Differential DiagnosisAlthough functional constipation isthe most common cause of constipation, other differential diagnosis should beconsidered and should be ruled out in history and examination. The followingdifferential diagnosis should be considered 13· Hirschprung’s disease· Hypothyroidism · Celiac disease· Electrolyte abnormalities (Hypercalcaemia,hypokalemia)· Dietary protein allergy· Diabetes mellitus· Toxins/drugsØ Opiates,anticholinergicsØ ChemotherapyØ AntidepressantsØ Heavymetal ingestion (e.g.
lead)· Botulism · Spinal cord anomalies, trauma, tetheredcord· Anatomic malformationsØ ImperforateanusØ Analstenosis· Vitamin D intoxication· Cystic fibrosis· Anal achalasia· Pelvic mass (e.g. sacral teratoma)· Colonic inertia· Abnormal abdominal musculature ( prunebelly, gastroschisis, Down syndrome)· Multiple endocrine neoplasia type 2B· Pseudo obstruction (visceralneuropathies, myopathies, mesenchymopathies)The following alarm signs andsymptoms would help to identify presence of an underlying disease causingconstipation 6,13· Passage of meconium after 48 hours of birth· Constipation starting very early in life(<1 month)· Ribbon stools· Family history of Hirschsprung's disease· Failure to thrive· Blood in stools in the absence of analfissures· Fever · Abnormal position of anus· Bilious vomiting· Absent cremasteric/anal reflex· Sacral dimple· Tuft of hair on spine· Decreased tone/strength/reflex in lowerextremities· Anal scars· Extreme fear during anal inspection· Deviation of gluteal cleftIn presence of any ofthe above mentioned alarm signs or in case constipation is not responding tousual treatment further work up is necessary to rule out organic causes ofconstipation.Role of Digital Rectal Examination (DRE)Role of DRE may be divided into following 3headings. A.
Diagnosis of ConstipationThe 2014 NASPGHAN and ESPGHAN guidelines tried tooverview nine clinical questions regarding management of functionalconstipation among which one clinical question was to ascertain the role ofvarious tests including DRE for diagnosis of constipation.13 As stated previously,”presence of fecal mass in rectum” is one of the criteria for ROME IIIdefinition of constipation which would require DRE.3,4 At least 2 ofthe 6 criteria should be fulfilled for diagnosing constipation by ROME IIIdefinition. So, when a child is presenting with typical symptoms ofconstipation, DRE may not be required for diagnosis because 2 of the remaining5 criteria may be fulfilled so presence of fecal mass in the rectum may notnecessary to evaluate. But, when a child is not presenting with typicalsymptoms of constipation, child may not fulfill 2 of the remaining 5 criteriaso, DRE may be required to confirm fecal mass in the rectum to make thediagnosis of constipation.13 For example when achild presents to pediatric OPD with abdominal pain and no other identifiablecause on history, DRE might help in making the diagnosis of constipation.
B. Differentiation between organic and functionalcauses of ConstipationAn organic cause is suspected when a child presentswith one or more of the alarm signs mentioned above along with constipation.Whenever there is a suspicion of an organic cause of constipation suggested byalarm signs or symptoms or in case of intractable constipation, it warrants DREand further evaluation.13,24 Although DRE may notalways diagnose an organic cause of constipation directly, it providessupportive evidence after which further diagnostic tests may be carried out.25 Many times an organiccause of constipation like anal stenosis may be diagnosed just by DRE.
26 C. Diagnosing and treating fecal impaction Fecal impactionis defined as a hard mass in the lower abdomen identified on physicalexamination or a dilated rectum filled with a large amount of stool on rectalexamination or excessive stool in the distal colon on abdominal radiography.13 History of CFI alsopoints out the diagnosis of fecal impaction. 27 Although abdominalradiography may give less discomfort to the child compared to rectalexamination, it consumes more time, cost and exposes to radiation.28 Abdominal radiographyis regarded as nonspecific for diagnosing fecal impaction and is notrecommended.
13 Hence in childrensuspected to have fecal impaction but without history of CFI or palpable fecalmass per abdomen, DRE becomes necessary. But the 2014 NASPGHAN and ESPGHANguidelines do not have definite recommendation on using DRE for diagnosingfecal impaction. The NICE guidelines recommend to look for fecal impaction inall cases of idiopathic constipation and to do DRE if indicated. But it is notdescribed what the indications are.
In children less than 1 year age itrecommends DRE to look for fecal impaction only if it is not responding totreatment in 4 weeks. These recommendations would result in unnecessary delayin the treatment of impaction. Treatment of constipation without priordisimpaction in a child is likely to be ineffective in a child with fecalimpaction.24Treatment In presence of fecal impaction, the first step is disimpaction.17 The most preferred agent used for disimpaction isoral Polyethylene glycol with electrolytes.29,30 Enemas although equally effective are consideredmore invasive can also be used if there is unavailability of polyethyleneglycol.
31 The next step is to start maintenance therapy.17 Among the various agents used polyethylene glycolis again the most effective one but the dose is lower than for disimpaction.32 In the absence of fecal impaction treatment isdirectly started with maintenance therapy. Maintenance therapy has to betitrated according to response.17 Meanwhile parents should be counseled about highfiber diet and toilet training. The gastro colic reflex is utilized and thechild is encouraged to sit in toilet for defecation after each meal.
33 Positive reinforcement by rewards and maintenanceof bowel diary is also advised.34 Treatment is continued for at least 2 months withsymptom free period of at least 1 month following which dose is graduallytapered.13 Many children require treatment for several monthsor years.35 Regular follow up is required to assess for relapseand to reinforce food and toilet habits. Starting maintenance therapy withoutdisimpaction in a child with fecal impaction is unlikely to succeed and causesunnecessary distress to the child and family and increases chances of poorcompliance.17Utilization of DREDRE seems to be underutilized in clinical practice.36 A study by Gold et alshowed that 77% of children referred to Pediatric Gastroenterology did notundergo prior rectal examination.
25 Another studyperformed by Scholer et al showed DRE was done in only 5% of childrenpresenting with acute abdominal pain in Clinic or emergency.37 Possible reason forthis underutilization could be physician not being comfortable with theprocedure, excess apprehension of the child and risk of ruining physician-childrelationship.25,36 Anotherpossible reason could be underestimation of fecal retention by the physician asfecal impaction may often have subtle and nonspecific presentation .38Usefulness of DREThough there have been studies on utilization ofDRE, there are no studies demonstrating actual usefulness of DRE. Hence it isdifficult to comment on what proportion of cases is likely to be missed if DREis omitted in routine evaluation. In 2014 NASPGHAN and ESPGHAN guidelines, DREis recommended for diagnosis of constipation if only one of the ROME IIIcriteria is present leading to doubt in the diagnosis.
13 The guideline alsorecommends DRE to evaluate underlying organic medical condition in the presenceof alarm signs and symptoms or in case of intractable constipation. But theguideline does not make any comment on use of DRE for diagnosis of fecalimpaction. Hence a study to demonstrate frequency of fecal impaction in DRE wouldtell us what proportion of DRE shows impaction and would provide a definiteevidence to support use of DRE.