What are the characteristics of large bowel obstruction, particularly in cases of colorectal cancer, and what laboratory findings, including anemia type, can be expected on general blood tests?

From the Guidelines

Large bowel obstruction (LBO) due to cancer is a serious condition that often presents with abdominal pain, distension, constipation, and vomiting, and is typically associated with microcytic, hypochromic anemia due to chronic blood loss from the tumor, as well as other abnormalities on blood tests such as leukocytosis, thrombocytosis, and elevated inflammatory markers 1.

Causes and Presentation

LBO can be caused by various factors, including colorectal cancer, diverticular disease, volvulus, and fecal impaction. Colorectal cancer is the most common cause of LBO, accounting for about 60% of cases. Patients with cancer-related LBO often have pain, nausea, and vomiting, and may also experience abdominal distension, constipation, and weight loss.

Blood Tests

Blood tests may reveal specific abnormalities in patients with cancer-related LBO, including:

• Anemia, typically microcytic, hypochromic anemia due to chronic blood loss from the tumor 1
• Leukocytosis (elevated white blood cells) if there's infection or inflammation
• Thrombocytosis (elevated platelets) as an inflammatory response
• Abnormal liver function tests if the cancer has metastasized to the liver
• Electrolyte imbalances like hypokalemia and metabolic alkalosis due to vomiting
• Elevated inflammatory markers such as C-reactive protein and erythrocyte sedimentation rate
• Tumor markers like CEA (carcinoembryonic antigen) may be elevated in colorectal cancer but aren't diagnostic on their own

Diagnosis and Management

Diagnosis of LBO is typically made using a combination of clinical presentation, imaging studies, and laboratory findings. Imaging studies such as computed tomography (CT) scan or water-soluble contrast enema can help confirm the diagnosis and identify the site and nature of the obstruction 1. Management of LBO due to cancer may involve surgical intervention, stenting, or other palliative measures, and the optimal approach depends on various factors, including the patient's overall health, the location and severity of the obstruction, and the presence of any complicating factors 1.

Recent Guidelines

Recent guidelines suggest that stenting as a bridge to surgery may be a viable option for patients with left-sided MBO, and can help reduce the need for emergency surgery and improve outcomes 1. However, the optimal management of LBO due to cancer remains a topic of debate, and further research is needed to determine the best approach for individual patients.

From the Research

Large Bowel Obstruction

• Large bowel obstruction is a serious and potentially life-threatening surgical emergency associated with high morbidity and mortality rate 2
• The most common etiology is colorectal cancer, which accounts for over 60% of all large bowel obstructions 2
• Proper assessment, thoughtful decision-making, and prompt treatment are necessary to decrease the high morbidity and mortality associated with this entity 2

Cancer and Large Bowel Obstruction

• Colorectal cancer is the most common cause of large bowel obstruction 2, 3
• The treatment of large bowel obstruction caused by cancer depends on the location of the obstruction, intraoperative local findings, and the patient's condition 4
• Resection and anastomosis as one-stage surgery is the preferred procedure, but anastomotic leakage highly elevates the risk of mortality and morbidity 4

Blood Tests and Anemia

• Severe hypoproteinemia and anemia are factors that may contraindicate primary resection and anastomosis in patients with large bowel obstruction caused by cancer 4
• The type of anemia seen in patients with large bowel obstruction is not specifically stated in the available evidence, but it is likely to be iron-deficiency anemia due to chronic blood loss from the tumor
• General blood tests may show signs of anemia, such as low hemoglobin and hematocrit levels, as well as elevated inflammatory markers and tumor markers, such as carcinoembryonic antigen (CEA) 5

Diagnosis and Management

• 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
• Management strategy is contingent on the etiology, severity, and location of the obstruction, and may include endoscopy, diversion, or resection 6
• CT findings, such as 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 of large bowel obstruction 5