A potential major complication of any abdominal operation

Transcription

1 21 S M A L L B O W E L O B S T R U C T I O N A N D F I S T U L A S EDWARD PASSARO, JR. A potential major complication of any abdominal operation is the subsequent development of small bowel obstruction. Why some patients are particularly susceptible to the formation of intra-abdominal adhesions leading to intestinal obstructions is unknown, although this has been the subject of considerable study and speculation. It is clear that extensive bowel handling and manipulation are conducive to adhesion formation. This chapter describes the principles underlying the development of small bowel obstruction and fistula formation. The goal is to provide the student with insight into this clinical problem that will aid both in its recognition and in its treatment. CASE 1 FEMORAL HERNIA A 55-year-old slightly obese male had rapid onset of nausea and vomiting over 6 hours. He had no previous operations. His last bowel movement was 12 hours earlier. His temperature was 38.6 C, WBC count 13,200. His abdomen was slightly distended and tender to deep palpation in the left lower quadrant. No groin hernias were felt. Plain abdominal films showed some dilated small bowel in the left lower quadrant without air-fluid levels. There was gas in the right colon and rectum. He was thought to have diverticulitis. He was started on a course of antibiotics and an NG tube was inserted. Four hours later, his abdominal pain had increased and his temperature remained unchanged; operation was recommended. At operation the descending and sigmoid colon was normal. Deep in the pelvis along the femoral vessels were several loops of dilated distal jejunum. During the process of retracting the small bowel into the field, the dilated jejunal loops were reduced from a femoral canal hernia. The incarcerated segment appeared reddish purple and slightly edematous and was sharply demarcated from the rest of the normal-appearing bowel. It was observed for the next 20 minutes and improved in color. The hernia defect was repaired and the abdomen closed. The patient was discharged on the fifth postoperative day. CASE 2 POSTOPERATIVE ILEUS A 47-year-old female had an abdominal hysterectomy for fibroids. An NG tube inserted during the operation was removed while she was awake in the recovery room. On 149

2 1 5 0 U P P E R G A S T R O I N T E S T I N A L T R A C T the second postoperative day she consumed a liquid diet. The following day, she was started on solid foods. Her appetite was rather limited. The next day, while attempting to eat, she started to experience nausea. A few hours later, she had onset of vomiting. Her abdomen had become slightly distended, but she was without pain. She was made NPO and intravenous fluids were restarted. Because of increasing discomfort with abdominal distention, an NG tube was inserted and 800 ml of gastric contents withdrawn. She began to feel better. The following day she was being considered for an upper gastrointestinal contrast study when she began to pass flatus. The study was canceled and the NG tube withdrawn; the following day she was again started on a liquid diet. Over the next 48 hours she progressed to a regular diet and was discharged without incidence. Three months later on follow-up examination, she was found to be entirely asymptomatic. CASE 3 POSTOPERATIVE ADHESIONS, FISTULA A 37-year-old male presented with progressive nausea, vomiting, and crampy bilateral lower quadrant abdominal pain over the previous 48 hours. He had not had a bowel movement or flatus during this time. He had a perforated appendix at age 23 complicated by small bowel obstruction requiring reoperation on the 10th postappendectomy day. He had several prior similar episodes of crampy abdominal pain, successfully treated with NG tube decompression and IV fluids for hours. His abdomen was distended, tympanitic, and tender to palpation in both lower abdominal quadrants, with the right greater than the left. He was afebrile, his Hct was 50%, and the WBC count 10,600. Plain films of the abdomen showed many loops of small bowel with air-fluid levels in them. Only a few widely scattered patches of gas were found in the colon. An NG tube returned 1,200 ml of a brownish feculent -smelling fluid. He received more than 1,500 ml of saline infusion before he began to urinate. Over the next 12 hours, he felt much better, but his abdomen remained distended and he had passed no flatus. The NG tube had removed an additional 1,200 ml of bowel contents. His temperature was now 38 C and his WBC count 13,000. Both lower abdominal quadrants remained tender. Another set of plain films of the abdomen failed to show progression of gas into the colon. He was prepared for operation, as his obstruction had not resolved. Considerable difficulty was encountered in entering the abdominal cavity because of the dense adhesions, which were lysed by a combination of both sharp and blunt dissection. Several inadvertent enterotomies were made in the process, which were sewn closed. No clear point of obstruction (dilated bowel proximal and collapsed bowel distal) could be discerned. On the seventh postoperative day he developed a temperature to 39 C and lower abdominal pain beneath the midline incision. The wound edges were gently spread apart, and bile-stained intestinal contents issued forth. Through a defect in the fascia, a sump drain was inserted, which promptly drained an additional 200 ml of enteric fluid. He was given antibiotics and 12 hours later was afebrile. He was started on TPN. Approximately 200 ml of fluid drained out daily. Five days later, he passed some flatus for the first time since operation and reported being hungry. Octreotide was started; 1 week later, catheter drainage was only 50 ml/day. The sump drain was removed, a small catheter inserted, and contrast injected by catheter ( fistulagram ). The contrast entered what appeared to be mid-small bowel and progressed into the colon. The catheter was removed and the fistula closed spontaneously 4 days later. He was maintained NPO on TPN for an additional 2 weeks before he was allowed to eat. He tolerated an oral diet and the TPN and octreotide were stopped. He remained asymptomatic during the next 2 years of follow-up. GENERAL CONSIDERATIONS Of the entire extent of the gastrointestinal (GI) tract only the duodenum and proximal 2 feet of the jejunum are essential for life. Seldom appreciated is that this meager portion of the bowel s length carries out most of its absorptive functions. The additional length of the bowel beyond this essential portion is thought to provide the great flexibility we enjoy in dietary habits. Also not widely appreciated is the great variation in location and diameter of the small bowel. The duodenum is exclusively retroperitoneal and fixed in position. Portions of the hepatic flexure and transverse colon overlie it. Its diameter is 3 4 times greater than that of the distal ileum. Most of the small bowel comes to lie in the left lower quadrant of the abdomen, as its mesentery is fixed at the ligament of Treitz and the ileocecal valve. Based on this mesenteric plane, the bowel could flop into the right upper quadrant or left lower quadrant. The liver occupies the right upper quadrant so the small bowel is predominantly in the left lower quadrant. From these anatomic considerations, we can deduce several important clinical considerations: 1. As the duodenum is large in diameter, retroperitoneal, and has portions of the colon as a shield, it is not the site of intestinal obstruction from adhesions or hernias, the two most common causes. 2. The distal ileum has the smallest diameter of the entire gastrointestinal tract and is therefore the easiest portion of the bowel to obstruct with adhesions. It is mobile in the lower abdomen and can be entrapped into hernias or be-

3 S M A L L B O W E L O B S T R U C T I O N A N D F I S T U L A S hind adhesive bands (internal hernias). Hernias are the second most common cause of obstruction. 3. Abdominal distention from intestinal obstruction will be primarily in the lower abdomen (the location of the small bowel). 4. As most obstruction occurs in the distal small bowel, the progressive symptoms of the obstruction (anorexia, nausea, abdominal distention, vomiting) take time (hours to days) to become manifest. Conversely, the more proximal the site of the obstruction the earlier and more prominent are the symptoms of the obstruction. 5. Plain abdominal films should show progressive loops of dilated small bowel proceeding from the ileocecal region to the ligament of Treitz (so-called stepladder pattern). The other important consideration relates to the pathophysiology of obstruction. Recall that the intestinal tract has fluxes of 7 10 L of a salt solution every day. A slight shift of that equilibrium will cause several liters of fluid to accumulate quickly in either the bowel lumen or bowel wall or to transudate into the free peritoneal cavity quickly. We are exquisitely tuned to the condition of our bowels; anorexia is the first sign that something is wrong. With little or no intake and the shift of several liters of body fluids, a decrease in urine output and mild hypovolemia ensues. A few days of this and the patient is cool to touch, with slow, deep respirations and swollen abdomen. The patient is moribund and in a state of chronic shock. So insidious is its development that patient and physician alike are misled as to the seriousness of the condition. If these basic considerations relating to anatomy and physiology are understood and kept in mind, what follows relative to the diagnosis and treatment is both simple and logical. Extensive bowel handling and manipulation are conducive to adhesion formation Duodenum is large in diameter, retroperitoneal, and has portions of colon as shield; therefore is not site of intestinal obstruction from adhesions or hernias, the two most common causes Distal ileum has smallest diameter of entire gastrointestinal tract; therefore easiest portion of bowel to be obstructed by adhesions; in lower abdomen it is mobile and can be entrapped into hernias or behind adhesive bands (internal hernias); hernias second most common cause of obstruction Abdominal distention from intestinal obstruction primarily occurs in lower abdomen (location of small bowel) Most obstruction occurs in distal small bowel; thus, progressive symptoms of obstruction (anorexia, nausea, abdominal distention, vomiting) take time (hours to days) to manifest The more proximal site of obstruction, the earlier and more prominent the symptoms of obstruction Plain abdominal films should show progressive loops of dilated small bowel proceeding from the ileocecal region to the ligament of Treitz (so-called stepladder pattern) Intestinal tract has fluxes of 7 10 L/day of salt solution; a small shift of that equilibrium will cause several liters of fluid to accumulate quickly in either bowel lumen or bowel wall or to transudate into the free peritoneal cavity DIAGNOSIS Depending on the clinical information, the diagnosis can be relatively easy (Case 3) or nearly impossible (Case 1) or unsure (Case 2). The important clinical information from the history is previous operations or bouts of presumed obstructions (Case 3). Other features are the insidious and progressive development of anorexia, followed by nausea and finally vomiting. During this time the patient usually has not passed much or any flatus or stool. Despite this understanding of the pathophysiology and progression of the symptoms, every study of this problem indicates that the clinical accuracy in arriving at a diagnosis based on history and physical findings alone is only fair. This is because many medical (e.g., pneumonia or surgical problems (Case 1) can mimic the findings. Progression of the disease process (Cases 1 and 2) is the single best guide to determining what needs to be done (see Ch. 12). In Cases 1 and 2, this is how the clinicians arrived at the proper course of action. The progression, or lack of it, is assessed by repeated physical examination, looking for increasing abdominal distention, areas of focal pain or tenderness, and signs of peritonitis, and by observations that the patient has not had passage of flatus or stool. Plain films of the abdomen to monitor the progression of intraluminal gas down the gastrointestinal tract can be helpful. In selected instances, a contrast study using water-soluble contrast media inserted via a nasogastric (NG) tube may be useful. Delayed films will show accumulation of the contrast at the point of the obstruction. In some instances in which the obstruction is incomplete or the patient has an ileus (discussed below), the hypertonic contrast media can be therapeutic as well. Water-soluble contrast agents (hypertonic), draw fluid into the lumen. Additionally, these iodinated compounds are irritating to the bowel and therefore promote peristaltic activity. In patients with partial obstruction or ileus, this increased peristalsis may be sufficient to cause passage of gas and stool with considerable relief for the patient. Obviously, if the obstruction is complete, nothing will pass. The increased bowel activity may cause focal pain, pointing to the area of obstruction and aiding in diagnosis. However, the test would not be advisable in patients with longstanding obstruction or when compromise of the blood supply to the bowel is possible or likely.

4 1 5 2 U P P E R G A S T R O I N T E S T I N A L T R A C T Another approach to establish the diagnosis is through the use of long intestinal tubes. These tubes are particularly useful in very complicated patients who have undergone several abdominal operations previously. The Baker, Miller-Abbott, and Cantor tubes have the advantage of being therapeutic as well as diagnostic. Their disadvantage is that they require patience and some skill in getting them beyond the ligament of Treitz into the dilated proximal small bowel. If the obstruction is longstanding, peristalsis may be absent, preventing their advancement by bowel activity. When successful, however, the passage of a long tube evacuates the bowel of both gas and fluid, decompressing it. The long tube will advance to or near the point of obstruction. As the proximal bowel is decompressed, what was formerly an emergency is now a less emergent condition. When the progression of the tube has stopped, contrast media in limited quantities can be instilled and a selective study near the region made. This aids in locating the obstructed point which is difficult (Case 3) in many instances. Intraoperatively the intraluminal tube assists the surgeon in locating the obstruction among the many areas of adhesions and kinked bowel. All in all, few conditions are as difficult to both diagnose and successfully manage as that of intestinal obstruction. Moreover, successful treatment in avoidance of major complications is absolutely dependent on the timely and proper management of this condition. Clinical accuracy is only fair in arriving at a diagnosis based on history and physical examination alone, despite understanding of pathophysiology and progression of symptoms Progression of disease process single best guide to determining what needs to be done DIFFERENTIAL DIAGNOSIS Any condition that can produce an ileus enters into the differential diagnosis of intestinal obstruction. Distinguishing an ileus from a presumed inflammatory process or from an obstruction is important. Ileus is a physiologic obstruction; that is, the bowel is patent but it lacks the force or peristaltic activity sufficient to propel bowel contents. Gas and fluid accumulate as in a mechanical obstruction where the lumen is blocked either partially or completely. Postoperative ileus is often indistinguishable from postoperative intestinal obstruction due to adhesive bands (Case 2). Ileus does not require operation in fact, operation only exacerbates the condition whereas mechanical obstructions often do require operation for correction. Postoperative ileus that never resolves to the point that the patient can be started on oral feeds is most apt to be due to mechanical obstruction and require reoperation in the postoperative period. Patients who appear to have resolved their postoperative ileus and who are started on diets, only to fail (Case 2) usually have ileus and not a mechanical problem. These cases typically resolve with additional supportive measures. Important to distinguish an ileus from a presumed inflammatory process (e.g., diverticulitis) from an obstruction Ileus does not require operation (which only exacerbates condition) Mechanical obstructions often do require operation for correction TREATMENT There are many oft-quoted statements regarding the treatment of intestinal obstruction ( the sun should never rise or set on a case of small bowel obstruction ). All convey a sense of urgency; that is, within a 12-hour period either the patient is better or should be operated on, or both, to make the diagnosis and treat it if correct. These aphorisms are misdirected, as there is universal agreement that if complete mechanical obstruction is present the patient will need operation for relief, and the more promptly this can be attended to, the less likely is the risk of complications such as bowel strangulation, infarction, or perforation. The problem therefore is not in treatment, it is in diagnosis. Does the patient have obstruction or ileus? Is the obstruction partial or complete? Where is the obstruction? Insertion of an NG tube reduces the likelihood of aspiration, makes the patient feel better, and can aid in the diagnosis when combined with a period of observation (Cases 1, 2, and 3). In the first case, although the patient initially felt better, he did not improve with observation and underwent operation. In the second case, the patient improved following NG tube insertion and observation. In the last case, insertion of a nasogastric tube and observation led to successful resolution of his abdominal distention on two occasions in the past. On this admission he did not improve on observation and required operation. The two most common causes of mechanical small bowel obstruction are postoperative adhesions and hernias of the abdominal wall. Obstructions resulting from adhesion formation is treated by dividing the adhesive bands producing the obstruction. Generally, many adhesive bands are found at operation, but only one is producing the obstruction. The rest need not be lysed. Hernias of the abdominal wall are repaired following a reduction of the obstructed bowel segment. On occasion, the area of obstruction is either inaccessible because of scarring, or is too dangerous to remove

5 S M A L L B O W E L O B S T R U C T I O N A N D F I S T U L A S because of an inflammatory process as in Crohn s disease. The obstruction can be relieved by bypass procedures, connecting proximal uninvolved bowel with bowel distal to the obstruction. Small bowel obstruction due to tumor is a not infrequent complication of widespread metastatic tumors from the large bowel, pancreas, and stomach. Finding a discrete solitary point of obstruction in these patients is rarely possible. Unfortunately most of these patients cannot be aided by operation. When the tumor is localized to a segment of the bowel, it can either be resected or bypassed or an ostomy for decompression made proximal to it. Problem not in treatment but in diagnosis Two most common causes of mechanical small bowel obstruction are postoperative adhesions and hernias of abdominal wall FOLLOW-UP Resumption of bowel activity with passage of gas and stool is the best measure of resolution of the obstruction. Patients with a discrete mechanical cause, as a solitary adhesive band, have an excellent prognosis on long term follow-up. Patients with extensive intra-abdominal adhesions and previous bouts of obstruction require life-long follow-up for further bouts of obstruction. Similarly, patients with obstruction from malignant tumors are at risk of additional episodes of obstruction before they succumb to the tumor. Many of these patients have small bowel obstruction as a terminal event. A complication of small bowel obstruction seen during the immediate postoperative period, but more commonly on follow-up, is the development of small bowel fistula. Small bowel fistulas arise because there is a recurrent obstruction (usually partial in nature) and a proximal weakened portion of the bowel that breaks down. The weakened area can be at a previous suture line or enterotomy closure (Case 3) or where the bowel was traumatized during the operation. Fistulas are a connection between the bowel lumen and the skin surface. They are readily apparent as drainage or bowel contents issue forth on the skin usually at incisions or drain sites. Infection, intra-abdominal as well as deep in the operative incision, are predisposing factors for fistula formation. Spontaneous fistulas can occur when an intra-abdominal infection, as from diverticulitis, erodes through the abdominal wall, draining externally. Fistulas are categorized by their location and volume of drainage. In general, fistulas proximal in the gastrointestinal tract have a higher morbidity and mortality (approximately 40%) than those more distal such as colon fistula (2%). Similarly, fistulas draining large volumes are more hazardous than those draining smaller volumes. Duodenal fistulas have much higher volume outputs than ileal fistulas, for example. The drainage contents are also important; bile, pancreatic juice, and other proteolytic juices from the duodenum are corrosive and extremely difficult to manage. Colonic fistulas draining fecal material are easier to control and can be managed similar to a colostomy. Proximal fistulas require extensive drainage of the discharge. Not infrequently, the involved area needs to be excluded by operation from the remainder of the gastrointestinal tract. The voluminous discharge of a protein and salt rich fluid will rapidly deplete the patient. Thus patients require vigorous nutritional and fluid support via chronic intravenous catheters. By contrast, distal fistulas can be treated by a nutritional liquid diet that is absorbed proximal to the fistula site (elemental diet), total parenteral nutrition (TPN), NG intubation, and octreotide. These measures work by decreasing the volume of intestinal secretions passing through the fistula. As the bowel mucosa exhibits very high proliferative activity, it will grow and seal a collapsed fistulous tract but cannot do so if the fistula is actively discharging fluids. Fistulas can close spontaneously when there is no diseased bowel involved and no obstruction distal to the fistula, and when the drainage through the fistula is minimal. Octreotide suppresses intestinal secretions of all kinds, reducing the volume of fluid passing through the fistula. Conversely, fistulas will remain open if there is injured or diseased bowel or some degree of obstruction of the bowel distal to the fistula site. Foreign bodies (nonabsorbable sutures, retained sponges) at a fistula site, will promote infection and keep the fistula open. Resumption of bowel activity with passage of gas and stool best measure of resolution of obstruction Small bowel fistulas arise because of recurrent obstruction (usually partial in nature) and a proximal weakened portion of bowel that breaks down Fistulas are connection between bowel lumen and skin surface SUGGESTED READINGS Brolin RE: The role of gastrointestinal tube decompression in the treatment of mechanical intestinal obstruction. Am Surg 49: 131, 1983 Livingston EH, Passaro EP Jr: Postoperative ileus. Dig Dis Sci 35:121, 1990

6 1 5 4 U P P E R G A S T R O I N T E S T I N A L T R A C T QUESTIONS 1. The major difficulty in managing a patient with small bowel obstruction is? A. Determining whether the obstruction is complete or incomplete. B. Determining whether the obstruction is high in the gastrointestinal tract or lower. C. Determining the etiology of the obstruction as from tumor or an inflammatory process. D. Distinguishing between whether the patient has ileus or a mechanical obstruction. 2. In patient with suspected small bowel obstruction, the best course of action is? A. Immediate operation in all patients. B. Observe patient and carry out investigative test (e.g., plain films of abdomen, UGI series, CT) until the diagnosis is established. C. Initial resuscitation and observation followed by urgent operation in all patients who do not improve or in whom doubt remains. D. Passage of long gastrointestinal tubes to decompress the bowel and help establish the diagnosis. (See p. 603 for answers.)