Potential of Confocal Laser Endomicroscopy in Detecting Small Bowel Transplant Rejection Based on Current Application in Real-Time Diagnosis of GVHD

Introduction: Graft versus host disease (GVHD) is a multi-system complication of allogeneic bone marrow transplant in which donor T cells falsely identify host’s tissue as a foreign body due to the presence of histo-incompatible antigens. In acute cases, the GI tract, liver, and skin are most commonly affected. Traditionally, histological features of GVHD affecting the small bowel and colon have been identified through forceps biopsy via esophagogastroduodenoscopy (EGD) and colonoscopy. The known small bowel histological features of GVHD closely mirror those of small bowel transplant rejection, such as crypt apoptosis and apoptotic body accumulation in the lamina propria. Confocal laser endomicroscopy (CLE) is a novel endoscopic method used to visualize the mucosal layer of the GI tract via magnification fluoroscopy for purposes of real time diagnosis. The present case study uses CLE to detect histomorphological colonic mucosal features of GVHD in the small bowel, accelerating the ability to diagnose GVHD intra-procedurally and initiate treatment. Due to the striking histological similarities between GVHD and small bowel transplant rejection, CLE is a potential modality for early diagnosis and treatment of small bowel transplant rejection. Methods: This is a case of a 67 year old male with past medical history of HIV, AML status post-stem cell transplant, and CMV colitis who presents with abdominal pain and multiple loose bowel movements per day over the last one week. Results: A 67 year old male presented with a one week history of abdominal pain and loose bowel movements. The patient had undergone stem cell transplant after an AML diagnosis two months prior to admission. He experienced a similar episode of abdominal pain one month prior, at which time a colonoscopy with biopsy demonstrated CMV colitis. Subsequently, he completed a course of valacyclovir and his symptoms had improved. Due to this history, CT-Abdomen and Pelvis with contrast was ordered upon admission, demonstrating persistent residual thickening of the right colon, and an area of mucosal enhancement and bowel wall thickening within the small bowel. Subsequently, EGD utilizing CLE visualized erythematous mucosa in the small bowel and intracryptal apoptosis, which is pathognomonic for GVHD. The patient was immediately initiated on Prednisone 60mg with symptom resolution and discharge within two days. Biopsies resulted a week after the procedure, confirming GVHD diagnosis. Notably, the patient was discharged four days before pathology results were available. Conclusion: Our case demonstrates the effective use of CLE in rapid diagnosis and staging of GVHD, minimizing time between symptom onset and treatment initiation. Moreover, this case demonstrates a strong indication for future use of CLE in early detection and diagnosis of small bowel transplant rejection, as the histological similarities can be captured on CLE and with the potential of initiating earlier treatment.