Abdominal pain is a commonly seen presenting concern in gastroenterology clinics. Establishing a diagnosis effectively and efficiently can be challenging given the broad differential. Abdominal wall pain is an often-overlooked diagnosis but accounts for up to 30% of cases of chronic abdominal pain1 and up to 10% of patients with chronic idiopathic abdominal pain seen in gastroenterology practices.2 Trigger point injection in the office can be both diagnostic and therapeutic.
Dr. Brian B. Park
The prevalence of chronic abdominal wall pain is highest in the fifth and sixth decades, and it is four times more likely to occur in women than in men. Common comorbid conditions include obesity, gastroesophageal reflux disease, irritable bowel syndrome, and fibromyalgia.3 Abdominal wall pain is often sharp or burning due to somatic innervation of the abdominal wall supplied by the anterior branches of thoracic intercostal nerves (T7 to T11). Abdominal wall pain may originate from entrapment of these nerves.2 Potential causes of entrapment include disruption of insulating fat, localized edema and distension, and scar tissue or fibrosis from prior surgical procedures.3 Symptoms are typically exacerbated with any actions or activities that engage the abdominal wall such as twisting or turning, and pain often improves with rest.
The classic physical exam finding for abdominal wall pain is a positive Carnett sign. This is determined via palpation of the point of maximal tenderness. First, this is done with a single finger while the patient’s abdominal wall is relaxed. The same point is then palpated again while the patient engages their abdominal muscles, most commonly while the patient to performs a “sit up” or lifts their legs off the exam table. Exacerbation of pain with these maneuvers indicates a positive test and suggests the abdominal wall as the underlying etiology.
While performing the maneuver for determining Carnett sign is a simple test in the traditional office visit, the COVID-19 pandemic has led to a burgeoning proportion of telehealth visits, limiting the physician’s ability to perform a direct physical exam. Fortunately, the maneuvers required when testing for Carnett sign are simple enough that a clinician can guide a patient step-by-step on how to perform the test. Ideally, if a family member or friend is available to serve as the clinician’s hands, the test can be performed with ease while directly visualizing proper technique. Sample videos of how the test is performed are readily available on the Internet for patients to view (the authors suggest screening the video yourself before providing a link to patients). The sensitivity and specificity of Carnett sign are very high (>70%) and even better when there is no apparent hernia.1
Management
Dr. Manish Singla
Trigger point injections with local anesthetic can be both diagnostic and therapeutic in patients with abdominal wall pain. An immediate reduction of pain by at least 50% with injection at the site of maximal tenderness strongly supports the diagnosis of abdominal wall pain.1 Patients should first be thoroughly counseled on potential side effects of local corticosteroid injection to include risk of infection, bleeding, pain, skin hypopigmentation, or thinning and fat atrophy. Repeat injections are rarely needed, and any additional injection should be performed after at least 3 months. Additional adjunct therapies include nonsteroidal anti-inflammatory medications, topical therapies such as lidocaine, and neuroleptic agents such as gabapentin.4 One previously described trigger point injection technique, involves a mix of triamcinolone and lidocaine injected at the point of maximal tenderness.5 This technique is easy to perform in clinic and has minimal risks.
Conclusion
Abdominal wall pain is a common, yet often-overlooked, condition that can be diagnosed with a good clinical history and physical exam. A simple in-office trigger point injection can confirm the diagnosis and offer durable relief for most patients. A shift to virtual medicine does not need to a barrier to diagnosis, particularly in the attentive patient.
Dr. Park is a fellow in the gastroenterology service in the Department of Internal Medicine at Naval Medical Center San Diego and an assistant professor in the department of medicine of the Uniformed Services University in Bethesda, Md. Dr. Singla is a gastroenterologist at Capital Digestive Care in Silver Spring, Md., and an associate professor in the department of medicine at the Uniformed Services University. The authors have no conflicts of interest.
References
1. Glissen Brown JR et al. J Clin Gastroenterol. 2016;50(10):828-35.
2. Srinivasan R, Greenbaum DS. Am J Gastroenterol. 2002;97(4):824-30.
3. Kambox AK et al. Mayo Clin Proc. 2019;94(1):139-44.
4. Scheltinga MR, Roumen RM. Hernia. 2018;22(3):507-16.
5. Singla M, Laczek JT. Am J Gastroenterol. 2020 May;115(5):645-7.
