Efficacy of Ultrasound Compared to Magnetic Resonance Imaging for the Preoperative Mapping of Pilonidal Sinus Disease: A Proof of Concept Study

Background Recurrence of pilonidal sinus disease (PSD) after minimally invasive surgery remains a significant challenge to surgeons and may be explained by incomplete obliteration of the sinus. Preoperative imaging could play an important role in addressing this problem. Magnetic resonance imaging (MRI) is considered the modality of choice but is costly and time-consuming. The objective of this study was to determine if ultrasound (US) is a feasible alternative to MRI in preoperative PSD mapping. Methods A prospective, proof of concept study was conducted on patients treated with laser ablation in 2 Belgian hospitals between Jan 2023 and Dec 2024. The patients underwent a preoperative US and MRI. Sinus characteristics were described according to a predefined protocol. The agreement between US and MRI was quantified using the intraclass correlation coefficient (ICC) for the measurement of 3 sinus dimensions (length, depth and width) and Cohen’s kappa coefficient (k) for the detection of side branches. Results 30 patients were included with a median age of 27 years (IQR 20-35). Median sinus dimensions were 3.3 cm (IQR 1.5-5.6), 0.5 cm (IQR 0.3-0.8) and 0.7 cm (IQR 0.4-1.2) on US, and 1.9 cm (IQR 1.5-3.9), 0.4 cm (IQR 0.2-0.6) and 0.4 cm (IQR 0.2-0.7) on MRI for length, depth and width respectively. Side branches were detected in 6 (22%) patients on US and in ten (40%) patients on MRI. The level of agreement between US and MRI was moderate for sinus length (ICC 0.74, 95% CI 0.49-0.87, P < 0.001), and poor for sinus depth (ICC 0.30, 95% CI -0.05-0.60, P = .041) and width (ICC 0.36, 95% CI -0.03-0.66, P = .008). The level of agreement for the detection of side branches was moderate (k 0.46, 95% CI 0.11-0.82, P = .013). Conclusion Preoperative US is not suitable for the preoperative mapping of PSD when compared to MRI. MRI remains the preferred imaging technique in our clinical practice especially for complex PSD.