Functional constipation is extremely common in children and is defined as painful, hard stools or firm stools for twice or less per week. Functional constipation accounts for 3% of general pediatric visits and up to 25% of pediatric gastroenterology visits. Constipation and fecal impaction can lead to a range of symptoms including decreased appetite, vomiting, and abdominal pain frequently resulting in Emergency Department (ED) presentation. In contrast to the outpatient setting where diet and oral medications work well to relieve symptoms related to functional constipation, ED management requires an approach with quicker results. For immediate relief of symptoms, disimpaction via enema use may be better than polyethylene glycol (PEG) 3350 for children. However, the type of enema to be used is not well studied. Currently, any patient presenting to the ED with a presumed diagnosis of abdominal pain due to functional constipation receives an oral dose of PEG and one of the following three types of enemas (based on the ED treating attending's discretion): phosphate or Fleets enema, normal saline enema, or mineral oil enema. There is no evidence in the literature that demonstrates any difference in the effectiveness of each of these enemas. The investigators propose a randomized control trial of the three types of pediatric enemas readily used in our ED to determine the best approach. There will be three arms within this study: a) PEG plus phosphate enema b) PEG plus normal saline enema and c) PEG plus mineral oil enema. The physicians enrolling patients will not be the treating physicians. The four principal investigators (blinded to the type of enema being used), following appropriate informed consent, will obtain pain scores (Faces Pain Scale - Revised) pre- and post-administration of each of the three treatments listed above in order to determine the best enema to use in children 4-12 years of age. Other outcomes to be analyzed will include the patient's weight pre- and post-administration of the enema, satisfaction ratings on a visual analog scale from the treating physician (who will also be blinded), and parental surveys on the day of administration and 3-5 days following discharge. Data analysis for pain scores will be completed with repeated measures anova. Categorical values will be compared using Chi Square analysis and continuous variables will be compared using parametric statistics.

Inclusion Criteria:

• Age 4-12 years
• Receiving enema in ED for presumed constipation

Exclusion Criteria:

• Critically ill patient
• Any history of renal insufficiency, renal disease, or elevated creatinine
• Any history of intestinal anatomic abnormality (i.e. anal stenosis, anal surgery, bowel obstruction, hirschprung's disease)
• An inability to self-report pain
• Presence of gastrostomy or jejunostomy tube
• Any history of gastrointestinal dysmotility
• Inability to read or speak English or Spanish