Irritable Bowel Syndrome (IBS): This is a common condition characterized by abdominal pain, bloating, and changes in bowel movements, which can include rectal spasms. The diagnosis is often made based on symptom criteria (Rome IV) in the absence of other explanatory conditions.

Proctalgia Fugax: A condition that causes sudden, severe pain in the rectum due to muscle spasms, often occurring at night. It's relatively common and can be diagnosed based on the characteristic pain pattern.
Levator Ani Syndrome: Characterized by aching or pressure in the rectum that lasts for at least 20 minutes, often associated with rectal spasms. It's less common than IBS but should be considered in patients with chronic rectal pain.
Anal Fissure: A small tear in the lining of the anus, which can cause sharp pain and spasms during and after bowel movements. The pain is typically severe and can be diagnosed with a physical exam.

Rectal Cancer: Although less common, rectal cancer can cause rectal spasms among other symptoms like changes in bowel habits, blood in stool, and weight loss. Early detection is crucial for treatment outcomes.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause rectal spasms along with diarrhea, blood in stool, and abdominal pain. Missing these diagnoses can lead to significant morbidity.
Infections (e.g., Proctitis): Infections of the rectum can cause spasms, pain, and discharge. These can be due to bacterial, viral, or fungal causes and require prompt treatment to prevent complications.

Coccygodynia: Pain in the coccyx (tailbone) area, which can sometimes be associated with rectal spasms due to the proximity of the structures. It's often related to trauma or falls onto the buttocks.
Pudendal Neuralgia: A condition characterized by pain in the distribution of the pudendal nerve, which can include the rectal area, causing spasms. It's a rare condition that can be challenging to diagnose and treat.
Rectal Endometriosis: A form of endometriosis where endometrial tissue grows in the rectum, leading to cyclical pain, including rectal spasms, especially during menstruation. It's a rare condition that requires a high index of suspicion for diagnosis.