Investigation of suspected intra-abdominal sepsis: the contribution of nuclear medicine.

The diagnosis of abdominal infections and inflammations often presents considerable difficulty, and various imaging techniques may be required to localize them accurately. At present, radiolabelled leucocytes offer the most widely accepted radionuclide method for imaging inflammation. Because of the many advantages of technetium-99m (99mTc) over indium-111 (111In), 99mTc-HMPAO-leucocyte scintigraphy is preferred for the investigation of acute abdominal sepsis and inflammatory bowel disease, and 111In-leucocyte scintigraphy for more chronic infections and renal sepsis. The 99mTc-HMPAO-labelled leucocytes technique is highly accurate within the first few hours postinjection, and is therefore useful also in acutely ill patients. It is sensitive in detecting abdominal abscesses in all locations except the liver and spleen. By whole body imaging, unsuspected sites and types of infection can be found. 99mTc-HMPAO-leucocyte scan is valuable also in the investigation of acute cholecystitis in problematic situations in which ultrasound is known to give misleading results, especially in acute acalculous cholecystitis. In inflammatory bowel disease it can reliably assess disease activity, but a normal scintigraphy does not exclude mild inflammation. Leucocyte scan is useful also in suspected acute appendicitis, acute diverticulitis, pelvic inflammatory disease, aortic graft infection, etc. But infection and inflammation cannot reliably be differentiated, which may cause misinterpretations in the early postoperative period. Radionuclide techniques have an important role to play in the investigation of abdominal sepsis if the nuclear medicine department can offer instant investigations when the clinical problem is acute.