Can a true intraluminal rectal mass occur after an abdominoperineal excision?

Can There Be a Mass in the Rectal Lumen After APE?

No, a true intraluminal rectal mass cannot occur after abdominoperineal excision (APE) because the entire rectum and anal canal are removed during this procedure. 1

Understanding APE Anatomy

During APE, the surgical specimen includes:

• The entire rectum from the peritoneal reflection to the anal canal 1
• The anal canal and sphincter complex 1
• The mesorectum with its surrounding fascia 1
• The levator ani muscles (in extralevator APE) 1

After APE, there is no remaining rectal lumen where an intraluminal mass could develop. 1 The patient is left with a permanent colostomy and the perineal wound is closed. 2, 3

What Can Appear as a "Mass" After APE

Presacral Soft-Tissue Masses

The most common finding that may be mistaken for recurrence is a presacral soft-tissue mass, which occurs in the space previously occupied by the rectum. 4 These masses can represent:

• Post-treatment fibrosis (most common, shows low T2 signal on MRI) 4
• Local tumor recurrence (shows high T2 signal on MRI with contrast enhancement) 4
• Hematoma or seroma in the early postoperative period 4

Diagnostic Approach to Presacral Masses

Pelvic MRI with intravenous contrast is the primary imaging modality to characterize presacral masses because it distinguishes recurrent tumor from post-treatment fibrosis. 4

PET/CT should be added for definitive differentiation, offering 100% sensitivity and 96% specificity for distinguishing benign from malignant lesions. 4

Pathological confirmation via biopsy is mandatory before any salvage surgery such as pelvic exenteration. 4 Biopsy should be performed after imaging characterization to target viable tumor areas. 4

Local Recurrence Patterns After APE

Local recurrence after APE occurs in the presacral space, perineal wound, or pelvic sidewall—never as an intraluminal mass. 1, 4 The recurrence rate after APE has historically been higher than after anterior resection, ranging from 10-30% at 5 years. 4, 2

Risk Factors for Local Recurrence

• Suboptimal surgical plane (intrasphincteric or sphincteric plane rather than extralevator plane) 1
• Inadvertent bowel perforation during surgery 1, 5
• Positive circumferential resection margin 1, 6
• Tumor within 5 cm of anal verge 1

Extralevator APE (ELAPE) reduces local recurrence compared to conventional APE by achieving wider radial margins and avoiding inadvertent perforation. 2, 3, 7, 5 ELAPE results in a cylindrical specimen with levator muscles forming a protective layer, whereas conventional APE often produces a "waisted" specimen with higher perforation rates. 1, 3, 5

Surveillance After APE

Intensive surveillance is warranted because most recurrences occur within 2-3 years postoperatively. 6, 4

The recommended surveillance protocol includes:

• CT chest/abdomen/pelvis every 6 months for 3 years, then annually through year 5 6, 4
• Pelvic MRI every 6 months for years 1-2, then annually for years 3-5 6, 4
• CEA testing every 3-6 months for 3 years, then every 6 months through year 5 (never in isolation, always with imaging) 6, 4
• Office visits every 3 months for 3 years, then every 6 months for years 4-5 6

Colonoscopy at 1 year postoperatively is still recommended to evaluate the remaining colon for metachronous lesions, even though there is no rectal lumen. 1, 6

Critical Pitfall to Avoid

Do not confuse a presacral soft-tissue mass with an intraluminal rectal mass. 4 The anatomic impossibility of intraluminal recurrence after APE should prompt immediate recognition that any mass-like finding represents either presacral recurrence, post-treatment changes, or a different pathologic process entirely. 1, 4