Differential Diagnosis for Abdominal Pain and Constipation

The patient's symptoms of a knot in the lower abdomen, pain, and constipation, which improve with a muscle relaxer and bowel movement, suggest several possible diagnoses. These can be categorized as follows:

• Single Most Likely Diagnosis

  • Irritable Bowel Syndrome (IBS): This condition is characterized by abdominal pain, changes in bowel habits (such as constipation), and relief of pain with bowel movements. The improvement with a muscle relaxer could be due to the relaxation of abdominal muscles, which might be tense due to the pain or the condition itself.

• Other Likely Diagnoses

  • Constipation: This could be a primary issue causing the abdominal pain and feeling of a knot, especially if the patient has a history of infrequent bowel movements or difficulty passing stools.
  • Abdominal wall pain or myofascial pain syndrome: This condition involves pain in the abdominal wall muscles and can mimic visceral pain. The relief with a muscle relaxer supports this possibility.
  • Diverticulitis: Although less likely without other symptoms like fever or changes in bowel habits, diverticulitis could cause lower abdominal pain and constipation, especially if there's a history of diverticulosis.

• Do Not Miss Diagnoses

  • Appendicitis: Although the pain typically starts near the navel and then moves to the lower right abdomen, atypical presentations can occur. The improvement with a bowel movement does not rule out appendicitis, as temporary relief can happen.
  • Ovarian torsion or other gynecological emergencies: These conditions can cause severe lower abdominal pain and might be associated with bowel symptoms due to the proximity of the ovaries to the intestines.
  • Intestinal obstruction: This is a serious condition that can cause abdominal pain, constipation (or obstipation), and could potentially improve temporarily with a bowel movement if there's a partial obstruction.

• Rare Diagnoses

  • Chronic intestinal pseudo-obstruction: A rare condition characterized by impairment of the muscle contractions that move food, fluid, and air through the intestines, leading to symptoms like constipation and abdominal pain.
  • Endometriosis: Although not typically associated with constipation as a primary symptom, endometriosis can cause abdominal pain and might contribute to bowel symptoms if endometrial implants are near the intestines.
  • Abdominal epilepsy: A rare condition where seizures manifest as abdominal pain, which could potentially be confused with other causes of abdominal pain and might improve with certain medications, including muscle relaxers.