RECTUM AND ANAL CANAL. 439 



keep the lower extremity of the ampulla of the rectum in close approximation to 

 the apex of the prostate. This is the part of the rectum which has been frequently 

 wounded in the operations of perineal lithotomy and prostatectomy. In the latter 

 operation division of this band allows the rectum to be pushed back and exposes the 

 apex of the prostate. 



The sacculation of the rectum is produced by three creases or crescentic folds, 

 called the rectal valves or valves of Houston {Dublin Hospital Reports, 1830). Of 

 these the middle is the largest. It springs from the right anterior quadrant about 

 5 to 6 cm. (2 to 2^ in.) above the margin of the anal canal. The superior and 

 inferior valves spring from the left posterior quadrant a short distance above and 

 below the middle valve. At the juncture of the rectum and sigmoid flexure there is 

 another fold on the anterior wall which tends to obstruct the view in making ex- 

 aminations. These valves are composed of connective tissue and circular muscular 

 fibres covered with mucous membrane. 



Peritoneal Relations. The posterior portion of the rectum has no peritoneal 

 covering, the mesosigmoid ceasing opposite the third sacral vertebra, about 12.50 

 cm. (5 in. ) from the anus. From this point the peritoneum slopes downward and 

 forward, covering the sides and anterior surface of the rectum 5 cm. (2 in.) lower. 

 The peritoneum is here reflected forward over the bladder in the male forming the 

 rectovesical pouch and over the vagina and uterus in the female forming the pouch 

 of Douglas. It is within 7.5 to 8.5 cm. (3 to 3^ in.) of the anus. This leaves 2.5 

 cm. (i in.) or more above the prostate which is not covered by peritoneum. It was 

 through this space that the bladder was formerly tapped with a trocar to relieve it 

 when distended. The peritoneum on the sides is less firmly attached to the rectum 

 and pelvic colon than it is on its anterior surface. 



Rectal Examination. The finger can palpate the anal canal and rectum for 

 a distance of 10 cm. (4 in. ) from the surface. Anteriorly as soon as the finger 

 passes the sphincters the apex of the prostate can be felt ; also the membranous 

 urethra, particularly if it contains a bougie or sound. The prostate can be outlined 

 and - its size determined. If the prostate is not enlarged the base of the bladder 

 above can be palpated and the tip of the finger will reach the rectovesical pouch. 

 From the upper or posterior edge of the prostate and extending from near the mid- 

 line upward and outward are the seminal vesicles, sometimes the seat of tuberculous 

 disease. Just to the outer side of the upper end of the seminal vesicles are the 

 lower ends of the ureters. Should a ureteral calculus become impacted at this 

 point it might possibly be felt through the rectum. Posteriorly the coccyx and the 

 hollow of the sacrum can be felt. The segments of the coccyx frequently are 

 luxated or fractured and it is the seat of pain coccygodynia for which excision is 

 done. These injuries cause either an ankylosis or a deformity of the coccyx which 

 can often readily be detected by a finger internally and the thumb externally. Later- 

 ally the finger can explore the region of the spine of the ischium, the sacrosciatic 

 foramina, and the tuberosities. If a patient is placed in the knee-chest position and 

 a speculum is introduced the rectum immediately distends with air and its interior is 

 visible as far as the promontory of the sacrum. By means of extra long tubes even 

 the sigmoid loop can sometimes be seen. The valves of Houston are readily seen 

 through the speculum. 



In introducing tubes and bougies for examination or therapeutic purposes the 

 greatest care is necessary, as death has not infrequently resulted from perforation into 

 the peritoneal cavity. 



The Anal Canal. This extends from the rectum to the anus or its opening 

 on the skin, a distance of 2.5 to 4 cm. (i to i^ in.}. It begins at the level of the 

 levator ani muscles and has the apex of the prostate directly in front of it and the tip 

 of the coccyx behind and a little above. With the body vertical the anal canal has 

 its axis inclining upward and forward toward the bladder ; as soon as the sphincter ani 

 is passed the axis of the rectum changes to upward and backward toward the hollow 

 of the sacrum. In intruducing a speculum it should always be inclined first ante- 

 riorly and then posteriorly. Opposite the level of the levator ani the circular mus- 

 cular fibres increase to form the internal sphincter. This extends down the anal 

 canal for a distance of approximately 2. 5 cm. ( i in. ) and ends above the skin margin 



