Nephrology Flashcards
Causes of transient non-visible haematuria
urinary tract infection
menstruation
vigorous exercise (this normally settles after around 3 days)
sexual intercourse
Causes of persistent non-visible haematuria
cancer (bladder, renal, prostate)
stones
benign prostatic hyperplasia
prostatitis
urethritis e.g. Chlamydia
renal causes: IgA nephropathy, thin basement membrane disease
Management of haematuria
urine dipstick is the test of choice for detecting haematuria
renal function, albumin:creatinine (ACR) or protein:creatinine ratio (PCR) and blood pressure should also be checked
urine microscopy may be used but time to analysis significantly affects the number of red blood cells detected
definition of persistent non-visible haematuria
blood being present in 2 out of 3 samples tested 2-3 weeks apart
when should haematuria be referred on to secondary care?
urgent:
Aged >= 45 years AND:
unexplained visible haematuria without UTI, or
visible haematuria that persists or recurs after successful treatment of UTI
Aged >= 60 years AND have unexplained nonvisible haematuria and either dysuria or a raised white cell count on a blood test
non-urgent:
Aged 60 >= 60 years with recurrent or persistent unexplained urinary tract infection
causes of polyuria
Common (>1 in 10)
diuretics, caffeine & alcohol
diabetes mellitus
lithium
heart failure
Infrequent (1 in 100)
hypercalcaemia
hyperthyroidism
Rare (1 in 1000)
chronic renal failure
primary polydipsia
hypokalaemia
Very rare (<1 in 10 000)
diabetes insipidus
causes of normal anion gap metabolic acidosis
Normal anion gap ( = hyperchloraemic metabolic acidosis)
gastrointestinal bicarbonate loss: diarrhoea, ureterosigmoidostomy, fistula
renal tubular acidosis
drugs: e.g. acetazolamide
ammonium chloride injection
Addison’s disease
causes of raised anion gap metabolic acidosis
Raised anion gap
lactate: shock, hypoxia
ketones: diabetic ketoacidosis, alcohol
urate: renal failure
acid poisoning: salicylates, methanol
causes of metabolic alkalosis
Metabolic alkalosis may be caused by a loss of hydrogen ions or a gain of bicarbonate. It is due mainly to problems of the kidney or gastrointestinal tract
Causes
vomiting / aspiration (e.g. peptic ulcer leading to pyloric stenos, nasogastric suction)
diuretics
liquorice, carbenoxolone
hypokalaemia
primary hyperaldosteronism
Cushing’s syndrome
Bartter’s syndrome
congenital adrenal hyperplasia
causes of respiratory acidosis
Respiratory acidosis may be caused by a number of conditions
COPD
decompensation in other respiratory conditions e.g. life-threatening asthma / pulmonary oedema
sedative drugs: benzodiazepines, opiate overdose
causes of respiratory alkalosis
Common causes
anxiety leading to hyperventilation
pulmonary embolism
salicylate poisoning
CNS disorders: stroke, subarachnoid haemorrhage, encephalitis
altitude
pregnancy
causes of nephrotic syndrome
minimal change disease
membranous glomerulonephropathy
focal segmental glomerulosclerosis
amyloidosis
diabetic nephropathy
definition of nephrotic syndrome
Triad of:
1. Proteinuria (> 3g/24hr) causing
2. Hypoalbuminaemia (< 30g/L) and
3. Oedema
Loss of antithrombin-III, proteins C and S and an associated rise in fibrinogen levels predispose to thrombosis. Loss of thyroxine-binding globulin lowers the total, but not free, thyroxine levels.
definition of nephritic syndrome
haematuria, hypertension
causes of nephritic syndrome
rapidly progressive glomerulonephrosis
IgA nephropathy
Alport syndrome
what is acute interstitial nephritis
fever, rash, arthralgia
eosinophilia
mild renal impairment
hypertension
Pathophysiology
histology: marked interstitial oedema and interstitial infiltrate in the connective tissue between renal tubules
causes of acute interstitial nephritis
drugs: the most common cause, particularly antibiotics
penicillin
rifampicin
NSAIDs
allopurinol
furosemide
systemic disease: SLE, sarcoidosis, and Sjögren’s syndrome
infection: Hanta virus , staphylococci
common findings in acute interstitial nephritis
Investigations
sterile pyuria
white cell casts
main differences between AKI and CKD
renal ultrasound - most patients with CKD have bilateral small kidneys.
Exceptions to this rule include:
autosomal dominant polycystic kidney disease
diabetic nephropathy (early stages)
amyloidosis
HIV-associated nephropathy
Other features suggesting CKD rather than AKI
hypocalcaemia (due to lack of vitamin D)
definition of AKI
a rise in serum creatinine of 26 micromol/litre or greater within 48 hours
a 50% or greater rise in serum creatinine known or presumed to have occurred within the past 7 days
a fall in urine output to less than 0.5 ml/kg/hour for more than 6 hours in adults and more than 8 hours in children
> = 25% fall in eGFR in children / young adults in 7 days.
causes of AKI
prerenal
hypovolaemia secondary to diarrhoea/vomiting
renal artery stenosis
intrinsic
The second group of causes relate to intrinsic damage to the glomeruli, renal tubules or interstitium of the kidneys themselves. This may be due to toxins (drugs, contrast etc) or immune-mediated glomuleronephritis.
glomerulonephritis
acute tubular necrosis (ATN)
acute interstitial nephritis (AIN), respectively
rhabdomyolysis
tumour lysis syndrome
postrenal
obstruction to the urine coming from the kidneys resulting in things ‘backing-up’ and affecting the normal renal function
kidney stone in ureter or bladder
benign prostatic hyperplasia
external compression of the ureter
signs of AKI
Many patients with early AKI may experience no symptoms. However, as renal failure progresses the following may be seen:
reduced urine output
pulmonary and peripheral oedema
arrhythmias (secondary to changes in potassium and acid-base balance)
features of uraemia (for example, pericarditis or encephalopathy)
findings in AKI
Urinalysis
all patients with suspected AKI should have urinalysis
Imaging
if patients have no identifiable cause for the deterioration or are at risk of urinary tract obstruction they should have a renal ultrasound within 24 hours of assessment.
drugs to stop in AKI
- NSAIDs (except if aspirin at cardiac dose e.g. 75mg od)
- Aminoglycosides
- ACE inhibitors
- Angiotensin II receptor antagonists
- Diuretics
may need to stop:
* Metformin
* Lithium
* Digoxin
treating AKI
supportive management - careful fluid balance to ensure that the kidneys are properly perfused but not excessively to avoid fluid overload
review a patient’s medication list
treating hyperkalaemia
All patients with suspected AKI secondary to urinary obstruction require prompt review by a urologist.
Renal replacement therapy (e.g. haemodialysis) is used when a patient is not responding to medical treatment of complications, for example hyperkalaemia, pulmonary oedema, acidosis or uraemia (e.g. pericarditis, encephalopathy).
treatments for hyperkalaemia
treating hyperkalaemia
IV calcium gluconate - stabilisation of cardiac membrane
short term EC to IC shift
* Combined insulin/dextrose infusion
* Nebulised salbutamol
removal of K+ from body
* Calcium resonium (orally or enema)
* Loop diuretics
* Dialysis
stages of AKI
Stage 1 Increase in creatinine to 1.5-1.9 times baseline, or
Increase in creatinine by ≥26.5 µmol/L, or
Reduction in urine output to <0.5 mL/kg/hour for ≥ 6 hours
Stage 2 Increase in creatinine to 2.0 to 2.9 times baseline, or
Reduction in urine output to <0.5 mL/kg/hour for ≥12 hours
Stage 3 Increase in creatinine to ≥ 3.0 times baseline, or
Increase in creatinine to ≥353.6 µmol/L or
Reduction in urine output to <0.3 mL/kg/hour for ≥24 hours, or
The initiation of kidney replacement therapy, or,
In patients <18 years, decrease in eGFR to <35 mL/min/1.73 m2
diagnostic criteria for ADPKD
The screening investigation for relatives is abdominal ultrasound:
Ultrasound diagnostic criteria (in patients with positive family history)
two cysts, unilateral or bilateral, if aged < 30 years
two cysts in both kidneys if aged 30-59 years
four cysts in both kidneys if aged > 60 years
managing ADPKD
tolvaptan (vasopressin receptor 2 antagonist) may be an option. NICE recommended it as an option for treating ADPKD in adults to slow the progression of cyst development and renal insufficiency only if:
they have chronic kidney disease stage 2 or 3 at the start of treatment
there is evidence of rapidly progressing disease and
the company provides it with the discount agreed in the patient access scheme.
what is ADPKD
Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited cause of kidney disease, affecting 1 in 1,000 Caucasians. Two disease loci have been identified, PKD1 and PKD2, which code for polycystin-1 and polycystin-2 respectively
ADPKD type 1 - 85% cases, chr16, presents with renal failure earlier
ADPKD type 2 - 15% cases, chr4
what are the features (and extra-renal features) of ADPKD
hypertension
recurrent UTIs
flank pain
haematuria
palpable kidneys
renal impairment
renal stones
Extra-renal manifestations
liver cysts (70% - the commonest extra-renal manifestation): may cause hepatomegaly
berry aneurysms (8%): rupture can cause subarachnoid haemorrhage
cardiovascular system: mitral valve prolapse, mitral/tricuspid incompetence, aortic root dilation, aortic dissection
cysts in other organs: pancreas, spleen; very rarely: thyroid, oesophagus, ovary
what is Alport’s syndrome
X-linked dominant pattern
defect in gene coding for type IV collagen - causes abnormal glomerular basement membrane
more severe in males
how is Alport syndrome diagnosed
molecular genetic testing
renal biopsy
electron microscopy: characteristic finding is of the longitudinal splitting of the lamina densa of the glomerular basement membrane, resulting in a ‘basket-weave’ appearance
what are the features of Alport syndrome
Alport’s syndrome usually presents in childhood. The following features may be seen:
microscopic haematuria
progressive renal failure
bilateral sensorineural deafness
lenticonus: protrusion of the lens surface into the anterior chamber
retinitis pigmentosa
renal biopsy: splitting of lamina densa seen on electron microscopy
what is amyloidosis
extracellular deposition of an insoluble fibrillar protein termed amyloid
the accumulation of amyloid fibrils leads to tissue/organ dysfunction
can be systemic or localized
further characterised by precursor protein (e.g. AL in myeloma - A for Amyloid, L for immunoglobulin Light chain fragments)
how is amyloidosis diagnosed
Congo red staining: apple-green birefringence
serum amyloid precursor (SAP) scan
biopsy of skin, rectal mucosa, or abdominal fat
what is the anion gap
The anion gap is calculated by:
(sodium + potassium) - (bicarbonate + chloride)
A normal anion gap is 8-14 mmol/L
what causes a raised anion gap metabolic acidosis
lactate: shock, hypoxia
ketones: diabetic ketoacidosis, alcohol
urate: renal failure
acid poisoning: salicylates, methanol
5-oxoproline: chronic paracetamol use
what causes a normal anion gap metabolic acidosis
gastrointestinal bicarbonate loss: diarrhoea, ureterosigmoidostomy, fistula
renal tubular acidosis
drugs: e.g. acetazolamide
ammonium chloride injection
Addison’s disease
what is anti-glomerular basement membrane (GBM) disease
Rare type of small-vessel vasculitis associated with both pulmonary haemorrhage and rapidly progressive glomerulonephritis
caused by anti-glomerular basement membrane (anti-GBM) antibodies against type IV collagen
more common in men (sex ratio 2:1) and has a bimodal age distribution (peaks in 20-30 and 60-70 age bracket)
associated with HLA DR2
what are some features of anti-glomerular basement membrane (GBM) disease
pulmonary haemorrhage
rapidly progressive glomerulonephritis
this typically results in a rapid onset acute kidney injury
nephritis → proteinuria + haematuria
what are the investigation findings for anti-glomerular basement membrane (GBM) disease
renal biopsy: linear IgG deposits along the basement membrane
raised transfer factor secondary to pulmonary haemorrhages
how is anti-glomerular basement membrane (GBM) disease managed
plasma exchange (plasmapheresis)
steroids
cyclophosphamide
what is an arteriovenous fistula
direct connections between arteries and veins. They may occur pathologically but are generally formed surgically to allow access for haemodialysis.
preferred method of access for haemodialysis due to the lower rates of complications.
The time taken for an arteriovenous fistula to develop is 6 to 8 weeks