Question: A 35-year-old woman presented with a 3-month history of postprandial abdominal discomfort and vomiting. The patient's history included left jugular foramen schwannoma with involvement of the vagus and spinal accessory nerves (cranial nerves X and XI) treated with left level II/III neck dissection 4 months before presentation; intraoperatively, electromyography (EMG) monitoring confirmed transection of both nerves in the process of tumor resection. Physical examination yielded a soft, nondistended abdomen with bowel sounds present; no guarding, rebound, or bruits were found. The only laboratory abnormality included a mildly elevated leukocyte count of 11.7 Â 10 9 /L (normal range, 3.5-10.5 Â 10 9 /L). Abdominal computed tomographic imaging demonstrated pronounced gallbladder contraction (Figure A [transverse plane] and Figure B [coronal plane]; arrows) without additional intra-abdominal pathology. Subsequent abdominal ultrasound performed in the fasting state also demonstrated gallbladder contraction (Figure C). The patient proceeded to cholecystectomy for diagnostic and therapeutic intent. Postoperative surgical pathology revealed chronic inflammation and thickened muscularis mucosa of the gallbladder (Figure D; star indicates thickened muscularis mucosa). After cholecystectomy, the patient reported complete symptomatic resolution. What are the diagnosis and the likely etiology? Look on page 47 for the answer and see the Gastroenterology web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI.