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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_927_Библиотеки_им_академика_М_И_Перельмана.pdf
FIGURE 70-1 A sitz marker study demonstrating colonic inertia, as
evidenced by sitz markers present throughout the entire colon on day
5 on a plain abdominal film.
COLON 351
Small bowel
Sigmoid
Sigmoid
Vagina
Vagina
Rectum
Rectum
A
Sometimes dynamic magnetic resonance imaging (MRI) is used;
protocols vary between institutions. Early MRI machines used a
closed magnet system with the patient supine or lying on the side
with the knees exed, whereas newer open MRI machines allow the
patient to be sitting. Some studies have indicated that assessment of
the pelvic organ prolapse and pelvic oor weakness in the supine
position underestimates the presence and width of anterior rectoceles (Fig. 70-3, A and B). MRI permits multiple views of various
compartments of the pelvic oor to be obtained in one examination
with high-resolution images. It provides an accurate assessment of
the structure and function of the anorectal and pelvic muscles. Pelvic
oor ndings may be secondary to chronic straining due to an underlying motility disorder, and therefore investigation is important.
A wireless capsule, Smart Pill (SmartPill Corp., Bualo, NY),
also can be used to measure intestinal motility. is wireless motility
capsule collects pH, pressure, and temperature data throughout the
gastrointestinal tract. e U.S. Food and Drug Administration has
approved the Smart Pill for evaluation of colonic transit in patients
with suspected chronic constipation. Clinical studies have shown that
the ecacy of the Smart Pill is equal to that of conventional testing,
with the advantage of providing a full gastrointestinal tract motility
prole (Fig. 70-4, A and B).
TREATMENT
Medical
A guideline to management of the patient with constipation is
reected in Fig. 70-5. Initially, treatment should focus on reassurance
by ruling out malignancy followed by the modication of medications and lifestyle changes. Increased physical activity and uid
intake should be emphasized, because these simple measures can
facilitate the easy passage of stool. Patients are encouraged to keep a
diet log and a stool diary detailing stool frequency and consistency,
along with associated symptoms such as straining.
A trial of ber supplementation may provide some benet in
patients with simple slow transit constipation, because insucient dietary ber intake is a common factor in the development of
RectoceleRectocele
B
FIGURE 70-2 Defecography images. A, The rectum/sigmoid and the
vagina are shown prior to defecation, with contrast material in the small
bowel. B, Demonstration of a rectocele during the act of defecation.
constipation. ese bulking agents facilitate the absorption of water
by the stool, increasing bulk, consistency, and weight, thus making
the stool easier to pass. e recommendation is to increase ber in the
diet from natural foods up to 25 g/day over a period of 2 to 3 weeks to
minimize adverse eects. A ber supplement is then recommended
to optimize daily ber content. For some patients, ber supplementation may actually exacerbate symptoms, causing bloating and gas
(these eects occur less frequently with use of synthetic ber). Such
patients may respond to a ber-restricted diet. Fiber is not tolerated
well by patients who have pelvic oor dysfunction, with only 20% to
37% experiencing improvement with psyllium supplementation.
Laxatives and enemas should be used for short periods for acute
attacks of discomfort. Osmotic laxatives (e.g., lactulose and magnesium hydroxide [Milk of Magnesia]) and lavage-type laxatives (e.g.,
MiraLax and GoLYTELY) promote large volumes of uid in the
colon, leading to soer stool that is propelled along the colon more
easily. Evidence supports the use of polyethylene glycol and lactulose
in the treatment of chronic constipation, but chronic use of osmotic
laxatives can lead to dehydration and electrolyte imbalance. Stimulant laxatives, such as senna, cascara, castor oil, and bisacodyl, are
associated with adverse eects, including abdominal pain/cramping
and electrolyte abnormalities. Long-term use of these agents can lead
to tolerance, requiring an increased dose to achieve the same eect.
Uterus
Bladder
A
Pubococcygeal line
Constipation352
Tegaserod maleate (Zelnorm) is a partial 5HT-4 agonist that
accelerates transit in the small bowel and colon and has been shown
to be benecial in patients with IBS.
Prucalopride is a selective high-anity serotonin receptor antagonist that improved defecation in several randomized controlled trials.
Probiotics (Bidobacterium lactis, Lactobacillus casei, and Esch-
erichia coli) have favorable eects on stool frequency and consistency
in patients with functional constipation. ey have both qualitative
Rectum
and quantitative eects on normalizing gut ora. A recent meta-analysis of three randomized placebo-controlled trials suggested that the
use of probiotics resulted in favorable eects in both stool frequency
and consistency.
Biofeedback for Pelvic Floor Dyssynergia
Patients diagnosed with outlet obstruction constipation due to nonrelaxing puborectalis are referred for biofeedback training with a specialized physical therapist. e goal is to retrain patients to relax their
pelvic oor while at the same time producing a propulsive force using
their abdominal muscles. Several randomized controlled trials have
shown that this type of pelvic oor retraining is eective. In addition, if the rectum is hyposensitive, it can be treated with electrical
stimulation administered by a physical therapist. If this treatment is
successful, a home device can be rented. Biofeedback has no complications and should be advised prior to the recommendation of more
invasive therapies.
Injection of botulinum A into the pelvic oor musculature can
chemically relax the muscles and has been shown to produce a shortterm improvement.
Cystocele
Rectocele
B
FIGURE 70-3 Dynamic magnetic resonance imaging images. A, Prior
to defecation with representative anatomy identified. B, Demonstration of a cystocele and rectocele during the act of defecation.
Mineral oil and docusate sodium (Colace) change the composition of the stool. Mineral oil coats the stool and prevents uid resorption. Colace lowers the surface tension, facilitating greater absorption
of water. ese agents are not very eective, and few data support
their use in persons with chronic constipation.
Enemas and suppositories help ease constipation by stimulating
the rectum or by soening the stool and producing an urge to defecate. Colon hydrotherapy removes dessicated feces and improves
muscular tone, facilitating peristalsis.
Newer Promotility Agents
Lubiprostone (Amitiza) is a chloride channel blocker that is used
in patients with functional constipation and IBS-C. e eect is an
increase in stool water content. A dose of 24 mcg twice a day has
been shown to be very eective in both open-label and randomized
controlled trials.
Linzess (linaclotide), which increases the secretion of chloride
and water into the colon via an agonist action on guanylate cyclase
2C, is used to treat chronic constipation or IBS-C. In a phase III clinical trial including 800 patients, Linzess was demonstrated to decrease
pain and constipation. e recommended dose is 145 mcg orally for
constipation and 290 mcg orally for IBS-C daily taken on an empty
stomach. Explosive diarrhea is a common adverse eect.
Change in Position of Defecation
A device that claims to enhance defecation by allowing the adoption
of a squatting position at defecation (Squatty Potty) has attracted considerable public attention. Use of this device is an inexpensive, noninvasive way of improving defecation and is worth a try in patients with
functional obstructive defecation.
Surgery
When supervised medical management fails to resolve serious constipation, surgery can be considered. Surgical options depend on
the type of constipation with which the patient has been diagnosed:
colonic inertia or rectal outlet obstruction.
Colonic inertia is a consequence of colonic dysmotility resulting
in constipation, a heavy, dull abdominal discomfort, bloating, and
the lack of an urge to defecate. Diagnosis requires documentation of
abnormal colonic transit (>20% of sitz markers retained at day 5),
and surgical options include ileostomy (with or without a colectomy),
a subtotal colectomy with ileosigmoid or cecorectal anastomosis, a
total abdominal colectomy with ileorectal anastomosis (IRA), and
antegrade colonic enema.
A total abdominal colectomy with IRA is the operation of
choice for slow-transit constipation. e risks of this procedure are
the same as with any other abdominal operation with an intestinal
anastomosis, and the procedure can be performed using a laparoscopic, robotic, hand-assisted, or open approach. e entire colon is
mobilized, usually starting at the cecum and right colon. e ileocolic pedicle is divided aer the duodenum and the right ureter have
been identied and protected. e mobilization then continues with
takedown of the hepatic exure, mobilization of the transverse colon
from the stomach by entry into the lesser sac, and mobilization of the
splenic exure. e right colic artery is ligated, if present, followed
by the middle colic vessels. Because the surgery is for benign disease,
mesenteric excision can be conservative. e descending colon and
COLON 353
Gastric transit Small bowel transit
pH
A
Pressure
Colonic transit
Temperature
Temperature
Confirms ingestion and
passage from the body.
Pressure
Provides motility indices
from the antrium and
duodenum.
pH
Identifies physiological
landmarks, calculating
regional transient times.
B
FIGURE 70-4 Smart Pill tracing. A, Normal whole gut transit and motility. B, Delayed motility in a
constipated patient.
the sigmoid colon are then mobilized, and the le colic vessels are
isolated and ligated, in addition to the inferior mesenteric vein. e
le ureter should be identied and protected. e terminal ileum is
then transected just proximal to the ileocecal valve and the rectum is
transected at the rectosigmoid junction. e terminal ileum is then
anastomosed to the top of the rectum (Fig. 70-6). Patients should be
appropriately counseled regarding the risk of ureteral injury, anastomotic leaks, postoperative complications, and realistic expectations
regarding postoperative bowel function (an average of four bowel
movements a day and a chance of diarrhea).
Proctocolectomy with ileoanal pouch–anal anastomosis (IPAA)
has been described as benecial in patients with recurrent constipation aer a total abdominal colectomy with IRA. is situation is
unusual and is due to either small bowel dysmotility or a rectal outlet
obstruction. Creating an IPAA may relieve the constipation temporarily, and signicant improvements in lifestyle scores (physical and
social function, pain, and general health) have been recorded, but this
result cannot be guaranteed. If the constipation is due to a nonrelaxing puborectalis, the improvements may be short-lived. Ultimately,
there is a high rate of pouch failure.
A subtotal colectomy with ileosigmoid or cecorectal anastomosis
is a conservative surgical option for treating constipation in patients
who may be worried about the diarrhea that can occur aer a total
colectomy and IRA. However, the results of this operation in treating
constipation are less predictable than aer an IRA, and up to 50% of
patients may have recurrent constipation. A cecorectal anastomosis is
associated with high complication rates.
When constipation is associated with pelvic adhesions to the sigmoid colon, a sigmoid colectomy may be helpful. is type of constipation, which is oen confused with IBS, is associated with the
painful pelvic cramping of a partial colonic obstruction.
An antegrade colonic enema involves the creation of a stoma to
allow access to the colon through the abdominal wall with intermittent catheterization and irrigation that produces controlled evacuation. is procedure avoids a functioning stoma while conferring
control of bowel function. e initial description used an appendicostomy for access to the colon, but since then the cecum, ileum,
and le colon also have been used. is procedure can have serious
adverse eects, with peritonitis reported in 10% and stoma-related
complications reported in 63% of patients.
History of chronic constipation
AB
C
History and physical
Investigations
Slow transit
constipation
Medical
management
Failure of treatment
Enema training program
Failure of treatment
Refer to colorectal
surgery for evaluation
FIGURE 70-5 Algorithm for office management of a constipated patient.
Biofeedback Intusussception Enterocele/sigmoidocele
Failure of treatment
Refer to colorectal
surgery for
evaluation
Outlet dysfunction
Refer to
colorectal
surgery
Refer to urogynecologist
D
FIGURE 70-6 Anatomic depiction of a total abdominal colectomy with ileorectal anastomosis.
COLON 355
Outlet Obstruction Constipation
Several surgical options exist for the treatment of outlet obstruction
constipation, depending on the cause of the obstruction. If rectal
intussusception or rectal prolapse is the cause (as is the case for 31% to
40% of patients undergoing defecography for obstructed defecation),
resection rectopexy can be eective. For this procedure, complete
mobilization of the rectum is performed down to the levator muscles,
leaving the lateral stalks intact. e rectum is then elevated cephalad with suture xation to the presacral fascia at the sacral promontory. A sigmoid colectomy is preferred in constipated patients with
rectal prolapse. Several variations of rectopexy may be performed,
and mesh may be used to anchor the rectum. Ventral rectopexy is
believed to avoid constipation without increased prolapse recurrence.
Rectocele repair can be useful in persons with large, symptomatic
rectoceles conrmed on defecography, although the rectoceles themselves are usually secondary to outlet obstruction rather than a cause
of it. Rectocele repair will fail in such patients unless the defecation
disorder is also addressed. Rectocele repair can be transabdominal,
transvaginal, transanal, or transperineal, with the choice of repair
depending on the size of the rectocele and its associated symptoms.
e goal is to strengthen the rectovaginal septum. Repair is indicated
for dicult evacuation, manual digitation, rectocele size larger than 4
cm, and residual contrast material in the rectocele as shown by defecography. Rectocele repair regardless of the technique used results
in a mean improvement of 75% to 80% in terms of bowel symptoms.
Techniques for rectocele repair are discussed in Chapter 24.
For patients with rectal intussusception, a rectocele, or rectal
mucosal prolapse, a stapled transanal rectal resection (STARR) may
be appropriate. e STARR procedure involves a double-stapled, circumferential, full-thickness resection. Prospective trials of patients
who underwent the STARR procedure reveal initial and long-term
symptom improvement, although the procedure itself is tricky and
should not be attempted without adequate and specic training.
Chronic straining, childbirth, and aging predispose to pelvic
oor weakness with an enterocele and sigmoidocele. Repair of an
enterocele improves defecation by directing defecatory forces more
eciently. e repair can be performed via a transabdominal, laparoscopic, or vaginal route and involves the obliteration of the posterior
cul-de-sac or pouch of Douglas by approximating peritoneum in a
purse-string fashion or plicating the uterosacral ligaments. Newer
techniques approximate the pubocervical and rectovaginal endopelvic fascia and reattach it to the uterosacral ligament.
Sigmoidoceles are uncommon and sometimes are palpable as a
bulge descending into the rectovaginal septum upon bearing down.
ey are identied upon defecography in 4% to 5% of studies performed for obstructed defecation. Treatment is sigmoid resection
or sigmoidopexy performed at the time of a posterior compartment
repair.
Puborectalis division has been described in a handful of patients
with refractory outlet obstruction due to paradoxical puborectalis
contraction, severe symptoms, and a strong desire to avoid a stoma.
e muscle is approached in the same manner as that described for
a Parks postanal repair, incising posteriorly at the intersphincteric
groove and dissecting between internal and external anal sphincters
until the puborectalis is reached. Both sides can be divided as they
pass forward from the coccyx. Although the number of reported
cases is small, incontinence is not a problem aer this procedure, and
in some patients the procedure is eective.
Sacral nerve stimulation was initially developed for patients with
urinary dysfunction but has been shown to help with abnormal defecation. is technology involves low-level, chronic electrical stimulation of the sacral plexus. Small series have demonstrated improved
rectal motility and sensitivity, although the mechanism of action is
unclear. It is currently postulated that neuromodulation of the extrinsic neural control of the colon or modulation of inhibitory reexes
accounts for its utility. irteen studies evaluating the use of sacral
nerve stimulation for constipation have been published. Kamm etal
reported a multicenter prospective study of 62 patients, 45 of whom
proceeded to undergo permanent implantation because of improvement in symptoms with test stimulation. Of these 45 patients, 39
showed improvement in symptoms (e.g., frequency of defecation,
straining, a sensation of incomplete evacuation, abdominal pain, and
bloating).
Fecal diversion with a permanent stoma is the last resort for the
constipated patient when symptoms are severe and all other management options have failed. Few data are available to guide the choice
of ileostomy versus colostomy, and even then, abdominal pain and
distention may not be alleviated.
S u g g e S t e d R e a d i n g
Cash BD, Chang L, Sabesin SM, etal. Update on the management of adults
with chronic idiopathic constipation. J Fam Pract. 2007;56:S13–S19.
Chmielewsha A, Szajewska H. Systematic review of randomized controlled
trials: probiotics for functional constipation. World J Gastroenterol.
2010;16:69–75.
FitzHarris GP, Garcia-Aguilar J, Parker SC, etal. Quality of life aer subtotal
colectomy for slow-transit constipation: both quality and quantity count.
Dis Colon Rectum. 2003;46:433–440.
Gallegos-Orozco JF, Foxx-Orenstein AE, Sterler SM, etal. Chronic constipa-
tion in the elderly. Gastroenterology. 2012;107:18–25.
Kamm MA, Dudding TC, Melenhorst J, etal. Sacral nerve stimulation for
intractable constipation. Gut. 2010;59(3):333–340.
Licup N, Baumrucker S. Methylnaltrexone: treatment for opioid-induced con-
stipation. Am J Hosp Palliat Care. 2011;28(1):59–61.
Pikarsky AJ, Singh J, Weiss EG, etal. Long-term follow-up of patients under-
going colectomy for colonic inertia. Dis Colon Rectum. 2001;44:170–183.
Singh S, Rao SS. Pharmacologic management of chronic constipation. Gastro-
enterol Clin North Am. 2010;39:509–527.
Sonnenberg A, Koch TR. Epidemiology of constipation in the United States.
Dis Colon Rectum. 1989;32:1–8.
van Wunnick BP, Baeten C, Southwell BR. Neuromodulation for constipa-
tion; sacral and transcutaneous stimulation. Clin Gastroenterol Hepatol.
2011;25:160–165.
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SMALL INTESTINE
71. Small Bowel Obstruction 359
72.
Medical Management of Short Bowel Syndrome 366
73.
Surgery for Gut Failure: Auto-Reconstruction and
Allo-Transplantation 372
74.
Crohn Disease of the Duodenum, Stomach, and
Esophagus 385
75.
Management of Small Bowel Crohn Disease 388
76.
Small Bowel Neoplasms 393
77.
Neuroendocrine Tumors of the Small and Large
Intestine 396
78.
Enterocutaneous Fistulas 404
79.
Acute and Chronic Mesenteric Ischemia 412
80.
Radiation Enteritis and Proctocolitis 418
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S B
O
Matthias Turina and Ravi P. Kiran
EXTENT OF THE PROBLEM
Small bowel obstruction is a common problem that is responsible for
more than 1 million inpatient hospital days and more than $1 billion
in health care costs per year in the United States. In some European
countries, medical expenses for small bowel obstruction exceed those
for gastric cancer and almost parallel those for colon cancer.
e most common cause of small bowel obstruction is intestinal adhesions from previous surgery, particularly colorectal surgery.
Hernias, malignancy, volvulus, Crohn disease, chronic radiation
enteritis, inammation involving other abdominal viscera, intussusception, volvulus, ischemia, and gallstone ileus are other less common causes. In a study using Medicare administrative data, Beck etal
reported that 14% of patients undergoing abdominal surgery will
require hospitalization for small bowel obstruction within 2 years of
their operation and 2.6% of these patients will require adhesiolysis.
Based on the Scottish Surgical and Clinical Adhesions Research database, an estimated 35% of patients with a previous laparotomy will
need to be readmitted for problems related to adhesive small bowel
obstruction more than once within 10 years. Approximately 2% to 5%
of these patients will have to undergo adhesiolysis aer failed nonoperative management.
CLINICAL PRESENTATION
Abdominal pain, nausea and vomiting, abdominal distension, and
obstipation are the cardinal signs of small bowel obstruction. e
presence of these signs, their order of appearance, and their intensity
depend upon the location, degree, and duration of the obstruction.
Other important factors to consider include the patient’s age and general condition, associated intra-abdominal disease, and the masking
eect of medications such as steroids. History should be directed at
factors known to be associated with the development of obstruction
such as previous laparotomies, hernias, or a history of malignancy,
especially if its treatment included abdominal or pelvic radiotherapy.
Physical examination should include an assessment of the general condition of the patient with an emphasis on hydration and end
organ perfusion, and then a complete examination of the abdomen
that encompasses the anks, groins, and a rectal examination. In
addition to surgical scars, hernias, or masses, abdominal examination
detects tenderness or peritoneal signs that may indicate an urgent
need for exploration. Percussion typically reveals a tympanitic abdomen, whereas upon auscultation, obstruction is associated with characteristic high-pitched, tinkling bowel sounds. e conversion of an
abdomen with exaggerated bowel sounds to a quiet abdomen without any bowel sounds has been described to be an ominous sign that
indicates the development of ileus, perhaps as a result of peritonitis
or ischemia. A digital rectal examination may detect fecal impaction
or an obstructing rectal cancer, whereas emptiness of the rectal vault
suggests a more proximal obstruction.
Uncomplicated small bowel obstruction may progress to strangulation, greatly increasing mortality. A high index of suspicion is
needed to identify and prevent this complication. Strangulation typically occurs in the setting of twisting or incarceration in an internal
hernia, causing disruption of the arterial supply or venous drainage
of a segment of small bowel. Simple mechanical obstruction due to
adhesions rarely results in infarction unless there is a tight adhesive
band or a longstanding obstruction, where the intraluminal pressure
may exceed the venous hydrostatic pressure, resulting in bowel wall
ischemia. Strangulation may be associated with fever, tachycardia,
leukocytosis, and peritonism. ese signs, however, are not specic
to bowel ischemia and may even be absent.
Investigations that help in the decision-making process include
laboratory tests such as a complete blood cell count, serum electrolytes, blood urea nitrogen and creatinine, serum amylase, and lipase.
ese tests may reveal the severity of the obstruction and its sequelae
and rule out conditions that mimic obstruction. At the same time,
these tests may be misleading because the results can be normal even
in cases of acute small bowel obstruction, and when the results are
abnormal, they cannot be relied upon as a sole determinant of the
need for a laparotomy. Similarly, serum lactate levels, pH, base decit, and anion gap measurements allow an assessment of acidosis but
again cannot be relied upon as sole indicators of intestinal ischemia.
Instead, they should be evaluated in the context of the overall clinical presentation, because other causes of metabolic acidosis such as
renal failure, ketoacidosis, or medication-related eects may inuence their levels.
IMAGING
A radiologic diagnosis of small bowel obstruction can be made using
several dierent imaging modalities, including plain radiographs,
contrast studies, computed tomography (CT), magnetic resonance
imaging (MRI), and even ultrasound. e presence of a segment of
dilated small bowel (usually dened as having a diameter >2.5 to 3
cm) proximal to a collapsed segment of bowel suggests obstruction.
e degree of dilatation has been shown to correlate both with the
duration and severity of obstruction, in particular the risk of segmental ischemia and subsequent transmural necrosis. Although plain
radiographs and contrast studies have some value as the initial imaging, many authors now recommend early contrast CT scanning.
In acute small bowel obstruction, plain radiographs of the abdomen usually reveal dilated, air-lled loops of small bowel, air-uid
levels with a “step-ladder pattern,” and a paucity or absence of air
in the colon. Pneumoperitoneum may be revealed on a radiograph
taken in the upright position when perforation has occurred and is
a late sign, as are pneumatosis intestinalis and portal vein gas, which
are worrisome for advanced bowel ischemia. Plain radiographs are
also helpful in the determination of the level of obstruction and the
identication of sigmoid and cecal volvulus. However, abdominal
359
Small Bowel oBStruction360
radiographs are diagnostic in only 50% to 60% of cases. An analysis
of the value of plain lms for obstruction revealed a sensitivity of only
66% in proven cases of small bowel obstruction, with a false-negative
rate of 21%. Considering these limitations of plain lms, careful correlation of clinical and radiologic ndings is crucial.
CT scanning is the most important imaging modality for the
evaluation of small bowel obstruction. e latest scanners provide
thin-slice imaging, faster scanning times, and less radiation exposure
compared with previous generations. Initial studies using conventional CT in small bowel obstruction reported a sensitivity of 96%,
a specicity of 96%, and an accuracy of 95%. Most of these studies,
however, included patients with high-grade obstruction, and thus
in a mixed population of patients with both high- and low-grade
obstruction, these percentages could be lower. In addition to establishing a diagnosis of small bowel obstruction, CT scanning may also
precisely dene a transition point and reveal the cause of obstruction
such as a tumor, hernia, intussusception, volvulus, or inammatory
condition such as Crohn disease and radiation enteritis. A CT scan
may also reveal closed loop obstruction and signs of progressive ischemia, such as bowel wall thickening, pneumatosis, or portal vein gas,
thereby greatly facilitating the identication of patients in need of
urgent laparotomy rather than nonoperative management.
Contrast studies with water-soluble agents are useful in several
circumstances. A Gastrogran follow-through helps dierentiate
partial from complete obstruction and hence facilitates the decision
for surgery. In fact, some authors have used small bowel contrast
studies as a “screening test” for patients presenting with adhesive
obstruction. Failure of contrast material administered orally or by
nasogastric tube to reach the colon by 24 hours is used as an indication for surgical exploration. At least two recent randomized studies
have reported improved outcomes with the use of oral water-soluble
contrast agents for patients presenting with adhesive small bowel
obstruction. Use of contrast studies either reduced the length of time
until spontaneous clinical resolution of the obstruction occurred
or reduced the proportion of patients requiring surgery. Even so,
it remains unclear whether antegrade contrast material may help
resolve small bowel obstruction in patients who are considered surgical candidates at initial presentation. In particular, early laparotomy
should not be withheld from patients who show clear signs of peritonitis or bowel ischemia. When a distal small bowel obstruction is
suspected, a contrast enema helps exclude colonic obstruction as the
predisposing cause. Although barium studies are not used in patients
with acute obstruction because of their risk of converting a partial
to a complete obstruction, they can be valuable for the evaluation of
chronic or vague symptoms, particularly when other investigations
have not been fruitful. In such cases, enteroclysis, in which barium
is administered beyond the pylorus via a nasoenteric catheter, is
worth consideration. Because this method minimizes the dilution of
the barium during its distal passage, it can reveal mucosal lesions.
CT (and MR) enterography is particularly useful in providing similar information. Intestinal malrotation presenting in adult life with
vague symptoms is also sometimes diagnosed with this modality.
MRI and Ultrasound
Several studies have evaluated the sensitivity and specicity of either
MRI or transabdominal ultrasound in the diagnosis of small bowel
obstruction, because these modalities do not expose the patient to
(sometimes repetitive) radiation. MRI has traditionally had limited
applicability in the radiologic evaluation of intestinal obstruction.
Reasons include its limited availability, long acquisition times, and
high cost. With progressively shorter acquisition times, it is now possible to provide MR imaging of the entire abdomen and pelvis within
10 minutes, and newer studies have shown sensitivity and specicity similar to that of CT scanning in the diagnosis of small bowel
obstruction. MR enteroclysis is another newly developed technique
with great potential because it allows direct multiplanar imaging with
functional information and so-tissue contrast obtained without
exposure to ionizing radiation. In contrast to most imaging modalities, abdominal ultrasound provides real-time information of small
bowel motility and peristalsis. Although both sensitivity and specicity have been shown to be high for both ultrasound and MRI, such
drawbacks as interobserver variability for abdominal ultrasound and
cost/availability for MRI outweigh any benets in most instances of
acute small bowel obstruction. Both modalities, however, have a role
in pregnant patients with suspected small bowel obstruction when
radiation exposure needs to be kept to a minimum.
MANAGEMENT OF SMALL BOWEL OBSTRUCTION
When suspicion for strangulation is low, and particularly when
postoperative adhesions are the most likely cause of obstruction,
management is initially nonoperative. e strategy includes bowel
rest with nasogastric decompression, intravenous uids, and close
monitoring of the intravascular volume status using clinical and laboratory parameters combined with sequential abdominal examinations. Partial small bowel obstruction resulting from adhesions will
resolve spontaneously in 80% of cases. e success rate for patients
initially presenting with complete obstruction is much lower. When
any change occurs in the patient’s condition that suggests the development of strangulation, or if no resolution occurs within 24 to 48
hours, laparotomy is required. Under certain circumstances, some
surgeons will wait for up to 5 days before proceeding to surgery.
e distinctions between obstruction with and without intestinal ischemia and partial and complete small bowel obstruction is
important because the need and threshold for operating are dierent. Although the need for surgery is obvious in some cases, neither
clinical nor laboratory parameters consistently identify patients at
risk for or with (imminent) ischemia and hence provide an indication for surgery. Serial abdominal examinations aided by a careful
interpretation of laboratory parameters and imaging studies in the
context of the patient’s clinical picture is the best approach. Early CT
imaging may identify strangulation or closed loop obstruction. In
the absence of CT ndings that are suspicious for ischemia, patients
should be aggressively rehydrated with isotonic intravenous uids.
Persistence of tachycardia, hypotension, or acidosis, particularly in
the setting of a change in the patient’s general condition or worsening
abdominal pain, should prompt an immediate laparotomy. Adherence to this simple algorithm should minimize the risk of progression
of obstruction to strangulation and limit the number of unnecessary
laparotomies.
In some cases, the need for an urgent laparotomy is apparent at
initial presentation. Patients without a previous history of abdominal surgery or other predisposing factors who present with the classical picture of obstruction, which is then corroborated on imaging
studies, and those who have symptoms and signs that raise a concern
for strangulation, should proceed to a laparotomy. us the presence
of obvious peritonitis or ndings suggesting that resolution of an
obstruction is unlikely, such as an incarcerated or strangulated hernia, an abdominal mass, unresolving intussusception (particularly
associated with a lead-point), or volvulus, should prompt immediate
surgery. While waiting for surgery, nasogastric decompression, active
uid resuscitation, and broad-spectrum antibiotic coverage allows
optimization of the patient.
Recent studies have shown that postoperative morbidity, return
of bowel function, and length of stay are all adversely aected in
patients in whom surgery was delayed for more than 48 hours.
e dierentiation of partial obstruction, which is more likely to
respond to conservative management, from complete obstruction
is important but can be challenging. Although stool or atus can
continue to occur in patients with complete obstruction until the
bowel distal to the site of obstruction is evacuated, it usually signals resolution of the obstruction. e continued passing of gas or