From the Guidelines
Large bowel obstruction (LBO) due to colorectal cancer is a medical emergency that requires prompt diagnosis and treatment to prevent morbidity and mortality, and the initial evaluation should include a complete blood count, renal function, and electrolytes, as well as a coagulation profile, as suggested by the most recent study 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 in adults, accounting for about 60% of cases. Patients typically present with abdominal pain, distension, constipation, and sometimes vomiting. When cancer is the cause, patients may also experience weight loss, rectal bleeding, and changes in bowel habits preceding the acute obstruction.
Diagnosis
Diagnosis involves physical examination, abdominal X-rays showing dilated colon with air-fluid levels, and CT scans which can identify the location and cause of obstruction. Blood tests are important but not diagnostic for LBO; they may show elevated white blood cell count indicating inflammation or infection, and electrolyte abnormalities from vomiting and dehydration. For cancer detection, carcinoembryonic antigen (CEA) may be elevated but isn't specific enough for diagnosis. Complete blood count might reveal anemia if chronic bleeding has occurred.
Treatment
Treatment depends on the cause and severity but often requires surgical intervention, especially for cancer-related obstructions. For partial obstructions, temporary measures like bowel rest, IV fluids, and nasogastric tube decompression may help. If cancer is confirmed, further staging and treatment planning will follow surgical management of the obstruction. Early recognition and treatment are crucial to prevent complications like perforation, peritonitis, and sepsis. According to the study 2, adjuvant chemotherapy is recommended for stages T1–4, N1–2, M0 (i.e. stage III, modified Dukes C1–3), and may be considered in selected node-negative patients, especially if high-risk factors for recurrence are found.
Key Laboratory Tests
The following laboratory tests are essential in the evaluation of LBO:
- Complete blood count to evaluate for anemia, inflammation, or infection
- Renal function and electrolytes to assess for dehydration and electrolyte imbalances
- Coagulation profile to evaluate the risk of bleeding
- Liver function tests to assess for liver metastasis
- CEA levels to aid in the diagnosis of colorectal cancer, although not specific enough for diagnosis alone, as noted in the study 3.
Risk Factors for Colorectal Cancer
Risk factors for colorectal cancer include:
- Family history
- Familial adenomatous polyposis (FAP) and attenuated FAP (AFAP) syndromes
- Hereditary non-polyposis colorectal cancer (HNPCC) syndrome
- Past history of colorectal cancer or adenoma
- Chronic ulcerative colitis and Crohn’s disease, as outlined in the study 2.
From the Research
Definition and Etiology of Large Bowel Obstruction
- Large bowel obstruction is a serious and potentially life-threatening surgical emergency associated with high morbidity and mortality rates 4.
- The most common etiology of large bowel obstruction is colorectal cancer, accounting for over 60% of all cases 4.
- Other causes of bowel obstruction include postsurgical adhesions, which are more common in the small bowel than in the large bowel 5.
Diagnosis of Large Bowel Obstruction
- Diagnosis of large bowel obstruction relies on astute history and physical examination, as well as imaging with computed tomography (CT) scan for stable patients 6.
- Multidetector computed tomography (MDCT) is commonly used to diagnose bowel obstruction, and reports should focus on confirming the obstruction, determining the transition point, establishing the cause, and seeking signs of complications 5.
- Radiological confirmation is an essential component in defining acute obstruction, and is included in 100% of evaluable randomized controlled trials (RCTs) and 54% of prospective observational studies 7.
Cancer and Large Bowel Obstruction
- Colorectal cancer is a common cause of large bowel obstruction, and its definition and urgency can vary greatly across studies 7.
- A systematic review found that only 31% of RCTs and 37% of prospective observational studies provided a definition of obstruction by colorectal cancer, and these definitions often included a combination of clinical symptoms, physical signs, endoscopic features, and radiological imaging findings 7.
Blood Tests and Large Bowel Obstruction
- There is no direct evidence in the provided studies on the use of blood tests in the diagnosis of large bowel obstruction.
- However, it is likely that blood tests may be used to assess the overall health of the patient and to check for signs of complications such as ischemia or infection 5, 6.
Management and Treatment
- Large bowel obstructions often require urgent surgical intervention, and decisive surgical decision-making is needed for optimal outcomes 6.
- The management of large bowel obstruction depends on the underlying cause, and may include surgery, endoscopy, or other interventions 4, 6.
- Early surgical intervention may be necessary to avoid greater morbidity and mortality associated with strangulation and ischemia of the obstructed bowel loop 5.