RECTUM AND ANAL CANAL. 443 



venous pile. The strawberry pile is composed of venous capillaries instead of the 

 larger venous canals usually present. They bleed more freely than does the ordinary 

 venous pile. When external hemorrhoids are operated on they are usually throm- 

 bosed. They are then incised and the clots turned out; at other times when not 

 inflamed they are excised and the edges stitched with catgut or the wound packed. 

 Internal piles are either ligated or treated with the clamp and cautery. In applying 

 the ligature the base of the pile is loosened below near the white line and detached 

 for some distance above and then ligated. This is facilitated by the loose attachment 

 of the mucous membrane. Bleeding is not marked because the blood-vessels enter 

 the pile from above. In Whitehead's operation, or excision of the pile-bearing area, 

 the mucous membrane is readily separated by blunt dissection from the parts beneath 

 owing to the laxity of the submucous tissue; it is then excised and the cut edge 

 sewn to the skin at the anus. 



Fistula. Fistula in ano may start as an ischiorectal abscess which perforates 

 internally into the rectum or anal canal and externally through the skin. It may 

 also start as an ulcer of the mucous membrane of the rectum or crypts of Morgagni 

 and then produce an ischiorectal abscess which finally opens on the skin. The most 

 common site of the internal opening is just above the anus and below the insertion 

 of the levator ani. This is in the groove between the external and internal sphinc- 

 ters. Sometimes, however, the fistula pierces the levator ani and opens into the 



Columns of Morgagni 



Internal sphincter 



Crypts of Morgagni 

 External sphincter 



\Internal hemorrhoids 



External hemorrhoids 

 FIG. 448. Hemorrhoids. 



ampulla of the rectum. As the external opening is usually to the outer side of the 

 external sphincter this latter is divided in operating, as is also a part or all of the 

 internal sphincter if the opening is high up. Incontinence of faeces is usually avoided 

 if the sphincter is only divided at one place and at right angles to its fibres, not 

 obliquely. 



Anal fissures occur usually on the posterior wall of the anus associated with 

 a hemorrhoid. Its location, involving the white line, explains its great pain. 



Excision of the Rectum. The rectum can be removed either by the perineal 

 or sacral route. Li the perineal operation the incision is made from near the base 

 of the scrotum to the coccyx, surrounding the anus. If the incision is made near the 

 white line the external sphincter is saved and turned to each side with the skin flap. 

 The external sphincter is split anteriorly as far as the central point of the perineum 

 and posteriorly to the coccyx. The rectum being drawn forward the levator ani 

 muscle is cut through on its sides and posterior surface about 4 cm. ( i ^ in. ) above 

 the anus, the coccyx, if necessary, being excised. The rectum is then drawn back, 

 the finger slipped beneath the anterior portion of the levator ani, which is farther 

 from the surface than the posterior, and it is divided. These fibres practically con- 

 stitute the recto-urethralis muscle of Proust. This is near the apex of the prostate; 

 from here up to the peritoneal reflection or rectovesical pouch the rectum is loosely 

 attached but at that point it is necessary to divide the rectal fascia (a part of the 

 rectovesical fascia, p. 435) on the sides, after which the rectum can be drawn still 



