Evaluation of Highest Point of Iliac Crest as a Safety Landmark for Supine Percutaneous Nephrolithotomy: A Retrospective Observational Study

Abstract

Introduction: Colonic injury is a rare but serious complication of supine Percutaneous Nephrolithotomy (PCNL), traditionally mitigated by using the Posterior Axillary Line (PAL) as a safety landmark. However, since the PAL is an arbitrary and variable landmark, it has several limitations. There is a need for fixed and reliable safety landmark to address these limitations. Aim: To evaluate the highest point of the iliac crest as a potentially reliable alternative safety landmark for preventing colonic injury in supine PCNL. Materials and Methods: This retrospective observational study was conducted at Shri Mahant Indiresh Hospital, Dehradun, Uttarakhand, India in October 2024. The study included 500 patients with a suspected diagnosis of renal stone disease based on clinical symptoms or ultrasound findings, who underwent Computed Tomography (CT) imaging (CT KUB or CT urography) at the centre between January 2021 to January 2024. The highest point of the iliac crest was evaluated as a potential safety landmark. The incidence of retrorenal and lateral colon positioning and the proximity of the colon to individual renal calyces were assessed. Descriptive statistics were utilised to summarise continuous variables, such as age (mean±SD) and categorical variables, such as colon positioning (frequencies and percentages). Results: The mean age of the patients was 44.5±12.7 years, ranging from 5 to 89 years. Of these, 313 patients (62.6%) were male and 187 patients (37.4%) were female. The colon was posterior to the line drawn at the level of the highest point of the iliac crest in 39 patients (7.8%) on left side and in 19 patients (3.8%) on right side. Retrorenal colon was observed in one patient (0.2%) on right side and in eight patients (1.6%) on left side. Lateral colon positioning was significantly higher on the left-side (178 patients; 35.6%) compared to the right side (131 patients; 26.2%). Additionally, colon proximity was most common to the lower calyx. Conclusion: The highest point of the Iliac crest demonstrates promise as a safety landmark for preventing colonic injury in supine PCNL, offering a reliable alternative to the PAL. Larger multicentre studies are needed for further validation.

Keywords

• kidney stones
• retrorenal colon
• supine position