Differential Diagnosis for Left Lower Quadrant Pain

The patient presents with a 4-day history of left lower quadrant pain, which has been recurring over the past six months. The pain is described as sharp and cramping, with varying intensity. Recent imaging studies, including ultrasound and CT scans, have revealed a heterogeneous lesion with calcifications inferior to the left kidney and a bulky, necrotic mass-like thickening in the distal transverse colon.

Single Most Likely Diagnosis

• Colorectal Cancer: The presence of a circumferential, heterogeneously enhancing, bulky, necrotic mass-like thickening in the distal transverse colon, with severe luminal narrowing and surrounding soft tissue stranding, is highly suggestive of colorectal cancer. The patient's symptoms, including changes in bowel habits and left lower quadrant pain, also support this diagnosis.

Other Likely Diagnoses

• Diverticulitis: The patient's symptoms, including left lower quadrant pain and changes in bowel habits, could also be consistent with diverticulitis. However, the presence of a bulky mass-like thickening in the distal transverse colon makes colorectal cancer a more likely diagnosis.
• Intestinal Obstruction: The patient's symptoms, including left lower quadrant pain and changes in bowel habits, could also be consistent with intestinal obstruction. However, the CT scan did not show any evidence of bowel obstruction proximal to the lesion.

Do Not Miss Diagnoses

• Appendicitis: Although the patient's symptoms are more consistent with a left lower quadrant pathology, appendicitis is a potentially life-threatening condition that should not be missed. However, the location of the pain and the imaging findings make this diagnosis less likely.
• Ectopic Pregnancy: Although the patient's symptoms are more consistent with a gastrointestinal pathology, ectopic pregnancy is a potentially life-threatening condition that should not be missed in women of childbearing age. However, the patient's symptoms and imaging findings do not support this diagnosis.

Rare Diagnoses

• Gastrointestinal Stromal Tumor (GIST): The patient's symptoms and imaging findings could be consistent with a GIST, although this is a rare diagnosis.
• Intussusception: The patient's symptoms, including left lower quadrant pain and changes in bowel habits, could also be consistent with intussusception. However, the CT scan did not show any evidence of intussusception.
• Inflammatory Bowel Disease: The patient's symptoms, including left lower quadrant pain and changes in bowel habits, could also be consistent with inflammatory bowel disease. However, the imaging findings and the patient's symptoms do not support this diagnosis.

Diagnostic Tests to Run

• Colonoscopy: To confirm the diagnosis of colorectal cancer and to rule out other gastrointestinal pathologies.
• Biopsy: To confirm the diagnosis of colorectal cancer and to determine the histological type and grade of the tumor.
• Complete Blood Count (CBC): To rule out infection or inflammation.
• Electrolyte Panel: To rule out electrolyte imbalances.
• Liver Function Tests: To rule out liver metastases.
• Carcinoembryonic Antigen (CEA) Level: To monitor the patient's response to treatment and to detect recurrence.