Long-term follow-up of trigger point injections for abdominal wall pain

Abdominal wall pain (AWP) is a common yet often overlooked source of abdominal pain. Trigger point injections (TPI) into the abdominal wall have been tried in the past. Few studies have looked at the long-term outcome from these injections.

A retrospective chart review was performed on 110 consecutive patients who received TPI for abdominal pain at the University of Western Ontario, London, Ontario. Outcomes from patients whose pain was due to AWP were determined. AWP was defined as fixed or localized pain and superficial or point tenderness (less than 2.5 cm diameter) or a positive Carnett sign (increased pain with tensing abdomen). The primary outcome was long-term efficacy of TPI. The number of diagnostic tests ordered to exclude AWP and the cost of investigating it were determined. Secondary analyses were done to determine if there were significant predictors of response to TPI.

Eighty-nine of 110 patients who received TPI met the criteria for AWP. In those who met the criteria for AWP, the average age was 42 years, 84% were female, and the average length of follow-up was 25 months. The primary outcome shows that, at follow-up, 77% had some or complete relief and 23% had no relief. An average of 4.3 diagnostic tests per patient were ordered to exclude other causes of abdominal pain. Secondary analyses show that meeting the criteria for AWP (P<0.0005), the absence of gastrointestinal symptoms (P<0.025), and an upper abdominal location of pain (P<0.025) were statistically significant predictors of a positive response to TPI.

This study demonstrates that TPI, in patients who meet criteria for AWP, are effective over the long term.