Enterovesical fistula in chronic lymphocytic leukemia transforming to Richter syndrome: a case report and literature review.

Richter transformation (RT) is an uncommon complication of chronic lymphocytic leukemia (CLL) that can lead to aggressive large B-cell lymphoma or Hodgkin lymphoma. Here, we present a rare case of enterovesical fistula (EVF) resulting from RT of CLL. A 59-year-old Caucasian male with CLL visited the hematology department with severe abdominal pain in the hypogastrium. Ultrasonography showed an increase in wall thickness in a segment of the ileum with adjacent lymphadenopathy, indicating lymphomatous involvement. A day after receiving chemotherapy, the patient complained of hematuria. He underwent a cystoscopy, which revealed no abnormal findings. After the cystoscopy, the patient's hematuria stopped, but he complained about the excretion of food from the previous day in his urine. The patient's CT cystography results were normal. However, the abdominopelvic CT scan revealed an increase in the thickness of the small intestine loops in the distal part of the jejunum without any evidence of obstruction, suggesting lymphomatous involvement. Based on the patient's fecaluria, he uneventfully underwent surgery, and EVF was confirmed. Resection of the involved small intestine and partial cystectomy were done. The pathology results suggested RT of CLL to diffuse large B-cell lymphoma (DLBCL). Not only EVF might be an uncommon complication of CLL, but it could also manifest in patients undergoing RT due to the disease's characteristics or as a result of treatment. It is essential for clinicians managing CLL patients to be aware of the RT and its complications.