Gastrocolic fistula in Crohn’s disease detected by oral agent contrast-enhanced ultrasound: A case report of a novel ultrasound modality

BACKGROUND Fistulas are common complications of Crohn’s disease (CD). Gastrocolic fistulas (GFs) are rare, occult and potentially life-threatening complications. Few cases of GFs have been reported. Oral agent contrast-enhanced ultrasound (OA-CEUS) is a novel technique of ultrasound (US) for gut. Contrast agent made by Chinese yam is taken orally to dilate the lumen of the upper gastrointestinal tract. Thus, the impediment of gas inside gastrointestinal tract is removed and a good acoustic window is provided for gastroin-testinal tract scanning. This paper describes a case of GF secondary to CD detected by OA-CEUS when it was missed by endoscopy and computed tomography (CT). To our knowledge, this is the first report of GF secondary to CD detected by OA-CEUS up to date. CASE SUMMARY A 29-year-old woman with a 6-year history of CD was admitted to our hospital for abdominal pain and diarrhea for 5 months without obvious predisposing causes. Initial gastroscopy failed to show any evidence of lesions. Colonoscopy revealed multiple erosions, mucosal nodularity, linear ulcers and a cobblestone appearance. A CT scan of her abdomen showed a complex multilocular structure adherent to the greater curvature of the stomach in her left lower abdomen, with fluid, gas and significant surrounding inflammation. CT also demonstrated an abdominal abscess, which was later treated with US-guided drainage. Colonoscopy, gastroscopy and CT missed the presence of a GF. OA-CEUS was performed. A contrast agent made from Chinese yam was taken orally to dilate the lumen of the gastrointestinal tract. A good acoustic window was provided for gastrointestinal tract scanning and the impediment of gas inside the gastrointestinal tract was removed. With the aid of the “window”, a canal with hypoechoic wall was identified connecting the greater curvature of stomach to the splenic colon flexure in free sections. We also observed the hyperechoic gas flowing dynamically inside the canal. Thus, a GF was suspected. US is the first imaging modality taking GF into account. At the same time, OA-CEUS identified the site of the fistula and its two orifices. Gastroscopy was performed again, revealing a small ulcer approximately 5 mm in diameter, which was considered as an orifice. On the basis of OA-CEUS and other examinations, the patient was diagnosed with a GF secondary to CD. Then, laparoscopic exploration, partial stomach resection, transverse colostomy and abdominal abscess drainage were performed. The patient recovered uneventfully. CONCLUSION GFs are rare, occult and potentially life-threatening complications in CD. US is one of the first-line modalities to evaluate CD and its complications. OA-CEUS, a novel technique of US for gut, may be helpful in reducing the possibility of a missed diagnosis of GF.