Overview
Definition:
Obstructing left colon cancer refers to a malignant neoplasm in the distal colon that causes a mechanical blockade to the passage of intraluminal contents, leading to acute intestinal obstruction
The left colon, including the sigmoid and descending colon, is a common site for colorectal cancer due to higher fecal residue and slower transit time.
Epidemiology:
Colorectal cancer is a leading cause of cancer worldwide
Approximately 10-20% of patients present with symptoms of bowel obstruction
Left-sided colonic tumors are more likely to cause obstruction than right-sided tumors due to the narrower lumen of the distal colon.
Clinical Significance:
Obstructing left colon cancer represents a surgical emergency requiring prompt diagnosis and management to prevent complications such as bowel perforation, ischemia, sepsis, and death
Understanding on-table lavage and resection techniques is crucial for surgical residents preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Abdominal pain, often crampy and colicky
Abdominal distension
Nausea and vomiting, typically feculent in complete obstruction
Alteration in bowel habits, including obstipation (inability to pass stool or gas)
Rectal bleeding, though less common with left-sided lesions causing obstruction
Weight loss and anorexia in advanced stages.
Signs:
Distended abdomen with hyperactive bowel sounds initially, progressing to hypoactive or absent sounds in paralytic ileus
Tenderness to palpation, potentially with guarding or rebound tenderness if peritonitis is present
Tympanitic percussion note
Signs of dehydration or hypovolemia
Fever may indicate perforation or sepsis.
Diagnostic Criteria:
Diagnosis is typically based on a combination of clinical suspicion, physical examination findings, and cross-sectional imaging (CT scan abdomen with oral and IV contrast)
Colonoscopy may be used for visualization and biopsy if the patient is stable, but is often contraindicated in acute obstruction due to risk of perforation.
Diagnostic Approach
History Taking:
Detailed history of bowel habits, onset and progression of symptoms, presence of nausea/vomiting, prior abdominal surgeries, and family history of colorectal cancer
Red flags include unintentional weight loss, change in bowel habits lasting more than a few weeks, and blood in stool.
Physical Examination:
Abdominal examination focusing on inspection for distension, auscultation for bowel sounds, percussion for tympany, and palpation for tenderness, masses, and signs of peritonitis
Digital rectal examination to assess for palpable masses or impacted feces.
Investigations:
Complete blood count (CBC) to assess for anemia and leukocytosis
Serum electrolytes and renal function tests to evaluate hydration and electrolyte imbalance
Liver function tests (LFTs) and tumor markers (CEA) for staging and prognosis
CT abdomen with IV and oral contrast is the gold standard for diagnosing obstruction, identifying the level and cause, and assessing for complications like perforation or ischemia
Plain abdominal X-ray may show dilated loops of bowel and air-fluid levels but is less sensitive for diagnosis and etiology.
Differential Diagnosis:
Other causes of colonic obstruction include diverticular stricture, inflammatory bowel disease (Crohn's disease or ulcerative colitis), intussusception, volvulus (sigmoid or cecal), hernia, and extrinsic compression
Distinguishing malignancy requires imaging and often biopsy.
Management
Initial Management:
Bowel rest (NPO)
Nasogastric (NG) tube decompression to relieve distension and reduce vomiting
Intravenous fluids for hydration and electrolyte correction
Analgesia for pain control
Broad-spectrum antibiotics if signs of infection or perforation are present.
Surgical Management:
The primary goal is relief of obstruction and definitive treatment of the tumor
For obstructing left colon cancer, a common strategy involves resection of the affected segment with primary anastomosis
However, in the setting of acute obstruction and potential contamination, surgeons often opt for a staged approach
1
Intraoperative On-table Lavage: If a primary anastomosis is considered but the bowel is unprepared and contaminated, on-table lavage can be performed
A sterile saline solution is introduced into the distal end of the resected bowel (e.g., through the rectal stump) and allowed to flow proximally to clear fecal matter and reduce bacterial load before anastomosis
This aims to decrease the risk of anastomotic leak
2
Resection: The segment of the colon containing the tumor is resected
For left-sided lesions, this typically involves a sigmoid colectomy or left hemicolectomy
3
Anastomosis: Depending on the patient's condition, bowel preparation, and surgeon's assessment, a primary anastomosis between the proximal and distal bowel ends may be performed
Alternatively, if there is significant contamination, edema, or concern for anastomotic integrity, a diverting stoma (e.g., end colostomy) may be created, with a plan for reversal at a later stage (Hartmann's procedure or two-stage anastomosis)
Indications for immediate diversion (stoma without anastomosis): Gross contamination, peritonitis, patient instability, severe distal tumor involvement making distal resection difficult.
Supportive Care:
Close monitoring of vital signs, urine output, and abdominal examination
Nutritional support, often starting with parenteral nutrition if prolonged bowel rest is anticipated
Management of pain and nausea
Serial laboratory monitoring for electrolyte balance and signs of infection.
Complications
Early Complications:
Anastomotic leak leading to peritonitis or abscess formation
Wound infection
Intra-abdominal abscess
Sepsis
Cardiopulmonary complications due to fluid shifts and stress
Retained fecal impaction.
Late Complications:
Adhesions leading to small bowel obstruction
Incisional hernia
Stoma-related complications (e.g., retraction, prolapse, skin irritation)
Stricture at the anastomosis
Recurrence of cancer.
Prevention Strategies:
Meticulous surgical technique and secure anastomosis
Appropriate use of antibiotics
Careful patient selection for primary anastomosis versus stoma
Adequate bowel preparation if feasible, or use of on-table lavage for unprepared bowel
Judicious fluid management
Early mobilization and pulmonary toilet postoperatively.
Prognosis
Factors Affecting Prognosis:
Stage of the cancer at diagnosis (TNM staging)
Presence of lymph node metastasis
Presence of distant metastases
Histological grade of the tumor
Patient's overall health and comorbidities
Degree of obstruction and promptness of treatment
Whether a complete surgical resection was achieved.
Outcomes:
With complete surgical resection and appropriate adjuvant therapy, the prognosis for localized left colon cancer can be favorable
However, the presence of obstruction often signifies a more advanced stage and may be associated with a poorer prognosis compared to asymptomatic disease
Five-year survival rates vary significantly with stage, ranging from over 90% for localized disease to less than 15% for distant metastases.
Follow Up:
Regular follow-up is essential and includes clinical examination, CEA monitoring, and periodic imaging (CT scans) to detect recurrence or metastases
Colonoscopy is typically recommended 1 year after surgery, then every 3-5 years based on guidelines.
Key Points
Exam Focus:
The management of obstructing left colon cancer often involves a dilemma between immediate anastomosis and staged approach with diverting stoma
On-table lavage is a technique to reduce bacterial contamination prior to anastomosis in unprepared bowel
Understand the indications for each approach and the potential complications.
Clinical Pearls:
In a patient with acute obstruction and a palpable mass, always suspect malignancy
CT scan is crucial for diagnosis and staging
For obstructing left colon cancer in a hemodynamically stable patient with a clean operative field, a resection with primary anastomosis might be considered, especially if intraoperative lavage is performed
However, if the patient is unstable, peritonitis is present, or the distal bowel is involved, a Hartmann's procedure or defunctioning stoma is safer.
Common Mistakes:
Performing a primary anastomosis in a grossly contaminated or unstable patient without adequate bowel preparation or lavage, leading to a high risk of anastomotic leak
Neglecting NG tube decompression in a patient with vomiting and distension
Failing to consider alternative diagnoses for obstruction
Delaying surgical intervention in the presence of signs of strangulation or perforation.