Renal Flashcards
What are the functions of the kidneys?
Water and electrolyte balance
Filter and secrete excess/ waste substances
Reabsorb glucose, amino acids and bicarbonates
Activates 25-hydroxy vitamin D
Synthesise erythropoietin
What is GFR?
Glomerular filtration rate–> How much blood is filtered through the glomeruli into Bowman’s space per minute
What is a normal GFR?
120ml/min (7.2L/h, 170L/day)
What is the eGFR and how is it calculated?
The estimated glomerular filtration rate–> Best estimation of kidney function. Calculated from blood creatinine tests, age, body size and gender
What is creatinine and what happens to it?
A chemical compound left over from energy producing processes in the muscles that is filtered out of the blood by the kidneys and excreted in urine.
What does elevated creatinine levels indicate?
impaired kidney function or kidney disease
What are the different parts of the nephron?
Glomerulus, Bowman’s capsule, proximal convoluted tubule, Loop of Henle, Distal convoluted tubule, collecting duct.
What is the afferent arteriole?
Blood vessel that supplies the nephron (ARRIVES)
What is the efferent arteriole?
Blood vessels that carry blood away from the glomerulus (EXITS)
What is the glomerulus and what happens here?
Loop of capillaries, where ultrafiltration occurs
What makes up the filtration barrier at Bowman’s capsule?
Endothelial cells
Glomerular basement membrane
Podocytes
How is a pressure gradient created in the glomerulus to allow filtration?
The afferent arteriole dilates at the proximal glomerulus and the efferent arteriole constricts at the distal glomerulus.
What is the PCT lined with?
Simple cuboidal epithelial cels with brush borders and filled with large amount of mitochondria.
What is reabsorbed at the PCT?
65% of sodium, potassium and chloride, followed by water
100% of glucose
100% of amino acids
90% of bicarbonate.
What is the action of the loop of Henle?
Reabsorbs 25% of sodium and water
Which limb of the loop of Henle is impermeable to water?
The thick ascending limb.
Where do loop diuretics usually target?
The loop of Henle as this is where the most sodium filtration takes place.
What is the macula densa?
Area of specialised cells lining the proximal distal tubule. Play key sensory and regulatory functions in the maintenance of body fluid, electrolyte homeostasis and blood pressure. (sense salt levels and generate chemical signals to control kidney functions)
What happens at the distal convoluted tubule?
Fine tunes salt and water reabsorption and plays a major role in acid-base balance
What diuretics tend to target the distal convoluted tubule?
Thiazide diuretics
What is the main role of the collecting duct and how?
Reabsorption of water under the influence of ADH and aquaporins.
What is the juxtaglomerular apparaturs?
The location of renin-secreting cells and macula densa between the loop of Henle and distal nephorn which regulates blood pressure and GFR.
Where is water concentration detected?
Through osmoreception in the hypothalamus
When is erythropoietin produced by the kidney and why?
Produced in response to tissue hypoxia as it produced haemoglobin.
What is calcitrol and what are its actions?
Acitve form of vitamin D produced by the kidney:
Increases gut absorption of Ca2+ and phosphate, suppresses PTH.
Why is there a drop in Ca2+ in kidney failure?
Due to decreased renal production of ,25 (OH)2 vitamin D. (and increased serum phosphorus)
When/ why do kidney stones form?
When the urine contains more crystal-forming substances (calcium, ocalate and uric acid) than the fluid can dilute. The urine may also lack substances that prevent crystals from sticking together.
What forms 80% of renal stones? What else may form them?
Calcium oxalate most common
Can also be calcium phosphate, uric acid or struvite
What are staghorn calculi?
Renal calculi (stones) that are usually composed of struvite have a characteristic staghorn shape.
Where do staghorn calculi tend to sit?
Body in renal pelvis with horns extending into renal calyxes.
When do staghorn calculi tend to form?
In recurrent urinary tract infections: the bacteria can hydrolyse urea in urine to ammonia, creating the solid struvite.
How do renal stones present?
May be asymptomatic/ never cause issue Renal colic Excruciating loin to groin pain Colicky pain as the stone moves Haematuria, nausea, vomiting, oliguria May have symptoms of sepsis if infected (e.g. fever)
What is renal colic?
Type of abdominal pain caused by the obstruction of the ureter due to a dislodged kidney stones.
How are renal stones diagnosed?
CT KUB (non-contrast scan of kidney, ureters and bladder)
(Urine dipstick
Bloods for infection and kidney function
X-ray (may not be visible)
How are renal stones managed?
- NSAIDs
- Antiemetic if nausea/ vomiting
- Fluids
- Antibiotics if necessary
- Wait for stone to pass: Tamsulosin can help spontaneous passage
- Surgical interventions in large stones/ stones that do not pass
What is the usual outcome of renal stones?
Stones <6mm have > 50% of passing without intervention.
Spontaneous passage can take several weeks
What surgical interventions can be used for large renal stones?
Extracorporeal shock wave lithotripsy
Ureteroscopy and laser lithotripsy
Percutaneous nephrolithotomy
Open surgery
What is Extracorporeal shock wave lithotripsy?
External machine generates shock waves and directs them at the stone under X-ray guidance, breaking it into smaller parts and therefore they are easier to pass.
What is a Ureteroscopy with laser lithotripsy?
When a camera is inserted via the urethra, bladder and ureter, the stone is identified and broken up by targeted lasers making it easier to pass.
What is percutaneous nephrolithotomy?
When a nephroscope (small camera) is inserted via a small incision at the patient’s back, and is inserted through the kidney to assess the ureter. The stones can either be removed or broken up. (Performed in theatre under anaestehetic) .
What advice is given to prevent recurrent stones?
- Increase oral fluids
- Reduce dietary salt intake
- Reduce intake of oxalate-rich foods for calcium stones
- Reduce intake of urate-rich foods for uric acid stones
- Limit dietary protein.
What is nephrolithiasis?
Kidney stones
What is AKI and how is it diagnosed?
Acute kidney injury–> diagnosed by measuring the serum creatinine.
What is the criteria for diagnosing an AKI?
- Rise in creatinine of > 25 micromol/L in 48 hours
- Rise in creatine of >50% in 7 days
- Urine output of < 0.5ml/kg/hour for >6 hours
What are the key risk factors of acute kidney injury?
Chronic kidney disease Heart failure Diabetes Liver disease Older age Cognitive impairment Nephrotoxic medications Use of contrast medium (e.g. CT scan)
What are the causes of renal impairment?
Pre-renal
Renal
Post-renal?
What is pre-renal AKI?
Acute kidney injury caused by inadequate blood supply to the kidneys reducing the filtration of blood.
What are the causes of pre-renal AKI?
Dehydration
Hypotension
Heart failure
What is renal AKI?
When intrinsic disease leads to reduced filtration of the blood and AKI.
What are the causes of renal AKI?
Glomerulonephritis
Interstitial nephritis
Acute tubular necrosis
What is post-renal AKI?
AKI caused by obstruction to the outflow of urine from the kidney, causing back-pressure into the kidney and reduced kidney function. (obstructive uropathy).
What causes post-renal AKI?
Kidney stones
Masses (e.g. cancer) in the abdomen or pelvis
Ureter or uretral strictures (narrowing)
Enlarged prostate or prostate cancer
What investigations are done to look into the cause of AKI?
Urinalysis for:
- Protein and blood (suggest acute nephritis)
- Leucocytes and nitrites (suggest infection)
- Glucose (suggests diabetes)
Ultrasound to look for obstruction.
How is the first step in AKI management?
Correct underlying cause:
- Fluid rehydration with IV fluids in pre-renal AKI
- Stop nephrotoxic medications (e.g. NSAIDS and antihypertensives)
- Relieve obstruction in post-renal (e.g. insert catheter)
What are the main complications of AKI?
Hyperkalaemia
Fluid overload, heart failure and pulmonary oedema
Metabolic acidosis
Uraemia (can lead to encephalopathy or pericarditis)
What is nephritis?
Inflammation of the kidneys
What is nephritic syndrome?
A group of symptoms that indicates inflammation of the kidney. (but not the underlying cause)
What are the features of nephritic syndrome?
Haematuria (blood in urine)
Oliguria (reduced urinary output)
Proteinuria (<3g in 24 hours)
Fluid retention
What is nephrotic syndrome and how is it classified?
Group of symptoms that indicate the presence of an underlying disease (but not what the disease is): Peripheral oedema Proteinuria (>3g in 24 hours) Serum albumin (<25g/L) Hypercholesterolaemia
How much protein must there be in urine to differentiate between nephritic and nephrotic syndrome?
Nephrotic syndrome >3g in 24 hours
What is glomerulonephritis?
A range of conditions that cause inflammation of/ around the glomerulus and nephron.
What is interstitial nephritis?
When there is inflammation of the interstitium (space between cells and tubules) in the kidney.
What are the two key forms of interstitial nephritis?
Acute interstitial nephritis
Chronic tubulointerstitial nephritis
What is glomerulosclerosis?
Pathological scarring of the glomerular tissue caused by other diagnoses.
What can cause glomerulosclerosis?
Glomerulonephritis, obstructive uropathy (urine outflow blockage) or focal segmental glomerulosclerosis (specific disease)
What are some examples of glomerulonephritis?
Minimal change disease Focal segmental glomerulosclerosis Membranous glomerulonephritis IgA nephropathy (Berger's disease) Post-streptococcal glomerulonephritis Goodpasture sydrome Rapidly progressive glomerulonephritis
How are most types of glomerulonephritis treated?
Immunosuppression (e.g. steroids)
Blood pressure control ( ACE inhibitors, Angiotensin-II receptor blockers)
How does nephrotic syndrome usually present?
Oedema
Frothy urine (proteinurea)
Pallor
What does nephrotic syndrome predispose patients to?
Thrombodis, hypertension and high cholesterol
What is the most common cause of nephrotic syndrome in children?
Minimal change disease
What is the most common cause of nephrotic syndrome in adults?
Focal segmental glomerulosclerosis
When does nephrotic syndrome occur?
When the glomerular basement membrane becomes highly permeable to proteins, allowing them to leak from the blood to the urine. (usually due to podocyte injury)
In what group is nephrotic syndrome most common?
2-5 year olds
What is the classic triad in nephrotic syndrome?
Low serum albumin
High urine protein content (>3)
Oedema
What other features occur in patients with nephrotic syndrome?
Deranged lipid profile (high cholesterol, triglyceride and LDL levels)
High blood pressure
Hyper-coagulability
What is minimal change disease?
The most common cause of nephrotic syndrome in children which occurs in isolation without any clear underlying condition of pathology.