Numerical model of deep venous thrombosis detection using venous occlusion strain gauge plethysmography.

Strain gauge plethysmography (SGP) is a non-invasive method used in the detection of deep venous thrombosis (DVT). The technique is based on the measurement of calf volume changes in response to venous occlusion by a thigh cuff, the volume changes reflecting the rates of arterial inflow and venous outflow. A numerical model of the blood circulation within the limb and the response of this to a SGP test has been derived, based on treating the different parts of the circulatory system in the leg as resistance and capacitance elements. The simulation results were compared with clinical studies and support the ability of SGP to detect non-occlusive clots of more than 50-60% of the lumen, as well detecting calf vein occlusion. The non-linear behaviour of the venous compliance with intra-luminal pressure appears to be a particularly important factor within the model. In addition, increases in venous tone due to post-operative venospasm were shown to be a potential source of false positive results.

Effects of short term sacral nerve stimulation on anal and rectal function in patients with anal incontinence.

BACKGROUND: Some patients with faecal incontinence are not amenable to simple surgical sphincter repair, due to sphincter weakness in the absence of a structural defect. AIMS: To evaluate the efficacy and possible mode of action of short term stimulation of sacral nerves in patients with faecal incontinence and a structurally intact external anal sphincter. PATIENTS: Twelve patients with faecal incontinence for solid or liquid stool at least once per week. METHODS: A stimulating electrode was placed (percutaneously in 10 patients, operatively in two) into the S3 or S4 foramen. The electrode was left in situ for a minimum of one week with chronic stimulation. RESULTS: Evaluable results were obtained in nine patients, with early electrode displacement in the other three. Incontinence ceased in seven of nine patients and improved notably in one; one patient with previous imperforate anus and sacral agenesis had no symptomatic response. Stimulation seemed to enhance maximum squeeze pressure but did not alter resting pressure. The rectum became less sensitive to distension with no change in rectal compliance. Ambulatory studies showed a possible reduction in rectal contractile activity and diminished episodes of spontaneous anal relaxation. CONCLUSIONS: Short term sacral nerve stimulation notably decreases episodes of faecal incontinence. The effect may be mediated via facilitation of striated sphincter muscle function, and via neuromodulation of sacral reflexes which regulate rectal sensitivity and contractility, and anal motility.

Biofeedback provides long-term benefit for patients with intractable, slow and normal transit constipation.

BACKGROUND: Many patients with idiopathic constipation do not respond to conventional medical treatments. Recently biofeedback has been proposed as an alternative treatment but the long-term results, and which patients benefit, are unknown. Treatment has usually been restricted to patients with normal colonic transit and impaired pelvic floor coordination on straining. AIMS: To determine the efficacy and long-term outcome of biofeedback treatment in idiopathic constipation. METHODS: One hundred consecutive contactable patients who had completed a course of biofeedback more than 12 months previously were identified. Pretreatment details of bowel function and symptoms, whole gut transit time, and anorectal physiological testing, which had been previously prospectively collected, were collated. Follow up consisted of structured interview. Sixty five per cent had slow transit and 59% had paradoxical pelvic floor contraction on straining. RESULTS: Median follow up was 23 months (range 12-44). On long-term follow up 55% felt that biofeedback had helped and 57% felt their constipation was improved. There was a significant reduction in need to strain, abdominal pain, bloating, and oral laxative use. Spontaneous bowel frequency was significantly improved by treatment. Patients with slow and normal transit, males and females, and those with and without paradoxical contraction of the anal sphincter on straining, benefited equally from treatment. Anorectal testing did not predict outcome. CONCLUSION: This study suggests that biofeedback is an effective long term treatment for the majority of patients with idiopathic constipation unresponsive to traditional treatments. Pelvic floor abnormalities and transit time should not form selection criteria for treatment.