S5171 Unusual Culprit as a Cause of Chronic Diarrhea

Introduction: There are numerous causes of diarrhea, ranging from medications and infections to secondary causes of GI conditions. One of the most effective diagnostic tools in the evaluation of chronic diarrhea is the comprehensive PCR stool test which detects more than 20 common causes of infectious diarrhea. We present a case of a patient with diarrhea, initially presumed to be post-infectious or functional, who was eventually found to have Dientamoeba fragilis after initial microbial evaluation. D. fragilis is a parasite that is often asymptomatic and difficult to detect with routine methods. Case Description/Methods: A 78-year-old woman with prior medical history of COVID, hypertension, major depressive disorder, arthritis presented with 10 months of watery diarrhea, occurring 8 times a day and weight loss. Denied any hematochezia, abdominal pain, dysphagia, recent international travel, sick contacts, outdoor exposures, or fevers. She received paxlovid for her first COVID episode. Pertinent medications include celecoxib and escitalopram. Outpatient workup showed normal CBC, CMP and C-reactive protein and negative stool culture and giardia and cryptosporidium. Stool ova, cysts, parasites (OCP) was positive for D. fragilis. She started paromomycin 25 mg/kg TID; subsequently her diarrhea resolved. Discussion: D. fragilis is an intestinal parasite transmitted via the fecal-oral route. It is frequently found in contaminated water, raw produce, pinworm co-infection, and poor hygiene. Many people are asymptomatic carriers, but symptomatic infections have been associated with chronic or intermittent diarrhea, abdominal pain, bloating, nausea, fatigue, or weight loss. This case raises several questions and hypotheses. This patient lacked common risks factors for symptomatic infection; however, her chronic diarrhea in the setting of COVID immune dysregulation rendered her more susceptible to developing symptoms. Additionally, COVID could have triggered a post-infectious irritable bowel syndrome (IBS) with coexistent D. fragilis colonization. This could represent a modifiable factor in her case. It could also be possible that prior to OCP testing, it did not detect the parasite due to its intermittent shedding and limited sensitivity to microscopy-based tests. While asymptomatic infections do not always warrant treatment, symptomatic patients often benefit from eradication. In this case, initiating treatment is appropriate to assess symptom resolution. If symptoms persist after therapy, alternative causes, such as post-infectious IBS, medication effects, or microscopic colitis should be considered.