Kidney Key Points

Plasma creatinine Urea Urate Sodium Potassium

Elevated creatinine and urea indicate an issue with Glomerular filtration A low glomerular filtration rate means waste products will build up in blood and there will be less of these products in the urine

Plasma creatinine concentration increases as GFR decreases, but it is not directly proportional to renal damage Normal creatinine levels are proportional to muscle mass Creatinine is a by-product of muscle metabolism 0% of creatinine should be absorbed by the kidneys, it should all be excreted The change in a patient’s creatinine values are more of a concern then a stand alone high value If plasma creatinine doubles, GFR has dropped by 50% Increase in creatinine can be used to predict when intervention is required in end stage renal failure Creatinine is used to calculate eGFR

A by-product of protein metabolism High plasma indicates uraemia which is the build up of toxic chemicals due to the kidney’s becoming damaged and no longer being able to excrete the urea Symptoms include nausea, vomiting, lethargy and confusion 40% of urea should be reabsorbed but the rest should be excreted If tubular flow decreases due to renal hypoperfusion urea absorption will increase Increased levels of urea indicate low GFR Plasma ureamia may be caused by GI bleed, trauma, renal hypoperfusion, decreased extracellular fluid volume, acute renal impairment, chronic renal disease, post-renal obstruction such as calculus tumour

GI bleed Trauma Renal hypoperfusion Decreased extracellular fluid volume Acute renal impairment Chronic renal disease Post-renal obstruction such as calculus tumour

Formed by the breaking down of purines in the liver Excreted in the urine and stool A build up of urate forms urate crystals Gout occurs when these urate crystals accumulate in your joints This causes inflammation and pain

Two forms: acute kidney injury and chronic kidney disease AKI - characterised by a reversible acute increase in nitrogen waste products measured through serum creatinine and urea or the kidneys inability to produce sufficient amount of urine over the course of hours to weeks. CKD - low GFR. Divided into stages 1 to 5 depending on severity.

A form of kidney disease Characterised by a reversible acute increase in nitrogen waste products measured through serum creatinine and urea or the kidneys inability to produce sufficient amount of urine over the course of hours to weeks Occurs because of damage to the kidney caused by decreased blood flow, exposure to substances harmful to the kidney, an inflammatory process in the kidney, or an obstruction of the urinary tract impeding flow Can lead to metabolic acidosis, high potassium levels, uraemia, changes in blood fluid balance and death Managed by treating the underlying cause of the condition

Occurs because of damage to the kidney caused by decreased blood flow, exposure to substances harmful to the kidney, an inflammatory process in the kidney, or an obstruction of the urinary tract impeding flow

Can lead to metabolic acidosis, high potassium levels, uraemia, changes in blood fluid balance and death

A type of kidney disease Grouped into stages depending on one’s GFR from stage 1 to stage 5 Stage 1 has a normal GFR but proteinuria Stage 5 has a GFR below 15 Caused by damage over time e.g. glomerulonephritis, diabetes or high blood pressure

Alteration of either pore size of negative charge on basement membrane of glomeruli causes loss of proteins such as albumin in the urine

Loss > 0.15g/day almost always indicates disease Three types of proteinuria occording to cause: functional, postural and nephrotic Functional: seen in fever or exercise < 0.5g loss per day Postural: seen in erect posture less than 1g loss a day Nephrotic: loss > 3.5g/day Three types according to type of loss: overflow, tubular, glomerular Overflow - capacity to reabsorb protein from proximal tubule overwhelmed e.g. haemoglobinuria or myoglobinuria, Bence Jones proteinuria Tubular - decreased tubular reabsorption of protein from proximal tubule < 2g daily e.g. Fanconi syndrome, tubulo-interstitial disease, acute renal insufficiency, chronic hypokalemia Glomerular - nil disease and other glomerular diseases

Functional: seen in fever or exercise < 0.5g loss per day Postural: seen in erect posture less than 1g loss a day Nephrotic: loss > 3.5g/day

Three types according to type of loss: overflow, tubular, glomerular Overflow - capacity to reabsorb protein from proximal tubule overwhelmed e.g. haemoglobinuria or myoglobinuria, Bence Jones proteinuria Tubular - decreased tubular reabsorption of protein from proximal tubule < 2g daily e.g. Fanconi syndrome, tubulo-interstitial disease, acute renal insufficiency, chronic hypokalemia Glomerular - nil disease and other glomerular diseases

Haemoglobinuria Myoglobinuria Bence Jones proteinuria

Fanconi syndrome Tubulo-interstitial disease Acute renal insufficiency Chronic hypokalemia

Nil disease and other glomerular diseases

Screening test 24-hour protein excretion Spot urine protein/creatinine ratio 24 hour urine collection for albumin or spot albumin to creatinine ratio if dip stick is negative

Allbustix Impregnated paper strips Does not detect light chains Sulfosalicylic acid = white precipitate

Normal ratio of 0:1 Ration greater than 3.5 indicates nephrotic range proteinuria

Orthostatic proteinuria

More severe proteinuria in the upright prone position, may disappear at night Commonest in adolescents and young adults Often harmless but may be a sign of renal disease in the future

Normal excretion of albumin < 0.05 g/day. DM patients who excrete more than this , but who have normal total protein excretion, are said to have microalbuminuria. At risk of progressive renal disease unless there is stringent control of plasma glucose concentrations and blood pressure.