Clinical Manifestation

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The most common complaint of patients with PH is difficult defecation, including frequent attempts, a sense of incomplete evacuation, and prolonged straining. Approximately 50% of these patients require 15 to 30 minutes, and some require 60 minutes or more, to evacuate. Although all patients desire to defecate once or more every day, they are usually unsuccessful. Digital rectal examination shows that there is increased anal sphincter tension in most of these patients and the puborectalis is clearly palpable, thick and stiff with a sharp border. When queried, these patients do try to push; however, the puborectalis has limited movement. The length of the anal canal is generally more than 4 cm and any attempt to force the examining finger through the anal canal causes more spasm and pain. There is a residue of dry and hard stool in the rectum even after defecation. Anorectal manometry generally confirms the functional length of the anal canal of more than 4 cm, although the resting pressures are in the normal range from 5 to 8.6 cm. The maximal squeeze pressures are generally 3 to 8 cm, without a significant amount of puborectalis contraction. Thus, the ability of the puborectalis to contract is decreased in patients with PH. Although balloon expulsion test shows that most patients can expel the balloon, the time of expulsion is longer than that in nonconstipated individuals. Colonic transit time study can show either rectal retention or colonic inertia, or it can be normal. Puborectalis electromyography (EMG) shows many fibrillation potentials at rest without significant increases in action potentials when the patient is asked to squeeze or push (Figs. 26.2 and 26.3). Single-fiber electromyography (SFEMG) shows that the single-fiber conduction time (SFCT) is often longer than 3.4 |isec and the fiber density increases.1114 Cui et al12 studied 64 patients with PH and found that 92.2% showed abnormal EMG and 95.3% showed abnormal SPEMG. The EMG and SPEMG differences between PPC and PH are reported in Table 26.1.

Figure 26.2. Electromyography (EMG) of the puborectalis muscle of patients with puborectalis hypertrophy (PH). A: EMG at rest. B: EMG during straining.
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Figure 26.3. Anal manometry of PH; the final functional anal canal length is increased, and the anal canal pressures do not change between the rest and strain phases. The anorectal reflex is inhibited.

The most important examination of PH is defecography. The anorectal angle becomes acute paradoxically in most cases of PH. At rest, the mean anorectal angle is 91 ± 11 degrees, and in most patients it is less than 90 degrees. During defecation, the mean anorectal angle is 93 ± 16 degrees and the angle is in fact less than 90 degrees in more than half of these patients. These angles see little change between rest and defecation,9 unlike the anorectal angle of normal individuals, which can increase by more than 20 degrees during defecation. Furthermore, the anal length becomes longer rather than shorter during evacuation as shown by defecography. The most significant sign of PH in defecography is the "shelf" sign, which can be noted in the lateral sitting position and is caused by the upper position of the anorectal junction without changing between rest and defecation (Fig. 26.4).9,10 This telltale sign can be noted in all patients with PH but is not seen in other patients with constipation. During a 10- to 15-minute evacuatory effort, little or none of the barium is

Table 26.1. The EMG and the SFEMG difference(s) between PPC and PH

Table 26.1. The EMG and the SFEMG difference(s) between PPC and PH


Little fibrillation

Great fibrillation



Slight contraction

Polyphasic motor

Dominant in short

unit potential

spike wave

Exertion contraction

High wave

Low wave





No or slight




Fiber density Normal Increase(d)


Fiber density Normal Increase(d)

EMG,electromyography SPEMG,single fiber electromyography PPC, paradoxical puborectalis contraction PH, puborectalis hypertrophy SFCT, single fiber conduction time

expelled.6,11,15 During videodefecography,16 the anorectal angle does not change or changes less than 3 degrees in patients with PH, while it can change more than 3 degrees between rest and defecation in patients with PPC or other reasons for constipation. Pathologic examination of the puborectalis demonstrates marked hypertrophy of the skeletal muscle in patients with PH.

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Constipation Prescription

Constipation Prescription

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