Teaching Case

A 37-year-old man presented in the ER with pain in the right iliac fossa. HIV+. No other relevant personal history.  Ultrasound was requested to rule out appendicitis.

Fig 1 – Ultrasound of the RLQ shows marked circumferential hypodense thickening of a bowel segment (arrows), with adjacent fat hyperecogenicity and a sliver of peritoneal fluid (arrowhead).

Fig 2 – Abdominopelvic CT shows hypodense and hypovascular marked thickening of the terminal ileum (arrows), with adjacent fat stranding and minimal ascites (arrowheads).

Fig 3– Coronal reformat of the abdominopelvic CT better depicts the thickness and length of the affection of the terminal ileum and shows adenopathy in the ileocolic and para-aortic areas. Note that there is no bowel obstruction.

Fig 4 – ADC map and DWI MRI (b=700) images show restricted diffusion in the mass (arrows).

Fig 5 – PET-CT-FDG shows uptake only in the terminal ileum mass. No uptake in other locations, namely in the lymphatic nodes, liver and spleen.

Fig 6 – Post chemotherapy CT shows marked improvement in the terminal ileum wall thickening although there is now a stenosis (arrow) with upstream ileum and jejunum dilatation (arrowheads).

Background

The gastrointestinal tract is the most common extranodal site for lymphoma. Most cases are secondary to widespread disease elsewhere in the body. Primary lymphoma of the GI tract is very rare (1-4% of GI neoplasms), with the most common sites being the stomach, small intestine and the ileocecal area. It is almost always a Non-Hodgkin lymphoma, most commonly of large B-cell or MALT types. HIV and Helicobacter pylori infections, celiac disease, inflammatory bowel disease, and immunosuppression are all risk factors. [1,2]

Clinical perspective

Clinical presentation is quite unspecific (abdominal pain, nausea and vomiting).

Imaging perspective

At Ultrasound these lesions are usually hypoechoic and most commonly are circumferential, like in our case (fig 1).

CT is often used to evaluate the extent and stage of disease. Bulky, hypodense and hypovascular thickening of the bowel wall (>2 cm) and extensive regional lymphadenopathy are reliable features of lymphoma - features seen in our case (fig 2). Aneurysmal dilatation is a typical finding and there is usually no bowel obstruction, like in our case (fig 3). Segmental, circumferential and mild wall thickening, double halo or target sign, and only mild or absent lymphadenopathy are features that point to inflammatory conditions. Adjacent fat stranding, invasion and obstruction favor adenocarcinoma. [1,3]

MRI is usually not necessary, as it depicts the same findings as CT, with the only additional information being increased restricted diffusion, like in our case (fig 4).

PET-CT-FDG should be used for staging. Since PET-CT-FDG showed uptake only in the bowel mass (fig 5), with no involvement of liver, spleen and lymph nodes, the diagnosis of a primary GI lymphoma was made.

Radiology findings alone are not sufficient for a definitive diagnosis. Histology is required. In our case, colonoscopic biopsy revealed a large B-cell lymphoma.

Outcome

There is currently no consensus for treatment of primary lymphoma of the bowel. Typically it involves chemotherapy, radiation therapy, surgery or a combination of the three. [4,5] Our patient underwent 6 cycles of chemotherapy (R-CHOP + IT-MTX/ARAC).

CT done 40 days after starting chemotherapy showed a terminal ileum stenosis with bowel obstruction (fig 6), so the patient ended up having bowel resection. The surgical specimen showed that the stenosis was caused by inflammation due to the chemotherapy with no active B lymphoma cells.

Teaching points

Bulky hypovascular wall thickening of the bowel, with or without aneurysmal dilatation and with associated local adenopathy are typical features of primary lymphoma of the bowel.