AGA technical review on anorectal testing techniques N.E. Diamant, M.A. Kamm, A. Wald, W.E. Whitehead  Gastroenterology  Volume 116, Issue 3, Pages 735-760 (March 1999) DOI: 10.1016/S0016-5085(99)70195-2 Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 1 Anatomy of the anal canal, rectum, and distal colon illustrating the mechanisms for preserving continence. (Reprinted with permission.17) Gastroenterology 1999 116, 735-760DOI: (10.1016/S0016-5085(99)70195-2) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 2 Normal anal ultrasound scan showing the anal sphincter muscles in cross section through the mid anal canal. The darker homogenous ring is the IAS smooth muscle (I). The white heterogeneous ring surrounding this is the EAS (arrows; E). The top of the figure is anterior. Gastroenterology 1999 116, 735-760DOI: (10.1016/S0016-5085(99)70195-2) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 3 Anal ultrasound scan of a woman with anterior obstetric sphincter damage. The top of the figure is anterior. There is disruption of both the IAS (small arrows) and EAS (large arrows) muscles. Gastroenterology 1999 116, 735-760DOI: (10.1016/S0016-5085(99)70195-2) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 4 Reflex relaxation of the anal sphincter. The rectal balloon is first rapidly inflated and deflated with 50 mL of air (arrow) using a syringe attached to a three-way stopcock. Reflex relaxation of the IAS is recorded as well as the ability of the patient to sense rectal distention. (Reprinted with permission from Gastroenterology 1974:67;216–220.) Gastroenterology 1999 116, 735-760DOI: (10.1016/S0016-5085(99)70195-2) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 5 Pressure changes in rectum and anal canal and EMG recordings from the EAS during pseudodefecation. (A) Normal defecation is characterized by increased rectal (intra-abdominal) pressure, decreased anal pressure, and decreased direct and integrated EMG activity as measured by surface electrodes. (B) In patients with pelvic floor dyssynergia, there is increased anal pressure and EMG activity of the external sphincter during attempted defecation. (Courtesy of Dr. Vera Loening, University of Iowa Hospitals, Iowa City, Iowa). (Reprinted with permission.223) Gastroenterology 1999 116, 735-760DOI: (10.1016/S0016-5085(99)70195-2) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 5 Pressure changes in rectum and anal canal and EMG recordings from the EAS during pseudodefecation. (A) Normal defecation is characterized by increased rectal (intra-abdominal) pressure, decreased anal pressure, and decreased direct and integrated EMG activity as measured by surface electrodes. (B) In patients with pelvic floor dyssynergia, there is increased anal pressure and EMG activity of the external sphincter during attempted defecation. (Courtesy of Dr. Vera Loening, University of Iowa Hospitals, Iowa City, Iowa). (Reprinted with permission.223) Gastroenterology 1999 116, 735-760DOI: (10.1016/S0016-5085(99)70195-2) Copyright © 1999 American Gastroenterological Association Terms and Conditions

Fig. 6 IAS responses to rectal distention in a patient with Hirschsprung's disease are compared with those of a normal subject using the Schuster-type balloon manometer. The congenital aganglionosis of Hirschsprung's disease invariably affects the IAS. In contrast to normal reflexive relaxation of the IAS after rectal distention (arrows), no such relaxation occurs in the patient with Hirschsprung's disease. Gastroenterology 1999 116, 735-760DOI: (10.1016/S0016-5085(99)70195-2) Copyright © 1999 American Gastroenterological Association Terms and Conditions