Final answer:
L.S.'s symptoms are indicative of Irritable Bowel Syndrome (IBS), which is characterized by abdominal pain, bloating, and alternating bowel habits. Tobacco use and stress can influence these symptoms. A medical examination is necessary to confirm the diagnosis and exclude other conditions.
Step-by-step explanation:
The symptom profile described for L.S., a 28-year-old white female, which includes abdominal pain, bloating, diarrhea alternating with constipation, is suggestive of Irritable Bowel Syndrome (IBS). IBS is a common functional gastrointestinal disorder characterized by a combination of symptoms that may also be influenced by factors such as stress and habits like tobacco use. Given the patient's presentation, IBS would be the most likely diagnosis; however, it is important to rule out other potential causes through proper medical examination and investigations.