Renal Flashcards
Effect of hyperventilation on pH
Hyperventilation –> reduced co2 –> increase in pH
Normal anion gap
10-20 mmol/L
How is anion gap calculated
Na+ - (Cl- + HCO3-)
What is high chloride in metabolic acidosis due to
Compensation for gastrointestinal bicarbonate loss(e.g., severe/prolonged diarrhoea)
Causes of metabolic acidosis with increased anion gap
MUDPILES!
M - Methanol U - Uremia(CKD) D - Diabetic ketoacidosis P - Paracetamol, propylene glycol I - Infection, iron, isoniazid L - Lactic acidosis E - Ethylene glycol S - Salicylates
How does kidney failure result in high anion-gap acidosis
Results in decreased acid excretion and increased bicarbonate excretion
Causes of metabolic acidosis with normal anion gap
Primary due to loss of bicarb or ingestion of H+
RTA Diarrhea Addison's disease Pancreatic fistula Drugs or toxins
Which drugs/toxins cause normal anion gap metabolic acidosis
Acetazolamide
Ammonium chloride
Causes of metabolic alkalosis
Vomiting
Hypokalaemia
Excessive alkali drugs(such as acid dyspepsia)
Burns
Acute causes of respiratory acidosis
Depression of central respiratory centre by cerebrovascular disease or drugs
Inability to ventilate adequately(myasthenia graves, amyotrophic lateral sclerosis, Guillain-barre)
Airway obstruction(asthma, copd exacerbation
Chronic cause of respiratory acidosis
COPD
Obesity
Hypoventilation syndrome
Neuromuscular disorders and restrictive ventilatory defects such as interstitial fibrosis or thoracic deformities.
Causes of respiratory alkalosis
Hyperventilation - eg, anxiety, stroke, meningitis, altitude, pregnancy (see the separate Hyperventilation article).
Definition of CKD
Is based on the presence of kidney damage (ie albuminuria) or decreased kidney function (ie glomerular filtration rate (GFR) <60 ml/minute per 1·73 m²) for three months or more, irrespective of clinical diagnosis.
Causes of CKD
diabetic nephropathy chronic glomerulonephritis chronic pyelonephritis hypertension adult polycystic kidney disease
CKD presentation
Usually asymptomatic oedema: e.g. ankle swelling, weight gain polyuria lethargy pruritus (secondary to uraemia) anorexia insomnia nausea and vomiting hypertension
1st line antihypertensives in CKD
ACE inhibitors(esp proteinic renal disease)
Furosemide is an alternative(added benefit of lowering serum K+)
How do CKD patients develop anaemia
Reduced EPO(normochromic normocytic anaemia)
Reduced absorption of iron
Anorexia/nausea due to uraemia
Reduced red cell survival
Blood loss due to capillary fragility and poor platelet function
Management of anaemia in CKD
Determination of iron status should be carried out prior to the administration of erythropoiesis-stimulating agents (ESA).
Many patients, especially those on haemodialysis, will require IV iron
ESAs such as erythropoietin and darbepoetin should be used in those ‘who are likely to benefit in terms of quality of life and physical function’
Factors which contribute to CKD bone disease
low vitamin D (1-alpha hydroxylation normally occurs in the kidneys)
high phosphate(excretion normally by kidneys)
low calcium: due to lack of vitamin D, high phosphate
secondary
hyperparathyroidism: due to low calcium, high phosphate and low vitamin D
Clinical manifestations of CKD bone disease
Osteitis fibrosa cystica
aka hyperparathyroid bone disease
Adynamic
reduction in cellular activity (both osteoblasts and osteoclasts) in bone
may be due to over treatment with vitamin D
Osteomalacia
due to low vitamin D
Osteosclerosis
Osteoporosis
How do high phosphate levels contribute to osteomalacia
High phosphate levels draw calcium from bones –> osteomalacia
Management of CKD mineral bone disease
reduced dietary intake of phosphate is the first-line management
phosphate binders
vitamin D: alfacalcidol, calcitriol
parathyroidectomy may be needed in some cases
What do NICE regard as clinically important proteinuria
ACR of 3mg/mmol or more
When do NICE advise referral to nephrologist in proteinuria
(ACR) of 70 mg/mmol or more, unless known to be caused by diabetes and already appropriately treated
a urinary ACR of 30 mg/mmol or more, together with persistent haematuria (two out of three dipstick tests show 1+ or more of blood) after exclusion of a urinary tract infection
consider referral to a nephrologist for people with an ACR between 3-29 mg/mmol who have persistent haematuria and other risk factors such as a declining eGFR, or cardiovascular disease
Management of proteinuria in CKD
ACE inhibitors (or angiotensin II receptor blockers) are key in the management of proteinuria
They should be used first-line in patients with coexistent hypertension and CKD, if the ACR is > 30 mg/mmol
if the ACR > 70 mg/mmol they are indicated regardless of the patient’s blood pressure
Drugs to avoid in renal failure
antibiotics: tetracycline, nitrofurantoin
NSAIDs
lithium
metformin
Drugs likely to accumulate in CKD which therefore need dose adjustment
most antibiotics including penicillins, cephalosporins, vancomycin, gentamicin, streptomycin digoxin, atenolol methotrexate sulphonylureas furosemide opioids
Which antibiotics are relatively safe in CKD
Erythromycin
Rifampicin
What is pyelonephritis
Pyelonephritis refers to inflammation of the kidney resulting from bacterial infection. The inflammation affects the renal pelvis (join between kidney and ureter) and parenchyma (tissue).
Risk factors for pyelonephritis
Female sex
Structural urological abnormalities
Vesico-ureteric reflux (urine refluxing from the bladder to the ureters – usually in children)
Diabetes
Causes of pyelonephritis
E.coli(most common)
Klebsiella pneumoniae
Enterococcus
Pseudomonas aeurginosa
Pyelonephritis presentation
Fever Loin or back pain (bilateral or unilateral) Nausea/vomiting Similar to LUTS(dysuria, suprapubic discomfort, increased frequency) Systemic illness Loss of appetite Haematuria Renal angle tenderness
Ix for pyelonephritis
Urine dip
MSU for microscopy, culture and sensitivity
Blood tests
Imaging(ultrasound or CT)
Abx for pyelonephritis
NICE guidelines (2018) recommend the following first-line antibiotics for 7-10 days when treating pyelonephritis in the community:
Cefalexin
Co-amoxiclav (if culture results are available)
Trimethoprim (if culture results are available)
Ciprofloxacin (keep tendon damage and lower seizure threshold in mind)
Mx of pyelonephritis
Oxygen to maintain oxygen saturations of 94-98% (or 88-92% in COPD)
Empirical broad-spectrum IV antibiotics (according to local guidelines)
IV fluids
Sepsis 6 if suspected
What should be considered in patients with pyelonephritis with significant symptoms or not responding to treatment
Renal abscess
Kidney stone obstructing the ureter, causing pyelonephritis
What is chronic pyelonephritis
Chronic pyelonephritis presents with recurrent episodes of infection in the kidneys.
Recurrent infections lead to scarring of the renal parenchyma, leading to chronic kidney disease (CKD). It can progress to end-stage renal failure.
Ix in recurrent pyelonephritis
Dimercaptosuccinic acid (DMSA) scans involve injecting radiolabeled DMSA, which builds up in healthy kidney tissue.
When imaged using gamma cameras, it indicates scarring or damage in areas that do not take up the DMSA. They are used in recurrent pyelonephritis to assess for renal damage.
Most common place for renal stones
Vesico-ureteric junction
Two key complications of kidney stones
Obstruction leading to acute kidney injury
Infection with obstructive pyelonephritis
Most common type of kidney stones
Calcium-based stones
Risk factors for calcium stones
raised serum calcium (hypercalcaemia) and a low urine output
Which kidney stones are not visible on x-ray
Uric acid
What are cystine kidney stones associated with
Associated with cystinuria, an autosomal recessive disease
What are struvite kidney stones produced by
Bacteria, therefore, associated with infection
What is a stag horn calculus
A staghorn calculus is where the stone forms in the shape of the renal pelvis, giving it a similar appearance to the antlers of a deer stag. The body sits in the renal pelvis with horns extending into the renal calyces. They may be seen on plain x-ray films.
Which stones most commonly cause stag horn calculus
Struvite stones
In recurrent upper urinary tract infections, the bacteria can hydrolyse the urea in urine to ammonia, creating the solid struvite.
Presentation of renal colic
Renal colic is the presenting complaint in symptomatic kidney stones. Renal colic is:
Unilateral loin to groin pain that can be excruciating (“worse than childbirth”)
Colicky (fluctuating in severity) as the stone moves and settles
Symptoms of renal colic
Patients often move restlessly due to the pain.
There may also be:
Haematuria
Nausea or vomiting
Reduced urine output
Symptoms of sepsis, if infection is present
Ix for renal colic
Urine dip
AXR
Non-contrast CT KUB
Ultrasound
Mx of renal stones
NSAIDs(IM diclofenac) Antiemetics Antibiotics Watchful waiting if less than 5mm Tamulosin Surgical intervention
Surgical interventions for kidney stones
Extracorporeal shock wave lithotripsy(ESWL)
Ureteroscopy and laser lithotripsy
Percutaneous nephrolithotomy(PCNL)
Open surgery
General advice for recurrent stones
Increase oral fluid intake (2.5 – 3 litres per day)
Add fresh lemon juice to water (citric acid binds to urinary calcium reducing the formation of stones)
Avoid carbonated drinks (cola drinks contain phosphoric acid, which promotes calcium oxalate formation)
Reduce dietary salt intake (less than 6g per day)
Maintain a normal calcium intake (low dietary calcium might increase the risk of kidney stones)
Dietary advice for calcium stones specifically
Reduce the intake of oxalate-rich foods (e.g., spinach, beetroot, nuts, rhubarb and black tea)
Dietary advice for uric acid stones specifically
reduce the intake of purine-rich foods (e.g., kidney, liver, anchovies, sardines and spinach)
Which medications may be used to reduce the risk of kidney stone recurrence
Potassium citrate in patients with calcium oxalate stones and raised urinary calcium
Thiazide diuretics (e.g., indapamide) in patients with calcium oxalate stones and raised urinary calcium
Prevention of oxalate stones
cholestyramine reduces urinary oxalate secretion
pyridoxine reduces urinary oxalate secretion
Risk factors for renal stones
dehydration
hypercalciuria, hyperparathyroidism, hypercalcaemia
cystinuria
high dietary oxalate
renal tubular acidosis
medullary sponge kidney, polycystic kidney disease
beryllium or cadmium exposure
Risk factors for urate stones
gout
ileostomy: loss of bicarbonate and fluid results in acidic urine, causing the precipitation of uric acid
Drug causes of renal stones
drugs that promote calcium stones: loop diuretics, steroids, acetazolamide, theophylline
thiazides can prevent calcium stones (increase distal tubular calcium resorption)
