What are the clinical features, diagnostic findings, and laboratory results, including complete blood count (CBC) and blood chemistry tests, of a large bowel obstruction, particularly in cases caused by colorectal cancer?

From the Guidelines

Large bowel obstruction (LBO) is a serious condition where the passage of stool through the colon is blocked, and colorectal cancer is the most common cause, accounting for about 60% of cases, with blood tests often revealing abnormalities such as leukocytosis, hypokalemia, hyponatremia, and elevated carcinoembryonic antigen (CEA) in cancer-related cases. The diagnosis of LBO is typically made using imaging studies like CT scans, which provide an optimal grade of information regarding the complications of cancer-related LBO 1. Blood tests in LBO may reveal several abnormalities, including:

• Complete blood count (CBC) often showing leukocytosis (elevated white blood cells) due to inflammation or infection
• Electrolyte panels demonstrating hypokalemia (low potassium), hyponatremia (low sodium), or metabolic acidosis from vomiting and dehydration
• Elevated blood urea nitrogen (BUN) and creatinine indicating dehydration or kidney dysfunction
• In cancer-related LBO, additional blood markers might include elevated carcinoembryonic antigen (CEA), which is often increased in colorectal cancer
• Liver function tests may be abnormal if metastases are present, showing elevated alkaline phosphatase, ALT, AST, or bilirubin
• C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are typically elevated due to inflammation
• Anemia might be present from chronic blood loss

The optimal management of left-sided malignant bowel obstruction (MBO) is less clear, with several surgical options existing, including primary resection, subtotal colectomy, or defunctioning ileostomy/colostomy with interval resection 1. However, self-expanding colonic endoluminal stents have been successfully used as a non-invasive technique to relieve left-sided MBO, allowing surgical resection to be performed on an elective rather than emergency basis 1. The use of self-expanding colonic endoluminal stents as a bridge to surgery has resulted in higher rates of primary anastomosis, reduced numbers of permanent stomas, and fewer wound infections with no increase in mortality compared to emergency surgery.

In terms of symptoms, LBO can present acutely or subacutely, with colic-like abdominal pain, abdominal bloating, and absence of bowel movement and flatus, while vomiting is less frequent than in small bowel obstruction 1. Abdominal examination shows tenderness, abdominal distension, and hyperactive or absent bowel sounds, with previous complaint of bloody stools and passage of blood per rectum, despite the absence of bowel movement, can be associated with colon cancer 1.

Laboratory tests are directed at evaluating the electrolyte imbalances, elevated urea nitrogen, and metabolic alkalosis that may occur as a consequence of vomiting and dehydration 1. While these blood tests can provide valuable information, they are not diagnostic on their own, and imaging studies like CT scans are essential for confirming LBO, and colonoscopy with biopsy is necessary to diagnose colorectal cancer definitively. Treatment depends on the cause but often requires surgical intervention, especially in cancer cases.

From the Research

Large Bowel Obstruction

• Large bowel obstruction is a serious and potentially life-threatening surgical emergency associated with high morbidity and mortality rates 2.
• The most common etiology of large bowel obstruction is colorectal cancer, accounting for over 60% of all cases 2.
• Other etiologies of large bowel obstruction include strictures, diverticulitis, ischemic colitis, endometriosis, and inflammatory disease 3, 4.

Diagnosis

• Diagnosis of large bowel obstruction relies on astute history and physical examination, as well as imaging with computed tomography (CT) scan for stable patients 3.
• CT findings can help identify the site, severity, and etiology of obstruction, and differentiate between malignant and benign causes 4.
• MDCT has become the standard of care to identify the site, severity, and etiology of obstruction, and can help identify signs of complications such as ischemia 4, 5.

Blood Tests

• There is no specific information available on what would be found on a bunch of blood tests for large bowel obstruction.
• However, blood tests may be used to evaluate the patient's overall health and to check for signs of complications such as infection or ischemia.

Management

• Management of large bowel obstruction depends on the etiology, severity, and presence of complications, and can include endoscopy, diversion, or resection 3, 6.
• Decisive surgical decision-making is needed for optimal outcomes, especially in cases of colonic perforation or ischemia 3, 5.
• Identifying signs of ischemia is important in the management of the patient, as it can enable early surgical intervention to avoid greater morbidity and mortality associated with strangulation and ischemia of the obstructed bowel loop 5.