Elliot K. Fishman M.D.
Johns Hopkins Hospital

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“Graft-versus-host disease occurs when functionally competent T lymphocytes are introduced into an immunocompromised recipient . Acute graft-versus-host disease presents within the first 100 days of allogeneic bone marrow transplantation and is one of the major complications of this procedure. The skin, gastrointestinal tract, and liver are the principal targeted organs in patients with acute graft-versus-host disease. Symptoms of this disease are often nonspecific and include abdominal cramping, diarrhea, fever, nausea, and vomiting. The differential diagnosis includes gastrointestinal infections, neutropenic enterocolitis, and, during the early posttransplantation period, sequelae of chemotherapy and radiation treatment.”
CT Features with Pathologic Correlation of Acute Gastrointestinal Graft-Versus-Host Disease After Bone Marrow Transplantation in Adults
Babak N. Kalantari et al.
American Journal of Roentgenology. 2003;181: 1621-1625.

“In summary, the CT appearance of acute gastrointestinal graft-versus-host disease in adults includes bowel wall thickening with or without proximal dilatation, engorgement of the vasa recta, mesenteric fat stranding, mucosal and serosal enhancement, gallbladder–biliary tract abnormalities, and ascites. The CT findings associated with high grade graft-versus-host disease were thickening of the distal esophagus, ileum, or ascending colon, as well as increasing numbers of thickened bowel wall segments.”
CT Features with Pathologic Correlation of Acute Gastrointestinal Graft-Versus-Host Disease After Bone Marrow Transplantation in Adults
Babak N. Kalantari et al.
American Journal of Roentgenology. 2003;181: 1621-1625.

“Intestinal CT abnormalities included bowel wall thickening, defined as >3 mm, and bowel wall dilatation, defined as region of small bowel with a diameter >2.5 cm, or of large bowel >8.0 cm. Extent of bowel involvement was defined as segmental (≤40 cm) or diffuse (>40 cm).Intestinal mucosal enhancement and attenuation patterns of bowel wall were assessed as well. The latter included the “water halo sign” (defined as a line of decreased attenuation within the bowel wall), the “accordion sign” (defined as broad transverse bands in the colon that trap oral contrast ) and pneumatosis intestinalis.”
CT in the clinical and prognostic evaluation of acute graft-vs-host disease of the gastrointestinal tract. 
Shimoni A, et al.
Br J Radiol. 2012 Aug;85(1016):e416-23.

”Pneumatosis intestinalis was observed in only one of our patients. It has been rarely reported in patients with GVHD, believed to be a benign entity related to high-dose steroids and chemotherapy. Occasionally it is asymptomatic and detected incidentally. Gas may also be detected in the retroperitoneum or peritoneal cavity, as was the case in our patient.”
CT in the clinical and prognostic evaluation of acute graft-vs-host disease of the gastrointestinal tract. 
Shimoni A, et al.
Br J Radiol. 2012 Aug;85(1016):e416-23.

“Abdominal emergencies in cancer patients can result from the underlying malignancy itself, cancer therapy and/or result from the standard pathologies causing acute abdomen in otherwise healthy population. Therapy-related or disease-related immunosuppression or high dose analgesics often blunt many of the findings which are usually expected in non-cancer general population. This complicates the clinical picture rendering the clinical exam less reliable in many cancer patients, and resulting in different pathologies which clinicians and the radiologists should remain aware of.”
Imaging of acute abdomen in cancer patients 
Morani AC et al.
Abdominal Radiology 2019 https://doi.org/10.1007/s00261-019-02332-5