Can Patients Develop Internal Anal Fissures That Are Not Visible?
Yes, patients can have anal fissures that are not visible on external inspection, particularly when they are located internally within the anal canal or when severe pain prevents adequate examination. 1
Anatomical Location and Visibility
Anal fissures are longitudinal tears in the squamous epithelium that can extend from the dentate line (internally) to the anal verge (externally), meaning they may exist entirely within the anal canal where they cannot be seen without proper examination technique. 2
Key Examination Considerations:
Fissures are best visualized by separating the buttocks with opposing traction to evert the anal canal—they cannot be seen with standard end-viewing endoscopes. 1, 2
When intense pain prevents examination, the anal canal should not be instrumented; examination under anesthesia may be required to visualize internal fissures. 1, 2
In cases where pain is severe enough to prevent adequate physical examination, fissures may remain undiagnosed on initial assessment. 1
Clinical Implications
Diagnosis Despite Limited Visualization:
The diagnosis should be suspected based solely on clinical history: acute anal pain during and after defecation, with bright red bleeding. 1
Even when direct visualization is impossible due to pain, the characteristic symptom pattern (severe pain described as "passing glass" during and after bowel movements) strongly suggests anal fissure. 1, 3
When Imaging May Be Needed:
Imaging with CT, MRI, or endoanal ultrasound is recommended only if there is suspicion of concomitant anorectal diseases such as abscess, inflammatory bowel disease, or neoplasm—not for routine fissure diagnosis. 3
Anorectal abscesses may be occult on physical examination, requiring imaging for detection. 4
Common Pitfall to Avoid
Do not force instrumentation or digital examination when a patient has severe anal pain—this is traumatic and inappropriate; instead, proceed with empiric treatment based on clinical history or arrange examination under anesthesia. 1, 2