Nephrology Flashcards
How can we divide up the causes of AKI?
Prerenal
Lack of blood flow to the kidneys
Intrarenal
Intrinsic damage to the glomeruli, renal tubules or interstitium
Postrenal
Obstruction to the urine coming from the kidneys
What findings can be expected in AKI?
Reduced urine output (<0.5ml/kg/hour is termed oliguria)
Fluid overload
Rise in molecules that the kidney normally excretes/maintains balance of, e.g. potassium, urea and creatinine
Symptoms of AKI
Reduced urine output
Pulmonary/peripheral oedema
Arrhythmias (due to potassium levels)
Uraemia features (pericarditis/encephalopathy)
What should we test in all AKI patients?
U+Es
Urinalysis
When should we do a renal ultrasound in AKI?
If there’s no identifiable cause for the deterioration OR are at risk of a urinary tract obstruction
What commonly used drugs should be stopped in AKI?
Metformin Lithium Digoxin NSAIDs Aminoglycosides ACEi Diuretics Angiotensin II receptor antagonists
How should we treat hyperkalaemia should it arise in AKI?
IV calcium gluconate Combined insulin/dextrose infusion Nebulised salbutamol Loop diuretics Calcium resonium Dialysis (last line)
Blood supply of the kidneys?
Renal arteries + veins
What is the normal blood urea nitrogen (BUN):creatinine ratio?
Causes of pre-renal AKI
Decreased bloodflow due to:
Absolute loss of fluid - Major haemorrhage Vomiting Diarrhoea Severe burns
Relative loss of fluid -
Distributive shock
Congestive heart failure (blood pools in the venous system)
Local to the kidney -
Renal artery stenosis
Embolus
What is azotemia?
High levels of nitrogen containing blood
What happens to the RAAS system during AKI?
Kidneys activate the RAAS, causing adrenal glands to secrete aldosterone which tells the kidneys to reabsorb sodium
Sodium reabsorption results in increased water reabsorption AND urea reabsorption
Is urine more concentrated in pre-renal AKI?
Yes. There is more urea relative to water than usual
What is the BUN:creatinine ratio in pre-renal AKI?
> 20:1
What is the most common cause of intrarenal AKI?
Acute tubular necrosis:
What are causes of acute tubular necrosis?
Ischaemia to the tubular cells Nephrotoxins: Aminoglycosides Heavy metals (e.g. lead) Myoglobin (from damaged muscle) Ethylene glycol (anti-freeze) Radiocontrast dye Uric acid (tumour lysis syndrome during cancer treatment)
How can you prevent uric acid causing tubular necrosis during cancer treatment?
Make sure they stay well hydrated
Give medications: allopurinol, urate oxidase
Trying to reduce the effects of tumour lysis syndrome
What happens to the tubule during acute tubular necrosis?
For whatever reason there is cell death. These cells then go into the tubule lumen and plug the tubule. This increases the pressure and makes it harder for fluid to flow down the tubules, reduced eGFR
What do you get a build up of in the blood during acute tubular necrosis resulting in AKI?
Acid (metabolic acidosis)
Hyperkalaemia
What might you find in the urine of someone with an acute tubular necrosis?
Brown grannular casts (these are the clumps of dead cells from the necrosis)
What is glomerulonephritis?
Inflammation of the glomerulus causing a reduction in eGFR. It is often caused by the deposition of antigen-antibody complexes in glomerular tissue
What do the antigen-antibody complexes activate in glomerulonephritis?
The complement system. This then attracts macrophages and neutrophils to the site. These release lysosomal enzymes which then damage podocytes in the glomerulus
Function of podocytes
They are negatively charged and have small gaps in between them. As a result larger molecules cannot get through.
What happens when podocytes are damaged (e.g. by lysosomal enzymes from neutrophils etc.)
They allow larger molecules to pass through (e.g. proteins and red cells)
Fluid leakage also reduces pressure difference which means lower GFR
This causes fluid build up and therefore oedema and HTN
Which condition affecting the interstitium can cause AKI?
Acute interstitial nephritis
Pathology of acute interstitial nephritis
Type I or type IV hypersensitivity reaction, usually in response to medications: NSAIDs, penicillins, diuretics.
These cause infiltration of immune cells (neutrophils, eosinophils) which cause inflammation of the interstium
Symptoms of acute interstitial nephritis?
Oliguria
Eosinophiluria
Fever
Rash
Complications of acute interstitial nephritis + cause?
If you don’t stop the medications causing interstitial nephritis, you can get renal papillary necrosis
Symptoms of renal papillary necrosis?
Haematuria
Flank pain
Causes of renal papillary necrosis?
Untreated acute interstitial nephritis
DM
Sickle cell disease
Pyelonephritis
What can cause obstruction to the outflow (postrenal AKI)?
Compression:
BPH
Intra-abdominal tumors
Blockage:
Kidney stones
Pathology of post-renal AKI?
Fluid backs up in post-renal AKI reducing the difference between the pressure between the tubule/glomerulus, thus reducing GFR
Longer-term effects of post-renal AKI?
Increased pressure in the renal tubule over time causes damage to the epithelial cells, reducing the amount of reabsorption of urea/sodium into the blood.
This then makes the urine higher in urea and thus the BUN:creatinine ratio falls
Damage to these epithelial cells also reduces the amount of water reabsorbed, and thus you start to produce less concentrated urine.
What are renal cysts?
Fluid filled sacs found in the kidney
How can we classify renal cysts?
Simple
Well-defined, homogenous features
Very common in older patients (50% prevalence over 50)
Complex
Complicated structures - thick walls, septations, calcification, heterogenous enhancement on imaging
Risk of malignancy
Risk factors for renal cysts?
Increasing age
Smoking
HTN
Male
What is polycystic kidney disease?
An autosomal dominant kidney caused by PKD1 or PKD2 genes. They result in individuals having multiple renal cysts
What is polycystic kidney disease associated with?
Berry aneurysm formation, leading to subarachnoid haemorrhage
Mitral valve disease
Liver cysts
Clinical features of renal cysts?
Usually asymptomatic
Can cause flank pain/haematuria if they rupture/become infected
Can also present with HTN/flank mass
What is the main differential of a renal cyst?
Renal cell carcinoma should be ruled out
How do we investigate renal cysts?
CT/MRI imaging both with and without IV contrast
What scoring system can we use for renal cysts?
Bosniak scoring system
Management of cysts?
If asymptomatic, no follow up required
Symptomatic simple renal cysts - simple analgesia +/- needle aspiration
Complex cyst - bosniak stage + continued surveillance/potential surgical intervention
Where do simple renal cysts originate from?
Renal tubule epithelium
Diagnostic criteria for autosomal dominant polycystic kidney disease?
US showing:
Two cysts (<30 y.o)
Two cysts in both kidneys (30-59 y.o)
Four cysts in both kidneys (aged >60)
Treatment for adpkd?
Tolvaptan (vasopressin receptor 2 antagonist)
What typically causes pyelonephritis?
Ascending infection typically from e. coli
Features of pyelonephritis
Fever Rigors Loin pain Vomiting White cell casts in urine
Management of pyelonephritis?
Broad-spectrum cephalosporin or quinolone (floxacins) for 10-14 days
Investigations in pyelonephritis?
Mid-stream urine sample or catheter specimen of urine and culture
You can do a urine dip to check for leukocytes and nitrites though this isn’t that necessary
Two names of kidney stones?
Urolithiasis (formation of stones in the urinary tract)
Nephrolithiasis (formation of stones in the nephron)
Guess renal calculi etc are also names
Where are the sites of ureteric constriction (where stones can get lodged)
Periureteric junction
Pelvic brim
Vesicoureteric junction
Formation of kidney stones?
Crystal like structures can be formed from electrolyte clusters. These usually pass in the urine but they can get larger and form a kidney stone which obstructs the tubule
What is renal colic caused by?
Pressure from the kidney stone on the renal tubules, causing pain
Also from the inflammatory response to the renal stones
Do you get a build up of pressure distal or proximal to the site of obstruction?
Proximal
What is hyperperistalsis?
This is where you get oedema proximal to the site of obstruction
The tubule then contracts more vigorously to try get rid of the stone
Risk factors for developing a renal stone?
High protein diet High salt intake Obesity Dehydration Drugs (antacids)
These all result in urine saturation with products that are used to make these crystals (stones)
Give 2 examples of stone formation inhibitors?
Citrate
Magnesium
Name the 5 types of renal calculi
Calcium oxalate (80%) Calcium phosphate Uric acid Struvite Cystine
Investigations in renal calculi?
FBC CRP Magnesium calcium phosphate levels Urinalysis 24hr urine electrolyte etc. levels (calcium, oxalate, urate, cystine etc.) X-ray Ultrasound CT
What might you see on ultrasound in renal calculi?
Acoustic shadowing (blocks out part of the wall with a shadow) Hydronephrosis if it is in the ureter (backflow of urine proximally)
Acute management of renal calculi?
Analgesia
Antiemetic
IV fluids
<0.5cm
Passes spontaneously
Surgical
What is percutaneous nephrostomy?
Placement of a catheter into the kidney to drain urine out if there’s obstruction (this is symptomatic relief)
What is ureteric stent insertion?
Rod up through the urethra, up through bladder/ureter up to the point of obstruction. Can then put in a stent to help urine bypass the obstruction
What is percutaneous nephrolitheotomy?
Removal of the stone from the kidney through a puncture wound
What is extracorporeal shock wave lithotripsy?
This uses focused shock waves to allow easy passage of the stone out through the urine.
What are bladder stones?
Small mineral deposits that can form in the bladder, usually only when the urine is very concentrated or when one is dehydrated
How do bladder stones present?
Lower abdo pain (can refer to back)
Painful urination
Blood in the urine
Nausea/vomiting/chills
What is the management of bladder stones?
Usually just drink lots of fluids to facilitate passage
If larger, may need to be fragmented by: laser lithotripsy or ultrasonic energy. Can sometimes need open cystotomy
What is cystolithotomy?
A treatment for bladder stones in which an incision is made and the stone is removed
What are jackstone calculi?
Urinary calculi that are almost always made of calcium oxalate. Located in the bladder, they have the appearance of jack toys
CKD stages
1 - >90ml/min 2 - 60-90ml/min 3a - 45-59ml/min 3b - 30-44ml/min 4 - 15-29ml/min 5 - <15ml/min (this is the level for dialysis/kidney transplant)
What causes CKD?
HTN Chronic pyelonephritis Chronic glomerulonephritis Diabetic nephropathy Adult polycystic kidney disease
How do we manage CKD?
Lifestyle changes
Drugs (to manage associated symptoms)
Dialysis
Kidney transplant
Lifestyle changes in CKD
Stop smoking Restrict salt intake Exercise (150 mins/week) Limit alcohol Lose weight
Medicines in CKD
BP control drugs (ACEi are first line, can use furosemide as well)
Statins (hyperlipidaemia)
Iron/erythropoetin/darbepoetin (for anaemia)
Calcium carbonate/acetate (to reduce blood phosphate)
Vitamin D (colecalciferol)
What are the 3 types of renal replacement therapy?
Haemodialysis
Peritoneal dialysis
Renal transplant
What is required for haemodialysis?
Creation of an arteriovenous fistula at least 8 weeks before treatment
What is peritoneal dialysis?
This is where filtration occurs within the patient’s abdomen
Dialysis solution is injected into the abdomen via a permanent catheter
High levels of dextrose in the cavity draws waste products from the blood into the abdominal cavity
After several hours, the fluid is then drained.
^ This describes CAPD
What are the two types of peritoneal dialysis?
Continuous ambulatory peritoneal dialysis (CAPD)
Automated peritoneal dialysis (APD) - a machine fills and drains the abdomen whilst the patient sleeps
Where is the site/what is the blood supply in a renal transplant?
Inserted into the groin
Renal vessels connect to the external iliac vessels
What must patients have for life following a renal transplant?
Immunosuppressants
What complications might you see in haemodialysis?
Site infection Endocarditis Stenosis at the site Hypotension Cardiac arrhythmia Disequilibrium syndrome
What is dialysis disequilibrium syndrome?
Occurrence of neurological signs and symptoms shortly after dialysis (papilloedema, focal neurological deficits)
Treatment of this is avoidance (i.e. no dialysis)
Make sure dialysis is a gradual process to lower risk of disequilibrium syndrome
What are complications of peritoneal dialysis?
Peritonitis Sclerosing peritonitis Catheter infection Catheter blockage Constipation Fluid retention Hyperglycaemia Hernia Back pain Malnutrition
What are the complications of renal transplants?
Graft rejection
Opportunistic infections
Malignancy (lymphona/skin cancer)
DVT/PE (surgery, duh)
What is nephritic syndrome?
Haematuria (red cell casts - indicating glomerular damage)
Proteinuria (less than 3.5g/24hrs though)
HTN
Low urine volume <300ml
What is nephrotic syndrome?
Massive proteinuria >3.5g/day
Hypoalbuminaemia <30g/L
Hyperlipidaemia
Oedema
Which glomerulonephridites cause nephrotic syndrome?
Minimal change glomerulonephritis
Focal segmental glomerulosclerosis
Membraneous glomerulonephritis
Which conditions can cause a secondary nephrotic syndrome?
SLE Hep B and C HIV DM Malignancy
What is the pathophysiology of nephritic syndrome?
Inflammatory response WITHIN the glomeruli causing glomerular basement membrane disruption
What is the pathophysiology of nephrotic syndrome?
Structural damage to the glomerular filtration barrier causing massive renal loss of protein
What are the glomerulonephridites that cause nephritic syndrome?
Poststreptococcal glomerulonephritis
IgA nephropathy (Berger’s disease)
Rapidly progressive glomerulonephritis (crescentic)
Other conditions that cause nephritic syndrome?
Goodpasture's Wegener's granulomatosis Churg-strauss Henoch-schonlein purpura Alport syndrome
What is the most common type of renal cancer?
Renal cell carcinoma
What are renal cell carcinomas?
An adenoma of the renal cortex
They make up 85% of all renal malignancies
Symptoms of renal cell carcinoma?
Haematuria (50%)
Loin pain (40%)
Mass (30%)
Investigations in renal cell carcinoma?
CT scan
Treatment for renal cell carcinoma?
If <7cm (i.e. T1), partial nephrectomy
If >7cm (i.e. T2), radical nephrectomy
What is a transitional cell carcinoma?
A cancer that typically occurs in the lower urinary tract - makes up 90% of all lower urinary tract cancers
It can affect the kidney, but only makes up 10% of these
Presentation of transitional cell carcinoma
Painless haematuria in 80% of cases
How do we diagnose transitional cell carcinoma?
CT IVU (intravenous urogram)
Treatment for transitional cell carcinoma?
Radical nephroureterectomy
What is renal tubular acidosis?
This is a condition in which the kidneys fail to adequately acidify the urine
What are the two ways in which we can acidify the urine?
Reabsorption of bicarbonate in the proximal tubule
Secretion of hydrogen ions in the distal tubule
Is the problem usually proximal or distal in RTA?
Classically it is distal (i.e. can’t secrete enough H+ into the urine)
What are the 4 types of RTA?
Type I - Distal
Type II - Proximal
Type III - Combined
Type IV - Aldosterone related
How do we treat type I RTA?
Correct hypokalaemia
Chronic - oral bicarbonate
What is hydronephrosis
Swelling of the kidney due to urine failing to drain from kidney to bladder
Causes of unilateral hydronephrosis
PACT Pelvic-ureteric obstruction Aberrant renal vessels Calculi Tumours
Causes of bilateral hydronephrosis
SUPER Stenosis of urethra Urethral valve Prosatic enlargement Extensive bladder tumour Retro-peritoneal fibrosis
Investigations in hydronephrosis
Ultrasound
CT Intravenous urogram - assess position of obstruction
Management of hydronephrosis
Remove the obstruction
Nephrostomy tube
Ureteric stent
