Campbell-Walsh Urology, 11th Edition

PART XV

Pediatric Urology

SECTION D

Lower Urinary Tract Conditions

144

Management of Defecation Disorders

Martin Allan Koyle; Armando J. Lorenzo

Questions

1. The Rome III criteria evaluate the following aspects of bowel function EXCEPT:
2. pain with bowel movements.
3. production of large stools that can block the toilet.
4. number of bowel movements per week.
5. duration of symptoms.
6. all of the above.
7. A 4-year-old girl presents with a 6-month history of urinary frequency and urgency. Parents report daily small bowel movements, which they attribute to poor diet ("picky eater"). Her physical exam is normal. There is no history of urinary tract infections. Which of the following interventions can lead to paradoxical worsening of her symptoms?
8. Increase in fluid intake
9. Polyethylene glycol (PEG)
10. Oxybutynin
11. Trimethoprim prophylaxis
12. Biofeedback
13. Which one of the following aspects of a patient's history and physical examination should raise suspicion for an underlying organic pathology causing constipation?
14. Early age of onset (before toilet training)
15. Presence of a palpable mass in the left lower quadrant
16. Onset after diet change
17. Poor dietary habits ("picky eater")
18. All of the above
19. Which part of the physical exam can be safely omitted during initial evaluation of a child with suspected functional constipation?
20. Height and weight
21. Inspection of the lower back
22. Lower extremity muscle tone and reflexes
23. Digital rectal exam
24. Visual inspection of the perineum
25. Which of the following metabolic/endocrinologic pathologies is unlikely to cause constipation?
26. Hypercalcemia
27. Hypokalemia
28. Hypothyroidism
29. Diabetes insipidus
30. Precocious puberty
31. Regarding the surgical management of refractory constipation, which one of the following statements is CORRECT?
32. Access for antegrade irrigations should be limited to the cecum.
33. Open surgical intervention carries a higher success rate than laparoscopic or percutaneous procedures.
34. Malone antegrade continence enema (MACE) channels and C-tubes provide better procedural independence than retrograde enemas for patients with neuropathic bowel dysfunction.
35. Similar success rates can be expected irrespective of the underlying pathology.
36. All of the above.
37. The main principle behind daily antegrade enemas for continence is:
38. washout with regular evacuation of the entire colon.
39. direct softening of stools to facilitate passage during the day.
40. improve hydration.
41. decrease colon motility.
42. decrease sphincter tone.
43. Initial workup of a child with constipation is most likely to benefit from including:
44. abdominal radiograph.
45. anal manometry
46. colonic transit time studies
47. magnetic resonance imaging (MRI) of lumbosacral spine
48. contrast enema study
49. Which of the following statements regarding creation of a MACE channel is TRUE?
50. Previous surgical interventions are a contraindication for a laparoscopic approach.
51. An aggressive bowel washout and mechanical preparation is always warranted before surgery.
52. Presence of a ventriculoperitoneal shunt is a contraindication for laparoscopic approach.
53. The appendix may be of sufficient length to be split in order to create a MACE and Mitrofanoff channel for neuropathic bowel and bladder management.
54. An antireflux mechanism (cecal wrap) is always required in order to prevent stool leakage.
55. Which of the following statements regarding cecostomy tubes is most accurate?
56. It is a good alternative for patients who have previously undergone an appendectomy.
57. It avoids the need for regular instrumentation.
58. It is difficult to remove or convert to a MACE channel.
59. The most common problem is stenosis and difficulty accessing for fluid instillation.
60. It is a great alternative for families who have problems with compliance.
61. Recommendations for antegrade enema regimens should include which of the following?
62. Sterile saline is preferred versus tap water or "home-made" saline solution.
63. Daily enemas are universally required to achieve continence.
64. Early morning irrigations are preferable as it allows the patients to enjoy better daytime continence.
65. Trial and error for more than 6 months may be warranted to reach a reliable enema routine.
66. All of the above.
67. What is the proposed mechanism of action of prucalopride?
68. Stool softener
69. Antispasmodic
70. Bulking agent
71. Prokinetic
72. None of the above
73. Which of the following agents is preferred (first-line) medication for maintenance management of constipation?
74. Milk of magnesia
75. Mineral oil
76. PEG
77. Prucalopride
78. Psyllium husk
79. Features of functional constipation include:
80. recurrence despite recommendations consistent with optimal medical management.
81. alternating constipation and diarrhea.
82. episodes of bowel obstruction.
83. bilious vomiting.
84. ribbon-like stools.
85. Which one of the following stool characteristics is NOT included in the Bristol scale?
86. Consistency
87. Shape
88. Difficulty having bowel movements
89. Odor
90. None of the above
91. Of the following, which one is the best diagnostic test to confirm Hirschsprung disease?
92. Barium enema
93. Computed tomography (CT) scan with oral and intravenous contrast
94. Rectal biopsy
95. Colonoscopy
96. Lumbosacral spine MRI
97. New onset of abdominal pain and distention after antegrade instillation of fluid in a child with a cecostomy tube in place for more than 6 months should alert the physician about:
98. spontaneous cecal perforation.
99. use of hypotonic fluid for irrigations.
100. presence of a large fecal load in the rectum and descending colon.
101. an incompetent ileocecal valve with retrograde irrigation into the terminal ileum.
102. irritable bowel syndrome.
103. Which of the following statements regarding abdominal plain film during initial assessment of a child with functional constipation is FALSE?
104. Amount and distribution of fecal material can predict likelihood of response and recurrence with medical therapy.
105. Helps assess for fecal impaction
106. Helps assess response to bowel wash out
107. Aids in demonstrating parents or caretakers the presence of constipation
108. Detects bony abnormalities that may be associated with neuropathic bowel dysfunction
109. Which statement regarding diagnosis and management of functional constipation is TRUE?
110. Assessment during evaluation of a child with recurrent urinary tract infections is warranted.
111. It is an integral part of a program dealing with dysfunctional voiding.
112. It should be addressed before proceeding with surgical interventions for vesicoureteral reflux.
113. It can be managed by pediatric urologists and urology nurse practitioners.
114. All of the above.

Imaging

1. The abdominal radiograph and pelvic ultrasound shown in Figure 144-1were obtained on a 5-year-old girl with recurrent abdominal pain and distention for the past year. She has a palpable soft, nontender mass in the left lower quadrant. Which one of the following interventions is LEAST likely to help with initial management?

FIGURE 144-1

1. Digital disimpaction under sedation
2. Enemas
3. ”High-dose“ polyethylene glycol
4. Supplement fiber intake
5. Increase fluid intake

Answers

1. e. All of the above. The Rome III criteria requires symptoms to be present for at least 1 or 2 months, and takes into account developmental age and absence of an underlying organic pathology.Pain with defecation, history of large-diameter stools that may obstruct the toilet, and infrequent bowel movements (≤ 2 defecations per week) are all included in the diagnosis of functional constipation.
2. c. Oxybutynin.Constipation is a common side effect of medications used to deal with lower urinary tract symptoms (particularly anticholinergics). Because of this common association, during the past few decades, pediatric urologists have become comfortable with assessing and managing bowel problems. Development or worsening of constipation will sometimes coincide or worsen with precipitating factors, such as change in diet (for example, transitioning out of breastfeeding) and introduction of new medications (such as oxybutynin for management of urinary frequency). Increase in fecal load in the rectum, coupled with toilet avoidance due to lower abdominal pain and discomfort with defecation, may lead to paradoxical worsening of lower urinary tract symptoms. Increase in fluid intake and use of PEG is unlikely to worsen lower urinary tract symptoms and is part of initial recommendations for bowel retraining. Similarly, biofeedback may have a neutral or beneficial effect. Antibiotic prophylaxis, in the absence of recurrent infections, is not expected to influence symptomatology.
3. a. Early age of onset (before toilet training). The age of onset of symptoms is one of the easiest and most important pieces of information to obtain, as it can be an important indicator for underlying pathology, particularly if symptoms have been present since early in life (infancy).Other critical information to be actively gathered includes failure to toilet train within an age-appropriate and developmental timeframe, pain with defecation, bleeding per rectum, associated abdominal pain, fecal incontinence, holding behaviors, nausea or vomiting, weight loss, growth pattern (including height and weight), developmental delay, and failure to thrive. Patients with functional constipation often present or worsen after dietary changes. Not uncommonly, otherwise healthy children are described by parents as very selective (or "picky"). In the setting of significant fecal load or impaction in a child with constipation, a palpable mass in the left lower quadrant ("fecaloma") may be detected during examination.
4. d. Digital rectal exam.Physical exam should routinely include weight and height, and inspection of the perineum and genital and perianal regions (including anal position, stool present around the anus or on the underwear, signs of trauma, anal fissures, sensation). Although potentially considered to be an integral part of a complete physical exam, digital rectal examination should not routinely conducted in children. It is reserved for difficult-to-treat cases and must be performed by health care professionals comfortable with interpreting features of anorectal anatomical abnormalities, to specifically evaluate for anal stenosis, a large fecal mass, or an empty rectum.
5. e. Precocious puberty. Endocrine disorders associated with chronic dehydration (such as diabetes insipidus), electrolyte disorders (most notably hypercalcemia and hypokalemia), hypothyroidism, and hypervitaminosis D are important potential organic etiologies.Precocious puberty presents with development of secondary sexual characteristics at an age before the expected onset during normal development. Constipation is not a presenting or common isolated feature of this condition.
6. c. Malone antegrade continence enema (MACE) channels and C-tubes provide better procedural independence than retrograde enemas for patients with neuropathic bowel dysfunction. In cases with severe constipation and a redundant colon, some have advocated the placement of conduits in the left colon rather than the cecum. By doing so, the length of bowel that has to be washed through is reduced and theoretically, so is the time taken for successful enema completion.Results with this approach have been encouraging. Both open and laparoscopic procedures are associated with similar success rates. Both C-tubes and MACE-type channels provide independence and allow patients greater ability to perform irrigations without assistance in comparison to self-administered retrograde enemas. The underlying diagnosis influences the success rate. Patients with a neuropathic bowel and anorectal malformations seem to fare better than those with chronic idiopathic constipation. Age at operation is also important, with failures more commonly seen in younger patients irrespective of the diagnosis.
7. a. Washout with regular evacuation of the entire colon.The success of antegrade enema regimens is based on two important principles: (1) complete colonic emptying can achieve bowel continence, and (2) antegrade colonic emptying is feasible. Regular complete emptying of the colon is the main mechanism associated with fecal continence.
8. a. Abdominal radiograph. Although of modest clinical value, abdominal radiographs are commonly used in the diagnosis and management of constipation. Proponents in favor of routine use argue that the study can clearly demonstrate the amount of fecal loading and delineate stool distribution throughout the colon and rectum, as well as help ascertain for the presence of fecal impaction. In addition, it may also reveal associated pathologies, such as bony abnormalities indicative of occult spinal dysraphism or sacral agenesis, and help provide a visual aid for family and patient recognition of stool retention despite a history of regular defecation.Colonic transit time studies are not recommended for routine diagnosis of functional constipation, being reserved for difficult-to-treat or unresponsive cases. Similarly, contrast enema series can be of value in selected cases, such as the evaluation of children with characteristics suggestive of Hirschsprung disease and repaired congenital anatomic abnormalities (i.e., anorectal malformation). Concern for a neuropathic process and/or lower spine stigmata should be evaluated with a spine ultrasound (if detected before calcification of the vertebral bodies in the first 3 to 6 months of life, or a lumbosacral MRI in older children. Anorectal manometry is useful only in very selected cases, such as suspected Hirschsprung disease and internal sphincter achalasia. In these conditions, the rectoanal relaxation reflex is absent. Nevertheless, in patients suspected of having functional constipation, manometry adds little to the diagnosis or therapeutic strategy.
9. d. The appendix may be of sufficient length to be split to create a MACE and Mitrofanoff channel for neuropathic bowel and bladder management.In children who require synchronous bladder reconstruction, a simultaneous MACE and Mitrofanoff urinary diversion offers the opportunity for dual fecal and urinary continence. If both a MACE and appendicovesicostomy are considered—and if the appendix is long enough with suitable, robust vascular anatomy—it is possible to split it. Previous surgical interventions are not an absolute contraindication for a laparoscopic approach, although the situation does demand for great care when entering the peritoneal cavity to avoid injuries related to adhesions or fibrosis. Although preoperative bowel preparation may facilitate the initiation of postoperative enemas, an aggressive cleanout is not necessary for the purpose of performing the procedure. Many patients with neuropathic bladder and bowel dysfunction have ventriculoperitoneal shunts. Although it is critical that appropriate use of prophylactic antibiotics and measures to minimize spillage be set in place, the presence of a shunt is not a contraindication for open or laparoscopic reconstruction involving bowel segments. Many descriptions of the MACE procedure propose an “antireflux” valve mechanism to prevent leakage of bowel contents via the cutaneous stoma. This is often achieved by wrapping the appendix with the cecal wall. However, recent reports have suggested that it is not always necessary to construct an antireflux mechanism. Thus far, data appear to support no increase in stomal bowel incontinence, based on retrospective reviews comparing MACE with and without cecal wrap.
10. a. It is a good alternative for patients who have previously undergone an appendectomy.Cecostomy tubes are favored when the appendix is known to be absent (i.e., postappendectomy), when the patient refuses to perform intermittent bowel catheterization, for patients who develop stomal complications such as stenosis (as an alternative to revision of the MACE channel), as a temporary therapeutic challenge to determine response to antegrade enemas, to determine if ideal placement of a permanent MACE should be in the right or left colon, and as a permanent option in cases in which a nonoperative access is favored. The main drawback is that the tube entry site can become unsightly, with granulation tissue and occasional fecal leakage. Stenosis is very rare, in contrast to issues related to MACE channels. In addition, regular instrumentation is needed in order to change the tube on a scheduled basis (i.e., every 6 to 12 months), or sooner if it dislodges or breaks. Patients may opt for subsequent formal conversion to a bowel-based MACE, which can be done either laparoscopically or open. Compliance with antegrade enema regimens is crucial for success, irrespective of how the bowel access has been achieved (C-tube or MACE).
11. d. Trial and error for more than 6 months may be warranted to reach a reliable enema routine. One of the most important points, especially in the early weeks and months after surgery, is to advise patients not to expect immediate success with the enema regimen, as early disappointment can lead to frustration and failure.In fact many children may not achieve a steady state or a reliable enema routine for a period of as long as 6 months. Enema protocols differ among centers, and patients and families will frequently modify them to suit their own particular needs. Initially, daily washouts with 20 mL/kg of solution are encouraged, but once the patient is comfortable with the process and a routine has been established, they may attempt to decrease frequency to alternate days. The time of day that the enema is administered is patient dependent, although most families prefer to give the enema during the early evening hours, after dinner. Purges can be done with large-volume tap or salt water, with the judicious mix of additives such as glycerin. The fluid does not have to be sterile.
12. d. Prokinetic.Prucalopride is a new oral, selective, high-affinity 5HT₄ receptor antagonist with gastrointestinal prokinetic activities, which shows particular promise for management of difficult-to-treat constipation and may eventually represent a reasonable choice for children who fail to respond to more conservative measures. Its main mechanism of action does not influence stool consistency or bulk. As a prokinetic drug, it is likely to stimulate bowel smooth muscle contractions and not provide an antispasmodic effect.
13. c. PEG.With the introduction of PEG into routine clinical practice, tolerance of medical management has improved, and it is currently the preferred agent in many centers. PEG is better tolerated and easier to administer than alternative medications such as lactulose, mineral oil, and milk of magnesia (magnesium hydroxide). It is virtually tasteless and dissolves easily within seconds.
14. a. Recurrence despite recommendations consistent with optimal medical management.Functional constipation can be difficult to treat and a long-lasting problem for some children. Nevertheless, with adequate management close to 50% of patients monitored for 6 to 12 months can recover and successfully discontinue medications, whereas as many as 80% can be adequately controlled with routine interventions. Unfortunately, subsequent recurrences are fairly common, with as many as 50% of children experiencing one in the first 5 years after successful treatment. All the other listed factors (alternating constipation and diarrhea, episodes of bowel obstruction, bilious vomiting, and ribbon-like stools) are "warning signs and symptoms" that should raise suspicion for alternative diagnosis and an underlying process (i.e., not functional constipation).
15. d. Odor.Stool characteristics should be recorded with a validated scale. The most commonly used (Bristol scale) takes into account consistency and stool shape, capturing also the degree of difficulty passing the bowel movement. Smell (odor) is not part of the scale.
16. c. Rectal biopsy.If Hirschsprung disease or colon aganglionosis is suspected, a deep suction rectal biopsy (including submucosal) should be obtained, favoring a transanal approach and aiming at a location 2 to 3 cm from the dentate line. Diagnosis is supported by absence of ganglion cells, hypertrophied nerve fibers, and increase in acetylcholinesterase activity in the lamina propria and muscularis mucosa.
17. c. Presence of a large fecal load in the rectum and descending colon. Several difficulties can be experienced during enema infusion. The most common problem is pain or discomfort during instillation. In the majority of patients, this is a transient phenomenon that subsides during the first 3 months. It is always important to ensure that the pain is not due to distal fecal impaction, which can occur despite regular washouts.The presence of a large amount of fecal material in the distal colon and rectum can certainly lead to impaction in patients doing infrequent antegrade enemas through a cecostomy access or MACE channel. Attempts at clearing this fecal load with antegrade flushes can lead to abdominal pain, lack of tolerance, and poor response. Spontaneous colon perforation with antegrade enema regimens is exceedingly rare. The use of hypotonic fluids (such as tap water) is commonplace in many centers. Retrograde flow of fluid into the distal ileum is not a common cause of pain with antegrade enemas and is unlikely to develop suddenly in a patient who has been doing enemas for a period of 6 months.
18. a. Amount and distribution of fecal material can predict likelihood of response and recurrence with medical therapy.As discussed in question 8, there are some potential benefits to obtaining an abdominal radiograph during the evaluation of children with constipation. These include assessment for fecal impaction, to determine response to a bowel washout, to provide evidence for parents and caretakers, and to detect bony abnormalities suggestive of a possible neuropathic process. The distribution and amount of fecal material on one film has not been described to have any predictive value in terms of response to medical therapy or recurrence.
19. e. All of the above.Constipation is common and should be suspected in any patient who presents with lower urinary tract symptoms. Programs dealing with incontinence and dysfunctional voiding have successfully included this aspect of care into their protocols. Dysfunctional voiding and constipation should be addressed before proceeding with surgical correction and can be done by a pediatric urologist or urology nurse practitioner, assisted by the child's primary care physician.

Imaging

1. d. Supplement fiber intake.The physical examination and imaging studies are suggestive of severe constipation and stool impaction. Decreasing fecal load in the colon and rectum is the first step towards establishing an optimal medical regimen. Impaction should be suspected when a mass is felt in the lower abdomen and/or left lower quadrant, or a dilated rectum filled with a large amount of stool is seen on pelvic ultrasound or abdominal radiography (as shown in the figure). Approximately 30% of children with functional constipation present with fecal impaction. Disimpaction and bowel washout address the problem in a relatively short period of time, often with enemas or suppositories, in contrast to maintenance therapy. Popular regimens also include "high dose" polyethylene glycol with or without sodium chloride, sodium phosphate or mineral oil enemas. In some circumstances clearance can only be achieved with digital disimpaction under sedation or anesthesia. The addition of fiber to the diet is bound to worsen the problem by increasing fecal load and is generally avoided during the initial management of fecal impaction.

Chapter review

1. Constipation may cause significant voiding dysfunction.
2. Functional constipation is a diagnosis of exclusion.
3. Three stools per day to three stools per week without straining or withholding is considered normal.
4. Organic conditions associated with elimination problems include cystic fibrosis, hypothyroidism, celiac disease, dietary allergies, Hirschsprung disease, anal stenosis, and trisomy 21. In the older child, mental health issues, eating disorders, sexual abuse, and irritable bowel syndrome should also be considered.
5. Initial medical management includes behavioral modification (regular defecation and nonsedentary activity), dietary changes (fluid and fiber intake), stool softeners and laxatives, and judicious use of enemas.
6. Antegrade continence enemas may be given through the cecum or left colon. It often requires that the child sit on the toilet for up to an hour before emptying is complete. The procedure is best employed in children 5 to 12 years of age who are motivated and is more successful in patients with neuropathic bowel or anorectal malformations.
7. Impaction should be suspected when a mass is felt in the lower abdomen and/or left lower quadrant, or a dilated rectum filled with a large amount of stool is seen on pelvic ultrasound or abdominal radiography.
8. In patients with fecal impaction, the addition of fiber to the diet is bound to worsen the problem by increasing fecal load and is generally avoided during the initial management.
9. The age of onset of symptoms is one of the easiest and most important pieces of information to obtain because it can be an important indicator for underlying pathology, particularly if it has been present since early in life (infancy).
10. Endocrine disorders associated with chronic dehydration (such as diabetes insipidus), electrolyte disorders (most notably hypercalcemia and hypokalemia), hypothyroidism, and hypervitaminosis D are important potential organic etiologies.
11. Although of modest clinical value, abdominal radiographs are commonly employed in the diagnosis and management of constipation. Proponents of routine use argue that the study can clearly demonstrate the amount of fecal loading and delineate stool distribution throughout the colon and rectum, as well as help ascertain the presence of fecal impaction. In addition, it may also reveal associated pathologies, such as bony abnormalities indicative of occult spinal dysraphism or sacral agenesis.
12. PEG is better tolerated and easier to administer than alternative medications such as lactulose, mineral oil, and milk of magnesia.
13. The most common problem with antegrade continence enemas is pain or discomfort during instillation. In the majority of patients, this is a transient phenomenon that subsides during the first 3 months. It is always important to ensure that the pain is not due to distal fecal impaction.