Percutaneous Nephrolithotomy in the Prone and Prone-Flexed Positions: Anatomic Considerations
Bibliographic record
Abstract
OBJECTIVES: Percutaneous nephrolithotomy is commonly performed in the prone position. Knowledge of renal anatomy and the relationship of adjacent organs is essential to minimize patient morbidity and iatrogenic organ injury. We present the anatomical basis for a prone-flexed modification to patient positioning and review the advantages and disadvantages of alternate positions. METHODS: Triphasic computed tomography was conducted with the patient in supine, prone, and prone-flexed positions, and an anatomical survey was conducted. A 30 degrees angle was used to approximate the plane of nephrostomy access and the risk of organ injury. RESULTS: For upper pole punctures, the liver and spleen were more medially situated, and thus more likely to be injured with supine positioning, compared with either prone or prone-flexed positioning (p < 0.001). In contrast, for lower pole punctures, the colon was more medially situated in the prone and prone-flexed positions compared to supine (p < 0.001). With prone-flexed positioning, the left kidney was displaced lower than the right in 92.3% of cases. The prone-flexed modification increased the distance from the posterior iliac crest to the 12th and 11th ribs by 2.9 and 3.0 cm, respectively (p < 0.001). If access was performed in the most superior calyx, this would have converted an upper pole access above the 11th rib to one above the 12th rib in 5 of 11 patients (45.5%). CONCLUSIONS: Prone-flexed positioning is a simple modification that provides improved access to the upper pole and more mobility for lower pole percutaneous nephrolithotomy. This position is well tolerated and has several advantages over other patient positions, including the supine position.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".