are not moved along Hypothyroidism (underactive thyroid gland ) Hypokalemia Injured anal sphincter (patulous anus ) Medications, such as loperamide , opioids (e.g. codeine & morphine ) and certain tricyclic antidepressants Severe illness due to other causes Acute porphyria (a rare inherited condition) Lead poisoning Lactose Intolerance Dyschezia (usually the result