Teaching Case

Diffuse abdominal pain, progressive difficulty to pass stools and occasional bouts of diarrhoea during the past week in a middle-aged man. His medical history recorded only previous segmental surgical resection of the sigmoid colon due to diverticulitis 16 months earlier.

At Emergency Department admission, plain abdominal radiographs disclosed findings consistent with the clinical suspicion of distal mechanical obstruction, including gaseous hyperdistension of ileal loops and of most large bowel up to the left iliac fossa, with multiple air-fluid levels.
Urgent contrast-enhanced MDCT acquisition confirmed overdistended ileum, right, transverse and descending colon with abundant endoluminal fluid and multiple air-fluid levels. Colonic dilatation reached the distal colic anastomosis, identified by the presence of metallic staples without significant wall thickening, abnormal endo- or extraluminal masses or fluid collections. Some stools were observed in the rectum.
Suspicion of postsurgical anastomotic stenosis was confirmed at endoscopy. Balloon dilatation was not successful in relieving obstruction, therefore surgical revision was planned.

Intestinal obstruction most usually occurs in the small bowel, whereas the colon is involved in only 25% of cases [1]. Causes of colonic obstructions include mostly primary cancer (in nearly two-third of patients), diverticulitis (10-15%) and other, more rare conditions such as volvulus, intussusception, faecal impaction in the elderly, radiation or ischemic colitis [2, 3].
Benign stenosis is a possible yet poorly understood complication following open or laparoscopic colorectal surgery for both carcinoma and diverticular disease, with hand-sewn or mechanically stapled anastomosis. The true incidence (probably approaching 1-2%) is not known and, and risk factors include obesity, postoperative leaks, infection or abscesses, postoperative radiotherapy.
Strictures are usually diagnosed three months to some years after initial intervention, become symptomatic in a variable proportion (5- 28%) of patients and may occasionally be complete [4-7].
Anastomotic stenosis, usually defined as the impossibility to pass through with the endoscope, may be confirmed with retrograde water-soluble contrast enema and biopsies when recurrent cancer is suspected. Balloon dilatation is the simplest, first-line and usually effective treatment, feasible even with stapled anastomoses, postoperative leakages or radiotherapy, sometimes combined with endoscopic laser or argon-plasma coagulation. Sometimes, intractable strictures need positioning of metallic stents of surgical anastomotic revision [4, 5].
Plain radiographs are usually obtained as the first diagnostic procedures in patients with suspicion of intestinal obstruction, in both supine (to assess abdominal content, intestinal gas distribution and bowel loops distension) and erect (to detect air-fluid levels) [1]. Currently, MDCT acquisition is the mainstay imaging modality to investigate intestinal obstruction. As in this case, oral contrast is usually not necessary since gas and fluid in the dilated bowel provide sufficient intrinsic contrast. Intravenous contrast is recommended, particularly for the assessment of neoplastic tissue and of mural ischaemia [1, 2].
MDCT allows differentiation from adynamic ileus and pseudo-obstruction (Ogilvie’s syndrome), confirmation and grading severity of obstruction: key signs include bowel dilatation (over 9 cm in the caecum, 6 cm in the remaining colon), fluid-filled lumen with air-fluid levels at different heights and distal collapsed bowels. As this case exemplifies, even with rare causes of obstruction multiplanar reformations are very helpful to identify the transition between normal and dilated bowel corresponding to the site of obstruction, and to accurately assess the underlying disease by viewing the transition point from a variety of perspectives. Furthermore, MDCT allows detecting complications such as incarcerated (closed-loop) obstruction and or necrosis from strangulation [1-3].