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?

Best Investigation for a Patient with History of Right Hemicolectomy Presenting with Right Lower Quadrant Pain, Weight Loss, and Constipation

Colonoscopy is the best investigation for this patient with a history of right hemicolectomy for T1a, N0, M0 colon cancer who now presents with right lower quadrant pain, weight loss, and constipation for 3 months. 1

Rationale for Colonoscopy

Colonoscopy is the preferred first-line investigation in this case for several important reasons:

1. Direct visualization and biopsy capability: Colonoscopy allows direct visualization of the anastomotic site and remaining colon, with the ability to obtain biopsies of any suspicious lesions 2.

2. Detection of local recurrence: The patient's symptoms (right lower quadrant pain, weight loss, constipation) are concerning for local recurrence at the anastomotic site, which colonoscopy can directly visualize.

3. Guideline recommendations: ESMO guidelines strongly recommend colonoscopy as part of follow-up after colon cancer resection, stating it must be carried out at year 1 and every 3-5 years thereafter to look for metachronous adenomas and cancers 2, 1.

4. Timing considerations: The patient is 3 years post-surgery, which falls within the critical surveillance period. ESMO guidelines note that 82% of stage III and 74% of stage II colon cancer recurrences are diagnosed within the first 3 years after primary cancer resection 2.

Alternative Imaging Options and Their Limitations

CT Scan (Option B)

• While CT scan can detect metastatic spread and complications like perforation or obstruction 2, it has limited sensitivity for early colon cancer detection.
• CT has only 70.2% sensitivity and 79.2% specificity for T staging, with poor agreement between CT and histopathology for individual T stages 3.
• However, CT would be an appropriate second-line investigation if colonoscopy is inconclusive or shows a lesion requiring further evaluation.

PET Scan (Option C)

• PET is not recommended as a first-line investigation.
• ESMO guidelines specifically state that "the routine use of positron emission tomography (PET) with the glucose analogue 18-fluoro-2-deoxy-D-glucose (FDG-PET) is not recommended at the time of initial diagnosis" 2.
• PET is classified as a Grade III recommendation (lowest priority) and is only recommended when there is clinical suspicion of recurrence while routine imaging is negative 1.

Ultrasound (Option D)

• While ultrasound may be useful for detecting liver metastases, its sensitivity is lower than CT (0.43 vs 0.67) 2.
• It is not the optimal first-line investigation for evaluating the anastomotic site or intraluminal recurrence.

MRI (Option E)

• MRI has excellent soft tissue resolution but has not been adequately evaluated for this specific indication 1.
• It might be useful for locally advanced tumors but is not the first-line investigation for suspected recurrence.

Follow-up Algorithm After Initial Colonoscopy

1. If colonoscopy reveals a lesion:

   • Obtain biopsies for histopathological confirmation
   • If positive for recurrence, proceed with CT chest/abdomen/pelvis for staging

2. If colonoscopy is negative but symptoms persist:

   • Proceed with abdominal CT scan to evaluate for extraluminal recurrence or other causes of symptoms
   • Consider CEA testing (if not already done) as CEA rise is often the first signal of recurrence 2

3. Further investigations based on findings:

   • If CT suggests metastatic disease, consider MRI for better characterization of liver lesions 2
   • PET scan only if other imaging is inconclusive but clinical suspicion remains high 1

Important Considerations

• The patient's original cancer was early stage (T1a, N0, M0), but the current symptoms are concerning for recurrence.
• The timing (3 years post-surgery) is significant as most recurrences occur within the first 3 years 2.
• Weight loss combined with localized symptoms significantly increases the likelihood of recurrence or metachronous cancer.
• The right lower quadrant pain may indicate recurrence at the anastomotic site, which is best visualized directly with colonoscopy.