irritable bowel syndrome ( ibs ) affects 520% of individuals worldwide , most often women < 50 years of age . similarly , endometriosis is very common in this same population , affecting up to 15% of menstruating women . gastrointestinal involvement in endometriosis occurs in only 37% of cases , mostly in the rectosigmoid region and only very rarely in the small intestine . typically endometriosis patients complain of dysmenorrhea , pelvic pain , ovulation pain , dyspareunia and dyschezia , while patients with ibs complain of abdominal pain associated with a change in the frequency or consistency of stools and abdominal bloating . alarm symptoms , which might indicate another diagnosis but are non - specific , include : fever , weight loss , blood in the stools , anemia , abnormal physical findings , abnormal blood tests , and a family history of cancer , inflammatory bowel disease or celiac disease . we present the case of a young woman with a 4-year history of ibs on the basis of abdominal pain associated with constipation , flatus , belching and bloating without gynecological symptoms , and who was eventually discovered to have endometriosis following surgery for a distal ileal stricture . a 44-year - old woman noted the onset of upper and lower abdominal pain associated with constipation approximately 4 years ago . her symptoms were worse following meals , especially if they included fried foods , fatty foods , coffee or carbonated beverages . episodes occurred every 23 days with occasional emesis but no history of hematemesis , melena or hematochezia . her appetite remained good , but she noted a weight loss of 25 lb over the past year . there was no history of alcohol , coffee , aspirin or non - steroidal inflammatory medication abuse . on physical examination she appeared to be well - developed , well - nourished and in no acute distress . rectal examination demonstrated no masses or tenderness , with brown guaiac negative stool present in the rectal ampulla . her diagnostic work - up included normal complete blood count , liver and kidney function tests , thyroid function and c - reactive protein . abdominal and pelvic sonography were normal except for evidence of a prior cholecystectomy , mild fatty liver and a simple right ovarian cyst . a lactose tolerance test was positive . on the basis of her symptoms and negative diagnostic work - up , the diagnoses of ibs treatment with antacids and an anti - cholinergic did not provide relief . due to her recurrent symptoms , this revealed a partial small bowel obstruction located approximately 5 cm proximal to the ileocecal valve ( fig . 1 ) . subsequent surgical resection and histology identified the cause of the partial obstruction to be endometriosis with focal submucosal hemorrhage and serosal scarring ( fig . endometriosis most commonly presents with gynecological symptoms of intermenstrual bleeding , premenstrual exacerbation of pain and forniceal tenderness , while ibs symptoms include more upper abdominal pain , colicky pain and exacerbation of pain by food or stress , as seen in this patient . our patient met the rome iii diagnostic criteria for ibs with onset greater than 6 months of abdominal discomfort for at least 3 days per month over the past 3 months plus a change in stool frequency ( constipation ) and appearance ( small hard stools ) , except for the alarm symptom of weight loss . other possible alarm symptoms include older age at symptom onset , gastrointestinal bleeding , dysphagia , anemia , fever and family history of cancer . even with the presence of an alarm symptom , most patients are clinically considered to have ibs if symptom - guided testing is negative , and our patient underwent upper endoscopy , colonoscopy , abdominal sonography , pelvic sonography and gynecological examinations , all of which failed to reveal any other diagnoses . a large chart review of 1,434 patients with a clinical diagnosis of ibs revealed alarm features in 84% , yet only 79% of them were found to have organic disease . in a study of 200 consecutive patients with a clinical diagnosis of an ibs who were prospectively evaluated , 70% had alarm symptoms , but significant organic disease could only be found in 5% , with another 20% having bacterial overgrowth , lactose or fructose malabsorption . an analysis of multiple studies involving diagnostic testing in patients with a clinical diagnosis the ibs concluded that the probability of finding organic disease was < 1% ; only celiac disease was found to be markedly higher than in the general population . the significance of weight loss , defined as at least 5% decrease in body weight over 612 months as seen in our patient , is uncertain . one review of published studies involving 881 patients found that in older patients ( ages 5972 ) the three most common causes of unexplained weight loss were malignancy , gastrointestinal disorders and psychiatric problems , yet despite extensive evaluation and prolonged follow - up , no diagnosis could be made in 536% of patients . another review on the evaluation of weight loss in adults of all ages found that approximately 25% of patients will not have any diagnosis after testing and follow - up for at least 6 months , and of the remaining 75% approximately one third will have a malignancy , one third hyperthyroidism , diabetes , peptic ulcer disease or cholelithiasis , and one third will have a psychiatric disorder . in a prospective study of 101 patients with unexplained weight loss presenting to a general internal medicine clinic , no etiology could be found in 28% after 9 months , and additionally 94% of patients with no baseline abnormality on standard laboratory tests , chest x - ray and abdominal sonography were not found to have an organic disease as the cause . in conclusion , both ibs and endometriosis are very common among young women of child - bearing age . endometriosis can often be diagnosed only by laparoscopic examination of the abdomen and pelvis , often leading to a delay in diagnosis . alarm symptoms are used to cull out patients with other organic diseases , but are often not sufficiently reliable . furthermore weight loss , which was the only alarm symptom present in our patient , can be non - specific in many cases . yet , as our patient illustrates , the presence of any alarm symptom in a young woman considered to have ibs should lead to close continued clinical follow - up and constant vigilance for other possible unusual causes of the presenting symptoms , including endometriosis .
both endometriosis and irritable bowel syndrome ( ibs ) are commonly found in young women and the diagnosis of either is challenging . 
 alarm symptoms can exclude the diagnosis of ibs , but their onset may be insidious and often no evidence of organic disease may be found . 
 we present a patient with a 4-year history of presumed ibs , absent gynecological symptoms , negative gastrointestinal as well as gynecological testing who developed the only alarm symptom of weight loss and was eventually found to have endometriosis of the small intestine . 
 this case illustrates the need for constant vigilance in patients with ibs .