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

From the Guidelines

Large bowel obstruction (LBO) is a serious gastrointestinal 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, and elevated tumor markers like CEA.

Causes and Presentation

LBO can present acutely or subacutely, with symptoms including abdominal pain, distension, constipation, and sometimes vomiting, as noted in a study published in the World Journal of Emergency Surgery in 2018 1. Other causes of LBO include diverticular disease, volvulus, and fecal impaction. Patients with cancer-related LBO may also present with bloody stools and passage of blood per rectum.

Blood Tests

Blood tests in LBO may reveal several abnormalities, including:

• Complete blood count showing leukocytosis (elevated white blood cells) indicating inflammation or infection
• Electrolyte panels demonstrating hypokalemia (low potassium) and metabolic alkalosis due to vomiting and dehydration
• Elevated blood urea nitrogen (BUN) and creatinine indicating dehydration or renal compromise
• Anemia from chronic blood loss in cancer-related LBO
• Elevated liver enzymes if metastasis is present
• Tumor markers like CEA (carcinoembryonic antigen) may be elevated
• Inflammatory markers such as C-reactive protein and erythrocyte sedimentation rate are often increased
• Lactate levels might be elevated in cases with bowel ischemia

Diagnosis and Management

Diagnosis of LBO typically requires imaging studies like CT scans, as noted in a study published in the World Journal of Emergency Surgery in 2018 1. Definitive management often involves surgical intervention, especially for cancer-related obstructions. However, self-expanding colonic endoluminal stents have been successfully used as a non-invasive technique to relieve left-sided LBO, allowing surgical resection to be performed on an elective rather than emergency basis, as noted in a study published in 2019 1.

Recent Guidelines

Recent guidelines, such as those published in 2018, recommend CT scan as the best imaging technique to evaluate large bowel obstruction and perforation, and suggest that self-expandable metallic stent (SEMS) offers interesting advantages as compared to emergency surgery, but may carry some long-term oncologic disadvantages 1.

Key Points

• LBO is a serious gastrointestinal condition with colorectal cancer as the most common cause
• Blood tests can reveal several abnormalities, including leukocytosis, hypokalemia, and elevated tumor markers
• Diagnosis typically requires imaging studies like CT scans
• Definitive management often involves surgical intervention, especially for cancer-related obstructions
• Self-expanding colonic endoluminal stents can be used as a non-invasive technique to relieve left-sided LBO.

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
• Large bowel obstructions can be classified as partial or complete, intrinsic or extrinsic, and benign or malignant 3

Etiologies of Large Bowel Obstruction

• Colorectal cancer is the most common cause of large bowel obstruction 2, 4, 5
• Other etiologies include strictures, volvulus, and extrinsic compression 3, 4
• Neoplastic diseases are the most common cause of large bowel obstruction, with colorectal cancer being the leading cause 5

Diagnosis of Large Bowel Obstruction

• Diagnosis relies on astute history and physical examination, as well as imaging with computed tomography (CT) scan for stable patients 4
• Abdominal radiography is usually the initial imaging study performed, but may not be sufficient to distinguish obstruction from other causes of colonic dilatation 6
• CT scan is the imaging method of choice, as it can establish the diagnosis and cause of large bowel obstruction 6, 5

Blood Tests for Large Bowel Obstruction

• There is no specific blood test for large bowel obstruction, but various blood tests may be ordered to evaluate the patient's overall health and to rule out other conditions 2, 3, 4
• Blood tests may include complete blood count (CBC), electrolyte panel, liver function tests, and tumor markers such as carcinoembryonic antigen (CEA) for colorectal cancer 2, 4

Management of Large Bowel Obstruction

• Management strategy is contingent on the etiology, severity, and characteristics of the obstruction 3, 4
• Treatment options include endoscopy, diversion, or resection, and may involve urgent surgical intervention 3, 4
• Decisive surgical decision-making is needed for optimal outcomes, especially in cases of colonic perforation 4