Laboratory Studies
A complete blood cell (CBC) count is used to confirm neutropenia. A serum bicarbonate level and pH value should be obtained to rule out acidosis.
Obtain stool studies for the following:
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Clostridium difficile toxin to rule out pseudomembranous colitis
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Culture for enteric pathogens to rule out infectious causes of enterocolitis
Obtain blood cultures for aerobic/anaerobic bacteria and fungus to rule out bacterial and fungal sepsis.
Imaging Studies
Radiography
Plain abdominal radiographs rarely help in the diagnosis of neutropenic enterocolitis. Radiographic findings usually are nonspecific and may even be normal. Nonspecific findings may include the following:
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Right-side colonic and small-bowel dilatation
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Thumbprinting (see the image below) of the right colon
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Paucity of air in the right colon because of a fluid-filled colon
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Intramural air or pneumatosis
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Soft-tissue mass displacing the small bowel
Neutropenic enterocolitis. Plain abdominal radiograph in a 44-year-old man known to have a long history of ulcerative colitis. The patient presented with an acute exacerbation of symptoms. Image shows thumbprinting in the region of the splenic flexure of the colon.
Barium enema is usually contraindicated, especially if a potential for perforation exists. Water-soluble contrast may demonstrate rigidity and thickening of the cecum.
Abdominal ultrasonography
Abdominal ultrasonography is one of the most important diagnostic studies for neutropenic enterocolitis, and it is preferable to contrast enemas. Ultrasonography may be also useful as a follow-up tool to assess the gradual decrease in bowel-wall thickening.
Findings include thickening of the bowel wall that produces a target or halo sign. However, this is a nonspecific finding and may be observed in other conditions listed under the differential diagnosis (see DDx).
Bowel-wall thickness has also been suggested as a significant prognostic factor regarding patient outcome in individuals with neutropenic enterocolitis. [31, 32] A retrospective study using ultrasonography showed that mortality was higher in patients with a bowel-wall thickness greater than 5 mm (29%) than in those without bowel-wall thickening (0%). [33] If the bowel-wall thickness cutoff was set at greater than 10 mm, the mortality was 60%, as compared with 4.2% in those without bowel-wall thickening.
Bowel-wall thickening has also been associated with the duration of illness and neutropenia in neutropenic enterocolitis. [34]
Ultrasonography also allows follow-up imaging without repeated exposure to ionizing radiation, an especially important consideration in children and younger adults. [30]
Abdominal computed tomography (CT) scanning
CT scanning of the abdomen (see the images below) is the diagnostic procedure of choice in neutropenic enterocolitis, [30] because it has a lower false-negative rate (15%) than ultrasonography (23%) or plain abdominal radiography (48%). CT scanning is also the test of choice for diagnosing alternative causes of abdominal pain, such as megacolon, appendicitis, and small-bowel obstruction. [15, 35, 36, 37]
Typhlitis. Marked asymmetric cecal wall thickening (arrow) in a 64-year-old patient whose status is postchemotherapy for lymphoma.
Typhlitis. Marked circumferential cecal and ascending colon wall thickening (large arrows) with mild pericolonic inflammatory stranding (small arrows).
CT scan findings include the following:
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Symmetrical thickening of the cecum
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Fluid-filled cecum
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Pericecal inflammation
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Free air if an underlying perforation exists
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Portal venous gas
Procedures
Endoscopic procedures that may be considered in the setting of neutropenic enterocolitis include colonoscopy and flexible sigmoidoscopy (see the images below). However, these procedures are relatively contraindicated in patients with neutropenic enterocolitis because of an increased risk of complications (eg, perforation), [30] especially in the context of underlying neutropenia and thrombocytopenia. They are usually unnecessary, except in rare circumstances in which a gentle sigmoidoscopy may aid in the diagnosis of pseudomembranous colitis.
Neutropenic enterocolitis. Colonic pseudomembranes of pseudomembranous colitis. Photographs courtesy of Eric M. Osgard, MD.
Histologic Findings
Gross and microscopic findings of neutropenic enterocolitis include diffuse bowel-wall thickening with mucosal and intramural edema and necrosis, mucosal ulcerations, and intramural or intraluminal hemorrhage. The bowel-wall specimens obtained during colectomy or at autopsy demonstrate an abundance of bacteria, a striking lack of lymphoid inflammatory cells, and a virtual absence of neutrophils.
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Neutropenic enterocolitis. Ulcerative oral mucositis lesion on the lateral and ventral surfaces of the tongue.
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Neutropenic enterocolitis. Colonic pseudomembranes of pseudomembranous colitis. Photographs courtesy of Eric M. Osgard, MD.
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Neutropenic enterocolitis. Frontal abdominal radiograph in a patient with proved pseudomembranous colitis. Note the nodular haustral thickening, most pronounced in the transverse colon.
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Neutropenic enterocolitis. Perforated appendicitis with abscess; computed tomography scan. Note the appendicolith (arrow) and air within the abscess. The terminal ileum lies anterior to the appendiceal abscess, and inflammatory change is noted in its wall, which appears thickened (open arrow).
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Neutropenic enterocolitis. Plain abdominal radiograph in a 44-year-old man known to have a long history of ulcerative colitis. The patient presented with an acute exacerbation of symptoms. Image shows thumbprinting in the region of the splenic flexure of the colon.
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Typhlitis. Marked asymmetric cecal wall thickening (arrow) in a 64-year-old patient whose status is postchemotherapy for lymphoma.
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Typhlitis. Marked circumferential cecal and ascending colon wall thickening (large arrows) with mild pericolonic inflammatory stranding (small arrows).
