The most likely diagnosis in this patient is "Irritable bowel syndrome (IBS)." 

IBS is a gastrointestinal condition characterized by abdominal pain or cramps, as well as acute episodes of diarrhea and/or constipation that is often triggered by psychological stressors such as depression or anxiety, or a preceding gastrointestinal infection. IBS is more common in young females than other demographics, and often can be co-morbid with clinical depression or anxiety disorders. Its pathophysiology has not yet been fully characterized. There is no definitive diagnostic test to confirm a diagnosis of IBS, but the lack of blood or mucus in the stool, as well as the lack of a fever or elevated white blood cell count all are consistent with a diagnosis of IBS. Further, in this patient, given that she is a young female whose symptoms for this episode and prior episodes coincided with psychological stressors and resolved with bowel movements and resolution of her stressors, and who also had no fever, elevated white blood cell count, vital sign abnormalities, or concerning historical details (foreign travel, dietary changes, sick contacts), IBS is the most likely diagnosis.

Ulcerative colitis would be more likely to present with recurrent episodes of bloody and/or mucoid diarrhea, as opposed to non-bloody, non-mucoid diarrhea. Further, given this patient's relationship of symptoms to immediate psychological stressors, her symptoms are more consistent with IBS than ulcerative colitis. 

Colon cancer would be an unlikely diagnosis in a young, otherwise healthy patient with no family history of colon cancer. The fact that she is experiencing non-bloody, non-mucoid diarrhea does not in and of itself provide evidence for colon cancer. Colon cancer may present with occult blood in the stool, melanotic stools, or blood streaked stools, but would be highly, highly unlikely in a healthy young patient.

Gluten intolerance and lactose intolerance are reasonable thoughts when evaluating a young, otherwise healthy patient with non-bloody, non-mucoid diarrhea. Lactose intolerance would likely present at a younger age though, and the patient's diet reportedly has not changed prior to her diarrhea episodes, which would argue against a dietary etiology of her diarrhea. Further, given the close relationship of her symptoms to acute psychological stressors, IBS is the most fitting diagnosis.

The correct answer choice is "post-operative ileus." This answer is correct because in the presented scenario, the patient is just 36 hours removed from a total abdominal hysterectomy, which is an invasive abdominal surgery. During a hysterectomy, the patient typically receives inhaled anesthesia, as well as opioid pain medications, which each individually can result in a post-operative ileus. Furthermore, given that there is manipulation of abdominal organs in accessing the uterus, simple mechanical manipulation of the bowels during surgery can be enough to result in a post-operative ileus. For each of these reasons, post-operative ileus is a common occurrence, and is the most likely cause of this patient's lack of passing of flatus or feces.

There is no reason to think that this patient received post-operative amphetamines. Furthermore, if the patient did receive amphetamines, that would likely stimulate the digestive tract, rather than inhibit its activity. 

Neither bacterial, viral, nor fungal infections would be likely causes of lack of flatus or feces passage following a surgery. These infections would be more likely to cause loose stools/diarrhea, rather than an ileus. 

The correct answer is "pyloric stenosis," as this is a congenital condition that most commonly affects firstborn male infants. Pyloric stenosis is a congenital narrowing and excessive tightness of the pyloric sphincter, resulting in difficulty passing food from the stomach to the duodenum in the infant. As a result, the child frequently forcefully vomits until a surgical intervention reduces the tone of the pyloric sphincter. On physical exam, a "palpable olive" can sometimes be felt within the upper abdomen, representing the pyloric sphincter. On lab work, due to the potassium and chloride lost in the vomited material, a hypokalemic, hypochloremic metabolic alkalosis can be observed. On occasion, there is a history of the mother having taken erythromycin antibiotics during gestation.

Esophageal tumor is highly, highly unlikely in a newborn, as both of the most common types of esophageal tumors typically occur in patients 50 and older.

Achalasia would present as difficulty swallowing, rather than as frequent vomiting of stomach contents. In achalasia, the food cannot pass beyond the esophagus, whereas in pyloric stenosis it cannot pass beyond the stomach. A "palpable olive" would not be felt in achalasia.

Type two diabetes is extremely unlikely in an infant, and would not likely present with gastroparesis as its first symptom.

Cirrhosis is a chronic liver disease, usually caused by alcoholism. It is characterized by fibrosis and destruction of the normal liver tissue. Patient's who have cirrhosis may have hepatomegaly on physical exam, which is enlargement of the liver (e.g., it may be felt on the abdomen).