate absorption and urinary excretion
- increased intestinal resorption due to GI disease e.g. Crohn’s
what are causes of uric acid stones?
- associated with hyperuricaemia with/without gout
- dehydration
- patients with ileostomies are at particular risk, both from dehydration and from bicarbonate loss from GI secretion resulting in the production of an acidic urine (uric acid is more soluble in alkaline than acidic) thereby stimulating stone formation
what causes infection-induced kidney stones?
- mixed infective stones are composed of magnesium ammonium phosphate as well as calcium
- these are often large
- usually due to UTI with an organism such as Proteus mirabilis that hydrolyses urea forming ammonium hydroxide
- the increased ammonium ions and the alkalinity both favour stone formation
what are cystine stones caused by?
- caused by cystinuria
* this results in excessive urinary excretion and formation of cysteine stones
what is clinical presentation of kidney stones?
- most are asymptomatic
- renal colic
- loin pain
- if urinary tract is obstructed then fluid/diuretics make the pain worse as peristaltic flow increases
- bowel sounds may be reduced
- BP may be low
- dysuria, strangury, frequency
- recurrent UTI’s
- haematuria
- acute pyelonephritis
what is the clinical presentation of renal colic?
- rapid onset - woken from sleep
- pain that results from upper urinary tract obstruction
- excruciating ureteric spasms
- pain is from loin to groin and comes and goes in waves as the ureters peristalise
- associated with nausea and vomiting
- worse with fluid loading
- radiates to groin and ipsilateral testis/labia
- often cannot lie still (differentiates from peritonitis)
what are differential diagnoses of kidney stones?
- vascular accident e.g. ruptured AAA if over 50 yrs until proven otherwise
- bowel pathology e.g. diverticulitis or appendicitis
- ectopic pregnancy or ovarian cyst torsion
- testicular torsion can present with loin pain and nothing else
what is used to diagnose kidney stones?
- history and examination
- urine dipstick
- mid-stream specimen of urine sent for microbiology culture and sensitivity
- bloods
- KUBXR
- NCCT-KUB
- ultrasound
how is a urine dipstick used to diagnose kidney stones?
- usually positive for blood - haematuria
* also looks for red cells, protein and glucose
how is KUBXR used to diagnose kidney stones?
Kidney Ureter Bladder X-ray
• first line investigation
• 80% sensitive
• see stone in line of renal tract
how is NCCT-KUB used to diagnose kidney stones?
non-contrast CT kidney ureter bladder
• gold standard
• very rapid
• 99% sensitive for stones - diagnostic
• no contrast so no renal damage or allergy
• but no functional info and gives radiation dose equivalent to 18 months background radiation
how is ultrasound used to diagnose kidney stones?
- shows kidney stones and renal pelvis dilatation well but ureteric stones can be missed
- sensitive for hydronephrosis
- very poor at visualising stones in ureter
- useful in pregnant and younger recurrent stone-formers
- rarely used acutely
what is the treatment of kidney stones?
- strong analgesic
- antibiotics if infection e.g. IV cefuroxime or IV gentamicin
- antiemetics to prevent vomiting
- observe for sepsis
- stones less than 5mm in lower ureter 90% pass spontaneously
- medical expulsive therapy (oral nifedipine or alpha blocker)
what is the treatment if kidney stones are still not passing?
- extracorporeal shockwave lithotripsy; ultrasound fragments stone
- endoscopy with YAG - laser for larger stones
- percutaneous nephrolithotomy; keyhole surgery to remove stones that are large, multiple or complex
how can kidney stones be prevented from recurring?
- overhydration
- normal/low Ca2+ dietary intake
- low salt diet
- normal daIry intake
- reduce BMI
- reduction in animal proteins
- active lifestyle
how can uric acid stones be prevented from recurring?
- can be caused by long term allopurinol use
- only form in acid urine
- deacidification of urine e.g. oral sodium bicarbonate to alkalinise urine
how can cysteine stones be prevented from recurring?
- overhydration
- urine alkalisation
- cysteine binders e.g. captopril
what is the definition of acute kidney injury/acute renal failure?
an abrupt (over hours to days) sustained rise in serum urea and creatinine due to a rapid decline in GFR leading to a failure to maintain fluid, electrolyte and acid-base homeostasis - it is usually but not always reversible or self-limiting
what is the RIFLE classification?
- old system that was used to define AKI
- uses either an increase in serum creatinine (SCr) or a decrease in urine output
- RIFLE describes three levels of renal dysfunction (RIF) and two outcome measures (LE) - these criteria indicate an increasing degree of renal damage and have a predictive value for mortality
- risk, injury, failure, loss, end-stage renal disease
what is the GFR and urine output criteria for the Risk category of RIFLE for AKI?
GFR criteria: 1.5 fold increase in creatinine or GFR decrease >25%
urine output criteria: UO <0.5 ml kg^-1 h^-1 x6h
what is the GFR and urine output criteria for the Injury category of RIFLE for AKI?
GFR criteria: 2 fold increase in creatinine or GFR decrease >50%
urine output criteria: UO <0.5 ml kg^-1 h^-1 x12h
what is the GFR and urine output criteria for the Failure category of RIFLE for AKI?
GFR criteria: 3 fold increase of GFR decrease >75% or creatinine >4mg per 100ml (acute rise of >0.5mg per 100ml dl)
urine output criteria: UO <0.3 ml kg^-1 h^-1 x24h or anuria x12h
what is the criteria for the Loss category of RIFLE for AKI?
persistent ARF = complete loss of kidney function >4hrs
what is the criteria for the ESKD category of RIFLE for AKI?
end-stage kidney disease (>3 months)
what is the KDIGO classification for AKI?
- staging system for AKI used currently
- also uses serum creatinine and urine output to assess severity
what is the serum creatinine (sCr) criteria for AKI in the KDIGO classification?
- increase >26umol/L in 48hrs OR increase >1.5 x baseline
- increase 2-2.9 x baseline
- increase >3 x baseline OR >354umol/L OR commenced on RRT irrespective of stage
what is the urine output criteria for AKI in the KDIGO classification?
- <0.5mL/kg/h for >6 consecutive hours
- <0.5mL/kg/h for >12hrs
- <0.3mL/kg/h for >24hrs or anuria for 12hrs
what is the epidemiology of AKI?
- AKI is common, occurring in 18% of hospital patients
- about 25% of patients with sepsis and 50% of patients with septic shock will have AKI
- severe AKI (creatinine > 500μmol/L, often requiring dialysis) affects about 130-140 per million population per year
- common in the elderly
what is AKI associated with?
- diarrhoea
- haematuria
- haemoptysis
- hypotension
- urine retention
what are the causes of AKI?
- commonest are ischaemia, sepsis and nephrotoxins
- pre-renal (40-70%)
- intrinsic renal (10-50%); required renal biopsy for diagnosis
- post-renal (10-25%)
what are causes of pre-renal (40-70%) AKI?
- renal hypoperfusion e.g. hypotension (due to hypovolaemia or sepsis) resulting in a drop in GFR
- hypovolaemia of any cause - dehydration or haemorrhage
- hypotension without hypovolaemia - cirrhosis or septic shock
- low cardiac output - cardiac failure or cardiogenic shock
- renal hypoperfusion - NSAIDs, ACE inhibitors
what are the causes of intrinsic renal AKI (10-50%)?
- renal parenchyma damage
- acute tubular necrosis - commonest renal cause of AKI, caused by pre-renal damage or nephrotoxins e.g. NSAIDs, radiological contrast, uric acid crystals, myeloma and increased Ca2+
- vascular
- glomerular
- interstitial
what are vascular causes of intrinsic renal AKI?
- renal artery/vein thrombosis
- cholesterol/thrombus emboli from angiography
- vasculitis e.g. in SLE
- haemolytic uraemic syndrome - thrombotic microangiopathy; haemolytic anaemia and reduced platelets
- malignant hypertension
what are glomerular causes of intrinsic renal AKI?
- glomerulonephritis or nephrotic syndrome
- autoimmune (SLE), drugs, infections
what are interstitial causes of intrinsic renal AKI?
drugs, infiltration with e.g lymphoma, infection, tumour lysis syndrome following chemo
what are causes of post-renal (10-25%) AKI?
- urinary tract obstruction at ureter, bladder or prostate
- luminal: stones, clots or sloughed papillae
- mural (wall)
- extrinsic compression from malignancy especially from pelvis or due to retroperitoneal fibrosis
what are causes of mural post-renal AKI?
- malignancy e.g. ureteric, bladder or prostate
- benign prostate hyperplasia (BPH)
- strictures
what are risk factors for AKI?
- age > 75 yrs
- heart failure
- peripheral vascular disease
- chronic liver disease
- sepsis
- poor fluid intake/increased losses
- history or urinary symptoms
- chronic kidney disease (CKD) especially if GFR < 60
- past history of AKI
- hypovolaemia
- haematological malignancy
- diabetes
- prostate cancer
- nephrotoxic drugs
- repeated use of radiological contrast
what is the clinical presentation of AKI?
- depends on underlying cause or severity
- on examination there may be palpable bladder, palpable kidneys, abdominal/pelvic masses, rashes
- oliguria occurs in early sages
- arrhythmias due to hyperkalemia
- breathlessness occurs from a combination of anaemia and pulmonary oedema secondary to volume overload
- pericarditis occurs with severe untreated uraemia and may be complicated by a pericardial effusion, tamponade or pericardial rub
- impaired platelet function causes bruising and GI bleeding
- infection due to immune suppression
- postural hypotension
- oedema
- thirst - indicated fluid depletion and dehydration (possible cause of AKI)
what are differential diagnoses of AKI?
abdominal aortic aneurysm, alcohol toxicity, alcoholic and diabetic ketoacidosis, chronic renal failure, dehydration, GI bleed, heart failure, metabolic acidosis
when should you suspect chronic kidney disease?
small kidneys on ultrasound, anaemia, low Ca2+, high phosphate or high creatinine/low GFR
how is a urine dipstick used to diagnose AKI?
can suggest infection (leucocytes + nitrites) and glomerular disease (blood + protein)
how is blood count used to diagnose AKI?
anaemia and very high ESR suggests myeloma or vasculitis as underlying cause
what is used to exclude infection in AKI?
- urine and blood cultures to exclude infection
- mid-stream-specimen of urine sent for microbiology culture and sensitivity
how is ultrasound used to diagnose AKI?
- give assessment of renal size (very small indicates CKD)
- can be used to distinguish obstruction and hydronephrosis and look for cysts, small kidneys (CKD), masses and corticomedullary differentiation (reduced in CKD)
how is CT-KUB used to diagnose AKI?
- complete anuria is rare but if present it suggests obstructive cause
- in elderly men this should be considered prostatic e.g BPH and can be relieved by catheterisation
- if catheterisation does not relieve anuria then suspect obstruction above prostate
what is done when catheterisation does not relieve anuria? what does this suggest? what is looked for?
- suspect obstruction above prostate
- get an urgent ultrasound to look for hydronephrosis
- get an urgent CT-KUB which can look for obstructing masses or calculi as well as retroperitoneal fibrosis
how is ECG used to diagnose AKI?
to look for hyperkalaemic changes
- tall tented T waves
- prolonged PR interval
- widening QRS complex
how is CXR used to diagnose AKI?
to look for pulmonary oedema
how is renal biopsy used to diagnose AKI?
- intrarenal causes of AKI
* perform for every patient with unexplained AKI and normal kidneys
what is the treatment of pre-renal AKI?
- correct volume depletion with fluids
- treat sepsis with antibiotics
what is the treatment of intrinsic renal AKI?
refer early to nephrology if concern over tubulointerstitial or glomerular pathology
what is the treatment of post-renal AKI?
- catheterise and consider CT of renal tract (CTKUB)
- if signs of obstruction and hydronephrosis then do cystoscopy and retrograde stents or nephrostomy insertion; this buys time to allows treatment of cause of obstruction
what are some nephrotoxic drugs?
- NSAIDs
- ACE-inhibitor
- gentamicin
- amphotericin
what is the treatment of hyperkalaemia in AKI?
- calcium gluconate; cardioprotective
- insulin to drive K+ into cells with glucose and dextrose to prevent hypoglycaemia
- use dialysis or haemofiltration
what is the treatment of AKI?
- hyperkalaemia treatment
- diuretics or dialysis/haemofiltration for pulmonary oedema
- sodium and potassium restriction and vitamin D supplied
what are indications for dialysis in AKI?
- symptomatic uraemia including pericarditis or tamponade
- hyperkalaemia not controlled by conservative measures
- pulmonary oedema thats unresponsive to diuretics
- severe acids
- high potassium
- tall T waves, low flat p waves, broad QRS or arrhythmias on ECG
- metabolic acidosis
- fluid overload that is resistant to diuretics
what are components of renal replacement therapy?
haemofiltration and haemodialysis
what are complications of RRT?
- cardiovascular disease due to combination of hypertension and calcium/phosphate dysregulation
- infection
- amyloid accumulates in long-term dialysis and may cause carpal tunnel syndrome, arthralgia and fractures
- malignancy is commoner in dialysis patients; may be due to causes of end-stage renal failure e.g. urothelial tumours
what is glomerulonephritis?
glomerulonephritis is a broad term that refers to a group of parenchymal kidney diseases that all result in the inflammation of the glomeruli and nephrons
what does glomerulonephritis cause?
- damage to the filtration mechanism resulting in haematuria and proteinuria
- damage to the glomerulus restricts blood flow, leading to compensatory hypertension
- loss of the usual filtration capacity leads to AKI
- causes 25% of end stage kidney failure
how can glomerulonephritis present itself?
- acute nephritic syndrome (acute glomerulonephritis)
- nephrotic syndrome
- asymptomatic urinary abnormalities; haematuria, proteinuria or both
- chronic kidney disease (CKD)
- haematuria; visible or non-visible (red cell casts seen on microscopy)
- proteinuria (usually < 2g in 24hrs)
- hypertension and oedema (periorbital, leg, or sacral)
what is acute nephritic syndrome often caused by?
often caused by an immune response triggered by an infection of other disease
what is the commonest primary cause of acute nephritic syndrome?
IgA nephropathy
what is the aetiology of acute nephritic syndrome?
- bacterial infection e.g. MRSA, typhoid or secondary syphilis
- Hepatitis B and C
- schistomiasis
- malaria
- post-streptococcal infection e.g. Strep. pyogenes
- infective endocarditis
- SLE
- systemic sclerosis
- ANCA associated vasculitis
- Goodpastures disease
- IgA nephropathy
what are features of post-streptococcal infection as a cause of acute nephritic syndrome?
- occurs classically 2 weeks after tonsillitis
* bacterial antigen becomes trapped in the glomerulus leading to diffuse proliferative glomerulonephritis
how can SLE cause acute nephritic syndrome? what is the clinical presentation of it?
- rash, arthralgia, kidney failure, neurological symptoms, pericarditis and pneumonitis
- anti-nuclear antibody (ANA) positive and double stranded DNA positive
- low complement C3 and C4
what is the treatment of SLE as a cause of acute nephritic syndrome?
immunosuppression; steroids, cyclophosphamide, rituximab
how does systemic sclerosis cause acute nephritic syndrome? what is the clinical presentation?
- ANA positive, Anti-Ro and Anti-La positive
- severe hypertension
- ‘onion skin’ changes on renal biopsy, raynauds phenomenon, fibrotic skin, oesophageal dysmotility
what is the treatment of ANCA associated vasculitis as a cause of acute nephritic syndrome?
immunosuppression, steroids, cyclophosphamide, rituximab, plasma exchange
what is Goodpastures disease?
- anti-glomerular basement membrane disease
- rare autoimmune disease in which antibodies attack the basement membrane in lungs and kidneys, leading to bleeding from the lungs and kidney failure
- attacks alpha-3 subunit of type IV collagen
- the co-existence of acute glomerulonephritis and pulmonary alveolar haemorrhage and the presence of circulating antibodies directed against an intrinsic antigen to the basement membrane of both kidney and lung
- antibodies against glomerular basement membrane
- rapidly progressive kidney failure
what is the treatment of Goodpastures disease?
- remove antibody via plasma exchange
- immunosuppression
- steroids/cyclophosphamide
what is the commonest cause of nephritic syndrome in the developed world?
IgA nephropathy
how does IgA nephropathy cause acute nephritic syndrome?
- form of glomerulonephritis
- deposition of IgA antibody in the glomerulus
- haematuria, IgA deposition in kidney mesangium (provides structural support to glomerulus) and kidney gets attacked
- associated with tonsillitis and results in haematuria
what is the treatment of IgA nephropathy?
BP control: ACEi/ARBs
what is the clinical presentation of acute nephritic syndrome?
- haematuria (mild macrocytic)
- proteinuria; usually less than 2g in 24 hours
- hypertension (moderate-severe increase) and oedema (periorbital (around eyes), leg or sacral) caused by salt and water retention
- oliguria (little urine)
- uraemia and symptoms of it
- deteriorating kidney function
- moderate-severe decrease in GFR
what are symptoms of uraemia?
- anorexia
- pruritus i.e rash
- lethargy and nausea
how is acute nephritic syndrome diagnosed?
- take history to determine cause
- measure eGFR, proteinuria, serum urea and electrolytes and albumin to determine current status and monitor progress
- culture; swab from throat or infected skin
- urine dipstick to detect proteinuria and haematuria
- renal biopsy if necessary
how is hypertension treated in acute nephritic syndrome?
salt restriction, loop diuretics, calcium channel blockers
what is the triad of nephrotic syndrome?
- proteinuria > 3.5g/24 hours
- hypoalbuminaemia
- oedema
- severe hyperlipidaemia is often present
why is severe hyperlipidaemia often present in nephrotic syndrome?
liver goes into overdrive due to albumin loss and other protein loss which increases risk of blood clots and produces raised cholesterol
what is nephrotic syndrome? what is it caused by? what is kidney function like?
- collection of symptoms due to kidney damage; includes protein in urine, low blood albumin levels, high blood lipids and significant swelling - don’t develop kidney failure but are leaking huge amounts of protein but kidney function remains the same
- caused by structural and functional abnormalities of podocytes
what is the epidemiology of nephrotic syndrome?
- relatively rare
- diabetes is most common secondary cause
- minimal change disease accounts for 10-25% of nephrotic syndrome in adults and is the commonest cause of nephrotic syndrome in children
what are the primary causes of nephrotic syndrome?
- minimal change disease - seen in children and adults
- membranous glomerulonephritis - adults
- focal segmental glomerulosclerosis
- membranoproliferative glomerulonephritis
- rapidly progressive glomerulonephritis
what is the most common cause of nephrotic syndrome in adults?
focal segmental glomerulosclerosis
what is membranous nephropathy?
- asymptomatic proteinuria/nephrotic syndrome +/- microscopic haematuria, hypertension and renal impairment
- deposition of IgG and C3 along outer aspect of glomerular basement membrane
- treated with immunosuppression
what are causes of membraneous nephropathy?
- drugs e.g. penicillamine, gold or NSAIDs
- autoimmune - SLE, thyroiditis
- infection e.g. hepatitis B or C, schistomiasis
- neoplasia e.g. lung, colon, stomach and breast
what is focal segmental glomerulosclerosis?
- unknown aetiology
- scarring that is focal and only some glomeruli involved and segmental (only part of glomerulus affected)
- CD80 deposited in podocytes resulting in increased permeability in glomeruli and thus proteinuria and haematuria
what is clinical presentation of focal segmental glomerulosclerosis?
secondary hypertension and renal impairment
what is treatment of focal segmental glomerulosclerosis?
corticosteroids and immunosuppressants
what are secondary causes of nephrotic syndrome?
- diabetes mellitus - most common secondary cause
- amyloid
- infections e.g. Hep B or C and HIV
- SLE, RA
- drugs e.g. gold, penicillamine, NSAIDs and ACE-inhibitors
- malignancy
what is the most common secondary cause of nephrotic syndrome?
diabetes mellitus
what are risk factors for nephrotic syndrome?
diabetes mellitus
what is the pathophysiology of nephrotic syndrome?
- injury to podocyte appears to be the main cause of proteinuria
- podocytes wrap around the glomerular capillaries and maintain the filtration barrier, preventing large molecular weight proteins from entering the urine
- damage to podocyte foot processes or loss of podocytes can cause heavy protein loss
what is the clinical presentation of nephrotic syndrome?
- normal-mild increase in BP
- proteinuria > 3.5g/day
- normal-mild decrease in GFR
- hypoalbuniaemia
- pitting oedema of ankles, genital, abdominal wall and sometimes face (periorbital)
- frothy urine
what are differential diagnoses of nephrotic syndrome?
- congestive heart failure
- cirrhosis
how can congestive heart failure be distinguished from nephrotic syndrome?
- where there is oedema and raised JVP
* in nephrotic syndrome there is normal or low JVP (unless there is renal failure and oliguria)
how can cirrhosis be distinguished from nephrotic syndrome?
- where there is hypoalbuminaemia and oedema
* but there are signs of chronic liver failure e.g. jaundice, fever and loss of body hair
how is nephrotic syndrome diagnosed?
- establish cause - usually via renal biopsy
- urine dipstick shows very high protein
- CXR or ultrasound for pleural effusion or ascites
- serum albumin is low
- BP is usually normal or mildly increased
- renal function is usually normal or mildly impaired
- serum creatinine, eGFR, lipids and glucose
- ANA, double-stranded DNA antibody, C3 and C4 indicates SLE
- antiphospholipase A2 receptor antibody indicated membranous nephropathy
- HepB surface antigen, HepC antibody or HIV
what are metabolic/immunologic levels like in nephrotic syndrome?
- serum creatinine, eGFR, lipids and glucose
- ANA, double-stranded DNA antibody, C3 and C4 indicates SLE
- antiphospholipase A2 receptor antibody indicates membranous nephropathy
- HepB surface antigen, HepC antibody or HIV
what are complications of nephrotic syndrome?
- susceptibility to infection
- thromboembolism
- hyperlipidaemia
what infections does nephrotic syndrome increase susceptibility to?
cellulitis, Streptococcus infections and spontaneous bacterial peritonitis
why does nephrotic syndrome cause increased susceptibility to infections?
due to low serum IgG, decreased complement activity and reduced T-cell function due in part to loss of immunoglobulin in urine and also to immunosuppressive treatment
how does nephrotic syndrome increase risk of thromboembolism?
hypercoaguable state due to increased clotting factors (produced by liver due to low albumin since liver goes into overdrive) and platelet abnormalities
how does nephrotic syndrome increase risk of hyperlipidaemia?
increased cholesterol and triglycerides due to hepatic lipoprotein synthesis in response to low oncotic pressure due to low albumin
what is the treatment of nephrotic syndrome?
- reduce oedema
- reduce proteinuria
- reduce risk of complications
- treat underlying cause
how is oedema reduced in nephrotic syndrome?
- loop diuretics e.g. IV furosemide - IV since gut oedema may prevent oral absorption
- thiazide diuretics e.g. IV bendroflumethiazide
- fluid and salt restriction while giving diuretics
how is proteinuria reduced in nephrotic syndrome?
- ACE inhibitor e.g. ramipril
- angiotensin receptor blocker e.g. candesartan
- eat normal rather than high protein diet
how is risk of complications reduced in nephrotic syndrome?
- prophylactic anticoagulation with warfarin, especially when albumin is low (<20g/l)
- reduce cholesterol with statins e.g. simvastatin
- treat infections promptly and vaccinate
what is the most common cause of nephrotic syndrome in children?
minimal change disease
what is minimal change disease?
disease affecting the kidneys which causes nephrotic syndrome
what is the epidemiology of minimal change disease?
- commonest cause of nephrotic syndrome in children
- occurs most commonly in boys under the age of 5
- accounts for 20% of adult nephritic syndrome
what are risk factors and causes of minimal change disease?
- can be idiopathic
- atopy is present in 30% of cases and allergic reactions can trigger nephrotic syndrome
- drugs
- Hep C, HIV and TB are rare causes
- associated with Hodgkins lymphoma
what are drugs that can cause minimal change disease?
- NSAIDs
- lithium
- antibiotics e.g. cephalosporins, rifampicin and ampicillin
- bisphosphonates
- sulfasalazine
what is the pathophysiology of minimal change disease?
- glomeruli appear normal on light microscopy, but on electron microscopy, fusion of the foot processes of the podocytes is seen, consistent with a disrupted podocyte actin cytoskeleton
- immature differentiating CD35 stem cells appear to be responsible for pathogenesis
what is the clinical presentation of minimal change disease?
- proteinuria
- oedema, predominantly around the face
- fatigue
- frothy urine
how is minimal change disease diagnosed?
biopsy
• normal under light microscopy
• electron microscopy shows fused podocyte foot processes
what is the treatment of minimal change disease?
- high dose corticosteroids can reverse proteinuria in 95% cases, however the majority relapse
- frequent relapse or steroid-dependent disease is treated with cyclophosphamide or ciclosporin/tacrolimus
what are asymptomatic urinary abnormalities? how is it diagnosed?
- incidental finding of dipstick haematuria +/- proteinuria
- kidney function and blood pressure are normal
- diagnosis is usually clinical, don’t biopsy unless kidney function abnormal or significant proteinuria
what are causes of asymptomatic urinary abnormalities?
- IgA nephropathy
- thin membrane disease
how does IgA nephropathy cause asymptomatic urinary abnormalities? what can it present as?
- abnormality in IgA glycosylation leads to deposition in mesangium (provides structural support for glomerulus)
- can present as nephritic, nephrotic, asymptomatic or as progressive chronic kidney disease
what is the commonest cause of glomerulonephritis worldwide?
IgA nephropathy
what is IgA nephropathy associated with?
tonsillitis and macroscopic haematuria
what is the treatment of IgA nephropathy?
treated with BP control and immunosuppression in aggressive disease
how does thin membrane disease cause asymptomatic urinary abnormalities?
thin basement membrane so more likely to leak blood into urine
what is chronic kidney disease? what is it defined as?
- CKD is longstanding, usually progressive impairment in renal function (haematuria, proteinuria or anatomical abnormality) for more than 3 months
- defined as a GFR < 60mL/min/1.73 m2 for more than 3 months with/without evidence of kidney damage (haematuria, proteinuria or anatomical abnormality)
what is the epidemiology of chronic kidney disease?
- between 6% - 11% of people can be defined as having CKD
- risk of CKD increases with age; incidence rising as we are living longer
- more common in females than males
what is stage 1 CKD?
- GFR >90mL/min
- normal or raised GFR with other evidence of renal damage