Differential Diagnosis for Sharp Perirectal Pain in the 1st Trimester

Single Most Likely Diagnosis

• Hemorrhoids: Sharp perirectal pain, especially in the absence of rectal bleeding, could be indicative of a thrombosed hemorrhoid, which is common during pregnancy due to increased venous pressure.

Other Likely Diagnoses

• Anal Fissure: This condition can cause sharp pain during and after bowel movements, and while it's less common than hemorrhoids, it's still a plausible cause for perirectal pain in pregnancy.
• Proctalgia Fugax: A condition characterized by fleeting, severe anal pain, often at night, which could be exacerbated by the physiological changes of pregnancy.

Do Not Miss Diagnoses

• Ectopic Pregnancy: Although the primary symptom is usually abdominal pain, ectopic pregnancy can sometimes present with perirectal pain due to the proximity of the ectopic implantation site to the rectum. Given its potential lethality, it's crucial not to miss this diagnosis.
• Appendicitis: While appendicitis typically presents with abdominal pain, in rare cases, especially if the appendix is retrocecal, it might cause perirectal pain. Appendicitis in pregnancy can be more challenging to diagnose and is a medical emergency.

Rare Diagnoses

• Pudendal Neuralgia: A rare condition involving the pudendal nerve that can cause sharp, stabbing pain in the perineal area, including the rectum. It's less common but should be considered if other diagnoses are ruled out.
• Levator Ani Syndrome: Characterized by chronic pain in the rectal area, this condition is rare and might be considered if the pain is persistent and other causes have been excluded.