Week 3 - Clinical Biochemistry of Renal Disease

Flashcards covering key vocabulary and concepts related to the clinical biochemistry of renal disease, including kidney function, renal function tests, acute kidney injury, chronic kidney disease, and electrolyte imbalances.

Kidney Functions

Regulate extracellular fluid volume and blood pressure, electrolyte and acid-base balance, and excretion of waste products (creatinine, urea, uric acid).

Kidney as Endocrine Organ

Vitamin D metabolism, erythropoietin production (stimulates red blood cell production), and renin production (controls sodium balance and blood pressure).

Nephron

Functional unit of the kidney; ~1 million in each kidney. Consists of the glomerulus and renal tubule.

Glomerulus

Cluster of capillaries acting as a high-pressure filter; permeable to water and low molecular mass substances but impermeable to large proteins. Receives around 25% of cardiac output.

Renal Tubules

Responsible for reabsorption of glucose, amino acids, urea, electrolytes (Na, Cl, K, Ca, Mg, bicarbonate, phosphate), and water, as well as secretion of certain substances.

Glomerular Filtration Rate (GFR)

Volume of blood filtered by the glomeruli per unit time. Normal range is approximately 90-120 mL/min.

Creatinine

Waste product of muscle breakdown, released at a constant rate. Used to assess renal function, but a late marker for renal disease.

Urea

Synthesized in the liver as an end product of protein breakdown; excreted by the kidney. Less reliable than creatinine as a marker of renal function.

Cystatin C

Small peptide produced by all nucleated cells, cleared by glomerular filtration. More accurate measure of GFR than creatinine but more expensive.

Estimated GFR (eGFR)

Uses serum creatinine, age, and sex to estimate GFR. The CKD-EPI formula is currently recommended. Used to screen for and monitor chronic kidney disease (CKD).

Proteinuria

Raised protein in the urine due to impaired glomerular integrity. Indicated by a protein:creatinine ratio (PCR) or albumin:creatinine ratio (ACR). ≥3 mg/mmol is clinically important proteinuria.

Acute Kidney Injury (AKI)

Rapid loss of renal function (≤ 7 days) with profound effects on the body's homeostatic mechanisms. Classified into stages 1, 2, or 3 based on serum creatinine and urine output criteria.

Chronic Kidney Disease (CKD)

Abnormalities in kidney function or structure present for more than 3 months. Diagnosed by GFR

Hyponatraemia

Serum Na+ < 133 mmol/L. Can be due to Na depletion, water excess, or Na and water excess.

Hypernatraemia

Serum Na+ > 146 mmol/L. Causes include water depletion, Na and water depletion, or (rarely) Na excess. Often associated with dehydration.

Hyperkalaemia

Serum K+ >5.5 mmol/L. Can be due to artefactual causes, increased intake, decreased excretion, or transcellular movement. Can cause cardiac arrest.

Hypokalaemia

Serum K+ < 3.5 mmol/L. Causes include decreased intake, increased loss (kidney or gut/skin), or intracellular shift. Can cause cardiac arrhythmias and muscle weakness.