Imaging the operated colon using water-enema multidetector CT, with emphasis on surgical anastomoses.

Water-enema multidetector CT (WE-MDCT) provides a detailed multiplanar visualisation of mural, intra- and extraluminal abnormalities of the large bowel, relying on preliminary bowel cleansing, retrograde luminal distension, pharmacological hypotonisation and intravenous contrast enhancement. In patients with a history of colorectal surgery for either carcinoma or Crohn's disease (CD), WE-MDCT may also be performed via a colostomy, which allows depicting the anatomy and position of the residual large bowel and evaluates the calibre, length, mural and extraluminal features of luminal strictures. Therefore, WE-MDCT may prove useful as a complementary technique after incomplete or inconclusive colonoscopy to assess features and suspected abnormalities of the surgical anastomosis, particularly when endoscopic or surgical interventions are being planned. This pictorial essay presents the WE-MDCT technique and pitfalls, the expected appearances after different colic surgeries and the imaging features of benign anastomotic disorders (fibrotic stricture, kinking, inflammatory ulcer) and of locally recurrent tumours and CD. TEACHING POINTS: • Water-enema multidetector CT (WE-MDCT) effectively visualises the operated colon • Complementary to endoscopy, WE-MDCT may helpfully depict abnormalities of surgical anastomoses • WE-MDCT allows assessment of strictures' features and abnormalities of the upstream bowel • Technical pitfalls, normal postsurgical findings and benign anastomotic disorders are presented • WE-MDCT allows detecting relapsing Crohn's disease, recurrent and metachronous tumours.