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Ahmed Shafik

Publications and source records attributed to Ahmed Shafik.

At least 73 records · Page 4Linked to original sources
PubMed2004

Diverticular disease: electrophysiologic study and a new concept of pathogenesis.

The cause of diverticular disease (DD) is not exactly known, although colonic motor disorder has been proposed as a factor in the pathogenesis of the condition. We investigated the hypothesis that disordered colonic electrical activity is responsible for the colonic motor dysfunction and the development of DD. The electromyographic (EMG) activity and pressure of the sigmoid colon (SC) were recorded in 36 patients [16 early cases, 20 advanced cases; age (mean +/- SD) 53.3 +/- 5.6 years; 19 women, 17 men] and 22 healthy volunteers. The percutaneous route was used for recording the SC EMG. The healthy volunteers exhibited SC slow waves with a regular rhythm and the same frequency, amplitude, and conduction velocity from the three electrodes in the same subject. The SC basal pressure (7.9 cm H(2)O) was interrupted by bouts of high pressure (26.8 cm H(2)O). The early-DD cases showed slow waves with an irregular rhythm and significantly higher variables ( p < 0.05) than the volunteers. Action potentials followed randomly or were superimposed on the slow waves. The SC basal pressure was significantly higher than that of the volunteers (21.4 cm H(2)O, p < 0.01). Bouts of pressure (58.6 cm H(2)O) coupled with action potentials were recorded. No waves were recorded from 15 of 20 of the advanced-DD patients. In 5 patients, slow waves with an irregular rhythm and lower variables ( p < 0.05) than those of the volunteers were recorded. The basal SC pressure was significantly above normal. Three electrical activity patterns could be identified in DD patients: "tachyrhythmic" in the early-DD patients and "bradyrhythmic" or "silent" in the late-DD patients. These dysrhythmias may result from a disordered colonic pacemaker. The similarity between early DD and the irritable bowel syndrome suggests that DD is an advanced stage of the irritable bowel syndrome; studies are required to investigate this hypothesis further.

Action Potentials↗
PubMed2004

'Objective' assessment of rectal sensation: a novel approach.

Rectal sensation is used as an investigative tool in the diagnosis of anorectal pathology. However, the data obtained are subjective depending on the patient's perception of the sensation. We investigated the hypothesis that sympathetic skin response (SSR) can be used as a tool for objective assessment of the rectal sensation. The SSR was recorded in 24 healthy volunteers (age 37.2 years, 14 men) using a surface electrode applied to the skin of the palmar surface of the subject's hand and a reference electrode to the dorsum of the same hand. The EMG activity of the pelvic floor muscles was registered by a surface electrode fixed to the perineal skin. The subject was asked before and after individual anesthetization of the rectum and palm to report the first rectal and urge sensations during balloon filling of the rectum in increments of 10 ml of saline. Low volume rectal distension effected no sympathetic skin or pelvic floor responses, while larger volumes produced the response. The skin and pelvic floor responses occurred with every rectal sensation and corresponded with the volunteers' subjective perception. Urge suppression was associated with synchronous decrease of skin and pelvic floor responses which disappeared on balloon expulsion. Rectal balloon distension, 20 minutes after individual anesthetization of the rectum or palm produced no palm skin response, which returned however 3 hours later. A novel approach which can objectively define subjective perceptions arising from the rectum has been identified. Rectal sensations produce coordinated sympathetic skin response and pelvic floor activity which seem to be mediated through a reflex which we term the "recto-palmar reflex". Further studies are required to investigate the role of this reflex in defection and sympathetic disorders.

Anal Canal↗
PubMed2004

Vesical pacing: pacing parameters required for normalization of vesical electric activity in patients with overactive bladder.

There are several modalities for the treatment of the overactive bladder (OAB), but the results may not be satisfactory. A recent study has demonstrated that the OAB has a dysrhythmic electric activity that seems to result from a disordered vesical pacemaker. We hypothesized that vesical pacing may correct the irregularities of the vesical electric waves and consequently normalize the vesical contractility. In this communication, we primarily defined the adequate pacing parameters required for correction of the vesical dysrhythmia. 36 patients with OAB were divided into a study group (22; 13 women; mean age 40.2 years) and a control group (14; 8 women; mean age 41.8 years). Ten healthy volunteers (6 women; mean age 39.8 years) were included in the study. Three 28-gauge cardiac pacing electrodes were hooked to the vesical mucosa: one (pacing) to the vault, and two (recording) to the lateral wall. Electric activity at rest and during stimulation of the pacing electrode was recorded in the study group and the healthy volunteers. In the control group, recording was done without pacing. Reproducible regular triphasic SWs were recorded from the 2 electrodes of the healthy volunteers with a similar pattern from the 2 electrodes of each individual subject. The optimal pacing parameters we determined were: an amplitude of 5 mA, a pulse width of 200 ms and a frequency of 20% higher than the frequency of the basal vesical waves. Vesical pacing effected a significant increase of waves' variables. The OAB patients exhibited a "dysrhythmic" wave pattern which was normalized during vesical pacing using the aforementioned pacing parameters. The optimal parameters required for vesical pacing of the dysrhythmic waves of the OAB were determined and succeeded in normalization of the vesical electric activity. Vesical pacing is suggested to be used as a therapeutic tool for the treatment of the OAB.

Adult↗
PubMed2004

Colonic pacing: a therapeutic option for the treatment of constipation due to total colonic inertia.

HYPOTHESIS: The treatment of constipation caused by total colonic inertia is problematic and its results are unsatisfactory. We speculated that colonic pacing would initiate electric activity in the inertial colon and effect rectal evacuation. METHODS: Nine patients with constipation due to total colonic inertia (age range, 39-52 years; 7 women, 2 men) were enrolled in the study. One pacing electrode was applied to each of the 4 potential colonic pacemaker sites, and 2 to 3 temporary recording electrodes were applied distally. A stimulator was embedded subcutaneously in the inguinal area. Home pacing was practiced after patients were trained; the recording electrodes were removed before home pacing was started. RESULTS: Colonic pacing evoked electric waves, which effected defecation in 6 of the 9 patients. Three of these 6 patients had spontaneous defecation after a few months of pacing, and their electrodes and stimulators were removed. In the other 3 of these 6 patients, the pacemakers are still in place and continue to effect rectal evacuation. Colonic pacing did not produce rectal evacuation in 3 patients and is believed to have failed because of an advanced stage of colonic inertia. CONCLUSION: Colonic pacing induced rectal evacuation in 66.6% of the patients with total colonic inertia. No complications were encountered. We suggest that colonic pacing be considered as a new therapeutic option in the treatment of total colonic inertia.

Adult↗
PubMed2004

Identification of interstitial cells of Cajal in human urinary bladder: concept of vesical pacemaker.

OBJECTIVES: To determine whether, given the presence of interstitial cells of Cajal (ICCs) in organs that discharge slow waves, such as the gastrointestinal tract, such cells could also be present in the human urinary bladder (UB) and might exist in great numbers in the bladder dome, constituting the "primary pacemaker" from which slow waves spread to the body of the UB. This hypothesis was based on previous studies that had demonstrated the vesical electric waves starting in the dome and spreading caudad. METHODS: Specimens (0.5 x 0.5 cm) from different vesical locations were obtained from the cystectomized UB of 18 patients (12 men, 6 women, mean age 42.6 +/- 3.8 years) with bladder cancer. Fixed sections were prepared and subjected to c-kit immunohistochemistry. Controls for the antiserum specificity consisted of incubation of the tissue with normal rabbit serum substituted for the primary antiserum. RESULTS: Fusiform, c-kit positive, and ICC-like cells were detected in the vesical muscle layers; they had dendritic processes. They occurred separately or were connected through the dendritic processes to form a cellular network. An accumulation of ICCs surrounded by a connective tissue layer was detected in all the dome specimens. Mast cells occurred in the vesical mucosa and submucosa; they were c-kit positive but had a rounded body with no dendritic processes. CONCLUSIONS: We identified cells in the UB with morphologic and immunologic phenotypes similar to the ICCs of the gut. An accumulation of these cells, detected in the vesical dome, seems to constitute the "primary" vesical pacemaker that initiates the slow waves that spread to the other vesical walls. We believe that a deficiency or absence of these cells may be involved in vesical motility disorders. Additional studies are needed to delineate the role of these cells in UB physiology and pathologic conditions.

Adult↗
PubMed2004

Vesical pacing in patients with overactive bladder: technique and results.

OBJECTIVES: A recent study has demonstrated that the electric activity of the overactive bladder (OAB) is 'dysrhythmic'. The cause was attributed to a disordered vesical pacemaker which discharges these waves. In a subsequent study, the dysrhythmic waves have been 'normalized' by vesical pacing and the optimal parameters which are required to achieve normalization have been defined. We investigated the hypothesis that vesical pacing of the OAB might improve not only the vesical electric activity but also the symptoms. METHODS: Vesical pacing was used in 9 patients (age 39.2 +/- 10.3; 5 women, 4 men) with OAB. Under anesthesia, the pacemaker was implanted in an inguinal subcutaneous pocket and connected to 2 pacing electrodes implanted into the vesical vault. The normalization of the waves was tested by 2 recording electrodes which were temporarily applied to the vesical wall and removed post-testing. The pacemaker was then programmed for home pacing to be activated at given times. RESULTS: Vesical pacing effected normalization of the dysrhythmic electric waves with disappearance of the OAB symptoms in 7 patients and failed in 2. Vesical pacing was abandoned in 3/7 patients after a few months following the spontaneous disappearance of the symptoms. CONCLUSIONS: Vesical pacing has normalized the dysrhythmic electric activity and suppressed the symptoms of the OAB in 77.7% of patients. The pacemaker was removed in 5 patients: 2 failures and 3 after spontaneous waves normalization. No complications were encountered. Vesical pacing is suggested as a treatment for OAB when commonly used therapeutic modalities have failed.

Adult↗
PubMed2004

Do vesical and voided urine have identical compositions?

OBJECTIVE: In view of the concept that the urothelium is a functioning epithelium, we investigated the hypothesis that the composition of urine is modified as it passes through the urethra from the urinary bladder to the exterior. MATERIAL AND METHODS: The study was performed in 22 healthy volunteers (13 males, 9 females; mean age 44.6+/-6.2 years). Vesical and voided urine were collected separately; pH was determined using a pH electrode, osmolality by means of micro-osmometry and electrolytes (Na, K) using flame photometry. RESULTS: Voided urine showed significant increases in pH, osmolality and Na and K concentrations compared to urine contained in the bladder (p < 0.05 for each). Gender and age differences were not significant. CONCLUSIONS: Vesical urine undergoes changes in some of its components during its passage through the urethra. These findings presumably indicate that the urethral urothelium is a functioning epithelium and also that voided and vesical urine are not identical. The study raises the question to what extent is the analysis of voided urine representative of that of vesical urine?

Adult↗
PubMed2004

Electric activity of the colon in irritable bowel syndrome: the 'tachyarrhythmic' electric pattern.

BACKGROUND AND AIM: The etiology of irritable bowel syndrome is unknown. It presents with crampy abdominal pain associated with alternating constipation and diarrhea but with no anatomic abnormality on diagnostic testing. Because the condition is related to motility disturbance, the hypothesis that a disorder of the colonic electromyographic activity is responsible for the colonic motile disorders in irritable bowel syndrome, was investigated. METHODS: The electromyographic activity of the sigmoid colon was recorded transcutaneously in 18 patients with irritable bowel syndrome (49.6 +/- 10.2 years, 12 women) and 14 healthy volunteers (47.2 +/- 9.9 years; eight women) by applying three electrodes to the abdominal skin below the umbilicus. The sigmoid colon pressure was measured by means of a saline-perfused tube connected to a pneumohydraulic capillary infusion system. RESULTS: Slow waves with a regular rhythm were recorded in the healthy volunteers exhibiting the same frequency, amplitude and conduction velocity from all three electrodes. Action potentials (AP) were not registered. The basal sigmoid colon pressure was interrupted by bouts of elevation. In irritable bowel syndrome, the electromyographic rhythm was irregular and the slow wave variables were higher than those of the normal volunteers and were not the same from the three electrodes; occasional AP were also recorded. The sigmoid colon basal pressure was significantly higher, and was interrupted by pressure bouts significantly higher, than those of the volunteers. CONCLUSIONS: Irritable bowel syndrome exhibited a 'tachyarrhythmic' pattern of electromyographic activity with higher slow wave variables than normal and occasional AP. The resulting elevated basal colonic pressure and tone may explain some of the irritable bowel syndrome symptoms. Because diagnostic testing of the irritable bowel syndrome shows no anatomic abnormalities, it is suggested that the cause of irritable bowel syndrome is related to an abnormal focus in one or more of the colonic pacemakers emitting these abnormal waves. However, further studies are required to verify these findings.

Adult↗
PubMed2004

Effect of vesical contraction on the non-sphincteric part of the urethra: recognition of vesicourethral inhibitory reflex.

OBJECTIVES: The effect of vesical contraction on the non-sphincteric part of the urethra has been scarcely addressed in the literature. In this study, the hypothesis that detrusor contraction effects dilatation of the non-sphincteric part of the urethra was investigated. METHODS: Non-sphincteric urethral pressure response to vesical balloon distension with normal saline in increments of 50 mL was recorded in 21 healthy volunteers (mean age 40.7 +/- 10.3 years, 13 men) before and after individual anesthetization of the urethra and urinary bladder. Vesical distension was effected by a 10F balloon-ended catheter introduced into bladder per urethram. Urethral and vesical pressures were measured by means of a two-channel microtip catheter. RESULTS: Small-volume vesical distension effected no significant urethral or vesical pressure changes while distension with 350 and 400 mL of saline produced vesical pressure elevation (P < 0.01) and urethral pressure decrease (P < 0.01). Vesical distension after individual vesical and urethral anesthetization effected no change in the urethral pressure. These results were reproducible. CONCLUSIONS: Dilatation of the non-sphincteric part of the urethra upon vesical contraction is suggested to be mediated through a 'vesicourethral inhibitory reflex' and to facilitate passage of urine through the urethra. The reflex may prove to be of diagnostic significance in micturition disorders.

Adult↗
PubMed2003

The electrovaginogram: study of the vaginal electric activity and its role in the sexual act and disorders.

OBJECTIVES: We investigated the hypothesis that the vagina generates electric waves which effect vaginal contraction during penile thrusting. METHODS: In 24 healthy female volunteers, the electric waves of the vagina were recorded by two electrodes applied to its wall. The vaginal pressure was registered by a manometric tube. The electric waves and vaginal pressure were recorded at rest and on vaginal distension by condom in increments of 10 ml of carbon dioxide. The test was repeated after vaginal anesthetization proximally and distally to the electrodes. RESULTS: Slow waves (SWs) were recorded from the two electrodes with regular rhythm and similar frequency, amplitude and conduction velocity. They were randomly followed or superimposed by action potentials (APs). Vaginal pressure increase was coupled with APs. Large-volume condom distension significantly increased the electric waves' variables and pressure. Upon vaginal anesthetization, the electric waves were recorded proximal but not distal to the anesthetized area. CONCLUSIONS: Electric waves could be recorded from the vagina. They spread caudad. A pacemaker was postulated to exist at the upper vagina evoking these waves. The electric waves seem to be responsible for the vaginal contractile activity. Large-volume vaginal distension effected an increase in the vaginal electric waves and pressure which probably denotes increased vaginal muscle contraction. It appears that penile thrusting during coitus stimulates the vaginal pacemaker which effects an increase in vaginal electric activity and muscle contractility and thus leading to an increase in sexual arousal. The vaginal pacemaker seems to represent the G spot, which is claimed to be a small area of erotic sensitivity in the vagina. The electrovaginogram may act as a diagnostic tool in the investigation of sexual disorders.

Action Potentials↗
PubMed2003

Anorectal motility in patients with achalasia of the esophagus: recognition of an esophago-rectal syndrome.

BACKGROUND: During my study of constipation, I encountered patients who had achalasia of the esophagus (AE) as well. The possibility of an existing relationship between the 2 conditions was studied. METHOD: Investigations to study the anorectal motility in 9 AE patients included: the intestinal transit time, anorectal manometry, rectoanal inhibitory reflex, defecography and electromyography (EMG) of external anal sphincter and levator ani muscle. Anorectal biopsy was done. The study comprised 8 healthy volunteers as controls. RESULTS: 6/9 AE patients had constipation presenting as strainodynia (excessive prolonged straining at stool). Rectocele was present in 4 of them. The 6 constipated patients showed significantly high rectal neck pressure (p < 0.05), absent rectoanal inhibitory reflex and aganglionosis in the anorectal biopsy. The EMG revealed diminished activity in 4 of the 6 constipated patients. The remaining 3 patients with AE had normal anorectal function. Heller's myotomy with Nissen's fundoplication improved the dysphagia, but not the constipation which was, however, relieved after performance of anorectal myectomy. CONCLUSION: The high incidence of constipation with AE postulates a relationship between the 2 conditions. Both have the same pathologic lesion which is aganglionosis. This study is preliminary and requires further studies on a larger number of patients.

Adult↗
PubMed2003

On the pathogenesis of rectocele: the concept of the rectovaginal pressure gradient.

Coughing or straining evokes reflex bulbocavernosus (BCM) and puborectalis (PRM) muscle contraction, which apparently transforms the vagina into a closed high-pressure cavity. This elevated vaginal pressure counteracts the increased intra-abdominal pressure and the tendency of the uterus to prolapse, and also supports the rectovaginal septum against the high straining-induced intrarectal pressure and possible consequent rectocele (posterior vaginal prolapse) formation. We investigated the hypothesis that a weak BCM and PRM share in the genesis of rectocele by changing the rectovaginal pressure gradient. Twenty-three women with rectocele (mean age 43.2+/-6.6 years) and 12 healthy women volunteers (mean age 41.6+/-6.2 years) were studied. The response of the intrarectal (intra-abdominal) and intravaginal pressure, as well as the EMG activity of the BCM and PRM to straining or coughing, was recorded. In the healthy volunteers the rectal and vaginal pressures showed a significant increase on coughing or straining, with no significant difference between the rectal or vaginal pressures. Also, the BCM and PRM EMG activity exhibited a significant increase. Rectocele patients showed a significantly low resting vaginal pressure. The increase in rectal and vaginal pressure, as well as of the EMG activity of the BCM and PRM on straining or coughing, was significantly lower and the latency of the EMG response was significantly longer than those of the healthy volunteers. A difference in the rectovaginal pressure gradient showing a significant increase in the rectal against the vaginal pressure, particularly on coughing or straining, is suggested to be the basic factor in the genesis of rectocele. This pressure difference appears to be caused by diminished BCM and PRM contractile activity. A disrupted rectovaginal septum is not a prerequisite for rectocele formation, as the septum appears normal in obstructed defecation despite the common occurrence of rectocele. A histopathologic study of the septum in rectocele seems necessary.

Adult↗
PubMed2003

Study of the effect of cervix uteri buffeting on the vaginal musculature with identification of the cervico-vaginal inhibitory reflex.

OBJECTIVES: During penile thrusting, the penis repeatedly buffets the cervix uteri (CU). We investigated the hypothesis that CU stimulation induces a change in the motor activity of the vaginal wall musculature. MATERIALS AND METHODS: The response of the vaginal wall musculature to electrical and mechanical CU stimulation was recorded in 27 healthy women (age 34.8+/-7.3 years). The test was repeated after separate anesthetization of CU and vagina and after normal saline injection. RESULTS: Resting electric activity in the form of slow waves (SWs), followed or superimposed by action potentials (APs), was recorded from two electrodes applied to the vagina. The waves displayed the same frequency, amplitude and conduction velocity from the two electrodes. Electrical or mechanical stimulation of the CU effected disappearance of the electric waves; this response was reproducible. Individual stimulation of the anesthetized CU or vagina did not evoke the response, but saline infiltration did. CONCLUSIONS: CU stimulation resulted in disappearance of the vaginal electric activity which presumably denotes vaginal tone disappearance. Meanwhile, stimulation of the anesthetized CU or vagina did not evoke that response. The data suggested the presence of a reproducible reflex relationship between the CU and vaginal musculature that seems to be mediated through a reflex which we call "cervico-vaginal inhibitory reflex". Disappearance of the vaginal tone probably enhances vaginal penetration and penile thrusting during the sexual act and penile buffeting of the CU. The cervico-vaginal reflex may be incorporated as an investigative tool in sexual act disorders.

Action Potentials↗
PubMed2003

Role of positive urethrovesical feedback in vesical evacuation. The concept of a second micturition reflex: the urethrovesical reflex.

Upon feeling the urge to urinate, the urinary bladder contracts, the urethral sphincters relax and urine flows through the urethra. These actions are mediated by the micturition reflex. We investigated the hypothesis that vesical contraction is maintained by positive feedback through continuous flow of urine through the urethra, and that the cessation of urine flow aborts detrusor contraction. Normal saline was infused into the urinary bladders of 17 healthy volunteers (age 35.2 years+/-4.2(SD); ten women and seven men) at a rate of 100 ml/min. On urge, which occurred at a mean volume of 408.6 ml+/-28.7 of saline, the subject micturated while the vesical and urethral pressures during voiding were being recorded; residual urine was measured. The test was repeated after anesthetizing the urethra with xylocaine gel or, on another occasion, after applying a bland gel. On micturition, the urine was evacuated as a continuous stream without straining; no residual fluid was collected. After urethral anesthetization, the fluid came out of the urethra in multiple intermittent spurts and only with excessive straining. There was a large amount of residual fluid (184.6 ml+/-28.4). The results of bland gel application showed no significant difference ( P>0.05) from those without gel. Detrusor contraction during micturition is suggested to be maintained by positive urethrovesical feedback elicited by the continued passage of urine through the urethra. This feedback seems to be effected through the urethrovesical reflex, which produces vesical contraction on stimulation of the urethral stretch receptors. Abortion of this reflex by urethral anesthetization resulted in failure of detrusor contraction and excessive straining was needed to achieve bladder evacuation in multiple spurts. The urethrovesical reflex is thus assumed to constitute a second micturition reflex responsible for the continuation of detrusor contraction and urination. The role of this reflex in the pathogenesis of micturition disorders needs to be studied.

Adult↗