What is the differential diagnosis and recommended workup for a 45-year-old female with a history of fibromyalgia, deep vein thrombosis (DVT), gastroesophageal reflux disease (GERD), asthma, and endometriosis status post hysterectomy, presenting with 2 days of left lower quadrant (LLQ) pain and decreased stool caliber?

Differential Diagnosis for 45 y/o Female with LLQ Pain and Decreased Caliber of Bowel Movements

Single Most Likely Diagnosis

• Constipation: Given the patient's history of decreased caliber of bowel movements, constipation is a likely cause of LLQ pain, especially in the context of her medical history, which includes medications that may contribute to constipation (e.g., pain medications for fibromyalgia).

Other Likely Diagnoses

• Diverticulitis: The patient's age and symptoms of LLQ pain are consistent with diverticulitis, a common condition in this demographic.
• Ovarian remnant syndrome: Although the patient has undergone a hysterectomy, ovarian remnant syndrome is possible if ovarian tissue was left behind, which can cause cyclic pain.
• Irritable Bowel Syndrome (IBS): The patient's history of abdominal pain, changes in bowel habits, and other chronic conditions (e.g., fibromyalgia, asthma) increase the likelihood of IBS.

Do Not Miss Diagnoses

• Ovarian torsion: Although less likely given the patient's history of hysterectomy, ovarian torsion can occur if ovarian tissue remains and can be a life-threatening emergency.
• Ectopic pregnancy: Despite the patient's hysterectomy, an ectopic pregnancy is theoretically possible if a portion of the fallopian tube remains, making this a critical diagnosis not to miss.
• Bowel obstruction: The patient's symptoms of decreased caliber of bowel movements and LLQ pain could indicate a bowel obstruction, which requires prompt diagnosis and treatment.
• Appendicitis: Although the pain is in the LLQ, appendicitis can present with pain in various locations and is a critical diagnosis to consider.

Rare Diagnoses

• Endometriosis of the bowel: Given the patient's history of endometriosis, it is possible that endometrial tissue has implanted on the bowel, causing pain and changes in bowel habits.
• Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis): The patient's symptoms could be indicative of an inflammatory bowel disease, although this would be less likely given the absence of other typical symptoms (e.g., diarrhea, weight loss).