Calcitonin gene-related peptide in viscerosensitive response to colorectal distension in rats

The role of calcitonin gene-related peptide (CGRP) on colorectal distension-induced visceral pain was investigated in conscious rats. Intracolonic administration of acetic acid (0.6%) resulted in a significantly increased number of abdominal contractions in response to colorectal balloon distension from 5.8 +/- 1.2 in controls to 16.6 +/- 1.0 in acetic acid-treated animals (P < 0.05), evidencing sensitization of visceral afferent pathways and subsequently visceral hyperalgesia. This sensitization phenomenon was not observed in animals previously treated with systemic capsaicin. Likewise, in animals not treated with capsaicin, use of an intravenous antagonist for CGRP [human CGRP-(8-37)], completely reversed the sensitizing effects of acetic acid. Furthermore, intravenous administration of CGRP dose dependently increased the number of abdominal contractions in response to colorectal distension from 3.0 +/- 1.1 (CGRP 250 ng) to 17.0 +/- 1.2 (CGRP 500 ng, P < 0.05), as previously observed in acetic acid-treated animals. Finally, intrathecal administration of hCGRP-(8-37) (mid-lumbar) also resulted in a total dose-dependent reversal of CGRP (500 ng) or acetic acid-induced visceral hypersensitivity. These results demonstrate that CGRP plays a major role in this model of visceral afferent nerve sensitization from gastrointestinal origin.

Anal sensitivity test: what does it measure and do we need it? Cause or derivative of anorectal complaints

PURPOSE

This study was undertaken to determine the anal sensitivity in controls and in different patient groups and to establish factors that determine anal sensitivity.

METHODS

Anorectal function tests were performed in 387 patients with different anorectal diseases. Anal sensitivity was measured in 36 controls. Anal sensitivity was measured by means of mucosal electrosensitivity (MES) using a catheter with two electrodes placed in the anal canal. A constant current (square wave stimuli 100 microsec, pulses per second) was increased stepwise from 1 to 20 mAmp until the threshold sensation was reached. Other tests used were anal manometry (maximum basal pressure, maximum squeeze pressure, rectal compliance (maximum rectal volume and pressure), endosonography (submucosal thickness), defects and thickness of internal and external sphincter), electromyography (maximum contraction pattern, Grade 1 (solitary contractions) to Grade 4 (interference pattern)), and pudendal nerve terminal motor latency. Multiple regression analysis was performed. It was postulated that age, local conditions (anal scars, anal fissures, hemorrhoids, mucosal prolapse, proctitis, sphincter thickness and defects, and submucosal thickness), and neurologic factors could influence anal sensitivity.

RESULTS

Controls had an MES of 3.4 +/- 1.7. MES was significantly increased compared with controls in patients with fecal incontinence, soiling, hemorrhoids, mucosal prolapse, constipation, anal scars, anal surgery, and sphincter defects; patients with fecal incontinence had the highest MES (6.7 +/- 4.3; P < 0.0001). Patients with anal fissures and proctitis showed no differences compared with controls. MES correlated significantly with age (R = 0.29), maximum basal pressure (R = -0.29), maximum squeeze pressure (R = -0.32), submucosal thickness (R = 0.19), maximum contraction pattern (R = -0.39), single-fiber electromyography (R = 0.39), and maximum rectal volume and pressure (0.14). Multiple regression analysis showed that age, internal sphincter defects, and submucosal thickness significantly influenced anal sensitivity, but explained only 10 percent of the variance.

CONCLUSION

Anal sensitivity is diminished in all patients with anorectal diseases except for anal fissures and proctitis. There are correlations with other anorectal function tests. Anal sensitivity is determined for 10 percent by age, internal sphincter defects, and thickness of the submucosa. Anal sensitivity measurement, therefore, has limited clinical value and should be used in conjunction with other tests in a research setting.

K-ras gene mutations in normal colorectal tissues from K-ras mutation-positive colorectal cancer patients

K-ras gene mutations have been reported as early events in colorectal tumorigenesis, but their role in tumor initiation and development is still unclear. To analyze and compare K-ras mutational patterns between colorectal tissues at different stages of tumor progression in individual patients, 65 colorectal tissue samples, including carcinoma, adenoma, histologically normal mucosa, submucosal muscularis propria, and histologically normal mucosa distant from tumor, were obtained from 13 patients with colorectal cancer. In addition, normal mucosal tissues obtained from four normal individuals were analyzed. Each of the 13 tumors was shown previously to harbor a mutation in either codon 12 or 13 of the K-ras gene by direct sequencing. These tissues were reanalyzed, using the recently established mutant allele enrichment + denaturing gradient gel electrophoresis method, which can detect one mutant allele in 10(4)-10(5) normal alleles, thus allowing for the analysis of infrequent cells bearing mutations against the background of wild-type cells. No K-ras codon 12 mutation was detected by this method in the histologically normal mucosal tissues sampled at the margin of resection distant from the tumor or in those obtained from four normal individuals. On the other hand, these mutations were detected in 9 of 10 adenoma and 6 of 10 mucosa samples from 10 patients with known K-ras codon 12 mutations, and also in 2 of 3 carcinoma, 2 of 3 adenoma, and 1 of 3 mucosa samples obtained from 3 patients with known K-ras codon 13 mutations. Thus, K-ras codon 12 mutations were found to occur with a high frequency (53.8%) in histologically normal mucosa adjacent to tumors of patients with K-ras mutation-positive colorectal cancer, suggesting that they may be useful biomarkers for early detection of colorectal cancer. Furthermore, multiple K-ras mutations were found in tissues of nearly half of the 13 patients, indicating that distinct evolutionary subclones may be involved in the development of tumor in some patients with colorectal cancer.

Role of nitric oxide in relaxation of the longitudinal layer of rectal smooth muscle

PURPOSE

This study was designed to investigate the role of nitric oxide in neurogenic relaxation of the longitudinal layer of human rectal smooth muscle.

METHODS

Tissue was obtained from the mid rectum of patients undergoing anterior resection for carcinoma. Adjacent strips of longitudinal muscle were dissected and mounted in organ baths for isometric tension recording. In preliminary experiments to determine the response of strips to cholinergic, adrenergic, and potential excitatory agonists, strips were superfused with standard Krebs solution (37 +/- 0.5 degrees C; pH, 7.4 +/- 0.05). Investigation of inhibitory, nonadrenergic noncholinergic responses required the addition of 3 x 10(-6) M histamine to induce reproducible and stable tension for five-minute "test" periods, during which electrical field stimulation (EFS) and additional drugs were applied. In these experiments, strips were superfused with Krebs solution that contained atropine sulfate (3 x 10(-6) M) and guanethidine (3 x 10(-6) M).

RESULTS

The response to cholinergic and adrenergic agonists was typical of nonsphincter specialized gastrointestinal smooth muscle. EFS elicited frequency-dependent, neurogenic (tetrodotoxin-sensitive) relaxations of precontracted strips, which were reduced in dose-dependent fashion by addition of N omega-nitro-L-arginine and restored by addition of 3 x 10(-4) M L-arginine but not by D-arginine. Addition of exogenous nitric oxide (sodium nitroprusside) mimicked the relaxant response induced by EFS.

CONCLUSION

Smooth muscle from the longitudinal layer of human rectum receives an intrinsic inhibitory innervation mediated by nitric oxide.

Manometric evaluation of defecation disorders: Part II. Fecal incontinence

Fecal incontinence is a silent affliction that often leads to self-imposed ostracism. For many years, a lack of understanding regarding its pathophysiology and a lack of empathy among many physicians has bedeviled this problem. However, during the last two decades, remarkable strides have been made, both in the evaluation and in the treatment of incontinence. These advances stem from the ability to perform a detailed and comprehensive assessment of anorectal physiology. Anorectal manometry has spearheaded this renaissance. Manometry is not a single test but consists of a series of measurements that include an assessment of anal sphincter function, rectal sensation, rectoanal reflexes, and rectal compliance. Electrophysiological assessments such as pudendal nerve terminal latency can provide additional information regarding neuromuscular integrity. Newer techniques such as vectography, saline continence test, impedance planimetry, and prolonged ambulatory anorectal manometry have added a new dimension to the overall assessment. Radiological tests such as defecography and anal endosonography can provide complimentary information. These tests of anorectal function have advanced immensely our understanding of the pathophysiological mechanisms that are responsible for fecal incontinence. Equipped with sound objective information, today, it is possible to treat most incontinent patients with novel treatments that include medical, biofeedback, or surgical therapies. This is the second article in a two-part evaluation of defecation disorders that discusses the manometric evaluation of fecal incontinence.

Rectal distention-induced colonic net water secretion in rats involves tachykinins, capsaicin sensory, and vagus nerves

BACKGROUND & AIMS

Distention of the intestine induces neural anion secretion in vitro. Both substance P and neurokinin A modify water and ion transport in vivo. This study investigated in vivo (1) the effect of rectal distention (RD) on proximal colonic net water flux, (2) the role of tachykinins, and muscarinic and nicotinic connections, and (3) the influence of capsaicin-sensitive nerves and vagotomy in this effect.

METHODS

In anesthetized rats, colonic loops were infused with [14C]polyethylene glycol 4000 Ringer's buffer. Net water flux was calculated according to 14C activity in the effluent collected. RD was performed by inflation of a balloon (2 mL) in the rectum.

RESULTS

RD induced a colonic net water hypersecretion. This effect was blocked by previous systemic capsaicin, vagotomy, atropine, and hexamethonium treatment. Both neurokinin 1 (NK1) (SR-140,333; 1 mg/kg) and NK2 (MEN-10,627; 150 microg/kg) antagonists administered intraperitoneally suppressed the RD-hypersecretory effect, whereas NK2 (MEN-10,627; 1.5 microg/kg) and NK3 (SR-142,801; 0.01 mg/kg) antagonists are active when injected intracerebroventricularly.

CONCLUSIONS

In vivo, RD induces colonic net water secretion in rats, involving capsaicin-sensitive innervation and vagal nerves. This effect involves tachykininergic pathways at both peripheral and central levels.

Defecation disorders and the role of defecography

This continuing education article discusses abnormalities of defecation and the physical mechanisms by which these abnormalities occur. The article also describes the role of defecography and other imaging techniques used to diagnose abnormalities of defecation.

Effects of transmural field stimulation in isolated smooth muscle of human rectum and internal anal sphincter

Smooth muscle preparations from the circular muscle layer of the most distal rectum and the proximal and distal human internal anal sphincter (IAS) mounted in organ baths to record isometric tension developed spontaneous tension. Transmural electrical field stimulation (TMS) induced frequency- and impulse duration-dependent relaxations sensitive to tetrodotoxin in the stimulation range of 0.5-40 Hz and 0.04-0.6 ms. Poststimulus contractions were most frequent and prominent in rectal preparations. Maximal relaxations were comparable in the three locations and were achieved at 10 Hz and 0.4 ms. The frequency inducing half-maximal response was lower in rectal strips compared with IAS. Phentolamine (10-(6) M) enhanced relaxations and diminished off-contractions at 40 Hz in distal IAS. N omega-nitro-L-arginine (L-NNA) concentration dependently inhibited both relaxations and off-contractions (10 Hz, 0.4 ms). The pD2 values (-log EC50) of L-NNA were lower in rectal muscle compared with those in IAS. L-Arginine (10-(4) M) inhibited the blocking effect of L-NNA. In one-half of the preparations, L-NNA reversed the relaxations to duration contractions (15-40 Hz), which were inhibited by atropine in rectal preparations and by phentolamine in IAS. In conclusion, excitatory innervation of the IAS is alpha-adrenergic and cholinergic in the rectum. A product of the L-arginine-nitric oxide pathway mediates the TMS-induced inhibition of the muscle and is also involved in poststimulus contractions.

Rectal response of cardiac origin in the cat: involvement of nitric oxide and acetylcholine

Local application of nicotine over the surface of the left ventricle and also occlusion of the left anterior descending coronary artery in the lightly anaesthetised, open-chested, artificially ventilated cat resulted a biphasic rectal movement--initial relaxation followed by sustained contraction. However, distension of the atrial appendage did not evoke any change in rectal motility, indicating the non-involvement of atrial volume receptors in initiating this rectal response of cardiac origin. The relaxation phase of this response was not abolished by pretreatment with atropine or with phentolamine or propranolol but was abolished by the nitric oxide inhibitor, N(G)-nitro-L-arginine (LNNA), and this blockade of the relaxation phase by LNNA was reversed by L-arginine. The contraction phase, however, was abolished by atropine. From these observations it is clear that the relaxation phase of the rectal response to coronary occlusion or epicardial nicotine is mediated through neither cholinergic nor adrenergic pathways but through the release of nitric oxide whereas the contraction phase of such a cardio-rectal response is mediated through the release of the neurotransmitter, acetylcholine.

High body temperature induces micronuclei in mouse bone marrow

The mouse micronucleus test was conducted to investigate the effect of high body temperature on micronucleus induction. Group of 10 male ddY mice were exposed to 30 degrees C for 1, 3 or 6 h, 37 degrees C for 0.5, 1, 2, 3 or 4 h, and 40 degrees C for 1 or 2 h. Bone marrow cells were sampled 24 h after heat exposure. Exposure of mice to 37 degrees C for 3 or 4 h and 40 degrees C for 1 or 2 h raised body temperature to approximately 40.5 degrees C and produced statistically significant increases in micronucleated polychromatic erythrocyte frequencies (8.1 +/- 4.5, 6.0 +/- 2.1, 5.3 +/- 3.3, 7.5 +/- 2.9%, respectively; control frequencies, 2.0 +/- 1.1%). In addition, about 25% of the induced micronuclei were relatively large (diameter of micronucleus > or = 1/4 diameter of cytoplasm). These results suggest that body temperatures of 39.5 degrees C or higher for more than 30 min induce micronuclei in bone marrow cells, and one possible mechanism is disturbance of the mitotic apparatus.

Is the rectum a conduit or storage organ?

The rectum is claimed to be a conduit; as it receives the stools, the rectoanal inhibitory reflex is evoked and defecation occurs. However, in many healthy subjects, stools could be palpated in the rectum by digital rectal examination (DRE) without the subject feeling the desire to defecate. The purpose of this communication is to study whether the rectum is a conduit or a storage organ. The study comprised 48 healthy volunteers (mean age 38.4 +/- 15.8 SD years; 30 men, 18 women). Number of stools per week was recorded and DRE was carried out followed by air enema radiography. The subjects had a normal stool frequency of 7.8 +/- 1.4 per week. Most of them last defecated a mean of 6.2 +/- 3.4 hours prior to the test. Stools were palpated in the lower rectum by DRE in 31/48 subjects and by radiography in 12/16. DRE correlated with radiologic examination in 9/12 subjects; in 3 of them, DRE revealed an empty rectum while radiography showed stools in the upper rectum. The 17 subjects with an empty rectum had their last defecation 5.2 +/- 3.6 hours before DRE, and the 31 subjects with palpable stools 15.6 +/- 12.9 hours. In conclusion, the rectum might be considered not simply as a conduit for stools but also as a storage organ. This occurs when it receives from the sigmoid colon an amount of stools too small to evoke the defecation reflex, or when this reflex is neglected due to unfavorable circumstances of defecation.

Anorectal manometry in women with urinary stress incontinence

OBJECTIVE

The aims of this prospective study were to determine the bowel function and the anal sphincter function in women with urinary stress incontinence by means of anorectal manometry and to look for manometric variables which could predict the development of surgery demanding genital prolapse after Burch colposuspension.

SUBJECTS

During 1991-1992 twenty-one women with urodynamically proven genuine stress urinary incontinence were consecutively operated upon with the Burch colposuspension. No concomitant prolapse repair surgery was performed. Forty-four healthy subjects without anorectal disorders were used as controls.

METHODS

All subjects were investigated with anorectal manometry using a microtransducer catheter. A standardized questionnaire concerning bowel function was answered at interview. The manometry and interview were performed preoperatively and one year after the Burch colposuspension.

RESULTS

According to the preoperative questionnaire, fecal incontinence was found in 62%, constipation in 38% and straining at defecation in 71%. There were no significant differences in any of the manometric parameters between the preoperative and the one-year postoperative assessment. The patients with prolapse operations after the colposuspension (n = 6) had a significantly lower anal squeeze pressure area (p = 0.029) preoperatively compared to the control subjects. The patients without prolapse surgery (n = 15) did not differ in manometric parameters from the control subjects.

CONCLUSION

Bowel dysfunction is common in women with stress urinary incontinence. The women with low anal squeeze pressure area preoperatively are at risk for the development of genital prolapse after Burch colposuspension.

Continuous versus intermittent thermodilution cardiac output measurement during orthotopic liver transplantation

We evaluated intermittent and continuous thermodilution cardiac output data in 12 patients undergoing orthotopic liver transplantation. Measurements were performed at 16 predefined time points between induction of anaesthesia and 3 h after reperfusion of the liver graft. Cardiac output measurements yielded 192 data pairs (intermittent cardiac output range: 1.8-18.9 l.min-1, continuous cardiac output range: 3.3-20.0 l.min-1). During most of the procedure the correlation between intermittent and continuous cardiac output measurements was significant (r = 0.87, p < 0.0001), accompanied with a bias of -0.240 l.min-1 and a degree of precision of 1.789 l.min-1 (< 10.0 l.min-1:1.137 l.min-1, > or = 10.0 l.min-1:2.220 l.min-1). However, in the early phases after caval clamping and after reperfusion, accuracy was not acceptable. Only during these phases did the difference between the mean values of pulmonary artery blood temperature and rectal temperature increase (after caval clamping) or decrease (after reperfusion). In conclusion, despite acceptable levels of accuracy and precision between intermittent and continuous cardiac output measurement under stable conditions, both methods showed markedly decreased accuracy and precision in the early phases after caval clamping and after reperfusion, possibly owing to increased thermal noise.

Age and anorectal sensibility in normal women

BACKGROUND

Our aim was to study associations between age and anorectal sensibility in healthy women.

METHODS

Seventy-five women, with a mean age of 50 (range, 20-83) years, and mean parity of 2 (range, 0-4), were studied. Anal mucosa electrosensitivity (AME) was measured 1 and 2 cm from the anal verge. Rectal sensibility was also measured (minimum perceived volume (MPV), desire to defaecate (DD), and urgency (U)). Associations between anorectal sensibility and age were corrected for parity by using multiple regression analysis.

RESULTS

Threshold values of AME increased with age (P = 0.03) (1 cm) and P = 0.01 (2 cm)). Rectal sensibility threshold values were also positively associated with age (MPV, P = 0.003; DD, P = 0.04; and U, P = 0.06). Changes in AME were greater after menopause, whereas associations between rectal sensibility and age seemed linear.

CONCLUSION

Impairment of the anorectal sensibility appears to be part of the normal ageing process, thus increasing the risk of faecal incontinence in old women.

Physiology of rectal sensations: a mathematic approach

PURPOSE

The first awareness of balloon inflation (first sensation (FS)), flatus sensation (constant sensation (CS)), urge to defecate (UD), and maximum tolerated threshold (MTT) are the four commonly evaluated rectal sensations. The traditional view that these sensations are attributable to pelvic floor mechanoreceptor stimulation is challenged by current evidence in favor of rectal wall mechanoreceptors. The aim of this study was to determine the physiology of these sensations, using a dynamic mathematic model of the rectum.

METHODS

In a group of 15 healthy adult volunteers (11 female and 4 male; median age, 51.5 (range, 31-74) years), the polynomial behavior of the two smooth muscle components of a dynamic mathematic model of the rectum was analyzed to find strain levels of smooth muscle activity in relation to corresponding strain levels of each of the four "rectal" sensations.

RESULTS

Longitudinal and circular smooth muscle relaxation appeared to be the rate detection and signaling mechanisms, respectively. The latter triggered sensations of CS, UD, and MTT. FS was an anal canal sensation, related temporally with onset of rectoanal inhibitory reflex. In vitro validation of the model suggested MTT to be a physiologic protective mechanism associated probably with tetanic smooth muscle contraction.

CONCLUSIONS

Evaluation of rectal sensations should be confined to CS and UD because MTT is painful and does not contribute any additional information, and FS is not a true rectal phenomenon.

Test-retest repeatability of anorectal physiology tests in healthy volunteers

PURPOSE

This study was undertaken to evaluate repeatability of tests of anorectal function in 58 healthy female volunteers, mean age 50 (range, 45-57) years.

METHODS

Participants were studied on two separate occasions by one investigator in one laboratory using the same equipment.

RESULTS

Mean difference for perineal position was 0.1 (95 percent confidence interval, -0.1-0.3) cm, and for perineal descent it was 0.02 (-0.2-0.3) cm. For anal mucosa electrosensitivity, mean difference was -0.1 (-0.4-0.1) mA, for maximum anal resting pressure it was 2.2 (-3.5-7.8) cm H2O, for maximum anal squeeze pressure it was -1 (-6.5-4.5) cm H2O, and for pudendal nerve terminal motor latency it was 0.04 (-0.02-0.09) msec. Coefficients of variation varied from 8 percent for pudendal nerve terminal motor latency to 49 percent for perineal descent.

CONCLUSION

There was no systematic variation in repeated measurements for any of the parameters studied; however, the nonsystematic variation was generally large.

Adaptation of the rectal wall to distension in children with constipation

OBJECTIVE

To determine whether there is significant change in the tension-length relationship of the digestive smooth-muscle mechanical function in constipation in children and to examine a new method of analysis of the mechanical properties of the rectal wall.

DESIGN

Case-control study.

PARTICIPANTS

Thirty children with constipation and 30 control children who did not have constipation.

INTERVENTION

Rapid distension of the rectal wall by inflation of a rectal balloon with air.

MAIN OUTCOME MEASURES

The in vivo rectal pressure-volume P[t,V] curve was determined according to the quasilinear viscoelasticity law. The recorded pressure was defined as the product of 2 functions: the elastic response P0[V] and the reduced relaxation function G[t], a normalized function of time such that P[t,V] = P0[V] x G[t]. Analysis of variance with repeated measures and modelling (linear for P0[V] and exponential plus constant term for G[t] were used for data analysis.

RESULTS

The quasilinear viscoelastic law can be applied to the in vivo determination of the mechanical properties of the rectal wall in controls and in children with constipation. The elastic response was similar in the 2 groups. The reduced relaxation function was significantly different between the 2 groups, with the absence of an asymptotic value in the group with constipation (p < 0.01).

CONCLUSION

Distension of the rectal wall with the use of an air-inflated balloon, with this type of interpretation according to the viscoelastic law, is useful in the analysis of chronic constipation.

[The efficiency of alprazolam for seasonal affective disorder (SAD, autumn/winter type)]

We experienced a 49 years old female SAD patient who showed a good response the next day after alprazolam 1.2 mg administration. The back ground EEG of the patient showed a abnormal EEG with slow waves. The personality was colored with historical features. The nadir of body core temperature from rectum slightly delayed in remission phase compared with depressive phase. The patient became hypomania and calmed down gradually. Alprazolam treatment is seemed to be available for SAD patients.

Effects of loperamide oxide on gastrointestinal transit time and anorectal function in patients with chronic diarrhoea and faecal incontinence

BACKGROUND

Loperamide improves anorectal function in patients with chronic diarrhoea. We wished to investigate whether the prodrug loperamide oxide has similar effects.

METHODS

Eleven patients with chronic diarrhoea and faecal incontinence participated in a randomized, placebo-controlled, double-blind, crossover study of the effects of loperamide oxide (4 mg twice daily for 1 week).

RESULTS

Loperamide oxide reduced wet stool weight and improved the patients' ratings of symptoms. Mouth-to-caecum transit time was not altered, but whole-gut transit time was prolonged. There were limited effects on anorectal function, but the mean minimum basal pressure mainly contributed by the internal anal sphincter (IAS) was increased, as was the mean volume infused before leakage occurred in the saline continence test.

CONCLUSION

Loperamide oxide is effective in the treatment of diarrhoea with faecal incontinence; normalization of colon transit time and an increase in the tone of the IAS seem to be the main determinants of efficacy.

Dynamic multi-planar EPI of the urinary bladder during voiding with simultaneous detrusor pressure measurement

Magnetic resonance imaging gives high quality images of the urinary bladder with excellent contrast. We report here the first application of dynamic, multi-slice, echo planar imaging to a study of urinary bladder emptying. Changes in urinary bladder volumes and rates of urine expulsion from the bladder have been measured simultaneously with bladder pressure. The method shows promise for clinical applications involving compromised bladder function, for reappraising bladder contraction strength-volume relationships, and for investigating the rate of change of length, three-dimensional shape, and wall tension in different parts of the bladder during micturition.

The discovery and a study of the adventitia rectalis, a fibrous layer of the rectal wall

In sacral anoplasty, it is frequently found that an outer layer of the rectal wall, which resembles the structure of the taenia bands of the colon, limits the elasticity of the rectum making it different from the small intestine, hence preventing the rectal stump from being advanced to reach the perineum. Results of autopsy studies on 40 human babies and 40 dogs showed that a special collagenous fibrous layer called adventitia rectalis was found to limit the free expansion of the rectal wall. This was responsible for keeping the rectum a straight tubular shape with a fixed volume. This tissue plays an important role in bowel movement by defining a threshold of intrarectal pressure in the bowel reflex of defecation and by transmitting the expulsive force from the abdomen above down to the anal opening. This discovery may explain why (1) in Hirschsprung's disease, the preservation of the rectal wall in Soave's or Rehbein's procedure or partial preservation in Duhamel's operation will preserve better bowel function; (2) in atresia ani, rectal tapering results in better bowel control than rectal pouch amputation; and (3) in sacral anoplasty, multiple releasing incisions of adventitia rectalis at different levels will lengthen the rectal stump to about double its original length to reach the perineal incision, and the divided fibers will soon regenerate.

Incremental elastic modulus--a challenge to compliance

Rectal compliance has theoretical and practical drawbacks resulting in wide variation in the reported normal values. Slope of stress-strain relation, a measure of rectal wall stiffness (Incremental elastic modulus; IEM) may be an effective alternative. The aim of this study was to compare IEM with rectal compliance during ramp inflation. In a group of 15 normal adults [Median age 51.5 years (range 31 to 74); 11 female and 4 male], these parameters were assessed at three rates of inflation, using a proctometrogram-catheter-balloon (PCB) complex and endorectal ultrasound scanner (7 Mhz; B & K) to measure intrarectal pressure and radius respectively. IEM had a linear relation with strain (Slope 33.55; R2 = 0.9815) in contrast to compliance (R2 = 0.0088). Series elastic component (SEC), a measure of passive viscoelasticity, was rate independent elasticity [Slope 1.02 (0.98 to 1.15); P = ns] and a rate dependent viscosity (P = 0.004; One way ANOVA). Both IEM and SEC were reproducible (R = 0.985; P < 0.01). This study emphasises the importance of rectal wall viscoelastic evaluation based on stress and strain rather than compliance.

Main trends in rectal temperature during sleep. Hypnogram and thermogram

Changes in sleep state and night-time body temperature were studied in 13 healthy young men. Temperature data showed serial dependence that was removed when considering three main segments of the thermogram: an initial rapid drop between 60 and 140 min after lights off, followed by a slower decrease to the thermal minimum and a final temperature increase until waking. The first segment was fitted by a two-term function, while the other two segments were fitted by linear regression. Temperature data obtained after fitting these models were stationary and used to calculate the fast Fourier transformation and the cross-correlation functions between the hypnogram and the thermogram of each subject. Attaining stationarity has unmasked short oscillations during sleep and some temperature series showed the presence of ultradian oscillations with a period of 90-100 min. Significant cross-correlations between sleep stages and body temperature were found, and the parameters of the two-term function fitted to the first temperature drop were related to the sign of the correlation and to that time series (sleep or temperature) which preceded the other during the night.