IPCEA全科医学教学病例——肠易激综合征误诊知多少

张永建，Bruce Kenney，吴 华

1 病史

胡先生，29岁，是一位公司职员，体形消瘦。前来就诊的主要问题是9个月来反复腹部不适、大便不成形，曾被多家医院诊断为肠易激综合征(IBS)。患者起初因吃过多冰激凌及长期饮食不规律，开始偶尔出现腹部不适，部位不定，大便呈稀糊状，1～2次/d，无黏液脓血便。6个月前上述症状加重，且间断出现大便稀水样，多发生于饭后或饮用凉白开后，2～4次/d，便前感下腹部绞痛，便后缓解，偶有大便带黏液。5个月来自感肠道有跳动感，与血管搏动无关，同时出现肠鸣音亢进，于卧位时较为明显。曾口服美常安及酸奶治疗，疗效不明显。腹泻症状可被“氟哌酸2粒，2次/d”改善，但病情较反复。既往有过敏性鼻炎病史7年。有羊肉过敏史。

2 查体及辅助检查

腹软，上腹部剑突下轻压痛，左下腹按压感酸胀且有便意感，腹主动脉搏动明显。肠鸣音无亢进。辅助检查：多次大便常规、血常规均未见异常。血生化全套、促甲状腺激素(TSH)、腹部B超及肠镜等检查未发现异常。

3 需要考虑的问题

3.1 这种病例的诊疗中经常忽略哪些问题？

3.2 是否有喝牛奶的习惯？喝牛奶后是否有不适症状？

3.3 可能的诊断是什么？

3.4 根据临时诊断，如何治疗？

4 诊断及初步处理

对于慢性腹部不适、腹泻，伴或不伴腹痛，无异常体征及检查结果的患者，在诊断IBS之前，我们应挖掘患者生活中可能与腹泻相关的饮食、情绪等因素，如精神紧张、进食牛奶、含麸类食物等。美国家庭医生Dr Bruce William Kenney指出IBS的诊断应在排除其他疾病时方可考虑，尤其应重视追问腹泻是否与进食奶制品、麦麸类食品及海鲜类食品有关。此患者平素无喝牛奶习惯，喝牛奶10分钟后常出现“呃逆”。因此可能的诊断是乳糖不耐受，应排除乳糖不耐受后再考虑IBS。建议患者可尝试避免进食鲜奶制品，更换为酸奶或羊奶。患者将牛奶更换为酸奶1个月后腹部不适、腹泻症状明显好转。可以初步证实该患者腹泻是与乳糖酶缺乏导致的乳糖不耐受相关。腹泻的罪魁祸首原来是牛奶。

5 讨论

因乳糖不耐受、果糖不耐受、乳糜泻(麸质不耐受)等疾病与IBS症状相似，长期以来上述病例常被误诊为IBS。我们全科医生要引起重视，如果是上述疾病，那么去除病因，病人是可以痊愈的。

乳糖不耐受是人体缺乏分解牛奶中乳糖的乳糖酶。因要消化母乳中的乳糖，所有婴幼儿几乎都能分泌乳糖酶。但大部分亚洲、非洲人群分泌乳糖酶的基因会随着年龄增长而关闭。而“自然选择”使长期以奶制品为生的欧美人群保留了乳糖酶基因(亚洲、非洲祖先是不喂养牛的，牛最早是生养在欧美国家)。不消化的乳糖被肠道存在的细菌分解产生一些气体如甲烷、H2、CO2等，可引起肠鸣、腹胀、腹痛、嗳气、腹泻等症状。对于乳糖不耐受的成人，可以食用酸奶、发酵乳、奶酪等替代，也可以饮用特制的不含乳糖的牛奶(舒化奶)。或少量多次，同谷物一起吃，避免空腹饮用牛奶。

乳糜泻[1]：麸质麦胶蛋白食物是主要致病因素，个体的遗传易患性、免疫反应和外界环境因素等共同作用导致患者的肠道黏膜损伤。主要临床表现为恶心、呕吐、腹胀、慢性腹泻、疲劳感等。可进一步通过抗组织转谷氨酰胺酶(tTG)抗体、抗肌内膜(EMA)IgA或小肠活组织检查等明确诊断[2]。对于此类患者应予无麸质饮食，食物应去除小麦、大麦、黑麦,经过饮食治疗,一般3～6 周症状开始明显好转[3]。

另外，对一个慢性腹泻病人一定要排除甲状腺功能异常，因为甲状腺功能亢进经常会导致腹泻。Dr Kenney在教学中还传授了如何做出正确的诊断与鉴别诊断的一个小技巧：准备2个篮子，第一步将所有可能的诊断装在第一个篮子里；第二步从第一个篮子里把所有不可能的诊断逐个拿到第二个篮子里；最后第一个篮子里剩下的诊断很可能就是本病人的诊断。当然有时需要进一步核实。这个技巧非常好，使我们在诊断上考虑的比较全面，诊断思维拓展，对防止漏诊误诊非常有帮助，大家不妨试一试。

1 Giuseppe Montalto.Celiac disease in the developing countries：A new and challenging public health problem [J].World Journal of Gastroenterology,2007,13(15):2153-2159.

2 李慕然,刘艳迪,李文.乳糜泻临床研究进展[J].世界华人消化杂志,2011,19(19):2053-2057.

3 Green PH,Cellier C.Celiac disease[J].N Engl J Med,2007,357(17):1731-1743.

(后续英文原文)

1 History

A 29 year old male hadoccasional diffuse discomfort of his abdomen,and his stools were like thin paste 1 to 2 times a day without purulence or blood,but sometimes with mucus His diet contained some dairy products,and at the time of symptoms onset he increased his ice cream consumption.His abdominal discomfort worsened 3 months after onset,with occasional watery stools after dinner or drinking hot or cold water,2-4 times/day.The abdominal cramping was followed by defecation,and this relieved his symptoms.5 months after onset he reported borgorgymi and bowel cramping,especially when he lied down.He was given live combined Bacillus Subtilize and Enterococcus Faecium enteric-coated capsules and yogurt trials without any effect.After a course of norfloxacin 200 mg bid he reported brief symptom improvement followed by symptom return.Other medical history:allergic rhinitis for seven years.Allergy:lamb.

2 Physical examination

Abdomen:flat and soft with mild tenderness at the epigastrium.The patient felt a defecationsensation with palpation of the left lower quadrant.Normal bowel sounds,no masses or hepatosplenomegaly.

3 Diagnostic examination

Stool microscopic analysis,CBC,CMP,TSH,abdominal ultrasound and colonoscopy examination did not reveal any abnormalities.

4 Questions to consider

4.1 What is the definition of IBS? Rome III Criteria of Diagnosis of IBS,which is the most widely accepted symptomatic classification of IBS:Symptoms of recurrent abdominal pain or discomfort and marked change in bowel habits for at least six months with symptoms experienced on at least 3 days of at least 3 months.

Two or more of the following must apply:

·Pain is relieved by a bowel movement.

·Onset of pain is related to a change in frequency of stool.

·Onset of pain is related to a change in the appearance of stool[1].

4.2 What is the definition of a syndrome? A group of signs and symptoms that occur together and characterize a particular abnormality[2].

4.3 What are the differential diagnosesof IBS? From Rakel Textbook of Family Medicine is the following summary of IBS differential diagnoses:The differential diagnosis of IBS includes inflammatory bowel disease,lactose intolerance,acute gastroenteritis,celiac disease,small intestinal bacterial overgrowth,colorectal cancer,and motility-altering metabolic disturbances (e.g.,hypothyroidism or hyperthyroidism).

4.4 What are some other differential diagnoses often overlooked in the diagnosis of IBS? Other root causes of IBS include food allergies or sensitivities such as gluten enteropathy,enzyme deficits such as pancreatic or lactase deficiencies,stress psychosomatic responses,GI (gastrointestinal) smooth muscle stimulation from stimulants like caffeine,medication side effects,hyperactive or hypoactive GI autonomic nervous system dysfunction,food allergies,low fiber intake,leading to constipation and obstipation.

In addition,FODMAPs (Fermentable,Oligo-,Di-,Monosaccharides,and Polyol sweetners) occurring naturally or added to foods can beresponsible for some cases of IBS.FODMAPs are incompletely digested short-chain carbohydrates that include fructose,lactose,fructans (found in wheat),galactans,and polyol sweeteners[3].

4.5 What are the most likely underlying causes?

4.6 How to confirm or eliminate various possibilities?

4.7 How does the practitioner determine the root cause of IBS & management recommendations? When patients have symptoms of IBS but the physical and laboratory examinations are normal,practitioners must work through the possible causes,often with a trial and error method.Using a food elimination and re-introduction diet is an efficient and effective method in the motivated patient.

Sometimes we are simply left with the diagnosis of the syndrome,IBS,after excluding other diseases and conditions.In this case example the physician preceptor recommended special attention to the patient′s diet.When this patient began to ingest more lactose-containing foods this corresponded with his IBS symptoms.Based upon his history,the most likely diagnosis was lactose intolerance.The patient was advised to avoid lactose products.On follow up one month later the patient′s symptoms were markedly improved after he switched from milk to yogurt.This is an empirical confirmation that he has lactose deficiency.

5 Discussion

The symptoms of IBS are often the same regardless of the root cause,and because there are so many possible causes often the workup is not completed,and thus many patients have been diagnosed as having IBS without any identified root cause.It is important to pay attention to any syndromes or diagnoses that don′t indicate a specific cause,for example headache,fatigue,or depression.It is the responsibility of the medical practitioner to attempt to find the root causes.When this is successful,truly holistic medicine has been practiced.

In the case of lactase deficiency the fermentation of the lactose causes excess gas production and often cramping and diarrhea.Humans typically have lactase production at birth in order to digest breast milk,but this declines or ends with time,especially in the Asian and African populations.However,in Europe and America and countries where cows milk is consumed throughout the life span lactase production continues much longer.

Celiac disease is related to hereditary susceptibility and exposure to gluten proteins.The main clinical features are nausea,vomiting,abdominal distension and pain,weight loss,chronic diarrhea and fatigue.The diagnosis can be aided by testing for TTG(tissue transglutaminase) antibody,while the gold standard is proximal small intestine biopsy. Elimination of all forms of gluten will typically eliminate the symptoms eventually,presuming there are no traces of any hidden gluten contamination in any GI intake.

Skill tips:

·One visual method of differential diagnosis demonstration is to put all possible causes in one big basket,and then move the most likely or common causes over to the smaller working basket for investigation.Once each possible cause is eliminated by history,exam,diagnostic test result,or empirical trial and error,it is removed from the small basket,and another possible cause is evaluated.Often it is practical to test several factors at once,like with an elimination diet.

·If there is no urgency or concern for a serious underlying cause,it is cost-effective to do empirical trials for testing possible causes first,and if later testing is needed,it can then be performed.

·Sometimes we do not find a root cause so we have to start all over with a more in-depth history and exam with the history and exam and more critically evaluating the various possible etiologies.These skills and methods are very effective and applicable to any medical diagnostic process.It assists practitioners to have more comprehensive and accurate diagnoses,and this greatly contributes to the satisfaction of being an effective doctor,to ultimately help our patients.

These are some of the major reasons why most physicians go into medicine.Once a practitioner puts these methods into regular practice,the appreciation of their enhanced diagnostic ability will motivate them to continue the methods.We encourage you to put it into action:you might give it a try.

Conflictsofinterests:Therearenopotential,perceived,orrealconflictsofinterestsofanyoftheauthors.

1 Rakel R,Rakel D.Textbook of a family medcine[M].8th editon,2011.

2 Merriam Webster Medical Dictionary.

3 Halmos EP.A diet low in FODMAPs reduces symptoms of irritable bowel syndrome[J].Gastroenterology,2014,146(1):67-75.