Biopsies of the suspected organs can be used to help diagnose GvHD. A tissue diagnosis is not necessary, but helps a clinician make the diagnosis in the correct clinical context. The skin, liver, or GI tract can be readily biopsied.

The diagnosis of GvHD can be made at the histologic level via tissue biopsy. Biopsies of the suspected organs involved can aid in the diagnosis. The sensitivities of tissue biopsy is somewhat limited though, and nearly 40% of cases can be missed.^[1]

• Skin: A skin biopsy will show findings such as vacuolar interface dermatitis. Skin biopsy is typically done via a punch biopsy at bedside, without the requirement of local or general anesthesia. This is the most readily obtainable biopsy as it is the least invasive.
• Liver: A liver biopsy can be obtained via transjugular or percutananeous approaches. This is a relatively invasive procedure that requires anesthesia and carries a risk for bleeding and bowel perforation.
• GI tract: A GI tract biopsy can be done via endoscopy (for upper GI tract) or colonoscopy or flexible sigmoidoscopy (for lower GI tract). These are moderately invasive procedures that requires sedation and carries a moderate risk for bleeding. GI tract biopsies are particular important if there is a clinical concern about CMV enteritis or CMV colitis, as it can be quite challenging to differentiate CMV infection from GI GvHD.