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J Nazareno, T Ponich, J Gregor

Department of Medicine, University of Western Ontario, London, Ontario

OBJECTIVE: 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.

METHODS: A retrospective chart review was performed on 130 consecutive patients who received TPI for AWP at the London Health Sciences Center, University of Western Ontario. Patients were excluded if the chart was missing or information on the injection or the results was incomplete. Patients were included if they met previously validated criteria for AWP defined as: (1) fixed in location or very localized AND (2) superficial or point tenderness <2.5 cm in diameter or positive Carnett test. The diagnostic tests ordered to exclude AWP and the cost of investigating it were determined. Gender, location and radiation of the pain, GI symptomatology, type of agent injected and presence of a surgical scar were examined to see if they were predictors of response.

RESULTS: 89 patients were included in the study, 79 of whom had long term followup available. The mean age was 42 years and 84% were women. The median length of followup was 10 months. The primary outcome shows that 34% of patients were pain free at followup, 43% were improved but not completely pain free, and 22% were not helped by TPI. On average, 4.33 diagnostic tests were ordered to exclude other causes of abdominal pain. The cost of evaluating these patients to rule out a visceral cause of the pain was conservatively estimated at CD$764 per patient. The secondary outcomes show that gender, radiation of pain and type of agent injected were not predictors of response to TPI. However, meeting the criteria for AWP, absence of GI symptoms, and upper abdominal location of pain were predictors of a positive response to TPI. Patients with a scar benefited from TPI but needed more reinjections than those without a scar to achieve the same benefit.

CONCLUSIONS: AWP is a prevalent yet often inadequately acknowledged and misdiagnosed condition. Our study demonstrates that trigger point injections in patients who meet criteria for AWP are effective over the long term.

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