Chapter 31

Colorectal Disorders

Jonathan Hong, D. Kagedan and Marcus Burnstein

Chapter Overview

Patients who require critical care may develop the same array of colorectal disorders as the general population. The disorders discussed in this chapter are those commonly encountered in patients requiring critical care, or conditions that may necessitate admission to a critical care unit. The patient may require ICU admission because of associated comorbidities, complications, or unusual presentations of the colorectal disorder. Information contained in this chapter will allow the intensivist to recognize the clinical presentation, and to understand the principles of management. Prompt management of disorders such as bowel obstruction, Clostridium difficile enterocolitis, and acute pseudo-obstruction improves patient outcomes, including reduction of the need for duration of mechanical ventilation.

Colon and Rectal Trauma

Introduction

Anatomically, the colon frames the abdomen, with the ascending and descending colon fixed to the retroperitoneum.¹ This makes the colon especially vulnerable to penetrating injury, with colonic injuries relatively rare in blunt trauma. Conversely, the rectum is contained within the bony pelvis, protecting it from external penetrating injury, but rendering it vulnerable to injuries associated with blunt pelvic trauma. Major controversies persist in the management of colon and rectal injuries, including the indications for primary repair, resection and anastomosis, and fecal diversion.

Traumatic colon injury is relatively rare, occurring in less than 1% of all trauma patients.2,3 The majority of colon trauma is caused by penetrating injury (56–71%), predominantly gunshots. In combat, colon injuries are frequent, occurring in up to 5% of trauma patients. In the combat setting, penetrating injuries are the most frequent mechanism of colon trauma with blast injuries the second most common, accounting for 35% of cases.⁴ In the civilian population, colon injury occurs in 0.1–0.5% of blunt trauma cases.³ The majority of these injuries occur among young males, ages 19–28.

Traumatic rectal injury is far less frequent, occurring in less than 0.1% of trauma patients.³ Blunt trauma is the more frequent mechanism of rectal injury, and motor vehicle accidents are the most common cause (39%). Isolated injuries to the rectum are very rare, usually occurring secondary to foreign bodies. In blunt trauma, rectal injury often occurs in combination with bony, urological, and/or vascular injury, and it is associated with high mortality (21.2%).³

Mechanisms and patterns of injury

Blunt injuries to the colon and its mesentery tend to occur at points of transition from intraperitoneal to retroperitoneal, such as the ileocecal region, and the sigmoid colon, where the mobile colon becomes fixed. Penetrating colorectal injuries should be suspected based on the path of the instrument or projectile. Blast injuries should raise suspicion for devascularization, which may present as a delayed perforation. Rectal injury is often associated with pelvic fractures. Based on their close anatomic relationship, injury to the sigmoid colon and rectum may be associated with genitourinary tract injuries.

Historically, traumatic colorectal injuries have been associated with mortality rates of 60–75%,² both due to associated injuries and to secondary intra-abdominal sepsis.

Presentation

Most traumatic colorectal injuries are diagnosed either during the initial evaluation, imaging studies, or intra-operatively during exploratory laparotomy. Findings of peritonitis, feculent abdominal discharge from a penetrating wound, or blood on digital rectal examination should raise suspicion for an injury to the intra-abdominal gastrointestinal tract. Signs of hemorrhagic shock may accompany a mesenteric injury. Evolving intra-abdominal sepsis should raise suspicion for an occult colorectal injury. At laparotomy, the anatomic location of the colon may obscure injuries, necessitating complete mobilization to permit inspection of the entire circumference of the colon and its mesentery to exclude a colon injury.

The primary and secondary Advanced Trauma Life Support (ATLS) surveys have a low sensitivity for detecting injuries to the colon and rectum. If Digital Rectal Exam (DRE) reveals blood, foreign objects, or bony protrusions, a rigid proctoscope may be used to examine the rectal mucosa for damage or defects.5 Unfortunately, the combined sensitivity of these two methods is approximately 33% for rectal injuries and 5% for any bowel injury. While non-specific for colorectal injury, an upright chest X-ray or Focused Assessment with Sonography for Trauma (FAST) ultrasound may reveal free air consistent with hollow viscus perforation.⁵

Triple contrast helical Computed Tomography (CT) scan has been shown to have 100% sensitivity, 96% specificity, 100% negative predictive value, and 97% accuracy in detecting peritoneal violation, colonic, major vascular, or genitourinary tract injuries following penetrating trauma.⁶ The indications for diagnostic peritoneal lavage have decreased dramatically with the increasing availability of CT scans; DPL has a sensitivity for intestinal injury between 84–97%, and is particularly useful in the combat setting.² Additionally, DPL can distinguish blood from enteric contents, which may not be possible with CT scan. Diagnostic laparoscopy can also be used to evaluate colorectal injuries in stable patients with equivocal imaging findings.

The American Association for the Surgery of Trauma (AAST) Organ Injury Scale provides a classification scheme for injuries of the colon and rectum. Injuries may be subdivided into “non-destructive,” involving <50% circumference of the bowel wall with no associated devascularization, and “destructive,” involving >50% of the bowel wall or with segmental devascularization. Destructive lesions correspond to AAST grades 3–5, and nondestructive lesions grades 1–2.

Colon:

Traditionally, colon trauma was treated with fecal diversion, either by exteriorizing the injured segment of colon or creating a proximal colostomy to defunction the injured segment. In 1979, Stone and Fabian published a prospective randomized trial comparing primary repair with diversion, and found equivalent rates of infection (48% versus 57%, p > 0.05) and mortality (1.5% versus 1.4%, p > 0.05).7 This study excluded patients with blood loss >1 L, hypotension, more than 2 intra-abdominal organs injured, significant peritoneal contamination, delay >8 hours following injury, destructive colon wounds, or major loss of abdominal wall; patients with any of these characteristics were treated with a colostomy. A 1991 trial randomized all patients with penetrating colonic trauma to either diversion or primary repair (simple closure or resection and anastomosis).⁸ No anastomotic leaks were reported in the primary repair group, and septic complications were not significantly different between those who were diverted and those who were not. Further studies in the 1990s confirmed that there is no benefit to diversion even among patients with large destructive colon injuries, fecal contamination, systemic hypotension, or excessive blood loss.

In 1998, the Eastern Association for the Surgery of Trauma published guidelines recommending diversion only for patients with destructive colon injuries (AAST Grade 3 or higher) who also had any of: hemodynamic instability; significant comorbidities; or a penetrating abdominal trauma index (PATI) >25.⁹ EAST guidelines recommended primary repair for all non-destructive (AAST Grade 2 or less) colon wounds in the absence of peritonitis. In 2003, a Cochrane Review found no difference in mortality comparing primary repair to diversion.10 Moreover, total complications, abdominal infections, wound complications, and dehiscence all significantly favored primary repair over diversion. While some authors have concluded based on level I data that primary repair without diversion may be performed independent of risk factors, this remains a contentious topic, with some experts advocating colostomy in select cases based on the surgeon’s judgment.

The decision to perform a primary suture repair or a segmental colon resection with anastomosis is based on the degree of injury and state of the bowel wall. As a general rule, patients with destructive injuries of the colon (AAST grade 3–5) require resection and anastomosis, whereas non-destructive injuries may be amenable to primary suture repair. No major differences in outcome have been found comparing hand-sewn versus stapled anastomoses, or injuries to the right colon versus the left colon. In critically ill patients undergoing damage control surgery, injured segments should be stapled off and the decision to perform an anastomosis or stoma delayed until hypothermia, coagulopathy and acidosis is corrected. If a temporary stoma must be fashioned in an open abdomen, the stoma should be sited as laterally as possible to maximize medial mobility of the abdominal wall for closure. As colon injuries are high-risk for infectious complications, interventions such as debridement of necrotic tissue, early administration of intravenous antibiotics, and leaving the skin open or partially open, decrease the risk of infectious complications.

Historically, rectal trauma was managed according to the “4 Ds” of proximal diversion, pre-sacral drainage, direct repair, and distal rectal washout.⁵ The evidence on this topic is limited, but current data supports treating intraperitoneal rectal injuries in a similar fashion to colonic injuries. Extraperitoneal injuries should usually be diverted proximally and, if feasible, repaired directly, although limited data suggests that direct repair is unnecessary if the fecal stream is diverted proximally, and the injury is allowed to heal by secondary intention. Distal rectal washout and presacral drainage have not been shown to improve outcomes, and current literature questions their usage, instead recommending they be used on a case-by-case basis at the discretion of the surgeon.

Mechanical Large Bowel Obstruction (LBO)

Introduction

Mechanical large bowel obstruction is defined as a physical blockage of the colon or rectum that prevents transit of the products of digestion.

Epidemiology

LBO is most commonly caused by malignancy (60%), diverticular strictures (20%), or colonic volvulus (5–15%). Infrequent causes include inflammatory bowel disease, radiation induced stricture, fecal impaction, intussusceptions, or extrinsic compression.11

Malignant large bowel obstruction occurs in up to 29% of patients with colorectal cancer.¹² Right-sided lesions cause obstruction only when large as the contents of this side of the colon are liquid and the caliber of the bowel is greater than the left.

The most common type of volvulus involves the sigmoid colon.¹³ The archetypal group of patient is an elderly nursing home resident, with limited mobility and multiple co-morbidities. Patients raised in Africa, the Middle East, India, or Russia (the volvulus belt) are also at risk of volvulus but tend to present aged 40–50 years.

Diverticular strictures predominantly affect the sigmoid colon.¹⁴ As with diverticular disease in general, patients are more likely to be older than 60 years.

Pathophysiology

Large bowel obstruction causes distension and increased secretions in the proximal bowel.¹² This damages the intestinal mucosa and impairs venous return, which leads to edema and ischemia. The resulting increase in bowel wall permeability can permit bacterial translocation and systemic toxicity. Continued ischemia will lead to bowel perforation. Consistent with Laplace’s law, the cecum is particularly vulnerable if there is a competent ileo-caecal valve.

Presentation

Typical symptoms of LBO include abdominal distension and abdominal pain.¹² Obstipation, vomiting, and nausea may be present. The duration of symptoms may give an indication of etiology. Rapid onset is more likely to be volvulus but gradual onset and use of laxatives suggest diverticular stricture or carcinoma.

Physical examination reveals a distended, tympanic abdomen, and bowel sounds can be tinkling, increased, reduced, or absent.¹²

Diagnosis

An erect chest X-ray is used excluding pneumoperitoneum. An abdominal X-ray may be sufficient to diagnose sigmoid volvulus but the characteristic coffee bean sign in the right upper quadrant is not always present and markedly distended sigmoid colon due to stricture or neoplasm can have a similar appearance.12 In the case of an axial caecal volvulus, the coffee bean sign points to the left upper quadrant.

A contrast enhanced CT scan of the abdomen and pelvis provides information on the site and nature of the obstruction and can help to confirm colorectal cancer but may not be necessary in volvulus.¹³

Water-soluble contrast enema can be used to diagnose and detort a sigmoid volvulus but should not be performed if there is localized lower abdominal peritonism suggestive of colonic ischemia.¹³

Treatment

Ensure adequate resuscitation and correction of electrolyte abnormalities. Surgery is indicated if a perforation is confirmed.

Colonic volvulus

A sigmoid volvulus may be treated in the emergency room using a rigid sigmoidoscope and a rectal tube to decompress the colon.¹³

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