What is the best investigation for a male patient with a history of right hemicolectomy (surgical removal of the right side of the colon) 3 years ago for colonic cancer (T1a, N0, M0), presenting with right lower quadrant pain, weight loss, and constipation for 3 months?

Colonoscopy is the Best Investigation for Post-Hemicolectomy Patient with New Symptoms

For a male patient with history of right hemicolectomy 3 years ago for T1a, N0, M0 colonic cancer who now presents with right lower quadrant pain, weight loss, and constipation for 3 months, colonoscopy (option A) is the best investigation. 1

Rationale for Colonoscopy as First-Line Investigation

Colonoscopy is strongly recommended by both the European Society for Medical Oncology (ESMO) and the Chinese Society of Clinical Oncology (CSCO) as the preferred examination for follow-up after colon cancer resection for several key reasons:

• It allows direct visualization of the anastomotic site and remaining colon
• It enables biopsies of any suspicious lesions
• It can detect metachronous adenomas and cancers
• It is classified as a Grade I recommendation (highest priority) by CSCO 1

The timing of this patient's presentation (3 years post-surgery) falls within the critical surveillance period, as the majority of stage II colon cancer recurrences (74%) are diagnosed within the first 3 years after primary cancer resection 1.

Diagnostic Algorithm for This Patient

1. Start with colonoscopy to directly visualize the anastomotic site and remaining colon
2. If colonoscopy is negative but symptoms persist, proceed with abdominal CT scan to evaluate for extraluminal recurrence
3. Consider CEA testing as CEA rise is often the first signal of recurrence
4. If CT suggests metastatic disease, consider MRI for better characterization of liver lesions 1

Comparative Analysis of Alternative Imaging Options

• CT scan (option B): While useful for detecting metastatic spread and complications, CT has lower sensitivity for early colon cancer. One study showed only 75% accuracy in identifying T1 and T2 cancers combined, with poor agreement between CT and histopathology for individual T stages 2. CT should be used as a second-line investigation if colonoscopy is negative.

• PET (option C): Routine use of PET is not recommended at the time of initial diagnosis according to ESMO guidelines. It is classified as a Grade III recommendation (lowest priority) in the CSCO guidelines and only recommended when there is clinical suspicion of recurrence while routine imaging is negative 1.

• Ultrasound (option D): May be useful for detecting liver metastases, but its sensitivity is lower than CT (0.43 vs 0.67) according to ESMO guidelines 1.

• MRI (option E): Recommended for better characterization of liver lesions if CT suggests metastatic disease, but not as a first-line investigation 1.

Important Clinical Considerations

• The patient's symptoms (right lower quadrant pain, weight loss, and constipation) could indicate local recurrence at the anastomotic site, which is best visualized by colonoscopy
• Intensive follow-up, including appropriate imaging, has been associated with a 7-13% improvement in overall survival 1
• If colonoscopy is negative, the diagnostic algorithm should proceed to CT imaging to evaluate for extraluminal causes of symptoms