What are the differences between anal fissure and rectal cancer?

Nov 11, 2025 Source: Cainiu Health

Dr. Li Jingxiang

Introduction

Anal fissure pain is cyclical: defecation causes stool to irritate the裂ure, triggering pain; after defecation, there is brief relief, followed by severe pain due to spasm of the anal sphincter, which lasts for a prolonged period. In contrast, rectal cancer usually causes no significant pain in the early stage. In advanced stages, when the tumor invades surrounding tissues or causes obstruction, persistent dull or distending pain may occur, but this pain lacks a distinct cyclical pattern.

　　The differences between anal fissure and rectal cancer generally include symptom presentation, site of occurrence, pain characteristics, features of bloody stool, and disease progression. Specific analysis is as follows:

　　1. Symptom Presentation: Anal fissures mainly present as severe anal pain during and after defecation, accompanied by small amounts of bloody stool, often causing patients to develop a fear of defecation due to the pain. In addition to bloody stool, rectal cancer may also cause changes in bowel habits, such as alternating diarrhea and constipation or increased frequency of bowel movements.

　　2. Site of Occurrence: Anal fissures most commonly occur near the edge of the anus, typically at the anterior or posterior midline of the anal canal. The lesions are superficial and a visible crack can often be directly observed. Rectal cancer occurs within the lumen of the rectum, at a deeper location; early-stage lesions usually require digital rectal examination or colonoscopy for detection.

　　3. Pain Characteristics: Pain from an anal fissure is cyclical—stool passage irritates the裂 (crack), causing pain during defecation, followed by brief relief, then renewed severe pain due to spasm of the anal sphincter muscle, which lasts for a prolonged period. In contrast, rectal cancer typically causes no significant pain in the early stages. In advanced stages, when the tumor invades surrounding tissues or causes obstruction, persistent dull or distending pain may occur, lacking a clear cyclical pattern.

　　4. Features of Bloody Stool: Blood from anal fissures is usually bright red, minimal in amount, seen on the surface of the stool or dripping after defecation, and does not mix with the stool. In rectal cancer, blood may appear bright red or dark red, vary in volume, and frequently mixes with stool. It may also be accompanied by mucus or pus, resulting in mucoid or purulent bloody stools.

　　5. Disease Progression: Anal fissures have a relatively short course; with timely treatment, they may heal gradually within weeks. Some patients may experience recurrent episodes, but there is no tendency toward significant deterioration. Rectal cancer progresses progressively. Early symptoms are often subtle, but gradually worsen over time. Without prompt treatment, the tumor continues to spread, seriously affecting overall health.

　　If symptoms such as anal discomfort or bloody stool occur, it is important to seek medical attention at a正规 hospital promptly for professional evaluation and accurate diagnosis, avoiding self-diagnosis that could delay treatment. Maintaining regular bowel habits in daily life, and preventing chronic constipation or diarrhea, helps protect intestinal health.

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Can the anus be preserved during surgery for rectal cancer?

In general, whether the anus is preserved during surgery for rectal cancer mainly depends on the tumor's location, size, stage, and the patient's specific health condition. Patients who retain their anus should initially follow a liquid diet after surgery, gradually transitioning to soft foods, and consume more high-fiber foods to maintain regular bowel movements. Patients with a stoma need to regularly clean the stoma site, change the ostomy bag, and prevent local skin infections.

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What causes blood in stool after surgery for rectal cancer?

In general, postoperative rectal bleeding after colorectal cancer surgery may be caused by oozing from the anastomotic site during healing, dietary irritation of the intestinal mucosa, intestinal flora imbalance, ulcerative colitis, or rectal polyps. It is recommended to seek medical attention promptly, identify the underlying cause, and receive symptomatic treatment under a doctor's guidance. Maintain regular bowel habits in daily life, avoid prolonged squatting and straining during defecation, and keep the perianal area clean.

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How is early-stage rectal cancer surgically treated?

Surgical approaches for early-stage rectal cancer include endoscopic mucosal resection, endoscopic submucosal dissection, laparoscopic radical rectal resection, robot-assisted laparoscopic radical rectal resection, and open radical rectal resection, with the choice depending on factors such as tumor location and size. If symptoms such as rectal bleeding or abdominal pain occur, prompt medical evaluation is recommended to establish an accurate diagnosis.

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What to do about intestinal obstruction due to rectal cancer

In general, intestinal obstruction caused by colorectal cancer may result from improper dietary habits, disordered bowel habits, direct tumor blockage of the intestinal lumen, intestinal adhesions, or gastrointestinal infections. It is recommended to seek medical attention promptly, identify the underlying cause, and then improve the condition through general management, medication, and other treatments under a doctor's guidance. In daily life, it is essential to strictly follow a low-fat, high-protein, easily digestible diet, and eat small meals frequently.