Text B Acute Intestinal Obstruction

Etiology and Classification

In 75％of patients，acute intestinal obstruction results from previous abdominal surgery secondary to adhesive bands or internal or external hernias． The incidence of acute intestinal obstruction requiring hospital admission within the first few postoperative weeks is 5％—25％，and10％—50％of these patients will require surgical intervention．1 The incidence of postoperative intestinal obstruction may be lower following laparoscopic surgery than open procedures．However，the laparoscopic gastric bypass procedure may be associated with an unexpected high rate of intestinal obstruction，with a higher reoperative rate．The reason for this is unknown．Other causes of intestinal obstruction not related to previous abdominal surgery include lesions intrinsic to the wall of the intestine（e．g．diverticulitis，carcinoma，regional enteritis），and luminal obstruction（e．g．gallstone obstruction，intussusception）．

Two other conditions that must be differentiated from acute intestinal obstruction include adynamic ileus and primary intestinal pseudo－obstruction． Adynamic ileus is mediated via the hormonal component of the sympatho－adrenal system and may occur after any peritoneal insult；its severity and duration will be dependent to some degree on the type of peritoneal injury． Hydrochloric acid，colonic contents，and pancreatic enzymes are among the most irritating substances，whereas blood and urine are less so．Adynamic ileus occurs to some degree after any abdominal operation．Retroperitoneal hematoma，particularly associated with vertebral fracture，may cause severe adynamic ileus，and the latter may occur with other retroperitoneal conditions， such as ureteral calculus or severe pyelonephritis．2 Thoracic diseases，including lower－lobe pneumonia，fractured ribs，and myocardial infarction，frequently produce adynamic ileus，as do electrolyte disturbances，particularly potassium depletion．3 Finally，intestinal ischemia，whether from vascular occasion or intestinal distention itself，may perpetuate an adynamic ileus．Intestinal pseudo－obstruction is chronic motility disorder that frequently mimics mechanical obstruction．This condition is often exacerbated by narcotic use．Unnecessary operations in such patients should be avoided．

Pathophysiology

Distention of the intestine is caused by the accumulation of gas and fluid proximal to and within the obstructed segment．Between 70％and 80％of intestinal gas consists of swallowed air，and because this is composed mainly of nitrogen，which is poorly absorbed from the intestinal lumen，removal of air by continuous gastric suction is a useful adjunct in the treatment of intestinal distention．The accumulation of fluid proximal to the obstructing mechanism results not only from ingested fluid，swallowed saliva，gastric juice，and biliary and pancreatic secretions but also from interference with normal sodium and water transport．During the first 12—24 h of obstruction，a marked depression of flux from lumen to blood occurs of sodium and consequently water in the distended proximal intestine．After 24 h，sodium and water move into the lumen，contributing further to the distention and fluid losses．Intraluminal pressure rises from a normal of 2—4 cm H2O to8—10 cm H2O．The loss of fluids and electrolytes may be extreme，and unless replacement is prompt，hypovolemia， renal insufficiency，and shock may result．Vomiting，accumulation of fluids within the lumen，and the sequestration of fluid into the edematous intestinal wall and peritoneal cavity as a result of impairment of venous return from the intestine all contribute to massive loss of fluid and electrolytes．

The most feared complication of acute intestinal obstruction is the presence of a“closed loop”．Closed－loop obstruction of the small intestine results when the lumen is occluded at two points by a single mechanism such as a fascial hernia or adhesive band，thus producing a closed loop whose blood supply is often occluded by the hernia or band as well．During peristalsis，when a“closed loop”is present，pressures reach 30—60 cm H2O．Strangulation of the closed－loop is common in association with marked distention proximal to the involved loop．A form of closed－loop obstruction is encountered when complete obstruction of the colon exists in the presence of a competent ileocecal valve （85％of individuals）．Although the blood supply of the colon is not entrapped within the obstructing mechanism，distention of cecum is extreme because its greater diameter，and impairment of the intramural blood supply is considerable，with consequent gangrene of the cecal wall．Once impairment of blood supply to the gastrointestinal tract occurs，bacterial invasion supervenes， and peritonitis develops．The systemic effects of extreme distention include elevation of the diaphragm with restricted ventilation and subsequent atelectasis．Venous return via the inferior vena cava may also be impaired．

Symptoms

Mechanical intestinal obstruction is characterized by cramping midabdominal pain，which tends to be more severe the higher the obstruction．The pain occurs in paroxysms，and the patient is relatively comfortable in the intervals between the pains．Audible borborygmi are often noted by the patient simultaneously with the paroxysms of pain．The pain may become less severe as distention progresses，probably because motility is impaired in the edematous intestine． When strangulation is present，the pain is usually more localized and may be steady and severe without a colicky component，a fact that often causes delay in diagnosis of obstruction．Vomiting is almost invariable，and it is earlier and more profuse than the higher obstruction．The vomitus initially contains bile and mucus and remains as such if the obstruction is high in the intestine．With low ileal obstruction，the vomitus becomes feculent，i．e．orange－brown in color with a foul odor，which results from the overgrowth of bacteria proximal to the obstruction．Hiccups are common．Obstruction and failure to pass gas by rectum are invariably present when the obstruction is complete，although some stool and gas may be passed spontaneously or after an enema shortly after onset of the complete obstruction．Diarrhea is occasionally observed in partial obstruction． Blood in the stool is rare but dose occur in cases of intussusception．

In adynamic ileus as well as colonic pseudo－obstruction，colicky pain is absent and only discomfort from distention is evident．Vomiting may be frequent but is rarely profuse．Complete obstipation may or may not occur．Hiccups are common．

Physical Findings

Abdominal distention is the hallmark of all forms of intestinal obstruction． It is least marked in cases of obstruction high in the small intestine and most marked in colonic obstruction．In early obstruction of small and large intestine， tenderness and rigidity are usually minimal；the temperature is rarely＞37．8℃． The appearance of shock，tenderness，rigidity，and fever indicates that contamination of the peritoneum with infected intestinal content has occurred． Hernial orifices should always be carefully examined for the presence of a mass． Auscultation may reveal loud，high－pitched borborygmi coincident with colicky pain，but this finding is often absent late in strangulating or nonstrangulating obstruction．A quiet abdomen does not eliminate the possibility of obstruction， nor dose it necessarily establish the diagnoses of adynamic ileus．The presence of a palpable abdominal mass usually signifies a closed－loop strangulating small－bowel obstruction；the tense fluid－filled loop is the palpable lesion．

Treatment

Small－intestinal obstruction．The overall mortality rate for obstruction of the small intestine is about 10％．While the mortality rate for nonstrangulating obstruction is 5％—8％，the mortality rate for a strangulating obstruction ranges from20％to 75％．Since strangulating small－bowel obstruction is always complete，surgical interventions should always be undertaken in such patients after suitable preparation．Before operating，fluid and electrolyte balance should be restored and decompression instituted by means of a nasogastric tube．Replacement of potassium is especially important because intake is nil and losses in vomitus are large．There are few，if any indications for the use of a long intestinal tube．Operative intervention may be undertaken successfully by laparoscopic techniques with a decreased incidence of wound complications． However，laparoscopic lysis of adhesions is associated with a longer operative time and higher conversion to open rate when compared to other laparoscopic procedures．Alternatively，lysis of adhesions can occur through an open abdominal incision．In general，＞50％of adhesions that occur are found at the previous incision site．Purely nonoperative therapy is safe only in the presence of incomplete obstruction and is best utilized in patients without increasing abdominal pain or leukocytosis．The overall recurrence of small－bowel obstruction is 16％．Population－based studies show that although the surgical management of small－bowel obstruction is associated with longer hospital stays， the rate of readmission for obstruction is lower．However，regardless of treatment type，following the index admission，only 20％of patients required readmission within a 5－year follow－up period．

Colonic obstruction．The mortality rate for colonic obstruction is about 20％．As in small－bowel obstruction，nonoperative treatment is contraindicated unless the obstruction is incomplete．Incomplete obstruction can be treated with colonoscopy decompression and placement of a metallic stent if a malignant lesion is present．The success rate approaches 90％depending on the location of the obstruction，with left－sided lesions being more successfully stented than right－sided lesions．In general，the colonic stent is considered to be a temporary solution or a“bridge to surgery”，which allows for colonic preparation before surgical intervention．When obstruction is complete，early operation is mandatory，especially when the ileocecal valve is competent，because of the concern for cecal perforation．Cecal perforation is more likely if the cecal diameter is＞10 cm on plain abdominal film．

Decisions regarding the operative management of colonic obstruction are based on the cause of the obstruction and the patient's overall well－being．4 For obstruction on the left side of the colon，operative management strategies include either decompression by cecostomy or transverse colostomy or resection with end－colostomy formation．Primary resection of obstructing left－sided lesions with on－table washout of the colon has also been accomplished safely．145 For a lesion of the right or transverse colon，primary resection and anastomosis can be performed safely because distention of the ileum with consequent discrepancy in size and hazard in suture are usually not present．Furthermore， the bacterial and stool content is less on the right side of the colon，decreasing the chance of infection．

Adynamic Ileus．This type of ileus usually responds to nonoperative decompression and treatment of the primary disease．The prognosis is usually good．Correction of electrolyte abnomalities should be performed（i．e． potassium，magnesium）．Successful decompression of a colonic ileus has been accomplished by repetitive colonoscopy．Neostigmine is also effective in cases of colonic ileus that have not responded to other conservative treatment．5 Rarely，adynamic colonic distention may become so great that cecostomy is required if cecal gangrene is feared．

（1，690 words）

New Words and Phrases

intestinal obstruction 肠梗阻

adhesive［əd'hiːsɪv］a． 黏着的，带黏性的

hernia［'hзːnɪə］n． 疝，突出

gastric bypass 胃旁路手术

intrinsic［ɪn'trɪnsɪk］a． 本质的；内在的

gallstone［'ɡɔːlstəʊn］n． 胆石；胆囊结石

intussusception［ɪntəssə'sepʃən］n． 肠套叠

adynamic［ædaɪ'næmɪk］a． 无力的，衰弱的

pseudo－［'psjuːdəʊ，'psuː－］ 假，伪的

sympathoadrenal［,sɪmpəθəʊə'driːnəl］systemn． 交感肾上腺系统

hydrochloric acid 盐酸

retroperitoneal［'retrəʊ,perɪtə'niːəl］a． 腹膜后的

hematoma［hiːmə'təʊmə，hem－］n． 血肿

vertebral［'vзːtɪbrəl］a． 脊椎的，椎骨的

thoracic［θɔː'ræsɪk，θəʊ－］a． 胸的；胸廓的

infarction［ɪn'frækʃən］n． 梗死

potassium［pəʊ'tæsɪəm］n． 钾

distention［dɪs'tenʃən］n． 膨胀，扩张

motility［məʊ'tɪlətɪ，'məʊtaɪlɪtɪ］n． 能动性；机动性

nitrogen［'naɪtrədʒən］n． 氮

suction［'sʌkʃən］n． 吸；吸力；抽吸

adjunct［'ædʒʌŋkt］n． 附属物；助手a． 附属的

ingest［ɪn'dʒest］v． 摄取；吸收

saliva［sə'laɪvə］n． 唾液，涎

sodium［'səʊdɪəm］n． 钠

flux［flʌks］n． 流量；流出

sequestration［,siːkwe'streɪʃən］n． 隔离

edematous［ə'demətəs］a． 水肿的；浮肿的

closed－loop 闭环，闭合环路

peristalsis［,perɪ'stælsɪs，－'stɔːl－］n． 蠕动

strangulation［,stræŋɡjʊ'leɪʃən］n． 绞窄；窒息

intramural［,ɪntrə'mjʊərəl］a． 内部的

cecal［'siːkəl］a． 盲肠的

gastrointestinal tract 胃肠道；胃肠管

supervene［,sjuːpə'viːn］v． 意外发生，并发

diaphragm［'daɪəfræm］n． 隔膜；膈

ventilation［,ventɪ'leɪʃən］n． 通风；换气

paroxysm［'pærəksɪzəm］n． （疾病周期性）发作；突发

audible［'ɔːdəbl］a． 听得见的

borborygmus［,bɔːbə'rɪɡməs］ 腹鸣

（［复］borborygmi）n．

colicky［'kɒlɪkɪ］a． 腹痛的；绞痛的

vomitus［'vɒmɪtəs］n． 呕吐物；呕吐

bile［baɪl］n． 胆汁

feculent［'fekjʊlənt］a． 浑浊的；污秽的

foul［faʊl］a． 污秽的；淤塞的

rectum［'rektəm］n． 直肠

stool［stuːl］n． 粪便

enema［'enɪmə］n． 灌肠剂；灌肠法

obstipation［,ɒbstɪ'peɪʃən］n． 顽固性便秘

hallmark［'hɔːlmɑːk］n． 特点；标志

colonic［kə'lɒnɪk］a． 结肠的

orifice［'ɒrɪfɪs，'ɔː－］n． 孔口

auscultation［,ɔːskəl'teɪʃən］n． 听诊

bowel［'baʊəl］n． 肠

electrolyte balance 电解质平衡

decompression［,diːkəm'preʃən］n． 解压，降压

institute［'ɪnstɪtjuːt］v． 创立，设置

nasogastric tube 鼻胃管

nil［nɪl］n． 无，零

laparoscopic［,læpərə'skɒpɪk］a． 腹腔镜检查的

lysis［'laɪsɪs］n． 溶解

recurrence［rɪ'kʌrəns］n． 再发，复发

metallic［mɪ'tælɪk，me－］a． 金属的，含金属的

stent［stent］n． 肠道扩撑支架

perforation［,pзːfə'reɪʃən］n． 穿孔；贯穿

cecostomy［siː'kɔːstəmɪ］n． 盲肠造口术

transverse［trænz'vзːs］a． 横向的，横切的

colostomy［kə'lɒstəmɪ］n． 结肠造口术

washout［'wɒʃəʊt，'wɔːʃ－］n． 冲刷

transverse colon 横结肠

ileum［'ɪlɪəm］n． 回肠

discrepancy［dɪs'krepənsɪ］n． 不符；差异

suture［'suːtʃə］n． 缝合

magnesium［mæɡ'niːzɪəm］n． 镁

colonoscopy［,kəʊlə'nɒskəpɪ］n． 结肠镜检查

neostigmine［,niːəʊ'stɪɡmiːn，－mɪn］n． 新斯的明（一种胆碱能药）

Notes

1．The incidence of acute intestinal obstruction requiring hospital admission within the first few post－operative weeks is 5％—25％，and 10％—50％of these patients will require surgical intervention．

参考译文：术后前几周需要入院治疗的急性肠梗阻的发病率是5％～25％，其中10％～50％的患者需要手术干预。

句中The incidence是主语，is是谓语，requiring hospital admission within the first few post－operative weeks是现在分词短语作后置定语修饰acute intestinal obstruction．

2．Retroperitoneal hematoma，particularly associated with vertebral fracture， may cause severe adynamic ileus，and the latter may occur with other retroperitoneal conditions，such as ureteral calculus or severe pyelonephritis．

参考译文：腹膜后血肿，特别是脊椎骨折引起的腹膜后血肿，也许会导致严重的无力性肠梗阻。而且，无力性肠梗阻可能还伴有其他腹膜后疾病，如输尿管结石或严重的肾盂肾炎。

句中particularly associated with vertebral fracture是分词短语做非限制性定语，修饰retroperitoneal hematoma。the latter（后者）指代severe adynamic ileus。

3．Thoracic diseases，including lower－lobe pneumonia，fractured ribs，and myocardial infarction，frequently produce adynamic ileus，as do electrolyte disturbances，particularly potassium depletion．

参考译文：胸部疾病，包括下叶性肺炎、肋骨骨折和心肌梗死，通常会引起无力性肠梗阻；电解质紊乱，尤其是钾损耗也会引起无力性肠梗阻。

as do electrolyte disturbances是非限制性定语从句，as做关系代词，do做谓语，指代前面的produce。

4．Decisions regarding the operative management of colonic obstruction are based on the cause of the obstruction and the patient's overall well－being．参考译文：决定是否为结肠梗阻患者实施手术应综合考虑梗阻的原因及患者的整体健康状况。

regarding the operative management of colonic obstruction，是介词短语做定语，修饰主语decisions；regarding是介词，意为“关于”。e．g．He knew nothing regarding the case．关于这事他一无所知。

5．Neostigmine is also effective in cases of colonic ileus that have not responded to other conservative treatment．

参考译文：新斯的明对于经其他保守治疗无效的无力性结肠梗阻病例也有效。

句中in cases of意为“在……的病例中”，case此处指“病例；患者”。

e．g．an emergency（urgent）case急症病例。

Exercises

Ⅰ．Answer the following questions．

1．What are the two other conditions that must be differentiated from acute intestinal obstruction？

2．In what kind of condition is colicky pain absent？

3．Is intestinal pseudo－obstruction a chronic motility disorder that frequently mimics mechanical obstruction？

4．How is mechanical intestinal obstruction characterized？

5．What is the mortality rate for colonic obstruction？

Ⅱ．Decide whether the following statements are True or False．

1．The incidence of postoperative intestinal obstruction may be higher following laparoscopic surgery than open procedures．

2．Intestinal pseudo－obstruction is a chronic motility disorder that frequently mimics mechanical obstruction．

3．Distention of the intestine is caused by the accumulation of gas and fluid proximal to and within the obstructed segment．

4．In adynamic ileus as well as colonic pseudo－obstruction，colicky pain and discomfort from distention are evident．

5．Since strangulating small－bowel obstruction is always complete，surgical interventions should always be undertaken in such patients after suitable preparation．