What is the recommended workup for a rectal mass?

Recommended Workup for a Rectal Mass

The recommended workup for a rectal mass should include digital rectal examination with rigid sigmoidoscopy and biopsy, followed by complete staging with endorectal ultrasound or MRI, and assessment for distant metastases with CT imaging of chest, abdomen, and pelvis. 1

Initial Evaluation

• Digital rectal examination (DRE) and rigid sigmoidoscopy with biopsy are essential first steps for morphological verification and histopathological classification 1
• Complete history and physical examination should be performed to identify risk factors and symptoms 1
• Laboratory tests including complete blood count, liver and renal function tests, and carcinoembryonic antigen (CEA) should be obtained 1
• Complete colonoscopy to the cecal pole is required to exclude synchronous colonic tumors; if obstructive, virtual colonoscopy or barium enema can be used initially 1

Local Staging

• Endorectal ultrasound (ERUS) is preferred for early tumors (cT1-T2) to assess depth of invasion and guide treatment decisions 1
• Magnetic resonance imaging (MRI) is recommended for all rectal tumors, particularly intermediate/advanced cases, to evaluate:
  • T stage (depth of invasion) 1
  • Sphincter infiltration 1
  • Circumferential resection margin (CRM) status 1
  • Extramural vascular invasion 1
• For T1 tumors, subclassification using Haggitt's or Kikuchi (sm) systems helps predict lymph node metastasis risk and guides surgical approach 1

Nodal and Distant Metastasis Assessment

• Regional lymph node evaluation is best performed with MRI, though nodal staging remains challenging even with advanced imaging 1
• Distant metastasis (M stage) assessment requires:
  • CT or MRI of liver and abdomen 1
  • CT or chest X-ray of thorax 1
  • PET-CT may be considered if extensive extramural vascular invasion is present to detect occult metastases 1, 2

Multidisciplinary Evaluation

• All cases should be discussed at a multidisciplinary team (MDT) conference including radiologists, surgeons, radiation oncologists, medical oncologists, and pathologists 1
• For patients over 70 years, formal geriatric assessment or screening for frailty is recommended before treatment planning 1

Pathological Assessment

• Biopsy specimens should be evaluated for histological type (95-98% are adenocarcinomas) 1
• Surgical specimens require assessment of:
  • Proximal, distal, and circumferential margins 1
  • At least 12 regional lymph nodes 1
  • Vascular and nerve invasion 1
  • Tumor regression grade following neoadjuvant therapy 3

Common Pitfalls to Avoid

• Failing to perform digital rectal examination, which can miss early malignancies, especially in younger patients 4
• Confusing anal squamous cell carcinoma with rectal adenocarcinoma, which require different staging and treatment approaches 5
• Relying solely on one imaging modality; multimodal imaging provides complementary information for accurate staging 2
• Inadequate assessment of the circumferential resection margin, which is critical for determining recurrence risk 1
• Overlooking the need for complete colonoscopy to rule out synchronous lesions 1

Special Considerations

• Rectal masses may include non-adenocarcinoma tumors such as lymphoma, GIST, neuroendocrine tumors, or perirectal developmental cysts that require different management 6
• Restaging after neoadjuvant chemoradiotherapy remains challenging with all imaging modalities due to radiation-induced changes 2, 3
• For fixed tumors or local recurrences, preoperative radiotherapy with or without chemotherapy should be considered before attempting radical surgery 1