Page 166 - Color Atlas Of Pathophysiology (S Silbernagl Et Al, Thieme 2000)

Constipation and (Pseudo-)Obstruction
The symptom of constipation may signify distance reflexes, can cause pseudo-obstruc-
different things in individual cases, depend- tion.
ing on what is considered to be “normal”: ! Myogenic causes. Muscular dystrophies,
too little, too hard or rare a stool, difficult scleroderma (see also Plate 6.3), dermato-
defecation, or the sensation of incomplete myositis, and systemic lupus erythematosus.
emptying. Constipation is often harmless, ! Mechanical obstruction in the intestinal
but it can be a sign of numerous diseases. lumen (e.g., foreign bodies, roundworms [As-
The causes of constipation are: caris], gallstones), in the intestinal wall (e.g.,
! Low-fiber diet, as intestinal motility de- tumor, diverticulum, stenosis, stricture, he-
pends on the volume of intestinal contents. matoma, infection) or from outside (e.g.,
Liver The larger the volume the greater the motili- pregnancy, adhesion, hernia, volvulus, tu-
ty.
mor, cyst). The result is mechanical intestinal
Stomach, Intestines, These include: 1) anal fissure that is painful ! Finally, in some patients constipation (al-
disorders.
psychogenic
and/or
! Reflex
occlusion (obstruction).
and reflexly raises the tone of the anal
ternating with diarrhea) may occur without
any of the above causes being identified.
sphincter, thus increasing the pain, and so
Emotional or physical stress is often the pre-
on; 2) so-called anismus (outlet obstruction),
cipitating factor in what is called irritable co-
i.e., contraction (rather than the normal re-
is stretched. Such a “false” reflex is commonly
found in women who were abused as chil-
struction. Complete occlusion leads to a
6 laxation) of the pelvic floor when the rectum lon. Effects of obstruction and pseudo-ob-
dren, but also in patients with Parkinson’s proximal accumulation of gases and fluid
disease; 3) paralytic ileus (acute pseudo-ob- and dilates the intestine, which initially con-
struction) that may be caused reflexly by op- tracts painfully every few minutes. Especially
erations (particularly in the abdomen), trau- if the proximal small intestine is affected, the
ma, or peritonitis, and may persist in the co- advancing dilation impairs blood flow, causes
lon for several days. vomiting and results in dehydration (hypo-
! Functional disorders of transport, wheth- volemia). This can progress rapidly because
er of neurogenic, myogenic, reflex (see increased amounts of fluid can be secreted
above), medicinal (e.g., opiates), or ischemic in the intestine. As well as dilation, bacteria
cause (e.g., trauma or arteriosclerosis of the ascending from the large to the small intes-
mesenteric arteries). Functional intestinal tine also cause this; their endotoxins result
obstruction is called pseudo-obstruction. in the liberation of VIP, PGI 2 , and PGF 2 . In-
! Neurogenic causes. Congenital absence of flammation caused by bacteria along with
ganglion cells near the anus (aganglionosis edema formation in the intestinal wall and
in Hirschsprung’s disease), resulting in per- peritonitis as well as possibly resulting is-
sisting spasm of the affected segment due to chemia (see above) can quickly become life-
failure of receptive relaxation (→ A, bottom threatening. If the (pseudo-)obstruction is
right) and absence of anorectal inhibitory re- located far toward the anus, megacolon may
flexes (internal anal sphincter fails to open develop (→ A). It may occur acutely in case of
when rectum fills). In Chagas’ disease the fulminant colitis, volvulus, or without recog-
causative organism (Trypanosoma cruci) de- nizable cause (Ogilvie syndrome). Distinc-
nervates the intestinal ganglia, thus produc- tion between this and paralytic ileus (see
ing dilation of the colon (megacolon; see above) is largely made from the patient’s his-
below). In addition, systemic nervous diseases tory.
(Parkinson’s disease, diabetic polyneuropa-
thy, viral neuritis, tabes dorsalis, multiple
sclerosis) or nerve and spinal cord lesions
156 that, among other effects, interrupt intestinal
Silbernagl/Lang, Color Atlas of Pathophysiology © 2000 Thieme
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