What are the clinical features, laboratory findings, and implications of large bowel obstruction, particularly in the context of colorectal cancer, including the type of anemia and elevated C-Reactive Protein (CRP) levels?

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 a common cause, accounting for about 60% of cases.

Causes and Symptoms

Other causes of LBO include diverticular disease, volvulus, and fecal impaction. Symptoms of LBO can present acutely or subacutely, with abdominal pain, distension, and altered bowel habits being common presentations, as noted in the 2017 WSES guidelines on colon and rectal cancer emergencies: obstruction and perforation 1.

Blood Tests and Findings

Blood tests in LBO patients often reveal several abnormalities, including:

• Anemia, typically a microcytic, hypochromic anemia due to chronic blood loss from the tumor, leading to iron deficiency, which appears on complete blood count (CBC) as low hemoglobin, low mean corpuscular volume (MCV), and low mean corpuscular hemoglobin (MCH) 1.
• C-reactive protein (CRP) is commonly elevated due to inflammation from the obstruction itself or from bacterial translocation across the compromised bowel wall.
• White blood cell count may be increased, indicating inflammation or infection.
• Electrolyte imbalances often occur, particularly hypokalemia from vomiting and dehydration.
• Liver function tests may be abnormal if metastatic disease is present.
• Blood urea nitrogen (BUN) and creatinine might be elevated due to dehydration.
• Carcinoembryonic antigen (CEA) is often elevated in colorectal cancer but isn't diagnostic.

Diagnosis and Management

The diagnosis of LBO is based on a combination of clinical symptoms, laboratory findings, and imaging studies. The 2017 WSES guidelines recommend the use of computed tomography (CT) scan or water-soluble colonic contrast enema to confirm the diagnosis of LBO 1.

Treatment Options

Treatment options for LBO depend on the underlying cause and severity of the obstruction. For colorectal cancer, treatment may involve surgery, chemotherapy, and radiation therapy. The guidelines recommend Hartmann’s procedure or resection and primary anastomosis for left-sided obstruction, and right colectomy with primary anastomosis for right-sided obstruction 1.

Recent Guidelines

Recent guidelines from the World Journal of Emergency Surgery emphasize the importance of early diagnosis and treatment of LBO, and recommend the use of antibiotic prophylaxis and prompt surgical intervention in cases of perforation or strangulation 1.

Key Points

• LBO is a serious condition that requires prompt diagnosis and treatment.
• Colorectal cancer is a common cause of LBO.
• Blood tests can reveal several abnormalities, including anemia, elevated CRP, and electrolyte imbalances.
• Imaging studies, such as CT scan or water-soluble colonic contrast enema, can confirm the diagnosis of LBO.
• Treatment options depend on the underlying cause and severity of the obstruction.

From the Research

Large Bowel Obstruction

• Large bowel obstruction is a serious condition that can be caused by various factors, including cancer, and requires prompt diagnosis and treatment 2, 3.
• The work-up for a large bowel obstruction should focus on the etiology of the obstruction as well as its severity, and management strategies can include endoscopy, diversion, or resection 2.

Cancer as a Cause of Large Bowel Obstruction

• Colorectal cancer is a common cause of large bowel obstruction, and computed tomography (CT) scans can be used to identify the site, severity, and etiology of the obstruction 4.
• CT features of colonic cancer responsible for large bowel obstruction can include classical and atypical features, and the presence of local lymph nodes, other colic localizations, length of involved segment, presence of diverticula, or other features can help differentiate malignant from benign causes 4.

Blood Tests in Large Bowel Obstruction

• Patients with large bowel obstruction caused by cancer may have anemia, which can be due to chronic blood loss or other factors 5.
• The type of anemia seen in these patients is not specified, but it is likely to be iron-deficiency anemia or anemia of chronic disease.
• C-reactive protein (CRP) levels may be raised in patients with large bowel obstruction due to inflammation or infection, and this can be a useful marker for monitoring the patient's condition 5.

General Blood Tests

• General blood tests, such as complete blood count (CBC), electrolyte panel, and liver function tests, can be useful in evaluating patients with large bowel obstruction 5.
• These tests can help identify underlying conditions, such as anemia, electrolyte imbalances, or liver disease, that may be contributing to the patient's symptoms.
• However, the specific findings on these tests will depend on the individual patient and the underlying cause of the large bowel obstruction.