Role of Digital Rectal Examination (DRE)
Role of DRE may be divided into following 3 headings.
A. Diagnosis of Constipation
The 2014 NASPGHAN and ESPGHAN guidelines tried to analyze nine clinical questions regarding management of functional constipation among which one clinical question was to determine the role of various tests including DRE for diagnosis of constipation.19 As stated previously, “presence of fecal mass in rectum” is one of the criteria for ROME III definition of constipation which would require DRE.3,4 At least 2 of the 6 criteria should be fulfilled for diagnosing constipation by ROME III definition. When a child is presenting with typical symptoms of constipation, DRE may not be required for diagnosis because 2 of the remaining 5 criteria may be fulfilled so the presence of a fecal mass in the rectum may not necessary to evaluate. But, when a child is not fulfilling 2 out of 6 criteria without DRE, it may be done so that Rome III criteria are fulfilled and diagnosis of constipation is established.19 In certain situations like a child presenting to OPD with abdominal pain and no other identifiable cause on history, DRE might help in making the diagnosis of constipation.
B. Differentiation between organic and functional causes of Constipation
An organic cause is suspected when a child has one or more of the alarm signs stated above along with constipation. Whenever there is a suspicion of an organic cause of constipation suggested by alarm signs or symptoms or in case of intractable constipation, it warrants DRE and further evaluation.19,27 Although DRE may not always diagnose an organic cause of constipation directly, it provides supportive evidence after which further diagnostic tests may be carried out.28 Many times an organic cause of constipation like anal stenosis may be diagnosed just by DRE.29
C. Diagnosing and treating fecal impaction
Fecal impaction is defined as a hard mass in the lower abdomen identified on physical examination or a dilated rectum loaded with stool on rectal examination or excessive stool in the distal colon on abdominal radiography.19 History of CFI also points out the diagnosis of fecal impaction. 30 Although abdominal radiography may give less discomfort to the child compared to rectal examination, it consumes more time, cost and exposes to radiation.31 It is not routinely recommended for diagnosing fecal impaction.19 Hence in children suspected to have fecal impaction but without history of CFI or palpable fecal mass per abdomen, DRE becomes necessary. But the 2014 NASPGHAN and ESPGHAN guidelines do not have definite recommendation on using DRE for diagnosing fecal impaction.19 The NICE guidelines recommend to look for fecal impaction in all cases of idiopathic constipation and to do DRE if indicated. But it is not described what the indications are. In children less than 1 year age it recommends DRE to look for fecal impaction only if it is not responding to treatment in 4 weeks.27 These recommendations would result in unnecessary delay in the treatment of impaction. Treatment of constipation without prior disimpaction in a child is likely to be ineffective in a child with fecal impaction.27
In presence of fecal impaction, the first step is disimpaction.16 The most preferred agent used for disimpaction is oral Polyethylene glycol with electrolytes.32,33 Enemas although equally effective are considered more invasive can also be used if there is unavailability of polyethylene glycol.34 The next step is to start maintenance therapy.16 Among the various agents used polyethylene glycol is again the most effective one but the dose is lower than for disimpaction.35 In the absence of fecal impaction treatment is directly started with maintenance therapy. Maintenance therapy has to be titrated according to response.16 Meanwhile parents should be counseled about high fiber diet and toilet training. The gastro colic reflex is utilized and the child is encouraged to sit in toilet for defecation after each meal.36 Positive reinforcement by rewards and maintenance of bowel diary is also advised.37 Treatment is continued for at least 2 months with symptom free period of at least 1 month following which dose is gradually tapered.19 Many children require treatment for several months or years.38 Regular follow up is required to assess for relapse and to reinforce food and toilet habits. Starting maintenance therapy without disimpaction in a child with fecal impaction is unlikely to succeed and causes unnecessary distress to the child and family and increases chances of poor compliance.16
Utilization of DRE
DRE seems to be underutilized in clinical practice.39 A study by Gold et al showed that 77% of children referred to Pediatric Gastroenterology did not undergo prior rectal examination.28 Another study performed by Scholer et al showed DRE was done in only 5% of children presenting with acute abdominal pain in Clinic or emergency.40 Possible reason for this underutilization could be physician not being comfortable with the procedure, excess apprehension of the child and risk of ruining physician-child relationship.28,39 Another possible reason could be underestimation of fecal retention by the physician as fecal impaction may often have subtle and nonspecific presentation .41
Usefulness of DRE
Though there have been studies on utilization of DRE, there are no studies demonstrating actual usefulness of DRE. So it is difficult to comment on what proportion of cases is likely to be missed if DRE is omitted in routine evaluation. In 2014 NASPGHAN and ESPGHAN guidelines, DRE is recommended for diagnosis of constipation if only one of the ROME III criteria is present leading to doubt in the diagnosis.19 The guideline also recommends DRE to evaluate underlying organic medical condition in the presence of alarm signs and symptoms or in case of intractable constipation. But the guideline does not make any comment on use of DRE for diagnosis of fecal impaction. Hence a study to demonstrate frequency of fecal impaction in DRE would tell us what proportion of DRE shows impaction and would provide a definite evidence to support use of DRE.