N M. Guaderrama

University of California, San Diego, San Diego, CA, United States

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Publications (9)23.8 Total impact

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    ABSTRACT: To evaluate whether transperineal three-dimensional (3D) ultrasound can be used to depict normal anal sphincter anatomy and to measure the thickness of muscle layers and the anteroposterior length of the levator hiatus. The study included 22 normal nulliparous female volunteers. Transperineal 3D sonographic evaluation of the anal canal included assessment of sphincter shape, echogenicity, marginal definition and muscle thickness. Measurements of the thickness of the internal anal sphincter (IAS) and puborectalis muscle (PRM) were determined with the women at rest and during squeezing by two observers, and interobserver reliability was determined. The anteroposterior length of the levator hiatus at rest and during squeezing was measured. The proximal end of the anal canal (towards the rectum) consisted of overlapping IAS and PRM, and the distal end (towards the anus) consisted of overlapping IAS and external anal sphincter (EAS). At the PRM level, the mean +/- SD IAS thickness was 2.3 +/- 0.5 mm at rest and 2.5 +/- 0.4 mm during squeezing, and at the mid-EAS level it was 2.9 +/- 0.5 mm at rest and 2.8 +/- 0.5 mm during squeezing. The PRM thickness was 6.5 +/- 1.0 mm at rest and 6.4 +/- 1.2 mm during squeezing. The difference in muscle thickness of the sphincter layers with the woman at rest and during squeezing was not significant. The anteroposterior length of the levator hiatus was 51.7 +/- 5.0 mm at rest and 47.4 +/- 4.1 mm during squeezing (P < 0.01). Transperineal 3D ultrasound may be useful in evaluating the anatomy of the anal canal.
    Ultrasound in Obstetrics and Gynecology 08/2007; 30(2):201-9. · 3.56 Impact Factor
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    ABSTRACT: Resting and squeeze pressures in the anal canal are thought to reflect the contributions of the internal anal sphincter (IAS) and the external anal sphincter (EAS) respectively. Role of the puborectalis muscle (PRM) in the genesis of anal canal pressure is not known. To determine the functional correlates of anal canal anatomy. Seventeen asymptomatic nulliparous women were studied using simultaneous 3D ultrasound images and manometry of the anal canal. Ultrasound images were recorded using a transducer placed at the vaginal introitus and pressures were recorded with a side-hole manometry catheter using a station (every 5 mm) pull-through technique. Pressures were recorded at rest and during voluntary squeeze. Anal canal high pressure zone was 39 +/- 1 mm in length. The IAS, EAS, and PRM were clearly visualized in the ultrasound images. EAS was located in the distal (length 19 +/- 1 mm) and PRM in the proximal part (length 18 +/- 1 mm) of the anal canal. The station pull-through technique revealed increases in pressure with voluntary squeeze in the proximal as well as distal parts of the anal canal. Proximal anal canal pressure, located in the PRM zone, showed greater circumferential asymmetry than the distal anal canal pressure, located in the EAS zone. (1) PRM contributes to the squeeze pressure in the proximal part of the anal canal and EAS to the distal anal canal. (2) PRM squeeze-related increase in anal canal pressure might be important in the anal continence mechanism.
    The American Journal of Gastroenterology 06/2006; 101(5):1092-7. · 9.21 Impact Factor
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    ABSTRACT: To evaluate whether the pudendal nerve innervates the levator ani muscles by assessing the effect of pudendal nerve blockade on pelvic floor muscle function. Eleven nulliparous women without symptoms of anal or urinary incontinence were studied before and after pudendal nerve blockade with vaginal manometry, electromyography of the external anal sphincter and puborectalis muscle, and 3-dimensional transperineal ultrasound imaging of the urogenital hiatus during rest and squeeze. After pudendal nerve blockade, mean vaginal resting pressures decreased from 19 +/- 10 mm Hg to 15 +/- 10 mm Hg (P < .05), and mean vaginal squeeze pressures decreased from 61 +/- 29 mm Hg to 37 +/- 24 mm Hg (P < .05). After pudendal nerve blockade, the anterior-posterior length of the urogenital hiatus increased from 51 +/- 4 mm to 55 +/- 5 mm at rest (P < .05) and increased from 47 +/- 3 mm to 52 +/- 5 mm during squeeze (P < .05). Resting and squeeze electromyography amplitude of the external anal sphincter and puborectalis muscle was markedly reduced by pudendal nerve blockade. Pudendal nerve blockade decreases vaginal pressures, increases length of urogenital hiatus, and decreases electromyography activity of the puborectalis muscle, all of which suggest that the pudendal nerve does innervate the levator ani muscle.
    Obstetrics and Gynecology 10/2005; 106(4):774-81. · 4.80 Impact Factor
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    Ultrasound in Obstetrics and Gynecology 09/2005; 26(4):370 - 370. · 3.56 Impact Factor
  • Journal of Pelvic Medicine and Surgery. 01/2005; 11.
  • Journal of Pelvic Medicine and Surgery 01/2005; 11.
  • Journal of Pelvic Medicine and Surgery. 01/2005; 11.
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    ABSTRACT: To describe the vaginal pressure profile in asymptomatic nulliparous women. Fourteen nulliparous women without symptoms of anal or urinary incontinence were studied with vaginal manometry. A rapid pull-through technique utilized a four-channel water-perfused catheter on a motor-driven puller to create a pressure profile for each subject. The profiles were measured with the subject at rest and during a sustained contraction of the levator ani muscle. The individual subject's pressure profiles were averaged to create a composite profile at rest and during squeeze. The vaginal pressure profile at rest and during squeeze contains three pressure zones: proximal, mid, and distal. The pressure is highest in the mid pressure zone and was labeled as the vaginal high-pressure zone. In the vaginal high-pressure zone, the maximum pressure during squeeze is significantly higher than the maximum pressure at rest (P < 0.05). The length of the high-pressure zone is longer during squeeze as compared to rest (P < 0.05). The maximum pressures exhibit circumferential asymmetry with the pressures in anterior and posterior directions being significantly higher than those in the lateral directions (P < 0.05). The vaginal pressure profile is more complex than previously described. Understanding of the vaginal pressure profile is crucial when employing vaginal manometry to assess pelvic floor muscle strength or as a surrogate for intra-abdominal pressure.
    Neurourology and Urodynamics 01/2005; 24(3):243-7. · 2.67 Impact Factor
  • Journal of Pelvic Medicine and Surgery 01/2004; 10.