Azotaemia and renal failure Flashcards
Do azotaemia and uraemia always appear together?
No
You can have azotaemia without uraemia
But you can’t get uraemia without azotaemia
What are the 3 (4) reasons for developing azotaemia?
Inadequate renal perfusion
Loss of nephrons
Back pressure
-Leading to decreased GFR
What are some causes of inadequate renal perfusion?
Shock
Heart failure
Severe dehydration
What are the 3 categories of azotaemia?
Prerenal
Renal
Postrenal
At what remaining renal function percentage do you see PU/PD in a dog that can no longer concentrate urine enough?
33% remaining
At what remaining renal function percentage will a patient become azotaemic?
25% remaining
-Also when creatinine levels will start to slowly change
What is SDMA and why is it useful?
New renal biomarker test
Can now detect damage earlier
Instead of having to loose 75%, now you can pick up on a patient that has lost 40%
(Just before renal insufficiency occurs)
Is creatinine or BUN more renal specific?
Creatinine
-Urea is made in the liver
What 4 things can BUN be affected by, other than renal function?
Diet -High in protein
GI bleeding
Catabolic rate
Dehydration
How do you manage a patient with suspected prerenal azotaemia?
Get baseline bloodwork and urine
-See that they can concentrate properly at the start
Rehydrate the patient over 4-8 hours
Continue with maintenance fluid therapy
Monitor urine output, hydration status, weight, central venous pressure
Avoid over-hydration
Repeat blood work after 24-48 hours and see what has changed
Why should you first try and correct any prerenal cause of azotaemia first?
Can re-check from baseline levels, if they become normal then only pre-renal problem
If there are renal or postrenal components you will at least get a better understanding of how badly they are affected, and make the patient feel better
If after fixing any fluid deficits of a suspected prerenal azotaemia, and the azotaemia still persists, what are the 2 possibilities?
-Further fluid therapy is needed
Degree of dehydration and renal perfusion impairment was underestimated or there are on-going losses
-Renal or postrenal azotaemia is present
What are 2 common causes of post-renal azotaemia?
Urolithial obstruction
Bladder rupture
In the correct order, how do you manage post-renal azotaemia?
Correct the life-threatening metabolic disturbances first
-IV catheter and any fluid
Relieve the urinary outflow obstruction
Anticipate post obstruction diuresis and monitor/treat accordingly
What is the first thing you need to work out when dealing with a patient with renal azotaemia?
If it is acute or chronic renal failure
Why can acute renal failure be better and also worse than chronic?
Acute renal failure usually present worse than a chronic case, with worse prognosis of survival
However for acute renal failure there may be improvement in renal function as nephrons repair after injury
-For chronic there is little chance of improved function
What is the aim of therapy for treating CKD?
Deal with prerenal and any post renal complications
- May slow down rate of progression
- Unlikely to improve GFR
Describe the pathogenesis of CKD?
Inciting cause occurs
-Often difficult to determine, histological changes are not process specific
Progressive, inexorably destruction of diseased nephrons
But done at a rate where there is time for compensatory hypertrophy of unaffected nephrons
Eventually the hypertrophied nephrons cannot maintain adequate renal function
Renal insufficiency - PU/PD
Chronic renal failure -Azotaemia
Why do dogs with CKD produce more urine, not less?
Because the tubule cells are not able to re-uptake all the solutes
-Mainly sodium
Describe some of the features of CRF?
PU/PD Vomiting Anorexia Dehydration \+/- Pale mucous membranes \+/- oral ulceration/halitosis \+/- abnormal kidneys Isosthenuria despite dehydration Azotaemia and hyperphosphataemia* \+/- metabolic acidosis in end stage Non-regenerative anaemia Hypokalaemia - early Hyperkalaemia - end stage Hyper/hypocalcaemia uncommon Thrombocytopathia
Describe some features of advanced CRF/uraemia?
Increased plasma hormone concentrations -Gastrin -Glucagon -Insulin -Growth hormone -PTH Immunodeficiency \+/- systemic arterial hypertension \+/- rare osteodystrophy (Rubber jaw) \+/- uraemic encephalopathy
What are some other clinical problems that you sometimes may see with uraemia/CRF?
Urinary incontinence -Underlying PU/PD Haematuria Proteinuria Stranguria Pollakiuria Dysuria Melaena Urinary outflow obstruction Urolithiasis Fever Urinary tract infection Urinary tract mass lesions
Describe a diagnostic approach to CRF?
Signalment and history Physical exam Routine blood work Urinalysis Response to rehydration Imaging of kidney size/shape Staging of disease
Describe how you would manage a patient with CRF?
*Identify and treat any contributing underlying causes
-Usually won’t find
-Systemic arterial hypertension, UTI, toxins, drugs
*Maintain optimal hydration
-Provide water ad lib.
-Short term i/v fluid therapy
-Maybe teach owners to administer fluids s/c
Restrict phosphorus intake
-Low phosphorus diet, enteric phosphate binders
Restrict protein intake as needed
*Supplement water-soluble vitamins
*Once hyperphosphataemia controlled give calcitriol
-Reduces hyperparathyroidism
*H2 receptor blocker like ranitidine
-Hypergastronemia
*Anti-emetic
*Anabolic steroids
-May help to feel better
*r-HuEPO
-Erythropoietin
-Good way to treat anaemia
-Expensive, may get hypertension and anti-EPO antibody
Describe how you can manage systemic hypertension complicating CRF?
\+/- salt restriction ACEI in dogs ACEI in mild-moderately affected cats ACEI & Amlodipine in severely affected cats Use combinations in refractory cases
Describe how you can manage proteinuria complicating CRF?
ACEI
Angiotension receptor blocker
What do you use to monitor a patient with CKD?
At home Attitude, activity, appetite, vomiting Thirst, drinking Body weight Urination habits
At the clinic
Measure BUN, creatinine, phosphorus (SDMA)
Arterial blood pressure
Urinary protein/ albumin
