Appendectomy for Chronic Abdominal Pain Caused by Appendiceal Neuroma

ABSTRACT

This case reports a 35-year-old man with recurrent right lower quadrant (RLQ) pain initially suggestive of acute appendicitis who was diagnosed with functional abdominal pain syndrome after negative imaging and colonoscopy. Because of persistent pain, he underwent a diagnostic laparoscopy and appendectomy, where an appendiceal neuroma was diagnosed; this led to complete symptom resolution. This case highlights the importance of considering appendiceal neuroma in the differential for unexplained appendicitis-like RLQ pain, particularly when standard workups are inconclusive. The resolution of symptoms postsurgery suggests that exploratory surgery should be considered in patients with severe and persistent RLQ pain, even with negative imaging.

INTRODUCTION

Patients with acute-onset right lower quadrant (RLQ) abdominal pain often present for urgent medical assessment. These patients undergo thorough investigations including cross-sectional imaging to rule out surgical causes of abdominal pain including acute appendicitis, ovarian torsion/abscesses, or other structural causes. When the initial workup has been nondiagnostic, gastroenterologists are frequently consulted to perform colonoscopy to rule out inflammatory bowel disease (IBD). However, with negative radiographic findings, the colonoscopy often fails to reveal a diagnosis. These patients often receive a diagnosis of a disorder of gut-brain interaction, such as irritable bowel syndrome or centrally mediated abdominal pain syndrome.

The following case describes a patient with acute on chronic RLQ pain with a negative workup who was presumptively diagnosed with a disorder of gut-brain interaction, who underwent empiric appendectomy, with symptom resolution. This case report highlights the importance of considering a diagnosis of appendiceal neuroma for patients with acute appendicitis–like pain but without radiographic abnormality.

CASE REPORT

A 35-year-old man presented to hospital with severe rapid-onset RLQ abdominal pain. He had been having episodic pain which began 14 months prior and superimposed over a constant, low-grade discomfort ranging from 2 to 5 out of 10 in intensity. Over this period, severe exacerbations occurred every 2 to 3 weeks, each lasting approximately 5 days and resolving spontaneously. During these exacerbations, the pain was sharp/stabbing, highly localized, and 10 out of 10 in severity. He reported subjective fever, nonbloody nonbilious vomiting, and watery diarrhea. The pain was not relieved nor exacerbated by position or food intake. Physical examination was notable for a positive Rovsing sign, obturator sign, and severe tenderness to palpation.

Because of his localized RLQ with possible peritoneal signs, acute appendicitis was strongly considered, but imaging failed to identify acute appendicitis or other definitive causes of the patient's pain. Laboratory investigations including CBCs, electrolytes, liver, kidney, and thyroid function, albumin, and inflammatory markers failed to show any meaningful abnormalities. The abdominal computed tomography revealed mild mural thickening at the base of the cecum and appendix, and nonspecific low-grade periappendiceal lymphadenopathy without surrounding inflammation (Figure 1). A subsequent MR enterography showed a normal appendix, and 2 colonoscopies with biopsies did not demonstrate any evidence of IBD, or any periappendiceal deformity or inflammation. The patient was given a presumptive diagnosis of a disorder of gut brain interacton; however, he failed to respond to neuromodulators and was significantly disabled by persistent pain.

Figure 1.

Coronal abdominal computed tomography identifying mural cecal and appendiceal thickening (red arrowhead) with periappendiceal lymphadenopathy (blue arrowhead).

He was otherwise healthy and had no prior surgeries. He was not taking any other prescription or over-the-counter medications.

Over the course of his follow-up visits, physical exam remained unremarkable aside from localized RLQ tenderness. Autoimmune workup, including celiac antibodies, was negative, as were stool cultures, ova and parasites, and Clostridioides difficile. A repeat computed tomography scan showed no progression.

After several hospital visits and the patient's request for further evaluation, a surgical consultation was obtained, and a diagnostic laparoscopy and appendectomy were performed. Intraoperatively, the appendix and cecum appeared normal. However, histopathological analysis of the 4.1 cm × 0.7 cm × 0.1 cm appendix demonstrated mild acute appendicitis and fibrous obliteration of the appendiceal lumen, consistent with a diagnosis of appendiceal neuroma (Figure 2). The patient was discharged home the following day. He was last seen 4 months postoperatively, where he reported complete relief of his pain with no recurrence.

Figure 2.

Histopathological cross section of appendix postappendectomy demonstrating fibrous obliteration of the lumen at 10× power (A) and spindle cells with collagen and adipose tissue at 200× power (B).

DISCUSSION

Appendiceal neuromas are benign tumors of neural origin that form nodular lesions in the appendix. Functionally, appendiceal neuromas have high substance P and vasoactive intestinal peptide production, neuropeptides, which cause pain and inflammation.¹ Histopathologically, they are characterized by the proliferation of spindle cells and fibrous obliteration of the appendiceal lumen.² Although they are often diagnosed incidentally during pathological examination of appendectomy specimens performed for other indications, they may also be a cause of persistent RLQ abdominal pain in patients without appendiceal anomaly identified on imaging, and complete symptom resolution after appendectomy due to removal of pronociceptive neuropeptides.^1,3–5

The prevalence of appendiceal neuroma has high variability between reports, often included within the category of “unusual pathology.” In a report of 2,408 appendix histopathology specimens, 5.3% had unusual histopathology, which included fibrous obliteration in 14.2% of those patients; however, the indication for appendectomy was not disclosed.⁶ In a retrospective study of 457 patients who underwent appendectomy for suspected acute appendicitis, 9.4% were diagnosed with appendiceal neuroma, without acute appendicitis.³ There are no studies that have measured the prevalence of appendiceal neuroma among persons with appendicitis-like or undifferentiated abdominal pain. A systematic review of 40 studies of appendiceal neuromas demonstrated that 82.4% of patients with appendiceal neuromas were pain-free at median follow-up of 6 months postappendectomy, with lower rate of surgery-related complications compared to patients with acute appendicitis.¹

A prospective cohort study by Hoseininejad et al assessed patients who presented to the emergency department with unspecified abdominal pain followed by gastroenterology in 1-month follow-up.⁷ They demonstrated significantly higher readmission rates over 1 month in patients without a clear cause of abdominal pain (64.5%) compared to patients with a clear cause (35.5%), suggesting an ongoing lack of diagnosis and worsening morbidity. There are significant implications of diagnostic delay in patients with abdominal pain without distinctive findings. Over that time, patients may experience a decline in quality of life and undergo multiple repeat tests, which have associated harms. Further, repeat visits to hospital, testing, and empiric treatments can place a cost burden on the healthcare system.⁸

This case underscores the importance of considering appendiceal neuroma in patients with persistent and recurrent peritoneal-type RLQ abdominal pain despite negative workup and failed conservative management.³ Given the low morbidity associated with an appendectomy and few negative consequences after removal of a normal appendix, clinicians can consider empiric appendectomy in patients with RLQ pain with macroscopically normal appearing appendix, as weakly recommended by current World Society of Emergency Surgery guidelines.^1,8,9 Although there are no formal guidelines, appendectomy can be considered in cases of suspected appendiceal neoplasm or mucocele, appendix involvement of endometriosis or IBD, and prophylactic during other abdominal surgeries. In such cases, appendectomy may relieve symptoms, prevent diagnostic dilemmas, and/or mitigate risk of complications.

DISCLOSURES

Author contributions: Project data – all authors. Manuscript drafting – J. Herblum and L. Targownik. Manuscript revision – all authors. Manuscript final approval – all authors. Accountability – all authors. L. Targownik is the article guarantor.

Financial disclosure: None to report.

Informed consent was obtained for this case report.

ABBREVIATIONS:

IBD

inflammatory bowel disease

MR

magnetic resonance

RLQ

right lower quadrant