Overview
Definition:
Malignant large bowel obstruction (LBO) refers to a mechanical blockage of the colon caused by a tumor, most commonly colorectal adenocarcinoma
It presents a significant clinical challenge requiring prompt management
Stenting, using self-expanding metal stents (SEMS), has emerged as a valuable temporizing measure, acting as a "bridge to surgery" in select patients, allowing for elective rather than emergency surgical intervention.
Epidemiology:
Malignant LBO accounts for approximately 15-20% of all acute bowel obstructions
Colorectal cancer is the most frequent cause, particularly in older adults
The incidence increases with tumor stage and extent
In India, colorectal cancer incidence is rising, making this a relevant topic for DNB and NEET SS aspirants.
Clinical Significance:
Malignant LBO is a life-threatening condition associated with high morbidity and mortality if not managed effectively
It necessitates a multidisciplinary approach involving surgeons, oncologists, radiologists, and gastroenterologists
Understanding the role of SEMS as a bridge to surgery is crucial for optimizing patient outcomes, reducing the need for emergency surgery, and facilitating a more controlled surgical approach.
Clinical Presentation
Symptoms:
Progressive abdominal pain, typically colicky
Abdominal distension
Nausea and vomiting, often feculent in complete obstruction
Cessation of flatus and bowel movements
Constipation or obstipation
Weight loss and anorexia in chronic cases
Hematochezia may be present if the tumor is bleeding.
Signs:
Abdominal distension with tympanitic percussion
Tenderness on palpation, which may be localized or generalized
Absent or high-pitched bowel sounds on auscultation
Signs of dehydration and electrolyte imbalance
In severe cases, signs of peritonitis or sepsis.
Diagnostic Criteria:
Diagnosis is primarily based on clinical presentation and confirmed with imaging
CT scan is the gold standard, demonstrating the site and cause of obstruction, extent of the tumor, and presence of complications like perforation or ischemia
Endoscopic visualization is also important for biopsy and tumor staging.
Diagnostic Approach
History Taking:
Detailed history of bowel habits, changes in stool, weight loss, and previous abdominal surgeries
Duration and progression of symptoms
History of known malignancy, particularly colorectal cancer
Presence of prior episodes of obstruction
Red flags include rapid onset of symptoms, severe abdominal pain, and signs of peritonitis.
Physical Examination:
Thorough abdominal examination, including inspection for distension, scars, and masses
auscultation for bowel sounds
percussion for tympanicity
and palpation for tenderness, guarding, rigidity, and masses
Digital rectal examination is essential to assess for distal rectal tumors or palpable masses.
Investigations:
Laboratory: Complete blood count (anemia, leukocytosis), electrolytes (imbalance due to vomiting/dehydration), liver function tests, renal function tests
Imaging: Plain abdominal X-rays may show dilated loops of bowel and air-fluid levels, but CT scan of the abdomen and pelvis with oral and IV contrast is the investigation of choice
CT can identify the obstructing lesion, its proximal extent, assess for mural invasion, lymphadenopathy, and metastatic disease, as well as rule out perforation or ischemia
Colonoscopy may be performed to obtain biopsy confirmation and assess the extent of luminal involvement, but is contraindicated in acute, complete obstruction due to risk of perforation.
Differential Diagnosis:
Other causes of large bowel obstruction include volvulus (sigmoid, cecal), intussusception, diverticular strictures, inflammatory bowel disease strictures, hernia incarceration, adhesions, and extrinsic compression by other pelvic masses
Distinguishing malignant obstruction often relies on CT findings and biopsy.
Management
Initial Management:
Bowel decompression with a nasogastric tube
Intravenous fluid resuscitation to correct dehydration and electrolyte imbalances
Broad-spectrum antibiotics if sepsis is suspected
Pain management
Correction of coagulopathy if present
NPO status.
Stent As Bridge To Surgery:
Self-expanding metal stents (SEMS) are indicated in patients with malignant LBO who are good surgical candidates but require decompression to allow for elective surgery
Contraindications include complete bowel obstruction with significant distension without proximal decompression, bowel ischemia, or perforation
SEMS placement involves colonoscopic or fluoroscopic guidance, allowing for restoration of luminal patency and relief of symptoms
This approach enables elective surgery with bowel preparation, reducing complications associated with emergency surgery.
Surgical Management:
For patients not suitable for stenting or those with complications, emergent surgical management is required
Options include primary resection and anastomosis (if obstruction is not complete and patient is stable), resection with stoma creation (Hartmann's procedure), or diversion with mucus fistula
Once the patient is optimized, elective surgery typically involves resection of the involved segment with primary anastomosis, with or without a temporary diverting stoma
The decision for stenting vs immediate surgery depends on the patient's overall condition, tumor resectability, and presence of complications.
Supportive Care:
Close monitoring of vital signs, urine output, and abdominal examination
Nutritional support, potentially including parenteral nutrition if oral intake is not possible for an extended period
Management of pain and nausea
Regular electrolyte monitoring and correction
Post-stenting monitoring for stent migration, perforation, or tumor ingrowth.
Complications
Early Complications:
Stent-related: perforation, migration, malapposition, bleeding
Procedure-related: deep vein thrombosis, pulmonary embolism, myocardial infarction
Delayed complications of obstruction: bowel ischemia, perforation, sepsis, abscess formation.
Late Complications:
Tumor progression, stent restenosis due to tumor ingrowth or overgrowth, chronic pain, recurrent obstruction, fistulas, anastomotic leaks (following surgery).
Prevention Strategies:
Careful patient selection for stenting
Meticulous stent placement technique
Adequate bowel preparation for elective surgery
Prophylactic antibiotics and anticoagulation as indicated
Close postoperative monitoring
Multidisciplinary team approach to treatment planning.
Prognosis
Factors Affecting Prognosis:
Tumor stage and grade, presence of metastatic disease, patient's overall health status and comorbidities, timeliness of diagnosis and treatment, and complications encountered
For patients undergoing stenting, successful decompression and subsequent elective surgery generally lead to better outcomes than emergency surgery.
Outcomes:
With appropriate management, including stenting as a bridge to surgery in selected patients, survival rates can be improved, and morbidity from emergency surgery reduced
The prognosis is primarily dictated by the underlying malignancy
Patients with resectable disease and no distant metastasis have the best outcomes.
Follow Up:
Regular follow-up is essential for monitoring for tumor recurrence, managing long-term complications, and assessing overall well-being
This typically involves physical examinations, laboratory tests (CEA levels), and imaging modalities like CT scans
Surveillance colonoscopy is also a key component.
Key Points
Exam Focus:
Understand the indications and contraindications for SEMS placement in malignant LBO
Differentiate between emergent surgery and stenting as a bridge to elective surgery
Recognize CT scan findings suggestive of malignant obstruction and its complications
Know the complications associated with stenting and surgical management.
Clinical Pearls:
Always consider malignant LBO in elderly patients with new-onset obstructive symptoms
CT scan is paramount for diagnosis and staging
Stenting is most beneficial for palliation and enabling elective surgery in fit patients
Avoid stenting in cases of complete obstruction with proximal colonic distension beyond the caecum, or signs of perforation/ischemia.
Common Mistakes:
Delaying definitive treatment in suspected malignant LBO
Performing emergency surgery without considering stenting in appropriate candidates
Misinterpreting CT findings, leading to incorrect management decisions
Inadequate bowel preparation for elective surgery following stenting
Not considering the multidisciplinary nature of managing these complex patients.