Kidney conditions Flashcards
What are the total body water volumes of men and women?
Men= 60% water, 42 litres
Women= 55% water, 38 litres
How much water a day is lost via sweat and evaporation?
Around 500ml a day- if unwell with a fever can lose upto 1L
How is water pushed in and out of cells?
Drawn due to osmotic pressure, pushed out to hydrostatic pressure
What are the names for patients who are volume deplete, volume overloaded or normal volume?
Volume deplete= hypovolaemic
Volume overloaded= Hypervolaemic
Normal= euvolaemic or normovolaemic
What are the 3 states of hyponatraemia that can occur?
Norvolaemic hyponatraemia
Hypovolaemic hyponatraemia
Hypervolaemic hyponatraemia
What happens when there is a increase of water in all compartments?
No clinical signs- is harder to spot
In what clinical scenarios does fluid loss occur?
Haemorrhage
Burns, water can evaporate
Vomiting- can lose a lot of salt. Same as diarrhoea
Diuretic states e.g. diabetes
Sequestration= pleural space in body is inflammaned and holds water in it
Iatrogenic- diuretics, stroma’s/fistulae and gastric aspiration
In what clinical scenarios does fluid gain occur?
Heart and liver failure
Renal failure- pass a reduced amount of urine
Hypothyroidism; unknown why. Oedema common
Psychogenic polydipsia
ADH excess
Iatrogenic= IV fluids, supplemental nutrition
What are the different ways hyponatraemia can occur?
Pure water gain
When water gain > Na+ gain
When Na+ loss > water loss
Or pure Na+ loss (not possible)
What conditions cause pure water gain?
SIADH, hypothyroidism and iatrogenic causes
Appears as normovolaemic as all compartments swell so hard to detect
What is hypovolaemia and hypervolaemia caused by?
Hypo= when Na+ loss > water loss
Hyper= When water gain > Na+ gain
What are the clinical symptoms of hypovolaemia?
Postural hypotension
Tachycardia
Reduced skin turgor
Organ failure
What are the clinical symptoms of hypervolaemia?
Hypertension
Tachycardia
Peripheral and pulmonary oedema
Organ failure
What type of hyponaetraemia is caused by diahorrea?
Hypovolaemic hyponatraemia
Excessive sodium losses; water losses are insufficient to concentrate sodium back up
What happens in euvolaemic hyponatraemia?
Water is distributed across all compartments
What happens in heart failure?
The pump stops working, and there is a reduced circulatating pressure and reduced organ perfusion.
The coresponding blood pressure mechanisms switch on, even though there is enough volume
There is renin/angiotensin/aldosterone/ADH stimulation, causing more water retetion
What is the vicious cycle of heart failure?
Retaining more water so there is more blood volume
However the weakened left ventricle cannot pump all that volume of water and the blood is very dilute
This causes the osmolaric pressure to pull water into the extracellular space
This leaves the blood volume low- cycle starts again
What is SIADH?
Syndrome of inappropriate ADH secretion- where the body makes too much ADH and there is water retention
What are the causes of SIADH?
Intracranial lesions, infection or inflammation of brain, antipsychotics, sedatives, pain and nausea
What is the treatment of SIADH?
Restrict fluids
Vasopressin antagonists- vaptans
What can cause hypervolaemic hyponatraemia?
- Heart failure
- Liver failure
- Nephrotic syndrome
Where water gains exceed sodium gains
What is the common treatment of hypovolaemia and hypervolaemia?
Hypo= restoration of volume state, blood and saline solution. Cessation of diuretics
Hyper= Diuretics, fluid restriction and treatment of underlying cause
What is the treatment for euvolaemia hyponatraemia?
Treat underlying cause
Stop IV fluids
Fluid restriction
Rarely= demeclocycline
What is the commonest form of malignancy that causes SIADH?
Small cell lung cancer
What are the different ways that hypernatraemia can occur?
Pure water loss
Water gain < water loss
Na loss < water loss
Pure Na gain
What state of volaemia is usually the case in hypernatraemia?
Hypovolaemia
Why can hypernatraemia occur with a stoma?
Salt is absorbed in the small bowel, left in colon is water and fibre. If there is a stoma you will lose alot of water but the salt has already been reabsorbed
Why does hypovolaemia occur in hypernatraemia?
There is water loss and thus a high conetration of salt in the blood. Osmotic pressure pulls water out from the cells
What are specific causes of hypernatraemia?
Water loss= fever, hyperventilation, diabetes insipidus
Reduced water intake= iatrogenic, psychosocial, stroke, coma, confusion
High sodium intake= IV fluids high in salt, emetics
What are emetics?
fluids with high conc of sodium that makes you vomit. Used to be given as treatment for people who had taken an overdose. Largely not used
What is the main cause of patients becoming dehydrated whilst in hospital?
Due to lack of access to water or no supplemental water given whilst they were in hospital
What is diabetes insipidus?
Failure of production of ADH (cranial) or inactivity of receptors (nephrogenic). Free water loss occurs, sodium becomes concentrated and hypernatraemia occurs
There is a failed feedback mechanism
What are the causes of cranial diabetes insipidus?
Pituitary tumour, head injury, meningitis, genetic and idiopathic
What are the causes of nephrogenic diabetes insipidus?
Reduced tubular response- inherited or drugs such as lithium
What is the treatment of diabetes insipidus?
Hydration= tends to cause polyuria
Desmopressin= for cranial. Synthetic ADH
NSAIDs and diuretics may help for nephrogenic but results are unsatisfactory
What are the different plasma and urine osmolarities for DI and SIADH?
What is given instead of water via an IV?
Dextrose 5%.
It is isotonic to plasma. Due to sugar, insulin is produced which will drive glucose into cells and water will follow
What can occur with rapid correction of hyponatraemia?
Central ponine myelinosis.
Symptoms= confusion, slurred speech, sensory problems and paralysis
What are the clinical symptoms and signs of volume depletion?
Volume depletion= thirst, dizziness, dysphagia, weakness, confusion, aggression and coma
Signs- postural hypotension, tachycardia, absence of JVP, reduced skin turgor, supine hypotension, oliguria and organ failure
Skin turgor= will be increased in elderly
What are the clinical symptoms and signs of volume excess?
Volume excess= localized discomfort, dyspnoea, confusion, aggression, coma, nausea
Signs= hypertension, tachycardia, raised JVP, oedema and organ failure
Odema can be commonly in ankles or in back whilst lying down. To be odema needs to be able to be displaced
What are the clinical manifestations of hypercalcaemia?
‘Stones, bones, aldominal moans and pyschic groans’
Muscle weakness, renal stone formation, abdominal pain, ECG changes, impaired water concentration in the urine, and central effects such as anorexia, nausea, mood changes.
Why is there muscle weakness in hypercalcaemia?
Competition betweem Na and Ca entering muscles
What are the ECG changes that occur in hypercalcaemia?
Shortened QT interval, risk of arrythmias
What is factitious hypercalcaemia?
Raised calcium due to high plasma albumin (venous stasis, dehydration and IV albumin can cause this)
Therefore it is important to interpret calcium and albumin levels together
What is hyperparathyroidism?
Causes hypercalcaemia
Can be due to solitary ademona, hyperplasia, carcinoma. Causes high levels of PTH to be produced and more calcium retained
What are the different types of hyperparathyroidism?
Primary= adenoma or hyperplasia of glands. Oversecretion of PTH despite normal Ca levels
Secondary= oversecretion of PTH in result to low Ca levels (due to chronic kidney disease or Vit D deficiency)
Tertiary= may occur following a prolonged period of secondary hyperparathyroidism. In response to chronic PTH secretion, the glands may become hyperplastic and begin to secrete PTH autonomously.
What are the blood tests for the 3 types of hyperparathyroidism?
Primary= increased PTH, increased Ca
Secondary= increased PTH, low Ca
Tertiary=increased PTH, increased Ca
What happens to the body in hyperparathyroidism?
Renal stones full of calcium precipitate can form
Loss of normal bone structure- osteopenia as bone becomes more reabsorbed and is weak
What is the diagnosis of primary hyperparathyroidism?
Raised Ca with raised PTH
Phosphate and bicarbonate tend to be low due to increased renal excretion
Alkaline phosphate normal or moderatly increased (bone marker)
What investigations can be done to prove primary hyperparathyroidism?
Parathyroid imaging scans using radio-isotopes
Use technicium
What is the treatment for primary hyperparathyroidism?
Re hydration and drugs such as bisphosphonates, furosemide, calcitonin and glucocorticoids
Surgery to remove adenoma
Why do 20-30% of cancer patients develop hypercalcaemia?
Endocrine factors secreted by malignant cells act on bone
Metastatic tumour deposits in bone, stimulating bone resoption via osteaclast activation
What endocrine factors are released from malignancies that cause hypercalcaemia?
Solid tumours may secrete PTH-related peptide (PTHrP) which are structuarally similar to PTH and shares simlar actions
What is ig called when PTHrP is the cause of hypercalcaemia?
Humoral hypercalcaemia of malignancy
What is malignant hypercalcaemia associated with and why?
Bony metastases
Secretion of osteoclast activating cytokines
What is multiple myeloma?
A type of bone cancer- cancer of the plasma cell
What happens to bone in multiple myeloma?
Hypercalcaemia is produced in patients with multiple myeloma due to the increased bone resorption caused by osteoclast activation, especially due to the hyperactivity of the RANK/RANK-L receptor.
Causes breakdown of bone- weakens the bones
What can happen specifically to the skull in multiple myeloma?
Pepperpot skull-
What do blood tests show when a patient has hypercalcaemia due to malignancy?
Raised Ca with supressed PTH
Phosphate tends to be high, alkaline phosphate may be very high
What is sarcoidosis?
A disease that causes granulomas (full of immune cells). Increases calcium levels leading to hypercalcaemia
What is familial hypocalciuric hypercalcaemia?
The calcium sensor on the parathyroid gland is less sensitive to Ca supression of PTH
PTH levels tend to be high normal or slightly raised.
What are the clinical neuromuscular affects of hypocalcaemia?
Numbness, tingling in fingertips and toes
Fatigue
Muscle cramps, bronchial or laryngeal spasm
Seizures
What are the mental state symptoms of hypocalcaemia?
Personality change
Mental confusion
Anxiety
Impaired intellectual ability
What can happen to the eye in hypocalcaemia?
Cloudiness of the lense
What happens to the ECG in hypocalcaemia?
Prolongation of the QT interval
Why do the main clinical symptoms of hypocalcaemia occur?
Predominantly due to an increase in neuromuscular excitability- when Ca are absent, there is a decrease in the threshold needed for the activation of neurons
What tests can be done to check for hypocalcaemia?
Chvostek’s sign= tap along facial nerve, will see contraction of the muscles of the eye
Trousseau’s sign= Brachial artery is occulded by a blood pressure monitor and will see spasm
What causes factitious hypocalcaemia?
Consequence of low plasma albumin from malnutrician, liver disease, nephrotic syndrome or malabsorbsion
What are the common causes of deficient Vit D or inaction of vit D?
Lack of sunlight
Inadequate dietary source
Malabsorpsion
Chronic renal disease
What are the effects of vit D deficiency on calcium metabolism?
Low vit D= low absorsion of calcium
Low blood calcium is detected by parathyroid; releases PTH which causes increased bone resorption and increased phosphate wasting
This can lead to problems with bones- osteomalacia/rickets
Where is vit D activated to its active form?
Vitamin D is metabolized sequentially in the liver and kidneys into 25-hydroxyvitamin D which is a major circulating form and 1,25-dihydroxyvitamin D or calcitriol
What is osteomalacia?
Pathological bone problem clssically associated with vit D deficiency
Osteoid laid down by osteoblasts is not adequately calcified
Bones are softened, weake and susceptible to fracture
Known as rickets in children
What are the symptoms of rickets?
Boney deformity- bowing of legs and widening of cartilage at growth plates e.g. wrists
Bone pain and weakness
What are the inherited causes of osteomalacia or rickets?
Deficient 1-hydroxylase
Defective receptor for calcitriol
Hypophosphataemic
What is the biochemistry of hypoparathyroidism?
Low Ca
Innappropriately low PTH
Phosphate may be raised
What are the causes opf hypoparathyroidism?
Surgical damage to PT
Drugs
Developmental parathyroid problems or genetic conditions e.g. DiGeorge syndrome
What are the principles of treating hypocalcaemia?
In acute situations, IV calcium can be given to stop arrythmias
Normally oral calcium and vit D are given
What is osteoporosis?
Weakening of bone- reduced bone mineral density and disruption of the microarchitecture
Increased risk of fracture
Routine biochemistry unaffected
What is the differences between osteoporosis and osteomalacia?
What is used to assess bone mineral density and diagnose osteoporosis?
Dual-energy X-ray absorptiometry (DEXA)
Scoring system measures bone loss against that of a healthy adult- number of SDs between these
-1 or above are normal, -1.1 – 2.4 is osteopenia and -2.5 and below is OP
What are the different forms of Vit D?
Cholecalciferol, calcidiol and calcitriol
What happens when plasma calcium falls?
PTH released- causes Ca reabsorption in the loop of henle, DCT and collecting duct
Vit D3 activation in kidney which stimulates Ca2+ intestinal absorption
Bone reabsorption by OCs and releases free Ca
How is calcium present in the plasma?
Three compartments-
How do you account for albumin bound calcium when calculating corrected calcium?
Albumin is in g/L
What are symptoms related to hypercalcaemia?
Anorexia, nausea and vomiting- all central effects of hypercalcaemia
Constipation, muscle weakness- reduced peripheral neuromuscular excitability
What is serum electrophoresis?
Shows the number and weight of proteins in the blood serum
What is the acute management of hypercalcaemia?
- Make sure patient is properly hydrated
- Calcium excretion can be promoted by using loop diuretics
- Bisphosphonates
How do bisphosponates work?
Bind to bone matrix and inhibit bone breakdown by preventing OC attachment and action
Why can raised PTH activity cause low serum phosphate and low total CO2?
PTH inhibits proximal tubule reabsorpsion of phosphate
PTH also inhibits the renal re-absorption of bicarbonate
What are the main functions affected in acute kidney injury?
Salt and water balance
Potassium excretion
Acid base balance
What happens to nephrons once they are destoryed by inflammation?
They are irreversibly damaged