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Am Fam Physician. 2007;75(10):1541-1542

Author disclosure: Nothing to disclose.

A 41-year-old woman presented with abdominal discomfort that began 12 hours earlier. The discomfort had shifted to her right lower quadrant just before she arrived at the hospital. The patient had poor appetite and nausea but no vomiting or fever. She denied having diarrhea, constipation, or weight loss. Her menstrual cycle began the previous day. Her history was notable for chronic dysmenorrhea, and she reported experiencing monthly menstruation pain similar to her current pain.

Physical examination revealed right lower quadrant tenderness and rebound pain with a positive Rovsing sign. The other physical findings, including those from a pelvic examination, were unremarkable. Ultrasonography and abdominal radiography showed no gynecologic abnormalities. Laboratory values included the following: white blood cell count, 13,900 per mm3 (13.9 × 109 per L); hemoglobin, 12.7 g per dL (127 g per L); neutrophils, 85 percent; sodium, 138 mEq per L (138 mmol per L); potassium, 4.1 mEq per L (4.1 mmol per L); blood urea nitrogen, 12 mg per dL (4.5 mmol per L); creatinine, 0.7 mg per dL (60 μmol per L); aspartate transaminase, 15 U per L; and alanine transaminase, 25 U per L.

Appendectomy was performed for the presumed diagnosis of acute appendicitis. The external surface of the appendix was markedly congested with moderate inflammation and dark red spots over the appendix tip. An enlarged right ovary with a hemorrhagic cyst also was found during surgery. A microscopic section of the appendix is shown in the accompanying figure.

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Based on the patient's history, physical examination, and laboratory findings, which one of the following is the most likely diagnosis?


The answer is D: endometriosis. The biopsy specimen revealed endometrial tissue. Endo-metriosis is a diagnosis based on the presence of extrauterine endometrial glands and stroma. An estimated 3 to 34 percent of women with endometriosis have some degree of gastrointestinal tract involvement, most commonly the rectum, followed by the sigmoid colon, appendix, terminal ileum, cecum, and ascending colon.1

Appendiceal involvement accounts for 3 percent of all cases of gastrointestinal endometriosis.2,3 Two thirds of patients with appendiceal endometriosis are asymptomatic and are diagnosed incidentally after appendectomy. Interestingly, muscular or seromuscular involvement associated with hemorrhage shows relatively good relation to the clinical acute symptoms. In symptomatic patients, a change in bowel habits, hematochezia, abdominal pain, and tenderness or mass in the right lower quadrant, similar to acute appendicitis, are the most common findings.35

Endometriosis affects approximately 6 to 10 percent of women, although it is hard to make precise estimates because of the difficulty in determining asymptomatic case prevalence.1,6 Periodic pain coinciding with menstruation is present in 30 percent of patients.1,5 This and other symptoms associated with endometriosis, such as dysmenorrhea, dyspareunia, and infertility, may help differentiate endometriosis of the appendix or other pelvic organs from acute or subacute appendicitis. In most cases, however, the absence of pathognomonic symptoms limits preoperative diagnosis of appendiceal endometriosis.

Typically, the initial presentation of acute appendicitis involves periumbilical pain that later localizes to the right lower quadrant with vomiting, fever, and leukocytosis. Biopsy should reveal significant neutrophilic infiltration. Appendiceal adenocarcinoma is uncommon and would be identified on biopsy. Malignant transformation of gastrointestinal endometriosis, although rare, may occur.7 Furthermore, carcinoid tumors would be more likely than adenocarcinoma. Carcinoid tumor of the appendix may or may not be associated with appendicitis and usually is an incidental finding. Histologic examination reveals nests of monotonous cells with occasional acinar or rosette formation.

Acute suppurative appendicitisRight lower quadrant pain, vomiting, fever, leukocytosis, and neutrophils in the muscularis
Adenocarcinoma of the appendixPrimary disease is uncommon
Carcinoid tumor of the appendixIncidental finding; nests of monotonous cells with occasional acinar or rosette formation
EndometriosisPeriodic pain with menstruation and presence of ectopic endometrial glands and stroma

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