Table 1.
Representative renal TFR for the proportional and adaptive models at different stages of CKD
| Model subsegment | Healthy (stage 1) GFR = 120 mL/min | Adaptation factor | Mild stage CKD (stage 2) GFR = 80 mL/min | Moderate stage CKD (stage 3) GFR = 40 mL/min | Severe stage CKD (stage 4) GFR = 20 mL/min | End‐stage CKD (stage 5) GFR = 5 mL/min | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| TFR | TFRP | TFRA | TFRP | TFRA | TFRP | TFRA | TFRP | TFRA | ||
| Proximal tubule1 | 120 | 0 | 80.00 | 80.00 | 40.00 | 40.00 | 20.00 | 20.00 | 5.00 | 5.00 |
| Proximal tubule2 | 94 | 0.0099 | 62.67 | 62.98 | 31.33 | 31.96 | 15.67 | 16.44 | 3.92 | 4.81 |
| Proximal tubule3 | 68 | 0.018 | 45.33 | 45.73 | 22.67 | 23.46 | 11.33 | 12.33 | 2.83 | 3.98 |
| Loop of HenleD | 43 | 0.038 | 28.67 | 29.22 | 14.33 | 15.44 | 7.17 | 8.55 | 1.79 | 3.38 |
| Loop of HenleA | 24 | 0.098 | 16.00 | 16.78 | 8.00 | 9.56 | 4.00 | 5.95 | 1.00 | 3.25 |
| Distal tubule | 24 | 0.098 | 16.00 | 16.78 | 8.00 | 9.56 | 4.00 | 5.95 | 1.00 | 3.25 |
| Collecting duct1 | 11 | 0.26 | 7.33 | 8.29 | 3.67 | 5.58 | 1.83 | 4.22 | 0.46 | 3.21 |
| Collecting duct2 | 9 | 0.31 | 6.00 | 6.94 | 3.00 | 4.87 | 1.50 | 3.84 | 0.38 | 3.07 |
| Collecting duct3 | 7 | 0.37 | 4.67 | 5.54 | 2.33 | 4.08 | 1.17 | 3.35 | 0.29 | 2.80 |
| Collecting duct4 | 5 | 0.44 | 3.33 | 4.07 | 1.67 | 3.14 | 0.83 | 2.68 | 0.21 | 2.33 |
| Collecting duct5 | 3 | 0.51 | 2.00 | 2.51 | 1.00 | 2.02 | 0.50 | 1.78 | 0.13 | 1.60 |
| Bladder (urine) | 1 | 0.56 | 0.67 | 0.85 | 0.33 | 0.71 | 0.17 | 0.63 | 0.04 | 0.58 |
The tubular subsegment‐dependent adaptation factors (AFi) were calculated according to Eq. 1 and implemented for the adaptive model. The renal TFRs were calculated using either proportional model (TFRP) by direct scaling to GFR, as described in Methods, or using the adaptive model (TFRA) according to Eqs. 2 and 3. The renal TFR (mL/min) shown here indicates the inflow rate of entering each renal subsegment, which equals the outflow rate exiting from the previous renal subsegment. The inflow rate of the first proximal tubule subsegment always equals the GFR. The outflow rate of the last subsegment of collecting duct always equals the inflow rate of bladder and the urine formation rate (as no reabsorption occurs within bladder). All flows are presented in mL/min.
CKD, chronic kidney disease; GFR, glomerular filtration rate; TFR, tubular flow rate.