Kidneys Flashcards
List six functions of the kidneys.
metabolic waste excretion endocrine functions drug metabolism/excretion control of solutes and fluid status blood pressure control acid/base balance
What is the normal amount of protein excreted from the kidneys over 24 hours?
150mg
Name the three ways that urinary protein excretion is measured.
- 24hr urine collection (g/24h)
- protein:creatinine ratio on morning spot sample
- albumin:creatinine ratio
Differentiate between non-visible haematuria and visible haematuria.
- non: can be blood detectable on dipstick only
- visible: can come from anywhere in the urinary tract
List causes of visible haematuria.
kidney stones, infection, malignancy, cysts, inflammation
Define renal clearance (GFR) and how it is calculated.
= volume of plasma which would be cleared of the substance per unit of time
(urine conc of substance x urine volume) / plasma conc of substance
The MDRD*4 formula for estimation of GFR from plasma creatinine concentration is based on which 4 factors?
plasma creatinine conc.
age
gender
race
Describe the staging of chronic kidney disease using eGFR.
1: eGFR > 90 ml/min normal
2. 60-89 normal unless evidence of kidney disease
3. 30-59 moderate impairment
4. 15-29 severe impairment
5. < 15 advanced renal failure
List some of the secondary causes of GN.
- diabetes
- haem: myeloma, CLL, PRV
- bacterial endocarditis
- resp: bronchiectasis, lung cancer, TB
- gastro: ALD, IBD, coeliac
- drugs: NSAIDs, bisphosphonates, heroin
- rhemu: RA, lupus, amyloid
- ID: hepatitis, HIV, antibiotics, malaria
Following presentation and history, what is required to make a diagnosis of GN?
kidney biopsy
What are the three ways in which the kidney cortex biopsy is examined?
- light microscopy (glomerular and tubular structure)
- immunofluorescence (looking for Ig and complement)
- electron microscopy (BM and deposits)
Describe how different types of GN present including RPGN, nephritic and nephrotic.
- RPGN: rapid rise in serum creatinine, crescentic damage, vasculitis, lupus, IgA
- nephritic: blood and protein in urine, high BP, rising sCr, proliferative/acute inflammation, IgA, lupus, post-infectious
- nephrotic: >3,5mg proteinuria, low sAlb, oedema, non-proliferative, podocyte damage, minimal change/FSGS/membranous
List the four criteria used to define nephrotic syndrome.
- 3.5g proteinuria per 24hr
- Serum albumin <30
- Oedema
- Hyperlipidaemia
What are the two main risks associated with nephrotic syndrome?
risk of venous thromboembolism
increased risk of infection
What are the possible therapeutic strategies of GN in relation to the stage:
- insult precipitant e.g. infection, antibody
- injury
- response to injury
- outcome
- control infection
- remove AB/IC
- steroids, cytotoxics, anti-hypertensives
- dialysis, transplantation, slow progression, resolution
Describe the four stage spectrum of IgA nephropathy.
1 minor urinary abnormalities
2 hypertension
3 renal impairment and heavy proteinuria
4 rapidly progressive GN
What is the most common primary glomerular disease?
IgA nephropathy causing mesangial disease
What causes IgA nephropathy?
precipitated by infection - Occurring intercurrently with an episode of pharyngitis (synpharyngitic)
secondary = HSP, cirrhosis, coeliac
Describe the brief pathophysiology of IgA nephropathy and how it presents.
abnormal/over-production of IgA1 leading to mesangial deposition and subsequent proliferation
haematuria, hypertension, proteinuria
What treatment is available for IgA nephropathy?
no specific therapy
antihypertensive Rx - ACEi
How does membranous GN present?
nephrotic syndrome
Which antibody is seen in 70% of cases of membranous GN?
anti-phospholipase A2 receptor antibody
Which type of GN is secondarily caused by malignancy, connective tissue diseases and drugs?
membranous
In membranous GN, where are immune complexes located?
in basement membrane and sub-epithelial space
Describe the variable natural history of membrane GN.
1/3 = spontaneously remit 1/3 = progress to ESRF over 1-2 years 1/3 = persistent proteinuria, maintain GFR
What are the three stages in treating membranous GN?
1 underlying cause if secondary
2 supportive non-immunological e.g. ACEi, statins, diuretics, salt restriction
3 immunotherapy e.g. steroids, alkylating agents, cyclosporin, rituximab (anti-CD20 MAB)
What is the commonest form of GN in children?
minimal change
What are the main pathological features seen in minimal change GN?
podocyte foot process fusion
T cell cytokine mediated - target glom. epithelial cell
causes nephrotic syndrome
How might minimal change GN present?
acute - may follow URTI
GFR normal or reduced due to intravascular depletion
Describe the treatment for minimal change GN.
high dose steroids - prednisolone 1mg/kg for up to 8 weeks
List the five commonest causes of crescentic/rapidly progressive GN.
ANCA vasculitis Goodpasture's syndrome (anti-GBM disease) Lupus nephritis infection associated HSP nephritis
What is RPGN?
group of conditions which demonstrate glomerular crescents on kidney biopsy
Discuss the approach to the patient in suspected glomerulonephritis.
- full medical and drug history
- basics: UEs, dip urine for blood, quantify proteinuria, check albumin, check USS
- glomerulonephritis screen
In a glomerulonephritis screen, many diseases may be detected. What are these and what substance are they associated with?
- diabetic nephropathy: HbA1c
- ANCA/anti-GBM: vasculitis
- ANA/PLA2R/virology: membranous
- complement/ANA/dsDNA: lupus
- complement/virology(hep B, C, HIV)/Igs/RF: MPGN, FSGS
Discuss the different types of glomerulonephritis including proliferative and non-proliferative.
proliferative = nephritic syndrome e.g. IgA nephropathy, post-infectious, RPGN non-proliferative = nephrotic syndrome e.g. minimal change disease, focal segmental GN, membranous GN
What is the triad of nephritic syndrome?
1 haematuria
2 decreased urine production
3 hypertension
leading to end-stage kidney failure
List four of the main systemic diseases associated with renal dysfunction.
diabetes mellitus
atheromatous vascular disease
amyloidosis
SLE
Briefly describe how diabetes leads to renal failure.
hyperglycaemia, volume expansion, intra-glomerular hypertension, hyperfiltration, proteinuria, hypertension and renal failure
Describe the structural changes seen in diabetic kidney disease.
thickening of glomerular BM
fusion of foot processes
loss of podocytes with denuding of the glomerular BM
mesangial matrix expansion
How might the risk of diabetic nephropathy be reduced?
tight glycaemic control
good BP control
SGLT2 inhibitors e.g. empagliflozin
Describe how SGLT2 inhibition leads to cardiac and renal protection.
- glycosuria and natriuresis
- weight loss, lower HbA1c, lower BP, decreased intraglomerular hypertension, decreased atherosclerosis
List three causes of non-proteinuric AKI.
- obstruction
- renovascular disease - renal artery stenosis
- interstitial nephritis
Discuss the pathogenesis of renovascular disease.
1 progressive narrowing of renal arteries with atheroma
2 perfusion falls, GFR falls but tissue oxygenation of cortex and medulla maintained
3 RA stenosis 70%, cortical hypoxia causes microvascular damage and activation of inflammatory pathways
4 parenchymal inflammation and fibrosis irreversible
Describe the 3 point management of renal artery stenosis.
- Medical - BP control (not ACEi/ARB), statin
- Lifestyle - smoking cessation, exercise
- Angioplasty - in rapidly deteriorating renal failure, uncontrolled hypertension, flash pulmonary oedema
What is amyloidosis and what organs does it affect?
deposition of highly stable insoluble proteineous material in extracellular space
kidney, heart, liver, gut
Describe the specific ultrastructural features of amyloid.
8nm linear aggregated fibrils of variable length forming a felt-like structure made of beta-pleated sheets
What type of amyloid is seen from previous TB and familial Mediterranean fever?
AA amyloid
How is amyloidosis detected using microscopy?
light microscopy: congo red stain = apple green birefringence
electron microscopy: amyloid fibrils 8nm cause mesangial expansion
Differentiate between the two classes of amyloidosis, AA and AL and how they are treated.
AA = systemic amyloidosis (inflammation/infection). Treat underlying infection source. AL = Ig fragments from haematological conditions e.g. myeloma. Treat underlying haematological condition.
What is systemic lupus erythematosis?
auto-immune disease, immune complex mediated glomerular disease
What are the autoantibodies present in SLE directed against?
DNA, histones, snRNPs, transcription/translation factors
Describe the pathophysiology of lupus nephritis.
- autoantibodies produced against dsDNA or nucleosomes (anti-dsDNA, anti-histone)
- form intravascular immune complexes or attach to GBM
- activate complement
- renal damage
How is SLE treated?
immunosuppression - steroids, MMF, cyclophosphamide, rituximab
Describe the presenting features of urinary tract infections to include both cystitis and pyelonephritis.
- cystitis: dysuria, frequency, urgency, suprapubic pain, haematuria
- pyelonephritis: the above PLUS fever, chills/rigors, flank pain, costo-vertebral angle tenderness, N+V
What are the risk factors to developing a UTI?
- infancy
- abnormal urinary tract
- female
- bladder dysfunction
- ‘foreign’ body e.g. catheter
- diabetes mellitus
- renal transplant
- immunosuppression
How is the diagnosis of UTI made?
- multistix: leucocytes + nitrites
- microscopy/flow cytometry: pus cells + bacteria
- urine culture - in all children <3 years if clinical suspicion
Which organism is the most likely cause of UTI?
E. coli
What criteria must be reached from the urine culture to define UTI?
single organism > 10^5 CFU/ml
Discuss the antibiotic treatment for UTI.
oral unless vomiting, severely unwell, infant <3 months = trimethoprim, co-amoxiclav, nitrofurantoin, cephalosporin
IV = 3rd gen cephalosporin e.g. ceftriaxone, gentamicin
What is the importance of investigation and management of UTI in childhood?
- imaging: US, micturating cystourethrogram (gold standard for VUR and PUV), nuclear medicine imaging e.g. DMSA (scarring)
- antibiotic prophylaxis: not in simple UTI, consider for CAKUT, trimethoprim, nitrofurantoin
What is vesico-ureteric reflux?
a condition in which urine flows retrograde, or backward, from the bladder into the ureters/kidneys
Give examples of two congenital abnormalities of kidney and urinary tract.
- vesico-ureteric reflux
- obstruction of urinary drainage tracts
What is oligohydramnios and what does it suggest?
deficiency of amniotic fluid
significant renal impairment
Describe the medical and surgical management of VUR and UTI.
- medical: antibiotic prophylaxis for high grade VUR until toilet trained
- surgical: if recurrent, proven febrile UTI and/or new scarring on meds, ‘STING’ procedure - narrows ureteric orifice
List common causes of bladder outlet obstruction.
- prostatic hypertrophy
- functional obstruction: neurogenic bladder (spina bifida, trauma etc), prune belly syndrome
- posterior urethral valve
What is Prune Belly Syndrome?
triad of:
- Megacystis/megaureters
- Absent abdominal wall muscles
- Bilateral cryptochidism
How does a posterior urethral valve present?
antenatal hydronephrosis
urinary tract infection
poor urinary stream
renal dysfunction
How is a posterior urethral valve managed?
valve resection
antibiotic prophylaxis
CKD care
What is the commonest cause of hydronephrosis in children?
pelvi-ureteric junction obstruction
What are the complications associated with PUJO?
abdominal mass, pain, haematuria, UTI
What does VUJO stand for?
vesico-ureteric junction obstruction