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Magnetic resonance imaging (MRI) offers important information regarding the morphology, location and size of a herniated disc, which influences the decision to offer lumbar diskectomy (LD). This study aims to examine the association between clinical neurophysiologic indices including pain intensity and quantitative sensory testing (QST), and the degree of lumbar nerve root compromise depicted on magnetic resonance (MR) in patients awaiting LD.With institutional ethical approval, 16 patients (American Society of Anaesthesiologists Grades I-II, 18-65 years) with radicular pain for greater than 3 months undergoing elective LD were studied. Preoperative pain was assessed using (i) a visual analogue scale measuring pain intensity at rest and with movement and (ii) by quantifying pain sensory thresholds (St), pain perception thresholds (PPt), and pain tolerance threshold (PTt) using QST. MR images were independently graded by two radiologists blinded to the clinical data using the Pfirrmann grading system. Statistical analyses using Student's t-tests and Pearson's correlation were preformed where appropriate.This study showed that: (i) findings on MR imaging corresponded with the symptomatic side and distribution of the pain; (ii) the degree of nerve root compromise, detected on MRI correlated with increased pain intensity at rest; and (iii) QST identified a trend towards higher St, PPt and PTt in patients with higher Pfirrmann grades.The Pfirrmann grading system of nerve root compromise may be clinically useful preoperatively as a method of identifying individuals who would benefit most from LD. However, additional studies with greater patient numbers and longer follow-up are required to definitively confirm the findings of this study.

561 Background: Liver resection remains the only potentially curative option for a subset of patients with metastatic colorectal cancer (CRC) to liver. Preoperative imaging used to determine resectability includes contrast enhanced computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). The objective of this study was to determine the utility of PET scanning for potentially resectable metastatic CRC to liver. Methods: We retrospectively reviewed a prospectively maintained database for all patients considered for liver resection of metastatic CRC from July 2010 to July 2012 in a specialist colorectal/hepatobiliary cancer centre. We extracted and analysed data with respect to preoperative staging imaging and definitive treatment performed on completion of staging. Results: We identified 50 patients who underwent preoperative staging investigations for potentially resectable metastatic CRC to liver. The imaging techniques performed included: CT (n=50, 100%), MRI liver (n=45, 90%), PET (n= 47, 94%). In 9 (9/47, 19%) patients PET scanning added to the preoperative cross sectional staging information, identifying local recurrence (n=1, 2%), confirming liver metastases following an inconclusive CT/MRI (n=1, 2%), and identifying extrahepatic sites suspicious for disease (n=7, 15%). The extrahepatic sites included either lung (n=4) or bone (n=1) or lymph nodes (n=2). One patient with FDG-avid mediastinal lymph nodes had no cancer on endobronchial biopsy. PET scanning definitively changed the therapeutic strategy in 6 patients (6/47, 12.8%): precluding liver resection in 2 patients (2/47, 4.3%), leading to resection of extrahepatic disease in 3 patients (3/47, 6.4%) and resection of hepatic metastases in one patient (1/47, 2.1%). Conclusions: In this small retrospective cohort the addition of metabolic imaging changed the management in 12.8% of patients with potentially resectable liver confined metastatic CRC. We plan to include data from other cancer centres in Ireland to confirm our findings.