What are the clinical features, laboratory findings, and metabolic changes associated with large bowel obstruction, particularly in cases of colorectal cancer, including the type of anemia, elevated C-Reactive Protein (CRP) levels, and other general blood test abnormalities?

From the Guidelines

Large bowel obstruction (LBO) is a life-threatening condition that requires prompt diagnosis and treatment, and in cases of cancer-related LBO, blood tests often reveal microcytic hypochromic anemia, elevated C-reactive protein (CRP), and metabolic derangements, including hypokalemia, hyponatremia, and metabolic alkalosis, as seen in studies such as 1 and 1.

Clinical Presentation and Diagnosis

LBO can present with acute or subacute symptoms, including colic-like abdominal pain, abdominal bloating, and absence of bowel movement and flatus, as noted in 1. The absence of passage of flatus and/or feces, and abdominal distension are common symptoms and physical signs. A rectal examination may reveal a palpable mass suggestive of colon cancer, and laboratory tests are essential to evaluate electrolyte imbalances, elevated urea nitrogen, and metabolic alkalosis that may occur as a consequence of vomiting and dehydration, as mentioned in 1.

Blood Test Abnormalities

Patients with cancer-related LBO often develop microcytic hypochromic anemia due to chronic blood loss from the tumor, resulting in low hemoglobin, decreased mean corpuscular volume (MCV), and reduced iron levels.

• C-reactive protein (CRP) is frequently elevated due to inflammation from the tumor itself and potential bacterial translocation if the bowel wall integrity is compromised, as seen in 1 and 1.
• Metabolic derangements are common, including hypokalemia, hyponatremia, and metabolic alkalosis resulting from vomiting and dehydration.
• Patients may develop elevated blood urea nitrogen (BUN) and creatinine from pre-renal acute kidney injury due to dehydration, as noted in 1 and 1.
• Liver function tests might show abnormalities if metastatic disease is present.
• White blood cell count is often elevated, indicating inflammation or infection, especially if perforation has occurred.
• Lactate levels may rise in severe cases due to bowel ischemia, as mentioned in 1.

Importance of Laboratory Tests

A complete blood count, renal function and electrolytes, and liver function tests are suggested as the first laboratory tests, as recommended in 1. Low serum bicarbonate levels, low arterial blood pH, high lactic acid level, marked leukocytosis, and hyperamylasemia may be useful in the diagnosis of intestinal ischemia. A coagulation profile should also be tested because of the potential need for emergency surgery, as noted in 1. In summary, the diagnosis and management of LBO require a comprehensive approach, including clinical evaluation, laboratory tests, and imaging studies, to promptly identify the cause and location of the obstruction and initiate appropriate treatment, as emphasized in 1 and 1.

From the Research

Large Bowel Obstruction

• Large bowel obstructions (LBOs) often require urgent surgical intervention, with diagnosis relying on astute history and physical examination, as well as imaging with computed tomography (CT) scan for stable patients 2.
• Nearly one-quarter of bowel obstructions occur in the large bowel, with LBOs having three defining characteristics: partial or complete, intrinsic or extrinsic, benign or malignant 3.

Cancer and Large Bowel Obstruction

• Malignant bowel obstruction is a common complication of advanced gastrointestinal, gynecologic, and genitourinary tumors, with patients presenting with nausea, vomiting, abdominal pain, and constipation 4.
• The global prevalence of malignant bowel obstruction (MBO) is estimated to be 3% to 15% of cancer patients, especially in those with abdominal tumors 5.
• In stage IV colorectal cancer patients, malignant bowel obstruction remains poorly understood, with optimal management requiring realistic assessment of treatment goals 6.

Blood Tests and Large Bowel Obstruction

• Anemia is commonly seen in patients with large bowel obstruction, particularly those with malignant bowel obstruction, due to chronic blood loss or malabsorption.
• C-reactive protein (CRP) levels may be raised in patients with large bowel obstruction, indicating inflammation or infection, which can be associated with malignant bowel obstruction or other complications 4, 5.
• Metabolic changes, such as electrolyte imbalances or acid-base disturbances, can occur in patients with large bowel obstruction due to vomiting, diarrhea, or malabsorption, and may be reflected in blood test results.

General Blood Tests

• Complete blood count (CBC) may show anemia, leukocytosis, or other abnormalities in patients with large bowel obstruction.
• Electrolyte panel may reveal imbalances, such as hypokalemia or hyponatremia, due to vomiting or malabsorption.
• Liver function tests (LFTs) may be abnormal in patients with malignant bowel obstruction or other complications, such as liver metastases.
• Inflammatory markers, such as CRP or erythrocyte sedimentation rate (ESR), may be elevated in patients with large bowel obstruction, indicating inflammation or infection.