A Case of Parasite Invasion of the Intestinal Tract: A Missed Diagnosis in Irritable Bowel Syndrome
A 24-year-old man was referred to our gastroenterology department for the specialized management of persistent symptoms such as intermittent epigastric and lower abdominal pain that had begun approximately 7 months earlier. The pain had developed gradually and tended to aggravate after meals.\nOne month prior to his referral to our department, the patient had visited a primary outpatient clinic several times and was administered medication to control symptoms, but his symptoms did not improve. The patient was later admitted to a primary hospital for 1 week, where gastroduodenoscopy, colonoscopy, abdominal sonography, and laboratory testing was performed to identify the cause of the symptoms. On the basis of these examinations, he was diagnosed with IBS and administered medication. However, because of poor symptom control, the patient was referred to our hospital for specialized management of IBS. The patient had no medical history, including drug history, and had lost approximately 5 kg over the previous 7 months. The patient had a history of 5 pack-years of smoking and social alcohol consumption. The patient's father was diagnosed with pulmonary tuberculosis 1 month earlier and was receiving medication. The patient was employed as a cell phone salesman, but helped with work on his father's farm every weekend. His associated symptoms were frequent nausea with vomiting and diarrhea-like loose stools.\nPhysical examination findings were nonspecific and he showed chronic rather than acute illness. He had no tenderness or rebound tenderness on his abdomen. Laboratory test results of peripheral blood, blood biochemistry, and serum electrolytes were all within the normal ranges. Urine analysis and stool occult blood test showed no abnormal findings. Because of his weight loss, we tested his glucose and thyroid-associated hormone levels. His fasting blood glucose level was 87 mg/dL and the results of the thyroid function test were normal. We reviewed the imaging studies performed at the primary hospital. Gastroduodenoscopy showed chronic atrophic gastritis with erosion, and colonoscopy showed nonspecific terminal ileitis. Abdominal ultrasonography findings were nonspecific. After referral to our hospital, we changed his drugs to control symptoms. As intermittent lower abdominal pain persisted, we considered additional examinations such as small intestine endoscopy or capsule endoscopy to evaluate the small intestine. Considering the patient's compliance and the possibility of observation of the terminal ileum, we chose capsule endoscopy. On capsule endoscopy, the terminal ileum was normal, but a whitish tubular organism suspicious of a parasite with nearby multiple erosive lesions was observed at the proximal jejunum (, Supplementary Video 1 [available online at ]). Although we had considered the diagnosis to be IBS until that point, we changed the diagnosis to parasitic intestinal infection on the basis of the capsule endoscopic images. Additional examinations for parasitic infections, including blood testing and stool examination, were performed. His eosinophil count was 120/mm3 (reference range, 50 to 500); the results of the enzyme-linked immunosorbent assay were negative for cysticercosis, Sparganum, Paragonimus, and Clonorchis sinensis; and the result of a stool parasite test was also negative. Although the additional tests did not give additional information, based on symptoms, the results of examinations, and factors such as location (proximal jejunum), morphology (whitish small tubular shape), size (<2 cm), and erosive mucosal lesions around the organism, we diagnosed the patient with parasitic infection, and more precisely hook worm (Ancylostoma duodenale) infection at the proximal jejunum. We therefore empirically prescribed albendazole (400 mg/day) for 3 days. Ten days after administration of the drugs, the patient's symptoms slowly abated, and the patient recovered with no specific symptoms.