Malignant enterocutaneous fistula in Crohn's disease

Clinical History

Man with long-standing history (over 30 years) of Crohn's disease including previous ileocaecal resection and anal fistulectomy. After a long period of disease quiescence, currently complained of weight loss and development of cutaneous fistulas. Physical examination revealed two orifices at the anterior abdominal wall yielding serous fluid.

Imaging Findings

Multiplanar CT-enterography (Fig. 1) with oral polyethylenglycole solution confirmed two ventral enterocutaneous fistulas with characteristic tram-track appearance, mixed fluid and air content, and showed a markedly thickened ileal segment with non-stratified enhancement which appeared to infiltrate the anterior abdominal wall. Another short poorly distensible ileal tract with mural thickening of lesser degree was consistent with known Crohn's disease. Additionally, minimal ascites and a centimetric hypovascular liver lesion were noted.
Laparotomic en-bloc resection of ileal mass, anterior abdominal wall and subcutaneous tissue involved by enterocutaneous fistulas and a segment of transverse colon was performed (post-surgical status shown in Fig. 2a, b). Pathology reported a 20x18x9 cm bowel mass including skin surface with fistulous orifices, with a 7-cm long ileal adenocarcinoma with transmural growth, infiltrating the perivisceral fat, anterior abdominal wall and subcutaneous planes.
Four months later, neoplastic progression was observed (Fig. 2c) with development of ascites and of multiple hypovascular liver metastases.

Discussion

Compared to past decades, currently enterocutaneous fistulas (ECFs) are rarely encountered in surgical practice. Most ECFs develop either through an abdominal scar weeks or months after gastrointestinal surgery, or as a complication of fistulizing Crohn's disease (CD). In the latter case, the characteristic transmural inflammation of the affected enteric wall leads to penetration into the adjacent anterior abdominal wall. Then, ECFs cross through the subcutaneous fat planes and ultimately reach the skin. The vast majority of ECFs communicate with the diseased ileum and occur in long-standing CD. Albeit rare, ECFs severely impair patients’ quality of life, and cause significant morbidity from bowel obstruction, sepsis, diarrhoea, malabsorption and weight loss [1-3].
ECF is generally diagnosed on clinical grounds, as intermittent purulent discharge from cutaneous orifices within inflamed anterior abdominal wall. In the past, direct contrast fistulography was performed to visualize ECFs, but lacked assessment of the involved anatomical planes [1, 4]. Nowadays suspected CD complications warrant investigation with CT or MR-enterography: multiplanar cross-sectional imaging readily visualizes the fistulous path and identifies the bowel segment of origin [1, 5, 6].
In this patient ECF resulted from spreading ileal carcinoma. Small bowel adenocarcinoma (SBAC) is a rare but dreaded occurrence in CD, which generally affects males with long-standing CD, 33 times more commonly than in the general population, but is disguised by nonspecific and varied manifestations mimicking active or obstructive disease. As a result, SBAC is often (60%) detected at an advanced stage with nodal and distant metastases [7-9].
Generally (75% of cases) located in the mid-to-distal ileum, SBAC may be indistinguishable from acute inflammatory CD or benign fibrotic stricture. Reported imaging patterns include ileal mass, long stenosis with heterogeneous submucosa, short severe stenosis with upstream bowel dilatation, irregular asymmetric circumferential thickening. Suspicious features include mural thickness >1 cm, abrupt “shouldering" transition, lost mural stratification, soft-tissue attenuation or solid MRI signal intensity, irregular serosal nodularity, regional adenopathy [10-11].
Particularly in patients with prolonged CD duration, with obstruction or worsening symptoms after quiescence, non-healing ECFs despite treatment should raise the possibility of SBAC, and thorough endoscopic and imaging assessment is required. Alternatively, squamous cell carcinoma developing in a chronic CD-related ECF has been reported [12].
Albeit difficult, preoperative diagnosis of malignant ECFs impacts treatment since it requires en-bloc resection plus chemotherapy. Conversely, non-malignant ECFs may close with conservative treatment or required fistula debridement plus resection of the diseased bowel segment [2].

Differential Diagnosis List

Final Diagnosis

Small bowel adenocarcinoma with enterocutaneous fistulization in Crohn's disease

URL:	https://eurorad.org/case/13194
DOI:	10.1594/EURORAD/CASE.13194
ISSN:	1563-4086