Abdominal pain is an extremely common complaint in the office and acute care settings. In 2010, abdominal pain accounted for more than 27 million healthcare visits with more than 10 million of those visits occurring in EDs.1 The most common diagnoses made in all patients with gastrointestinal (GI) complaints in the ED in 2012 were functional and organic motility disorders.1 These facts have major implications on healthcare costs: for example, the estimated annual per patient cost of irritable bowel syndrome (IBS) is $1,562 to $7,547 in direct costs and $791 to $7,737 in indirect costs.2 The ubiquity of these GI disorders along with the diagnostic uncertainly surrounding them means clinicians must understand their cause, presentation, diagnostic criteria, and approach to treatment.
The term functional GI disorder refers to syndromes characterized by patient experience and symptoms, rather than structural and motility disorders that are classified in terms of organ morphology and function.3 The Rome Foundation is the major body that has been responsible for characterizing and classifying functional GI disorders. The recently released Rome IV criteria cover 33 adult and 20 pediatric functional disorders.4 These conditions include functional heartburn and dyspepsia, IBS, sphincter of Oddi disorders, functional anorectal pain, defecatory disorders, and functional abdominal pain disorders. This article focuses on the most common functional abdominal pain disorders in adults and their presentation and management in the acute care setting.
The causes of functional abdominal pain disorders are not fully understood and likely are multifactorial. Although a full review of the pathogenesis of these disorders is beyond the scope of this article, we will briefly outline the proposed physiologic basis of disease to better understand current treatment strategies.
In patients without underlying pathology, visceral pain in the GI tract is generated secondary to noxious stimuli (physical, chemical, or inflammatory) that activates a peripheral nerve. This signal is then transduced via the peripheral nerve to the spinal cord and eventually the brain. The potential mechanisms proposed for functional abdominal pain are based on alterations in the function of this system at different anatomic locations. These include augmentation of peripheral nerve signaling, central sensitization, and disturbances in central pain modulation.5
Peripheral nerve signaling augmentation refers to altered nerve signaling or the generation of a pain sensation in the absence of noxious stimuli. Nerve endings may be hypersensitized by an acute insult (such as infection or surgery) and not return to baseline function after the insult is removed.6
Another proposed mechanism is central sensitization, a concept similar to peripheral augmentation. In this case, the brain is hyperresponsive to the input of the peripheral nerves rather than the nerves being hyperresponsive themselves.
Finally, disturbances in central pain modulation affect the system responsible for magnifying or limiting peripheral signals. These central mechanisms seem to be associated with psychosocial stressors rather than the residual effects of local noxious stimuli, as postulated in peripheral augmentation.7
The literature supports each of these mechanisms and their contribution but it is likely that they are all contributors to functional abdominal pain.5-7
PRESENTATION AND DIAGNOSTIC APPROACH
The clinical presentation of a patient with functional abdominal pain, particularly the physical examination, is nonspecific by nature, given the lack of organic disease. The fact that these disorders are defined by patient experience (that is, symptoms) rather than organ morphology or function makes the history integral to the diagnosis. Although functional GI disorder refers to a spectrum of disorders, all share a general diagnostic framework outlined in the Rome Criteria, which state that symptoms must last at least 3 months, with onset greater than 6 months before diagnosis, and without evidence of organic disease.8 Each specific disorder is then further defined by its own set of criteria.8 The Rome Criteria are the most widely used diagnostic criteria; the Manning Criteria for IBS have been shown to be less sensitive but more specific than the Rome Criteria for that disorder.9 These diagnostic criteria reinforce the importance of an adequate history, specifically regarding symptom duration.
In the acute care setting, the general approach to patients with abdominal pain should focus on history with particular emphasis on characterization of pain (including onset, location, and quality), evolution of pain, and what specific changes led the patient to seek urgent care. A comprehensive physical examination should include vital signs, abdominal examination, rectal examination, and pelvic examination for women. A complete medication history also is important as adverse reactions (for example, to nonsteroidal anti-inflammatory drugs) can cause organic dysfunction that emulates functional abdominal pain disorders. Abdominal wall pain, in particular, is a commonly missed diagnosis; this pain can be elicited by having patients tense their abdominal muscles while the clinician firmly palpates the site of pain (Carnett sign).10
A good psychiatric history also is important, as many patients with functional abdominal pain have comorbid psychiatric conditions. Between 54% and 94% of patients with IBS meet criteria for a primary psychiatric disorder.11 About 50% of patients with functional diagnoses have a history of sexual or physical abuse.12 These comorbid conditions may contribute to the patient's symptoms or symptom perception.
Diagnosing functional pain disorders in the acute care setting requires a basic understanding of the general presentation and diagnostic criteria. In the acute care setting, the most common disorders include functional dyspepsia, IBS, functional abdominal pain syndrome, and functional gallbladder disorder. Each clinical situation is different and the lack of objective testing makes generalizable recommendations difficult. Table 1 outlines an approach to each of these disorders. Also a new entity, opioid bowel syndrome, is closely related to functional abdominal pain syndrome and is characterized by worsening pain with increasing doses of opioids and relief after withdrawal of opioids.13
If a complete history and physical examination do not reveal a diagnosis of organic disease, further testing is needed. The diagnostic criteria for functional abdominal pain disorders include the caveat that organic disease has been ruled out. This, however, does not mean that advanced testing and imaging are necessary to make a diagnosis, as most organic processes can be ruled in or out with a comprehensive history and examination. If the history and examination are consistent with organic disease, then focused, rather than “shotgun” testing is indicated. Otherwise, testing should be avoided. In fact, the American Gastroenterological Association's Choosing Wisely Campaign recommends avoiding repeat CT scans in patients with functional abdominal pain syndrome, unless the patient has had major changes in condition.14 A cornerstone of limiting diagnostic testing is obtaining a history of previous tests so that recurrent testing may be avoided unless the patient has new symptoms or strong indications for testing. These conditions often are chronic, and recurrent interventions can be associated with significant cost and patient morbidity. Although functional abdominal pain disorders impair patient quality of life, most do not affect survival, making repeated testing even less useful unless there is a strong clinical indication.15
The general approach to abdominal pain can help define organic versus functional pain and thus can help narrowing testing. If the patient's presentation is consistent with a functional disorder, defining the specific disorder can help define the course of action. In the acute care setting, the following key points can aid the diagnostic approach:
- In patients with functional dyspepsia, test for Helicobacter pylori, especially in endemic areas such as Asia, Africa, and Central America. Esophagogastroduodenoscopy (EGD) is indicated in patients over age 55 years and in those with red flag symptoms (Table 1).
- Symptoms of IBS can be exacerbated by triggers including stress, caffeine, artificial sweeteners, legumes, and patient-specific triggers such as lactose or fructose intolerance. Review these with patients to identify causes of exacerbations and to educate patients on avoiding triggers. Screening for celiac disease and lactose intolerance is prudent because of the higher prevalence of these disorders in patients with irritable bowel syndrome.16,17
- Functional gallbladder syndrome, unlike other functional abdominal pain, calls for specific testing to exclude organic disease. Testing includes alkaline phosphatase, transaminases, and pancreatic enzyme tests and ultrasound evaluation of the gallbladder. Advanced imaging with cholescintigraphy (HIDA scan) can be used to assess gallbladder ejection fraction. If the patient's ejection fraction is less than 38%, consider referring the patient for a cholecystectomy.18
The provider-patient relationship is essential to treatment. However brief the interaction may be in the acute care setting, patients may extrapolate their experience to all healthcare providers in the future. Clinicians should validate the patient's symptoms, manage his or her expectations, and explain that these disorders often are chronic. Patients presenting for acute care may expect an inpatient workup but setting boundaries and working with patients to define goals will be important for long-term success. Long-term success is influenced by a strong patient-provider relationship, so one of the core responsibilities of acute care providers is arranging for close, high-quality outpatient follow-up.19
Patients with functional dyspepsia can be treated locally with proton-pump inhibitor therapy or systemically with antidepressants or other neuromodulating medications. The exact mechanism of action of these systemic medications is not completely understood but their therapeutic effects likely are secondary to their ability to help alter pathologic augmentation of peripheral nerve signaling, central sensitization, and disturbances in central pain modulation.
The type of IBS dictates treatment choice. Constipation-predominant IBS can be treated with lubiprostone, linaclotide, and selective serotonin reuptake inhibitors; diarrhea-predominant IBS responds best to tricyclic antidepressants.20
Pharmacologic management is the mainstay of therapy in the acute care setting, given the time and setting constraints. However, the importance of nonpharmacologic therapy cannot be overlooked as these disorders often show an insufficient response in more than half of patients.21 Therefore, patients with residual symptoms or known underlying psychiatric comorbidities should be referred for psychologic therapy.
The efficacy of several psychologic interventions has been evaluated. Cognitive behavioral therapy (CBT) and hypnosis have been shown to be effective in patients with functional abdominal pain disorders; relaxation training, psychodynamic therapy, and biofeedback have not been as promising.22,23
CBT is the most studied of the psychologic interventions for functional GI syndromes. CBT is based on the theory that maladaptive thoughts lead to anxiety and depressive symptoms, which can in turn lead to somatic symptoms. Treatment usually lasts from 6 to 12 sessions. This strategy has been shown to be effective when compared with usual medical care including medications, supportive therapy, education, and stress reduction training.23 Hypnotherapy also has been evaluated and shown to be effective with the potential for benefits lasting as long as 5 years after the intervention.24
With this in mind, part of the acute treatment strategy is identifying psychiatric comorbidities and stressors contributing to the presentation and making the correct referral, especially in patients with refractory symptoms.
Abdominal pain is an incredibly common complaint in acute care, and functional GI disorders are the underlying cause in many patients. The causes of these disorders are not completely understood but seem to have an underlying neurologic component. By understanding the diagnostic criteria of these common conditions, clinicians can intervene appropriately and limit testing. Acute care clinicians also can educate patients and may help establish ongoing outpatient care, helping patients achieve long-term success with their conditions.
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Keywords:Copyright © 2017 American Academy of Physician Assistants
functional abdominal pain; gastrointestinal disorder; irritable bowel syndrome; organic; Rome Criteria; central sensitization