Kidney presence and obstruction of TP approach per side and zone.
| Disc Level | Right Side | Left Side | ||||||
| Zone #1 | Zone #2 | Zone #3 | Zone #4 | Zone #1 | Zone #2 | Zone #3 | Zone #4 | |
| Percentage of Time Kidneys are Present in TP Approach | ||||||||
| L1 to L2 | 82% | 80% | 76% | 74% | 91% | 91% | 89% | 83% |
| L2 to L3 | 75% | 75% | 68% | 64% | 80% | 80% | 74% | 62% |
| L3 to L4 | 21% | 21% | 16% | 12% | 21% | 20% | 19% | 14% |
| L4 to L5 | 2% | 2% | 3% | 4% | 0% | 1% | 2% | 2% |
| L5 to S1 | 0% | 0% | 0% | 0% | 0% | 0% | 0% | 0% |
| Percentage of Obstruction Caused by Kidneys When Present in TP Approach | ||||||||
| L1 to L2 | 99.8% | 98.3% | 97.7% | 95.5% | 99.9% | 98.7% | 96.2% | 96.4% |
| L2 to L3 | 98.6% | 93.8% | 97.4% | 93.2% | 93.0% | 96.1% | 88.5% | 96.2% |
| L3 to L4 | 95.3% | 85.7% | 84.0% | 95.7% | 87.9% | 88.5% | 77.0% | 87.9% |
| L4 to L5 | 100% | 100% | 88.3% | 88.2% | NA | 58.5% | 67% | 100% |
| L5 to S1 | NA | NA | NA | NA | NA | NA | NA | NA |
Abbreviations: NA, not applicable; TP, transpsoas.