IPCEA全科醫學教學病例
——腸易激綜合征誤診知多少

張永建，Bruce Kenney，吳 華

1 病史

胡先生，29歲，是一位公司職員，體形消瘦。前來就診的主要問題是9個月來反復腹部不適、大便不成形，曾被多家醫院診斷為腸易激綜合征(IBS)。患者起初因吃過多冰激凌及長期飲食不規律，開始偶爾出現腹部不適，部位不定，大便呈稀糊狀，1～2次/d，無黏液膿血便。6個月前上述癥狀加重，且間斷出現大便稀水樣，多發生于飯后或飲用涼白開后，2～4次/d，便前感下腹部絞痛，便后緩解，偶有大便帶黏液。5個月來自感腸道有跳動感，與血管搏動無關，同時出現腸鳴音亢進，于臥位時較為明顯。曾口服美常安及酸奶治療，療效不明顯。腹瀉癥狀可被“氟哌酸2粒，2次/d”改善，但病情較反復。既往有過敏性鼻炎病史7年。有羊肉過敏史。

2 查體及輔助檢查

腹軟，上腹部劍突下輕壓痛，左下腹按壓感酸脹且有便意感，腹主動脈搏動明顯。腸鳴音無亢進。輔助檢查：多次大便常規、血常規均未見異常。血生化全套、促甲狀腺激素(TSH)、腹部B超及腸鏡等檢查未發現異常。

3 需要考慮的問題

3.1 這種病例的診療中經常忽略哪些問題？

3.2 是否有喝牛奶的習慣？喝牛奶后是否有不適癥狀？

3.3 可能的診斷是什么？

3.4 根據臨時診斷，如何治療？

4 診斷及初步處理

對于慢性腹部不適、腹瀉，伴或不伴腹痛，無異常體征及檢查結果的患者，在診斷IBS之前，我們應挖掘患者生活中可能與腹瀉相關的飲食、情緒等因素，如精神緊張、進食牛奶、含麩類食物等。美國家庭醫生Dr Bruce William Kenney指出IBS的診斷應在排除其他疾病時方可考慮，尤其應重視追問腹瀉是否與進食奶制品、麥麩類食品及海鮮類食品有關。此患者平素無喝牛奶習慣，喝牛奶10分鐘后常出現“呃逆”。因此可能的診斷是乳糖不耐受，應排除乳糖不耐受后再考慮IBS。建議患者可嘗試避免進食鮮奶制品，更換為酸奶或羊奶。患者將牛奶更換為酸奶1個月后腹部不適、腹瀉癥狀明顯好轉。可以初步證實該患者腹瀉是與乳糖酶缺乏導致的乳糖不耐受相關。腹瀉的罪魁禍首原來是牛奶。

5 討論

因乳糖不耐受、果糖不耐受、乳糜瀉(麩質不耐受)等疾病與IBS癥狀相似，長期以來上述病例常被誤診為IBS。我們全科醫生要引起重視，如果是上述疾病，那么去除病因，病人是可以痊愈的。

乳糖不耐受是人體缺乏分解牛奶中乳糖的乳糖酶。因要消化母乳中的乳糖，所有嬰幼兒幾乎都能分泌乳糖酶。但大部分亞洲、非洲人群分泌乳糖酶的基因會隨著年齡增長而關閉。而“自然選擇”使長期以奶制品為生的歐美人群保留了乳糖酶基因(亞洲、非洲祖先是不喂養牛的，牛最早是生養在歐美國家)。不消化的乳糖被腸道存在的細菌分解產生一些氣體如甲烷、H2、CO2等，可引起腸鳴、腹脹、腹痛、噯氣、腹瀉等癥狀。對于乳糖不耐受的成人，可以食用酸奶、發酵乳、奶酪等替代，也可以飲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，避免空腹飲用牛奶。

乳糜瀉[1]：麩質麥膠蛋白食物是主要致病因素，個體的遺傳易患性、免疫反應和外界環境因素等共同作用導致患者的腸道黏膜損傷。主要臨床表現為惡心、嘔吐、腹脹、慢性腹瀉、疲勞感等。可進一步通過抗組織轉谷氨酰胺酶(tTG)抗體、抗肌內膜(EMA)IgA或小腸活組織檢查等明確診斷[2]。對于此類患者應予無麩質飲食，食物應去除小麥、大麥、黑麥,經過飲食治療,一般3～6 周癥狀開始明顯好轉[3]。

另外，對一個慢性腹瀉病人一定要排除甲狀腺功能異常，因為甲狀腺功能亢進經常會導致腹瀉。Dr Kenney在教學中還傳授了如何做出正確的診斷與鑒別診斷的一個小技巧：準備2個籃子，第一步將所有可能的診斷裝在第一個籃子里；第二步從第一個籃子里把所有不可能的診斷逐個拿到第二個籃子里；最后第一個籃子里剩下的診斷很可能就是本病人的診斷。當然有時需要進一步核實。這個技巧非常好，使我們在診斷上考慮的比較全面，診斷思維拓展，對防止漏診誤診非常有幫助，大家不妨試一試。

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,劉艷迪,李文.乳糜瀉臨床研究進展[J].世界華人消化雜志,2011,19(19):2053-2057.

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

(后續英文原文)

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.