LAUSR

INTRODUCTION Supracostal access for percutaneous nephrolithotomy (PNL) has a known increased risk for thoracic complications (TC). In this study, we perform a radiological review of preoperative and postoperative abdominal CT to assess the relationship of the upper pole of the kidney to surrounding landmarks to determine radiographic predictors of TC. METHODS We performed a retrospective matched cohort comparison of patients who underwent supracostal PNL with and without TC's from 2012-2019. An experienced GU radiologist reviewed pre and post-operative CT scans to measure the cranial-caudal distance (CCD) between the upper renal pole and the most superior calyx to the upper edge of the tip of the 12th rib, the costophrenic angle, and the posterior insertion of the diaphragm. RESULTS We identified 19 patients who developed TCs after undergoing PNL and compared their CT scans to 24 control patients without TCs. On a pre-operative abdominal CT scan, the relationship of the upper edge of renal parenchyma or upper pole calyx to the superior edge of the tip of the 12th rib or costophrenic angle were not found to be predictive of TCs. On ROC analysis, diaphragmatic insertion of ≤2.5cm below the upper edge of renal parenchyma on sagittal and transverse views was predictive of TCs (p = 0.046). On post-operative CT scan, the percutaneous nephrostomy tract traversed the posterior insertion of diaphragm in 80% of patients who had TCs compared to 20% of patients who had no thoracic complications. CONCLUSION Decreased distance between the posterior insertion of the diaphragm (medial and lateral arcuate ligaments) to the superior edge of the renal upper pole on preoperative CT scan was associated with thoracic complications from supracostal puncture during PNL. Critical preoperative recognition of this anatomic relationship can help preoperative planning, patient counseling and may prevent or reduce thoracic complications.