TTKG Calculator
Calculate Transtubular Potassium Gradient for kidney function assessment
Calculate TTKG
⚠️ Prerequisites for Accurate TTKG Calculation
Serum Parameters
Normal range: 3.5-5.0 mmol/L
Normal range: 280-300 mOsm/kg H₂O
Urine Parameters
Typical range: 25-100 mmol/L
Must be ≥300 mOsm/kg H₂O for accurate calculation
Must be ≥25 mmol/L for accurate calculation
TTKG Results
Clinical Interpretation Guide
| Serum K+ (mmol/L) | TTKG Value | Interpretation |
|---|---|---|
| <3.5 | <3 | Normal renal response |
| <3.5 | >3 | Renal potassium wasting |
| 3.5-5.0 | <8 | TTKG too low |
| 3.5-5.0 | 8-9 | Normal (with normal diet) |
| 3.5-5.0 | >9 | TTKG too high |
| >5.0 | >7 | Normal (optimally >10) |
| >5.0 | <7 | Type IV renal tubular acidosis |
Example Calculation
Hyperkalemia Case Example
Patient: 65-year-old with serum K+ = 6.2 mmol/L
Serum potassium: 6.2 mmol/L
Urine potassium: 45 mmol/L
Serum osmolality: 290 mOsm/kg H₂O
Urine osmolality: 580 mOsm/kg H₂O
Urine sodium: 78 mmol/L
Calculation
TTKG = (45/6.2) / (580/290)
TTKG = 7.26 / 2.0
TTKG = 3.63
Interpretation: TTKG <7 in hyperkalemia suggests impaired renal potassium excretion
Medical Disclaimer
This calculator is for educational purposes only and should not replace professional medical advice. TTKG interpretation requires clinical context and should always be evaluated by qualified healthcare professionals. The results should be considered alongside other clinical findings, patient history, and additional laboratory tests.
Quick Reference
Normal Ranges
TTKG Formula
Clinical Uses
Evaluate renal potassium handling disorders
Differentiate causes of hypokalemia
Assess hyperkalemia mechanisms
Distinguish mineralocorticoid deficiency vs. resistance
Limitations
Requires urine osmolality ≥300 mOsm/kg
Requires urine sodium ≥25 mmol/L
Cannot be used in diuretic therapy
Diet affects interpretation
Understanding TTKG - Transtubular Potassium Gradient
What is TTKG?
The Transtubular Potassium Gradient (TTKG) is a calculated parameter that estimates the potassium concentration gradient between the cortical collecting duct and the peritubular capillaries. It helps assess renal potassium handling and distinguish between renal and non-renal causes of potassium disorders.
Why is TTKG Important?
- •Evaluates renal potassium secretion capacity
- •Helps differentiate mineralocorticoid disorders
- •Guides diagnosis in potassium imbalances
- •Assesses aldosterone responsiveness
Clinical Applications
Hypokalemia (K+ <3.5)
TTKG >3 suggests renal potassium wasting (hyperaldosteronism, diuretics). TTKG <3 suggests extrarenal losses (diarrhea, poor intake).
Hyperkalemia (K+ >5.0)
TTKG <7 suggests impaired renal potassium excretion (type IV RTA, hypoaldosteronism). TTKG >10 suggests appropriate renal response to hyperkalemia.
Physiological Basis
TTKG reflects the driving force for potassium secretion in the cortical collecting duct. It normalizes for water reabsorption (using osmolality ratio) to provide a more accurate assessment of potassium handling than simple urinary potassium concentration alone.
Key Physiological Points
- • Potassium is primarily secreted in the distal nephron
- • Aldosterone regulates potassium secretion
- • ADH affects water reabsorption and urine concentration
- • Sodium delivery affects potassium secretion capacity