Benign Colonic Strictures

CASE SUMMARY:

A 46-year-old man with no significant medical or surgical history presented to the emergency department with a 1-week history of worsening constipation, abdominal distension, nausea, and nonbloody, nonbilious emesis. Workup included a CT scan that was notable for a 5.3 × 3.9 cm “apple core-type” mass located within the sigmoid colon with proximal large-bowel dilation. Carcinoembryonic antigen was 1.4. No metastatic disease was seen on chest, abdominal, or pelvic CT scans. Flexible sigmoidoscopy identified a sigmoid colon mass 30 cm from the anal verge with near complete obstruction. Biopsies of the mass did not show evidence of dysplasia or malignancy. The Gastroenterology service declined to place a stent without a malignancy diagnosis. The patient subsequently underwent exploratory laparotomy, sigmoid colectomy, and end colostomy. Recovery was uneventful. Final pathology showed diverticulitis with abscess formation and no evidence of malignancy. A completion colonoscopy was unremarkable, and the patient underwent colostomy reversal 3 months later.

Colon cancer is the leading cause of large-bowel obstructions, accounting for more than 60% of cases; however, benign colonic strictures are an important source of morbidity whose management is unique from that of malignant strictures and obstructions. Common causes of benign strictures include diverticular disease, IBD, ischemic colitis, radiation-induced colitis, and anastomotic strictures.¹ Other rare causes include cytomegalovirus colitis, amyloidosis, tuberculosis, amebic colonic strictures, and endometriosis.²

Colonic obstruction can be attributed to diverticular disease in as many as 10% of cases,³ most commonly because of a combination of acute inflammation or progressive colonic wall fibrosis. Bowel edema may improve with antibiotics, but fibrosis will not. Similarly, long-standing inflammation in patients with Crohn’s disease or ulcerative colitis can result in fibrostenotic colonic strictures, with benign strictures identified in as many as 5% of patients admitted with complications of ulcerative colitis.⁴ Differentiation between benign or malignant strictures in IBD can be challenging, but it is critical because up to 29% of IBD-related colonic strictures contain malignancy.⁴

Ischemic colitis is an increasingly common condition, particularly in younger women, often associated with hormonal contraceptives, rigorous exercise, dehydration, and cardiac and vascular disorders. Strictures from ischemic colitis may occur in younger patients, but predominantly affect patients older than 60 years of age and are often the result of full-thickness injury, which is seldom seen in younger patients. As many as 15% of patients will develop ischemic stricutres, with watershed areas of the colon such as the splenic flexure and proximal rectum, as well as patients with a history of coagulopathy and vasculopathy, being particularly susceptible to this type of injury.⁵

Radiation-induced injury to the colon after treatment of gynecologic, GI, and urologic malignancies can result in colonic strictures. The rectosigmoid colon is particularly susceptible to this type of injury because of its relatively fixed nature.¹ Strictures secondary to radiation are the result of colonic ischemia driven by obliterative endarteritis of the colonic vasculature and are often seen 6 to 24 months after exposure.

Last, anastomotic strictures of the colon following colorectal anastomosis have been reported to occur in as many as 32% of patients.⁶ Among patients who have developed stricture following a colorectal anastomosis, as many as 54% were persistently symptomatic.⁶ Risk factors for postanastomotic strictures include low rectal anastomosis and anastomotic leak.¹

PRESENTATION AND DIAGNOSIS

A significant proportion of benign strictures are incidentally discovered and asymptomatic. Symptomatic strictures are most often characterized by abdominal distension, but may present with chronic, intermittent large-bowel obstruction, constipation, and pain. Occasionally, patients may present with acute obstruction with abdominal pain, obstipation, and signs or symptoms of intravascular hypovolemia such as hypotension and tachycardia. In contrast to small-bowel obstructions, nausea and emesis are less common in colonic obstructions because a competent ileocecal valve (ICV) will limit proximal small-bowel distension. A competent ICV can contribute to the development of a closed-loop obstruction, as well, between the ICV and the obstructing stricture. A variable degree of abdominal distension may be present, and peritonitis may be seen in cases where severe colonic dilation has resulted in the development of colonic ischemia or perforation.

Diagnostic evaluations in both the asymptomatic and acutely obstructed patient should be directed at identifying common causes of large-bowel obstruction including malignancy, volvulus, hernia, colonic pseudo-obstruction, as well as colonic stricture. Initial imaging studies include abdominal radiographs and CT scans of the abdomen and pelvis. Water-soluble contrast enemas may better identify the site of stricture and can provide important additional information including stricture length, severity, and any associated lesions. Colonoscopy is useful in both the diagnosis and treatment of benign strictures, but it is contraindicated in cases of peritonitis or complete obstruction because of the risk of perforation with further bowel distension. When performed, endoscopic interventions should include biopsy of strictures. Not uncommonly, diagnostic uncertainty remains after thorough evaluation and operative intervention is required to allow for pathological evaluation of the diseased segment.

MANAGEMENT

The approach and urgency taken in the management of a patient presenting with a benign colonic stricture depends on the acuity and severity of the patient’s symptoms (see the Algorithm). In patients presenting with acute obstruction from a presumed benign colonic stricture, initial management consists of intravenous fluid administration for resuscitation; nasogastric tube placement for gastric decompression if the stomach is distended; and correction of electrolyte abnormalities. In patients with evidence of complete obstruction, peritonitis, or perforation, emergent surgery is indicated. Surgical options include diversion with loop colostomy, resection of the strictured segment with end colostomy, or segmental colectomy with primary anastomosis with or without diverting loop ileostomy. Proximal diversion without resection fails to address the diagnostic uncertainty, but it may allay the patient’s condition and allow for further diagnostic evaluations. Additionally, on-table colonic lavage may be a useful tool that, while cumbersome, may allow for conversion of multistage procedures (eg, Hartmann’s) to a lesser-staged procedure in patients with inadequate mechanical bowel preparation. Operative approach and surgical management ultimately depend on patient presenting factors, as well as surgeon experience and preference.

In stable patients with partial obstruction or chronic obstructive symptoms, a variety of therapeutic interventions may be considered, beginning with dilation. The technique of stricture dilation is dependent on the level of stricture with distal rectal strictures often amenable to digital and/or bougie dilation, at times performed at home by patients themselves. Endoscopic techniques include balloon dilation with or without intralesional steroid injection or electroincision⁷ and, in rare cases, endoscopic stent placement.¹ Technical success of endoscopic balloon dilation in the treatment of anastomotic and benign inflammatory strictures is seen in greater than 73% to 100% of patients with good long-term clinical efficacy, although repeated dilations are frequently needed.^6,7 Long strictures (>2 cm), severe bowel angulation, and the inability to endoscopically reach the stricture are associated with technical failure or the need for repeat dilation.⁷ Complications following balloon dilations occur in 2% of cases, and most commonly include perforation and bleeding.⁷ Surgery is appropriate for strictures that are not amenable to or fail endoscopic treatment but should also be considered in patients if malignancy is a possibility or cannot be ruled out. In patients with continued passage of flatus, a more gradual preoperative bowel preparation regimen may improve tolerance and allow for elective resection.

Colonic stents are commonly used in the management of malignant colonic obstruction, but their role in the management of benign strictures remains controversial. Studies have shown colonic stenting to be effective in temporizing obstruction as a bridge to surgery or as definitive treatment for benign strictures.^8–10 However, stent placement for benign causes represents only 3% of cases.¹¹ Technical success in stent placement is variable with some reporting high rates of failure,¹² whereas larger, more recent series have reported success rates above 72%.^8,9 In the largest series of patients to date, 22 of 23 patients presenting with acute obstruction secondary to benign causes were relieved of obstruction.⁹ Four patients did not undergo subsequent colectomy; however, of the remaining patients that did, 16 (84%) were converted to an elective operation and 8 (42%) did not require a stoma after stent insertion.⁹ Complications following stent placement have been reported in 38% to 62.5% of cases; stent migration was the most frequent complication, occurring in 9% to 40% of patients.^8–10,12 Overall, the rates of stent migration appear to be higher for benign stricture than for malignant strictures with migration occurring in 10% to 16% of malignant cases.^10,11

EVALUATION AND TREATMENT ALGORITHM

CONCLUSION

Benign colonic strictures are a rare but important cause of large-bowel obstruction and are due to a variety of pathologies. Although resection remains the mainstay of treatment, alternate therapies such as dilation and stenting may be considered on a case-by-case basis once malignancy has been ruled out. The role of endoluminal stents in benign colonic strictures remains an area of evolving research.

CLINICAL QUESTIONS.

• What are the causes of benign colonic strictures?

• What are the key differences in management between benign and malignant strictures?

• What is the role of endoscopic interventions in the management of benign colonic strictures?