Table 4. Differential Diagnosis of Noninfectious Diarrhea in Patients With Neuroendocrine Tumors.

Type	Causes	Symptoms
Carcinoid syndrome	• Overproduction of serotonin produced by neuroendocrine tumors	• Diarrhea
		• Cutaneous flushing
		• /asthma-like symptoms
Short gastrointestinal transit time	• Surgical resection of the small intestine for Crohn disease, trauma, malignancy, radiation, or mesenteric ischemia	• Diarrhea, loose watery stool
		• Dehydration, malnutrition, weight loss
	• Necrotizing enterocolitis and congenital intestinal anomalies, such as mid-gut volvulus, atresias, or gastroschisis	• Bloating, cramping, gas
		• Weakness, fatigue
		• Food allergies
Steatorrhea	• Pancreatic insufficiency due to chronic pancreatic inflammation and loss of acinar cells	• Passage of pale, bulky, and malodorous stool
	• Bile salt deficiency due to impaired production or secretion	• Usually BM right after eating, can be associated with bloating or abdominal discomfort, and with fatty foods
	• Malabsorption due to small intestinal disease, surgery, or medications
	• Serotonin-induced hypermotility
	• Side effect of treatment with somatostatin analogs
Bile acid diarrhea	• Ileal dysfunction and impaired reabsorption	• Watery stool
	• Small intestinal bacterial overgrowth	• Urgency
	• Celiac disease	• Fecal incontinence
	• Chronic pancreatitis
	• Excessive hepatic bile acid synthesis
Uncontrolled blood glucose	• Development of diabetes, or worsening of preexisting diabetes due to SSA use	• Diarrhea, loose watery stools

Note. BM = bowel movement; SSA = somatostatin analog. Information from Camilleri (2015); Riechelmann et al. (2017); Strosberg et al. (2017b).