Stomata and bypasses for large gut obstruction

The gut is a tube from the mouth to the anus which can become obstructed in various places. One way of overcoming such an obstruction is to make an opening or stoma or ''ostomy' above or below it, from the lumen of the gut out to the abdominal wall. In the upper part of the gut the purpose of an ostomy (a gastrostomy, or a jejunostomy) is usually to let food and fluid in; in the lower part it is to let the contents of the gut out (an ileostomy, a caecostomy or a colostomy).

An ostomy is seldom necessary in the small gut, because it contains so few bacteria that you can usually resect the obstruction, and anastomose its cut ends quite safely. Ostomies of the small gut cause large losses of water and electrolytes, so try to avoid them if you can. But you cannot so easily anastomose the large gut, which is not only full of dangerous bacteria, but also has a much poorer blood supply, so that anastomoses more easily break down and leak. The standard way to operate safely on the large gut is to wash it out and then to ''sterilize' it with a preoperative course of antibiotics, neither of which are possible in an emergency. So, in an emergency, you have to bring the cut ends of the large gut out to the surface as a colostomy, and close them later. There are two main ways of doing this: (1) You can bring a loop of gut to the surface and make an ostomy at its apex, without resecting any gut. Or, you can bring most of the loop out of the abdominal wall, close it and then resect the loop. This is called exteriorization. If you are not skilled, it is useful way of resecting gangrenous or injured gut, and making an ostomy without soiling the abdominal cavity.

Types of ostomy There are several types of ostomy for the large gut, and three standard places in which to make them. First the types. A loop colostomy is the most useful of these. In many cultures a patient would rather die than have any of them. So you may have to do some firm persuasion. Fortunately, ostomies are usually only needed temporarily. You can make any of these:

(1) A loop colostomy brings a loop of gut out of the abdomen over a short length of rubber tube, or a glass rod. This is the easiest ostomy to make and close extraperitoneally, and is suitable for most purposes.

(2) A double-barrelled colostomy, is a loop colostomy modified by stitching the last few centimetres of its limbs together inside the abdomen, so that they resemble a double-barrelled shotgun. The spur (wall) between the two loops is later crushed to make the colostomy easier to close with the special crushing clamp in G, Fig. 9-19. If you are not going to close a colostomy by crushing the spur, there is no point in double-barrelling it.

The advantage of both a loop and a double-barrelled colostomy is that you can close them extraperitoneally.

(3) A ''spectacles colostomy' has limbs that are separated by a small bridge of skin, as in Fig. 9-17. It is useful: (a) if a patient needs a colostomy for a long time, and (b) during the repair of a rectovaginal or vesicovaginal fistula, when work on the rectum and bladder has to be completed before the fistula can be closed. Because the loops of a spectacles colostomy are separated, it has to be closed intraperitoneally with a full anastomosis.

(4) An end (terminal) colostomy forms the ''end' of the gut after excision of the rectum, or in Hartmann's operation (see below).

(5) A mucus fistula (colostomy). A colostomy normally has two openings. The proximal one discharges faeces, and the distal one only mucus. This is the term which is sometimes given to the distal opening.

If you are making a colostomy low in the sigmoid colon, the distal loop may not be long enough to reach the surface as a mucus colostomy, so you have to close it and drop it back into the abdomen[md]this is Hartmann's operation (G, in Fig. 9-14). If necessary, you can drop a blind loop back into the abdomen anywhere; it will fill with mucus and discharge through the anus.

Some kinds of ostomy ''defunction' the colon better than others. This means that they are better at preventing faeces from entering the distal limb. This may be useful, for example, in protecting a wound in the rectum which you have just sutured. There are several degrees of defunctioning. It is most effective when the two ends of the gut are brought out through separate stab wounds, with the distal one above the proximal one. A ''spectacles colostomy' (9-17) is the next best. Neither a loop, nor a double barrelled colostomy, defunction completely, and a caecostomy is even less effective. Fortunately, a high degree of defunctioning is seldom important.

Fig. 9-14 OSTOMIES. A, exteriorization; the gut outside the abdominal wall is later resected to produce a colostomy. B, and C, stages in a loop colostomy. D, a double-barrelled colostomy. E, the ends of a colostomy come out of the same wound. F, they come out of different wounds. G, Hartmann's procedure, in which the distal end of the sigmoid colon is dropped back into the abdomen. H, an ostomy in the transverse colon. I, a caecostomy. J, a caecostomy with a large catheter inserted. K, an ostomy in the sigmoid colon. L, if the small gut is gangrenous, you can excise it and anastomose its ends, you cannot do this safely in an emergency with the large gut, because you do not have time to prepare it first. The sites for ostomies are shown in Fig. 9-14. There are three common places to make them: (1) In the caecum in the right iliac fossa (a caecostomy). (2) In the right side of the transverse colon in the right epigastrium. (3) In the sigmoid colon in the left iliac fossa.

A caecostomy can be made by placing a tube in the caecum and letting the liquid faeces drain. This is easier than doing a transverse colostomy, but: (1) The risks of soiling the peritoneum are greater. (2) A caecostomy often does not work well, and needs much washing out, so it is difficult to manage postoperatively. (3) It diverts little of the faecal stream. But, provided the tube is not too small, it may do this adequately. (4) It can only be temporary. A caecostomy is useful if a patient is desperately ill, and you can, if necessary, do one under local anaesthesia without exploring his abdomen. You will find a caecostomy useful if he has: (a) a caecal injury, or (b) a more distal obstruction, but is too ill for a colostomy.

A transverse colostomy can be made as a loop, or double barrelled, or as a spectacles colostomy. Always make it in the right side of the transverse colon. This should not be difficult unless the colon is very distended, or the mesocolon is short. Use a transverse colostomy as a preliminary to resection of the large gut for a left sided obstruction for carcinoma (32.27), for anal atresia (28.6), and for an injury (66.14).

A sigmoid colostomy is an alternative to a transverse colostomy for obstruction in the rectum or sigmoid colon, such as a sigmoid volvulus. Here again you can make a loop, or double-barrel it.

Closing ostomies can be more difficult than making them. A caecostomy will close by itself, but a transverse or a sigmoid colostomy will have to be carefully closed, unless the patient is to have his colostomy permanently. If you cannot refer him to have it closed, you will have to close it yourself. If possible, try to do this extraperitoneally, so that you avoid the risk of contaminating his peritoneal cavity. You can usually free the ends of a loop colostomy (9-15), or a double-barrelled colostomy (9-19), and sew them together without entering his peritoneal cavity. The ends of the loop may be partly united already, so that you have only to complete the rest of the anastomosis. If you cannot close a colostomy extraperitoneally, you will have to lift out the two loops of gut and close it intraperitoneally as in Fig. 9-18.

There is another way of closing a double-barrelled colostomy extraperitoneally, which is to slowly crush the spur between the two loops of the barrel with a special clamp, as in Fig. 9-19. This makes the barrels join one another, and makes the colostomy easier to close. Some surgeons like this method and others don't. It has the disadvantage of needing a special clamp, although you can use a large haemostat, as described later. Closing Hartmann's operation is much more difficult; if you have to do it, it is decribed in Section 10.10a.

Bypasses. The ostomies above all open a patient's gut to the outside. You can also relieve his obstruction by connecting one part of his gut to another with a bypass. It is often anatomcally difficult and it can be surgically dangerous to bypass one part of his large gut to another, but you can bypass his small gut to his small gut, or his small gut to his large gut. You can: (1) Bypass one part of his small gut to another, when it is obstructed and bound down by septic (10.7) or tuberculous (29-8) adhesions, which are difficult to free. This is an entero-enterostomy, usually an ileo-ileostomy. (2) You can bypass his small gut into to his large gut, by anastomosing his terminal ileum to his transverse colon, and closing the free end of his ileum, or leaving it open. This leaves the end of his ileum and his ascending colon as a blind loop. It is useful in amoebiasis (31.11) and carcinoma (32.27). Anastomosing his ileum to his transverse colon is more difficult than doing a caecostomy to relieve his obstruction, but is easier than removing his right colon (right hemicolectomy, 66-20). (3) You can bypass his ileum into his descending colon or rectum. This is major surgery: it will give him diarrhoea and most surgeons prefer a colostomy (32.27). (4) You can bypass his stomach into his small gut when his pylorus is obstructed (11.3).