Enterocolic Fistula Associated With an Intestinal Lymphoma

Introduction and Case Report

Introduction

Enterocolic fistulas are usually caused by inflammatory conditions such as inflammatory bowel disease (eg, Crohn's disease). This abnormal communication can also be caused by prior surgery, foreign bodies, pancreatitis, diverticulitis, and, most ominously, by malignancy.

The following case describes an elderly patient with failure to thrive and new-onset diarrhea who underwent colonoscopic examination; findings on colonoscopy revealed a large intestinal lymphoma with an associated enterocolic fistula.

Case Report

An 86-year-old woman presented with an acute diarrheal illness starting 10 days prior to admission. She described 3 to 4 daily episodes of large-volume nonbloody stools with occasional nocturnal episodes. She had occasional diffuse crampy abdominal pain without nausea, and had notable weight loss over the last month. She had daily fevers, chills, and night sweats. There was no recent use of antibiotics, no recent travel, and no history of exposure to sick contacts.

Her past medical history was significant for chronic obstructive pulmonary disease, a recent discovery of a left-sided lung mass with pleural effusion, chronic autoimmune hemolytic anemia, and cholelithiasis. There was no prior history of abdominal surgery. Her sister had colon cancer diagnosed late in life.

The patient was febrile to 101.6°F (38.7°C), with stable hemodynamic vital signs. She was cachetic but appeared nontoxic on exam, with a mildly protuberant abdomen with normal active bowel sounds and no palpable tenderness. Her laboratory tests showed normal electrolytes, serum calcium, thyroid-stimulating hormone, and hepatic panel. The complete blood count revealed a microcytic anemia. The infectious diarrhea work-up was negative. A computed tomographic (CT) scan of the abdomen with oral and intravenous contrast showed no specific abdominal masses or bowel wall abnormalities (not shown).

Results of Colonoscopy

A large enterocolic fistula was identified at the mid-transverse colon with a large communication to the small bowel (Figure 1). The colonoscope moved freely through this fistula (Video). A 5-cm length of friable tumor mass was circumferential, but nonobstructing at the small intestinal side of the fistula (Figure 2). Multiple biopsies were taken from this mass. The remainder of the colon examination yielded normal results.

Figure 1.

Colonic fistula opening.

Figure 2.

Small bowel mass.

Download video file ^{(2.4MB, wmv)}

Video: Colonoscopy Views of the Enterocolic Fistula Within the Colon and the Small Bowel

Pathology Results

The biopsy sample showed diffuse large B-cell lymphoma (Figure 3). Specifically, the biopsy sections showed necroinflammatory debris and granulation tissue with sheets of atypical large lymphoid cells with round to irregular nuclei, vesicular chromatin, distinct single to multiple nucleoli, and scant to moderate cytoplasm. Frequent mitotic figures were present. The atypical cells stained positive for pan-B cell marker CD20 and germinal center markers CD10 and BCL-6, BCL-2, and CD43. These results indicate that the neoplasm is derived from germinal center B cells, a prognostically favorable subtype of diffuse large B-cell lymphoma. MIB-1 (Ki-67) staining, to evaluate the proliferative activity of large neoplastic lymphocytes, revealed a proliferation fraction of 90%, indicating that the neoplasm had a high proliferation rate (Figure 4).

Figure 3.

Hematoxylin and eosin stain at 400x.

Figure 4.

Immunohistochemistry stain with CD20 marker.

Approach to Management and Clinical Outcome

The patient ultimately decided not to pursue further diagnostic studies or active treatment for her lymphoma given her age and comorbidities. She was treated with a course of doxycycline to address bacterial overgrowth, and kept on a lactose-free diet. She was also put on loperamide as needed. She had improvement in her symptoms thereafter.

Discussion

The diagnosis of lymphoma in this case explains the patient's B symptoms (B symptoms include unexplained weight loss, fevers, and drenching night sweats). The histologic diagnosis, diffuse large B-cell lymphoma (DLBCL), is the most common histologic type of nonHodgkin's lymphoma, representing 30% of all such cases.[1] DLBCL is a neoplasm of large transformed B-cells that resemble centroblasts or immunoblasts, with a moderate-to-high proliferation fraction (> 40%–90%). Forty percent of cases of DLBCL present at extranodal sites, most commonly in the gastrointestinal tract. One series reported 18% gastrointestinal involvement in DLBCL.[2] In a series of 371 patients with primary gastrointestinal nonHodgkin's lymphoma, evaluation of anatomic distribution showed the majority to be gastric (75%), with 9% in the small bowel and approximately 9% localized in colonic sites.[3] In the literature, lymphomas have been rarely cited as a cause of enterocolic fistulas.[4] Cancers in general, however, are well known to cause invasion into neighboring structures.

The patient's diarrhea and weight loss may be explained by several mechanisms. The fistula between the small intestine and transverse colon was quite large and might have caused a short bowel syndrome. This in turn may have caused malabsorption, with early dumping of small bowel contents. An increased fluid load in the mid-distal colon also cannot be reabsorbed easily. However, the patient's symptoms were somewhat acute and her electrolytes were not deranged, which argues against the possibility of a chronically open high-output fistula. The other possibility is steatorrhea, which is caused by a loss of bile acids over time due to bypassed absorption of bile salts in the terminal ileum because of the fistula. Alternatively, bile salts themselves can cause diarrhea by stimulating secretion in the colon. Both of these mechanisms could lead to malabsorption of fat and fat-soluble vitamins. Last, the diarrhea could also be due to colonization of the small bowel by colonic bacteria, resulting in small bowel bacterial overgrowth. This problem can be treated with nonabsorbable and absorbable antibiotics.

The treatment of an enterocolic fistula depends on the etiology. Foremost is the correction of fluid and electrolyte abnormalities. Nutritional repletion and treatment of associated infections or abscesses with antibiotics, and possibly drainage, should be addressed. Closure of the fistula is best done surgically if feasible. In Crohn's disease-related fistulas, medical therapy with infliximab may have less efficacy in healing high-output internal fistulas as compared with enterocutaneous and perianal fistulas.[5] Factors that make closure of the fistula more difficult include size of the fistula, presence of cancer, highly active inflammatory bowel disease, foreign body presence, and uncontrolled infection.

Conclusions

Chronic diarrhea in the elderly patient with associated systemic symptoms is suspicious for an underlying organic cause. Colonoscopy should be considered in all such patients. Intestinal lymphomas are rare, and even more rarely cause internal fistulous connections. Enterocolic fistulas may cause diarrhea by excessive fluid load to the colon, short bowel syndrome, loss of bile salts, or small bowel bacterial overgrowth.