Contractile activity of the human colon: lessons from 24 hour studies.

The motor function of the colon is probably the least understood of the various hollow viscera of the human body. This is partly because of the marked variability of colonic motor function and the short recording periods usually used, generally not exceeding three hours. Most of the data available on human colonic motility originate from investigations conducted in the most distal portions of the viscus, because of technical difficulties in reaching its proximal portions. Although attempts have been made to solve these problems through the ingestion of radiotelemetric pressure sensors, these efforts have been hampered by intermittent signal loss and the inability to control the location of the capsule within the gastrointestinal tract. To overcome these problems, techniques have recently been developed that permit prolonged recordings (24 hours or more) of myoelectrical and contractile activity of the human colon, with both perfused and solid-state manometric systems. The present paper reviews the current experience in 24 hour recording from the human colon, with a primary emphasis on the more forceful propulsive contractile activity associated with the so called mass movements.     

Effects of Octreotide on Manometric Variables in Patients with Neuropathic Abnormalities of the Small Bowel

At present, there are few therapeutic options inpatients with chronic intestinal dysmotilities.Octreotide, a long-acting somatostatin analog, hasrecently been shown to be a potentially useful drug in this setting, being able to start activityfronts (AF) in the small bowel in both healthy subjectsand patients with intestinal motor disorders. We studiedthe effects of octreotide on manometric variables in 10 patients with chronic uppergastrointestinal symptoms and an intrinsic neuropathicdisorder of the small intestine. Gastrointestinalmanometry was carried out for 6 hr during fasting and 2hr after a standard 605-kcal mixed meal. Thereafteroctreotide, 50 g subcutaneously was administered andthe recording session continued for a further hour.Analysis of the tracings during fasting showed that 44% of the AF were abnormal; octreotidesignificantly increased the hourly number of AF (2± 0.26 vs 0.67 ± 0.14, P < 0.0001) andtheir duration (8.33 ± 1.3 vs 6.12 ± 0.34min, P < 0.05) with respect to the baseline (fasting) period, and the propagation velocityalso significantly slowed (3.4 ± 0.4 vs 11± 0.6 cm/min, P < 0.05). After the drug, 80%of patients displayed two AF and 10% more than two AF;the first AF after octreotide was always abnormally propagated. Analmost complete inhibition of small bowel postprandialcontractile activity was observed in 80% of patients,and the remaining 20% showed decreases. In three subjects, octreotide injection evoked theappearance of pylorospasm. From these results weconclude that octreotide could be of some benefit inpatients with neuropathic disorders of the small bowel,although it remains to be established whether it is mostuseful in patients with more severe conditions,characterized by the complete absence of AF. Theappearance of pylorospasm may contribute to the delayedgastric emptying observed after the drug isadministered.     

Pneumococcal vaccination in celiac disease

Introduction: Celiac disease (CD) is an immune-mediated disorder associated with gluten exposure in genetically predisposed subjects.

Areas covered: Infectious disease is one of the causes of morbidity and mortality in CD patients. Invasive streptococcus pneumoniae (pneumococcus) is a particularly dangerous morbid condition in both the general population and celiac patients. Pneumococcal vaccination is the most effective means for its prevention.

Expert opinion: In CD, evaluation of spleen function should be useful to select patients who may benefit from vaccination to reduce the risk of pneumococcal disease. Different strategies could be employed: physicians could search for signs of hyposplenism on peripheral blood smear or abdominal ultrasound. However, the best strategy to identify which patients will benefit from pneumococcal vaccination has not yet been defined.     

Use of polyethylene glycol solution in slow transit constipation

Patients with long-standing functional slow-transit constipation were treated with low daily doses of polyethylene glycol solutions. Bowel frequency, stool consistency and colonic transit time improved markedly during the treatment. No relevant side-effects were reported during the study period.     

Dynamic imaging of the normal pelvic floor

Purpose: To provide quantitative data by a modern cross-sectional imaging technique (CT) for defining normal physiological values of pelvic floor structures. Patients and methods: Twenty seven subjects, 7 males, 20 females, aged 20 – 75 yrs (mean 46.3±5 yrs) without pelvic floor or defecation dysfunction underwent Direct Coronal (DC) CT scanning of the pelvis with the patient seated instead of lying. Scans obtained at rest and on straining were compared by bony landmarks. Three anatomical compartments, i. e. anterior, middle and posterior, were identified by two planes drawn tangential to the ischial for-amina and the ischial tuberosities, respectively. Measurements of (1) Levator ani muscle length (mm); (2) Levator-anal angle (degrees); (3) Rectal floor-to-ischial line distance (mm) and (4) Supra/Infralevator spaces (square cm) were independently performed twice by two radiologists. The statistical analysis included calculation of intra and interobserver agreement (correlation coefficient). The differences between the means of the resting and straining values from each compartment (Student's t test) and the correlation between parameters (Pearson's coefficient) to evaluate whether resting values allowed a prediction of those on straining were determined. Results: DC scans of diagnostic quality were obtained in all but two patients (92.5%). Both intra- and interobserver agreement indices were always greater than 80% (except for a 0.63 value by one observer obtained in the infralevator space from the anterior compartment at rest). A significant difference between the resting and straining values of all parameters was noted in the three compartments. At rest the levator ani muscle length was significantly shorter and the supralevator space smaller in the posterior compartment (48.3±7.9 mm vs 48.8±7 mm vs 42.6±9.4 mm, P<0.05 and 70.6±cm² vs 66.9±11.5 cm² vs 27.2±4.8 cm², P<0.01 anterior, middle and posterior respectively). On straining, these two parameters increased by +42% and +17.8%, respectively, in the same compartment, while the most pronounced variation of the infralevator space occurred in the middle compartment (–51.1%). The increase in the supralevator space correlated with a decrease in the rectal floor-to-ischial line distance and widening of the levator-anal angle (r = –0.64, P<0.01 and 0.48, P<0.05, respectively). A close correlation between resting and straining values was observed in all parameters, especially in the supralevator space in the three compartments (r = 0.82, 0.93 and 0.88, P<0.01). Conclusions: Direct Coronal CT scanning showed that on straining the posterior component of the levator ani muscle, i. e. the coccygeus muscle, undergoes ``physiological overstretching' and the supralevator space acts as a ``compliant cavity', whose behaviour can be predicted at rest.

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Résumé. Buts: Etablir des données quantitatives à l'aide d'une technique d'imagerie axiale moderne (CT) afin de définir des valeurs physiologiques normales des struc-tures pelviennes. Matériel et méthode: Vingt-sept sujets, 7 hommes et 20 femmes, agés de 20 à 75 ans (moyenne 46,3±5 ans) ne présentant pas de dysfonction du plancher pelvien ou de la défécation ont été soumis à un CT-Scan avec des coupes frontales directes du pelvis, le patient étant en position assise au lieu de coucher. Les coupes ont été obtenues au repos et en effort d'exonération en utilisant des repères osseux identiques. Trois compartiments anatomiques ont été identifiés, l'antérieur, le moyen et le postérieur, à l'aide de deux plans tracés tangentiellement ou trou ischiatique et à la tubérosité ischiatique respectivement. Des mesures de (1), la longueur du releveur de l'anus (mm), (2) l'angle en degré du releveur de l'anus, (3), la distance en mm du plancher rectal aligne la ligne ischiatique et (4) la surface en cm² des espaces supra- et infralévatoriens ont été réalisés indépendamment par deux radiologues à deux reprises. Des analyses statistiques ont inclus le calcul de l'agrément intra- et inter-observateur (coefficient de corrélation). Les différences entre les valeurs au repos et à l'effort de chacun des compartiments (le test T de Student) et la corrélation entre les différents paramètres (le coefficient de Pearson) ont été déterminées pour évaluer si les valeurs de repos permettent une prédiction de ceux obtenus en phase d'effort. Résultats: Des coupes coronales permettant un diagnostic de qualité ont été obtenues au CT-Scan chez tous les patients à l'exception de deux (92,5%). La corrélation intra- et inter-observateurs a montré des indices toujours supérieurs à 80% (à l'exception d'une valeur de 0,63 chez un observateur lors de la mesure de l'espace infralévatorien dans le compartiment antérieur au repos). Une différence significative a été obtenue pour tous les paramètres mesurés au repos et à l'effort dans les trois compartiments. Au repos, la longueur du muscle releveur était significativement plus courte et l'espace supralévatorien plus petit dans le compartiment postérieur (48,3±7,9 mm vs 48,8±7 mm vs 42,6±9,4 mm, P<0.05 et 70,6±cm² vs 66,9±11,5 cm² vs 27,2±4,8 cm², P<0.01 dans l'espace antérieur moyen et postérieur respectivement). A l'effort, ces deux paramètres augmentent de plus 42% et plus 17,8% dans un même compartiment alors que la variation la plus importante survient dans l'espace infralévatorien dans le compartiment moyen (–51,1%). L'augmentation de l'espace supralévatorien est corrélée avec une diminution de la distance entre le plancher rectal et la ligne ischiatique et un élargissement de l'angle anolévatorien (r=–0,64, P<0,01 et 0,48 P<0,05 respectivement). Une corrélation étroite a été observée au repos et a l'effort pour tous les paramètres en particulier dans l'espace supralévatorien au niveau des trois compartiments (r=0,82, 0,93 et 0,88, P<0,01). Conclusion: Des coupes coronales au CT-Scan montrent que lors de l'effort d'exonération, le releveur de l'anus, c'est-à-dire le muscle coccygien subit au niveau du compartiment postérieur une élongation physiologique et que l'espace supralévatorien agit comme une cavité d'expansion dont le comportement peut être prédit au repos.

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Accepted: 12 December 1996     

Efficiency of different criteria for selecting pharmacokinetic multiexponential equations

Several statistical and empirical approaches have been proposed to select the multiexponential equation that best describes the time course of the plasma concentration of a drug. Recently, a new criterion (Ip) has been proposed according to which the model that best interprets a set of experimental data points is the one with the smallest area between the approximate confidence limits of estimated plasma concentration. We used large Montecarlo simulations to compare the ability of different selection criteria to select the correct model from data generated with an independent, normally distributed random error. The new criterion (Ip), Akaike's information criterion, the Schwartz test, and the F ratio test were studied. In this situation, the correct model was known and the performances of different selecting methods were assessed by examining their sensitivity to the number of exponential terms, the number of data points, and the size of the exponents in the true model. Mono-, bi-, and triexponential equations were studied. Overall mean percentages of right identification were 98.1 per cent for the new index, 82.8 per cent for Akaike's information criterion, 89.5 per cent for the Schwartz test, and 97.7 per cent for the F ratio test. The Akaike and Schwartz tests were not as efficient as the other tests with few (8-10) data points. The Ip and the F test raise the percentages of right identification of the model when the hybrid elimination rate macroconstants differ by at least a factor of four.(ABSTRACT TRUNCATED AT 250 WORDS)