Graft Recipient Weight Ratio Calculator
Essential tool for Living Donor Liver Transplantation (LDLT) planning
Enter the weight of the transplant recipient in kilograms.
Please enter a valid positive weight.
Enter the estimated or actual weight of the liver graft in grams.
Please enter a valid positive graft weight.
Calculated GRWR
–%
Awaiting Input
Min. Graft Required (0.8%)
— g
Recipient SLV (Est.)
— ml
Graft % of SLV
–%
Current GRWR
Safe Threshold (0.8%)
What is the Graft Recipient Weight Ratio (GRWR)?
The Graft Recipient Weight Ratio (GRWR) is a critical anthropometric index used in liver transplantation, particularly in Living Donor Liver Transplantation (LDLT). It represents the ratio of the donor liver graft weight to the recipient's body weight, expressed as a percentage.
This metric is the primary predictor for Small-for-Size Syndrome (SFSS), a potentially fatal complication that occurs when the transplanted liver mass is insufficient to sustain the recipient's metabolic demands. Ensuring an adequate GRWR is vital for graft survival, regeneration, and the overall recovery of the patient.
Clinical Standard: A GRWR of ≥ 0.8% is generally accepted as the safety threshold to prevent SFSS. Ratios between 0.6% and 0.8% may be considered in select cases with optimized inflow modulation, while ratios below 0.6% are typically contraindicated.
GRWR Formula and Mathematical Explanation
The calculation for the graft recipient weight ratio is straightforward but requires precise measurements. The formula compares the mass of the organ to the total body mass of the patient.
The Formula
GRWR (%) = ( Graft Weight (g) / Recipient Weight (kg) ) ÷ 10
Note: Alternatively, if converting graft weight to kg first: GRWR = (Graft kg / Recipient kg) × 100.
Variables Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Graft Weight | Mass of the donor liver segment | Grams (g) | 300g – 1200g |
| Recipient Weight | Total body weight of the patient | Kilograms (kg) | 40kg – 120kg |
| GRWR | Ratio of graft to body weight | Percentage (%) | 0.6% – 2.5% |
Practical Examples (Real-World Use Cases)
Example 1: Safe Transplantation Scenario
A 50-year-old recipient weighs 70 kg. The donor's right lobe graft is estimated to weigh 650 g.
- Calculation: 650 ÷ 70 = 9.28
- Result: GRWR is 0.93%.
- Interpretation: This is above the 0.8% threshold. The risk of Small-for-Size Syndrome is low, making this a viable transplant option.
Example 2: High-Risk Scenario
A recipient with end-stage liver disease weighs 90 kg. The available left lobe graft weighs 450 g.
- Calculation: 450 ÷ 90 = 5.0
- Result: GRWR is 0.50%.
- Interpretation: This is significantly below the 0.8% safety margin and even below the extended criteria of 0.6%. Proceeding with this graft would carry an extremely high risk of liver failure and mortality.
How to Use This Graft Recipient Weight Ratio Calculator
- Enter Recipient Weight: Input the current weight of the patient in kilograms. Ensure this is the dry weight if the patient has significant ascites (fluid retention).
- Enter Graft Weight: Input the weight of the liver graft in grams. In a pre-operative setting, this is often derived from CT volumetry.
- Review the Result: The calculator will instantly display the GRWR percentage.
- Check the Status:
- Green (Safe): > 0.8%
- Yellow (Caution): 0.6% – 0.8%
- Red (High Risk): < 0.6%
- Analyze Metrics: Review the "Min. Graft Required" to understand the target weight needed for a safe procedure.
Key Factors That Affect GRWR Results
While GRWR is the primary metric, clinical decisions are nuanced. Several factors influence whether a specific ratio is acceptable:
- Portal Vein Flow: High portal inflow can damage a small graft. Modulation techniques (like splenic artery ligation) can sometimes allow for lower GRWRs.
- Donor Age: Grafts from younger donors regenerate faster. A GRWR of 0.7% might be acceptable from a 25-year-old donor but risky from a 55-year-old donor.
- Steatosis (Fatty Liver): A graft with high fat content functions poorly. A fatty graft requires a higher GRWR (often > 1.0%) to be safe.
- MELD Score: Recipients with higher MELD scores (sicker patients) require more metabolic support, making a higher GRWR necessary.
- Ascites and Fluid Retention: If the recipient's weight includes significant fluid, the calculated GRWR might be artificially low. Using "dry weight" is crucial for accuracy.
- Graft Outflow: Proper venous drainage is as important as graft mass. Congestion can functionally reduce the effective graft volume.
Frequently Asked Questions (FAQ)
1. What is the absolute minimum GRWR for a safe transplant?
The widely accepted safety limit is 0.8%. However, experienced centers may perform transplants with a GRWR as low as 0.6% if the donor is young, the graft quality is excellent, and portal inflow is modulated.
2. How is graft weight estimated before surgery?
Graft weight is estimated using CT volumetry software which calculates the volume of the liver lobes. The volume (mL) is roughly equivalent to weight (g) as the density of liver tissue is approximately 1.0 g/mL.
3. What happens if the GRWR is too low?
A low GRWR leads to Small-for-Size Syndrome (SFSS). Symptoms include prolonged cholestasis, coagulopathy, ascites, and potentially graft failure or death.
4. Can a GRWR be too high?
Yes, though less common in adult-to-adult LDLT. A very large graft (Large-for-Size) can cause compression issues or difficulty in abdominal closure, known as compartment syndrome.
5. Does the recipient's disease severity affect the required GRWR?
Yes. Patients with high MELD scores or acute liver failure have higher metabolic demands and typically require a GRWR > 0.8% or even > 1.0%.
6. How does this differ from Standard Liver Volume (SLV)?
SLV estimates the ideal liver size for a person's body surface area. GRWR compares the actual graft to the recipient's weight. Both are used, but GRWR is the standard for assessing size mismatch risk.
7. Is GRWR calculated differently for pediatric patients?
In pediatric transplantation, higher ratios are often targeted (e.g., > 2.0% or > 3.0%) to accommodate rapid growth, though the risk of "Large-for-Size" is a greater concern than in adults.
8. Why do I need to input graft weight in grams?
Medical imaging and surgical scales typically measure organ mass in grams. Using grams ensures precision, as even a 50g difference can impact the ratio significantly.
Related Tools and Internal Resources
Explore our other medical calculators to assist in transplant planning and hepatology:
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- Standard Liver Volume (SLV) Calculator – Estimate the ideal liver volume based on Body Surface Area (BSA).
- Child-Pugh Score Calculator – Determine the prognosis of chronic liver disease and cirrhosis.
- BMI Calculator for Patients – Calculate Body Mass Index to assist in nutritional assessment.
- Creatinine Clearance Calculator – Evaluate kidney function, a crucial factor in liver transplant candidates.
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