O5 Dose mean opening pressure predominantly assess internal anal sphincter function

Introduction We have suggested that mean Opening Pressure (Op) recorded during Anal Acoustic Reflectometry (AAR) predominantly represents IAS function however, the extent remains unknown. The aim was to investigate this by excluding the external anal sphincter during general anaesthetic (GA) with confirmed neuromuscular blockade (NMB). Method Patients undergoing elective abdominal surgery requiring GA+NMB were approached. Patients had pre-operative (awake) and during GA + NMB (asleep) AAR measurements performed. The rectoanal inhibitory reflex (RAIR) was assessed permitting the Op value to also be recorded when the IAS was inhibited. Op was recorded at prerectal distension and then after 100 mls of air was inflated within a balloon in the rectum (post-rectal distension). Result 19 patients were included. The values of Op (cmH20) and the reductions observed during the RAIR when awake/asleep are as follows: Awake Op: prerectal distension (64.94) and post-rectal distension (35.35) therefore mean change 29.59 cmH2O i.e. 44.6% reduction Asleep Op: prerectal distension (37.64) and post-rectal distension (15.55) therefore mean change 22.1 i.e. 55.3% reduction The contribution of the IAS to Op is calculated as follows: (Mean change Op awake x 100)/% reduction in RAIR asleep = IAS contribution awake (29.59cmH20 x 100)/55.3 = 53.51cmH20 Total mean Op awake—IAS contribution awake = EAS contribution awake 64.94cmH20–53.51cmH20 (82.4%) = 11.43cmH20 (17.6%) Conclusion The IAS accounts for 82.4% of Op at rest and it remains our hypothesis that Op primarily represents IAS function. Take-home Message Opening pressure primarily represents internal anal sphincter function.

Megarectum: systematic histopathological evaluation of 35 patients and new common pathways in chronic rectal dilatation

AimsMegarectum is well described in the surgical literature but few contemporary pathological studies have been undertaken. There is uncertainty whether ‘idiopathic’ megarectum is a primary neuromuscular disorder or whether chronic dilatation leads to previously reported and unreported pathological changes. We sought to answer this question.MethodsSystematic histopathological evaluation (in accord with international guidance) of 35 consecutive patients undergoing rectal excision surgery for megarectum (primary: n=24) or megarectum following surgical correction of anorectal malformation (secondary: n=11) in a UK university hospital with adult/paediatric surgical and gastrointestinal neuropathology expertise.ResultsWe confirmed some previously reported observations, notably hypertrophy of the muscularis propria (27 of 35, 77.1% of patients) and extensive fibrosis (30 of 35, 85.7% of patients). We also observed unique and previously unreported features including elastosis (19 of 33, 57.6%) and the presence of polyglucosan bodies (15 of 32, 46.9% of patients). In contrast to previous literature, few patients had any strong evidence of specific forms of visceral neuropathy (5 of 35, including 3 plexus duplications) or myopathy (6 of 35, including 3 muscle duplications). All major pathological findings were common to both primary and secondary forms of the disease, implying that these may be a response to chronic rectal distension rather than of primary aetiology.ConclusionsIn the largest case series reported to date, we challenge the current perception of idiopathic megarectum as a primary neuromuscular disease and propose a cellular pathway model for the features present. The severe morphological changes account for some of the irreversibility of the condition and reinforce the need to prevent ongoing rectal distension when first identified.

Common and distinct neural representations of aversive somatic and visceral stimulation in healthy individuals

Different pain types may be encoded in different brain circuits. Here, we examine similarities and differences in brain processing of visceral and somatic pain. We analyze data from seven fMRI studies (N = 165) and five types of pain and discomfort (esophageal, gastric, and rectal distension, cutaneous thermal stimulation, and vulvar pressure) to establish and validate generalizable pain representations. We first evaluate an established multivariate brain measure, the Neurologic Pain Signature (NPS), as a common nociceptive pain system across pain types. Then, we develop a multivariate classifier to distinguish visceral from somatic pain. The NPS responds robustly in 98% of participants across pain types, correlates with perceived intensity of visceral pain and discomfort, and shows specificity to pain when compared with cognitive and affective conditions from twelve additional studies (N = 180). Pre-defined signatures for non-pain negative affect do not respond to visceral pain. The visceral versus the somatic classifier reliably distinguishes somatic (thermal) from visceral (rectal) stimulation in both cross-validation and independent cohorts. Other pain types reflect mixtures of somatic and visceral patterns. These results validate the NPS as measuring a common core nociceptive pain system across pain types, and provide a new classifier for visceral versus somatic pain.

Time-dependent dose distribution changes in prostate brachytherapy with iodine seeds.

115 Background: Prostate brachytherapy with iodine seeds has a lasting dose delivery due to a long half life of I125 (i.e. 2 months). To assess changes in dose metrics over time in low-dose rate prostate brachytherapy with iodine seeds and its relationship with rectal distension. Methods: One hundred and twenty-one post-implant CT scans performed every 2 weeks over 2 months after the treatment procedure were analyzed for dosimetry. Each CT-scan was performed without and with rectal enema. The following rectal parameters were collected to evaluate the influence of rectal distension over time: rectal volume, cross-sectional surface area (CSA) and relative CSA calculated from the first CT-scan chosen as reference (CTref). Results: Mean V150% and V200% of the prostate volume increased significantly over time (p < 0.0001) and were significantly higher on postimplant CT scan performed at day 45 (CT45) (p = 0.024 and p = 0.003, respectively) and CT scan performed at day 60 (CT60) (p = 0.0005 and p < 0.0001, respectively) compared with CTref. All dosimetric parameters for the rectum were significantly increased over time. No rectal parameters were significantly different after rectal enema and there was no difference in doses delivered to the prostate and the rectum after rectal emptying. Conclusions: Increased hot spots in the prostate and the rectum during the 2 months following the procedure with iodine seeds may be related to prostate shrinkage rather than rectal distension. We hypothesize that radioelements with shorter half-life (Pd103 or Cs131) or HDR may give less toxicity, as dose distribution is less time-dependent.