The laboratory findings in a patient with acute radiation proctitis can be within reference range however, in case of chronic injury anemia, leukocytosis, deranged LFTs and electrolyte abnormalities can be seen.

The initial diagnostic workup for radiation proctitis includes the following:^[1][2]

• A complete blood count shows
  • Anemia, in case of chronic injury and rectal bleeding
  • Elevated white blood cell count due to small-bowel obstruction and intra-abdominal sepsis because of bowel perforation or necrosis in chronic injury
• ESR
• Serum albumin
• Electrolyte studies and renal function tests are done, as chronic diarrhea may be associated with
  • Hypokalemia
  • Hypomagnesemia
  • Pre-renal failure
• Liver function tests
• Stool culture, to rule out parasites and infectious causes.
• Stool C. difficile toxin
• C-reactive protein can be measured, with an elevated level being an indication of inflammation.
• Sexually transmitted infections testing, particularly in homosexual male or patients with severe rectal symptoms including urgency and tenesmus.
• Fecal biomarkers (fecal calprotectin and fecal lactoferrin) are rapid and inexpensive noninvasive tests, which used diagnosis and follow-up of treatment of radiation proctitis however these are not specific for may be elevated in a range of organic conditions.^[3]