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Acute small bowel obstruction due to bands or adhesions

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Abstract

The description of acute small bowel obstruction due to bands or adhesions covers all aspects of the surgical procedure used for the management of acute small bowel obstruction.
Operating room set up, position of patient and equipment, instruments used are thoroughly described. The technical key steps of the surgical procedure are presented in a step by step way: abdominal exploration, exposure, dissection, lavage/drainage, closure.
Consequently, this operating technique is well standardized for the management of this condition.

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Publication

2001-05

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WeBSurg.com, May 2001;1(05).
URL: http://www.websurg.com/doi-ot02en215a.htm

Acute small bowel obstruction due to bands or adhesions

1. Introduction

60% of small bowel obstructions are due to bands or adhesions.
These adhesions are:
- secondary to previous abdominal surgery (90% of cases);
- spontaneous (4%);
- secondary to a condition affecting adjacent organs (3%);
- due to Meckel’s diverticulum (2%).

Acute obstruction of the small bowel is a surgical emergency whose severity depends on electrolyte and fluid imbalances induced by third spacing and on the presence of ischemic injuries of the small bowel which may be non reversible.

Etiology
A) Simple mechanical obstruction
Extrinsic obstruction: bands or adhesions; extrinsic masses: neoplasm, abscess.
Intrinsic obstruction: intraluminal: bile stone, bezoar, foreign body in the wall of the small bowel: tumor, hematoma, Crohn’s disease, ischemic stenosis

B) Strangulation obstruction
- volvulus: primary or over a band,
- strangulated hernias: external (eg, inguinal, femoral, umbilical, incisional); internal congenital (eg, paraduodenal, paracecal) or acquired (defects in peritoneal coverage).

C) Mechanical obstruction by intussusception
- tumor of the small bowel, Meckel’s diverticulum, lymphoid hyperplasia.

D) Paralytic ileus (due to alteration in intestinal motility)
Local origin: sepsis and intraperitoneal or retroperitoneal inflammatory processes, ureterohydronephrosis, retroperitoneal trauma, hemoperitoneum, vascular condition, etc.
General origin: metabolic (hypokalemia), drug-induced (opiates, antidepressants, anticholinergic agents).

Pathophysiologic consequences
- dehydration, electrolyte and acid-base disturbances: due to loss of fluids (vomiting, nasogastric intubation and suction) and formation of a third spacing of fluids in the obstructed lumen (filled with water, electrolytes and proteins);
- intestinal ischemia: following a volvulus, strangulation or massive distention of the small bowel;
- microbial proliferation in the intestinal lumen after the obstruction.

Diagnosis of acute small bowel obstruction
In addition to clinical examinations, certain radiological investigations may be conducted to confirm the diagnosis of acute small bowel obstruction, determine its place of onset and its cause:
- plain abdominal radiographs;
- CT scan;
- water-soluble enema;
- follow-through examination of the small bowel;
- ultrasound.

2. Anatomy

• Small bowel

• Generalities

The small bowel theoretically consists of the duodenum, duodenojejunal flexure, jejunum and ileum. It is about 6.50 m long. In practice, obstruction due to an adhesive band is always situated on the jejunoileum whose mobile loops are intraperitoneal.

• Localization

The greater omentum and the transverse colon should be pulled up in order to identify the jejunoileum.

• Topographical anatomy

The jejunoileum is situated in an area surrounded by the large bowel. The jejunum comprises the upper two fifths and the ileum the lower three fifths. There is no definite boundary between the two. The mesentery comprises the mesentery of the small bowel encompassing the superior mesenteric vessels. It is fixed to the posterior abdominal wall by its base, following a diagonal line caudad and to the right. The 15 to 16 small bowel loops can be mobilized around the mesentery.

• Local anatomy

• Generalities

The diameter of the small bowel decreases from 3 to 2 cm from its origin to its end. The mesenteric border of the small bowel (where the mesentery with vessels is attached) should be distinguished from the free border on the opposite side.

• Arteries

The arterial supply of the small bowel is made up of 12 to 15 jejunal and ileal arteries from the superior mesenteric artery. Each of these anastomose with neighboring arteries, forming several groups of marginal arteries (first, second, third and fourth types). The final marginal arteries give off terminal arteries or vasa recta which supply the intestine.

• Veins

Veins accompany their corresponding arteries and drain into the superior mesenteric vein.

• Lymphatics

Lymphatics run along the arteries and form the intestinal trunk. There are several dozen small superior mesenteric lymph nodes along their path.

• Anatomopathology

We distinguish:
1: thick bands which often strangulate the small bowel completely (risk of local ischemia) or result in a volvulus (risk of extensive necrosis);
2: multiple adhesions resulting in the cohesion of intestinal loops with bends and plications and often an incomplete obstruction;
- certain adhesions and bands may form an internal opening into which one or several intestinal loops can enter and strangulate (internal hernia).

• Pathophysiology

Most obstructions due to bands or adhesions occur in patients who have undergone previous laparotomy in the lower part of the abdominal cavity (20% during the first year following the intervention). Early or late obstruction develops in 5% of cases after an appendectomy or a gynecological procedure (uterus, ovaries) and in 10-20% of cases after a colectomy.
Several factors seem to be involved in the formation of bands/adhesions:
- regions of deperitonization;
- regions of tissue devascularization;
- regions of tissue trauma (eg, radiation);
- foreign bodies: talc, catgut, etc.

3. Indications

Patients with a high operative risk (ASA IV, non reversible state of shock) are contraindications because of the drop in cardiac output induced by the pneumoperitoneum. Massive distention of intestinal loops (ileus) strongly reduces the working space in laparoscopy and manipulation of the dilated intestinal loops with instruments is not advisable due to the risk of digestive tract injury.

Indication
Acute obstruction of the small bowel which does not respond to 24-48 hours of conservative treatment.
Preferably: previous history of appendectomy and/or gynecological procedure, moderate abdominal distention.

Contraindications
- patient with ASA IV and/or in a non reversible state of shock;
- massive abdominal distention (reduced working space);
- necrosis and/or perforation of the small bowel;
- limited laparoscopic experience.

4. Operating room set-up

• Principles

Patient positioning, operating room set-up and equipment depends on the preoperative workup (search for the site of obstruction) and abdominal scars. The surgeon should be on the side opposite the region to be dissected. The following set-up is the one used in case of suspected right pelvic band adhesions.
1. Surgeon
2. Assistant

• Patient

- patient in supine position;
- legs together;
- right arm stretched out.

• Team

The surgeon (1) is on the patient’s left opposite the monitor. The assistant (2) stands on the surgeon’s left.
The position of the team may vary during the procedure depending on the plane of dissection. Ideally, there should be several monitors to the patient’s left and right in order to let the surgeon change sides easily and always have a monitor placed opposite. For instance, in case of lateral pelvic adhesions, the surgeon stands on the patient’s right.

• Equipment

The laparoscopic unit is situated at the patient’s feet, slightly off to the right.
1. Anesthetic equipment
2. Monitors
3. Electrocautery
4. Laparoscopic unit
5. Instrument table
6. Operating table

5. Trocar placement

• Trocar placement

It is variable and depends on the patient’s previous surgical history. The following placement is the one used in case of scars of the McBurney type and/or median laparotomy for gynecological procedures. A minimum of 3 trocars are necessary: one optical trocar and 2 operating trocars. A fourth trocar may be needed to retract the small bowel loops.
The first trocar is always introduced in accordance with the open-laparoscopic technique, at a distance from existing scars. The left subcostal region is frequently chosen as it is often free of parietal adhesions. In order to prevent any leak of carbon dioxide around the trocar, it is advisable to fashion a musculoaponeurotic pursestring around it or use a balloon trocar.

• Optical trocar

Optical trocar (10/11 mm)
Its position varies during the procedure in order to safely perform adhesiolysis under visual guidance.

• Operating/retractor trocars

Operating trocars (5 mm or 10/11 mm)
Retractor (5 mm or 10/11 mm)
Variable positions, but preferably suprapubic, left iliac fossa, left flank and epigastrium, respecting the rule of triangular placement.

6. Instruments

• Principles

The instrumentation must enable atraumatic manipulation of the small bowel and sectioning of bands or adhesions.
Optical
Operating
Retractor

• Optical

0° laparoscope

• Operating

Atraumatic grasper
Bowel clamps
Bipolar cauterization
Scissors

• Retractors

Suction-irrigation device, probe or fan-type retractor (3 branches)

• Optional

Needle-holder
30° laparoscope

7. Major principles

- open-laparoscopy (Hasson’s technique);
- uncoil the small bowel starting from the ileocecal valve;
- avoid manipulation of the dilated, frail small bowel as much as possible;
- adhesiolysis using scissors;
- bipolar electrocauterization of thick and vascularized bands;
- if multiple and diffuse adhesions: conversion;
- best indications: single band or bowel loop adhesive to scar tissue.

8. Abdominal exploration

• Exploration/principles

Two operating trocars are required for thorough abdominal exploration in addition to the optical trocar.
The surgeon should look for:
- flat loops of small bowel and dilated loops of small bowel;
- types of adhesions: thick and few bands; loops adhesive to scar tissue; multiple adhesions(velamentous or dense), disseminated over a large part of the small bowel;
- signs of intestinal pain;
- bowel necrosis, dubious intraabdominal fluids (purulence, succus, blood, etc);
- hernia strangulation: external or internal.

• Flattened/distended loops

Flattened and distended loops of small bowel suggest the presence of a mechanical obstacle in the small bowel. In a reflex ileus, on the other hand, the entire small bowel is dilated from the duodenojejunal angle to the ileocecal valve.

• Types of adhesions

• Single band

Single, thick, band containing blood vessels and consisting of fibrotic tissue and omentum, it strangulates the small bowel at a precise location. Its division immediately relieves the obstruction.

• Multiple bands

Multiple adhesive bands are the most difficult to treat as the transitional zone between the flattened and distended loops of the small bowel is not always very clear. Extensive adhesiolysis often proves necessary.

• On scar tissue

One or several small bowel loops can adhere to parietal scar tissue. The resulting bend or the twisting of a loop on itself is a potential site of obstruction. In certain cases, fibrotic scar tissue stenosis can result, requiring segmental resection of the small bowel.

• Bowel necrosis

It is important to systematically check for the presence of a necrotized bowel segment caused by volvulus of a loop or a stenotic segment.

9. Exposure

• Inclined table

Tilting of the table (Trendelenburg or lateral decubitus) may help improve the exposure, especially at the pelvis level.

• Uncoiling the loops

Starting from the ileocecal junction, the flattened loops of small bowel are uncoiled towards the site of obstruction.

• Retraction

The small bowel loops must be carefully and atraumatically retracted to expose the adhesive regions.

• Isolation

The exposure and isolation of a single band is done by means of an open atraumatic grasper introduced between the intestinal wall and the band.
Grasping and manipulating distended loops of small bowel, even when using atraumatic graspers or clamps, involves a risk of accidental injury. This must be avoided.

10. Dissection

• Dissection

1. Strangulating band
2. Adhesion to the scarred wall
3. Multiple adhesions
Adhesions or bands between the visceral organs and the anterior abdominal wall are freed first. Dissection is performed from the last small bowel loop towards the proximal portion of the small bowel.

• Strangulating band

Strangulating bands are sectioned with scissors after performing bipolar cauterization.

• Adhesion to the scarred wall

Freeing of a small bowel loop adhesive to scar tissue can prove to be difficult when the loop is incarcerated in the abdominal wall. During adhesiolysis, the plane of dissection is artificial and situated at a distance from the supposed boundary of the small bowel. Care must be taken to leave some parietal tissue against it. This protects against seromuscular or mucosal leaks in the digestive wall.

• Multiple adhesions

Freeing of multiple adhesions between distended intestinal loops remains a very delicate act, because the serosa covering them has often disappeared and the plane of dissection is situated between the two muscle layers. As it is sometimes difficult to find, the exposure must be excellent and the operative act requires precision.

In the presence of an obvious adhesive obstructive site (flattened loops of small bowel coming after the obstruction and distended loops of small bowel coming before it), it is not necessary to perform total adhesiolysis of the small bowel, but only of the obstructive site. On the contrary, with a clinical picture indicating multiple adhesions without clear boundaries between flattened and distended loops of small bowel, the entire jejunoileum must be freed (frequent conversion).

11. Lavage/drainage

Intraoperative serosanguineous effusions must be aspirated.
Voiding of the small bowel is not performed.
Drainage of the peritoneal cavity is not necessary.

12. Closure

Trocars are withdrawn one by one and hemostasis of the trocar openings is carefully controlled. The musculoaponeurotic plane is closed for 10/11 mm openings only. The skin is closed in a conventional fashion using staples or suture.

13. Postoperative period

Bowel function is generally recovered rapidly on the day following surgery. It is sometimes restored on the evening of the procedure.
There is no specific care apart from general abdominal monitoring.
Persistence of the ileus, an onset of major abdominal pain or fever should lead to a suspicion of one of the following complications:
- perforation of the small bowel by an unrecognized injury or evolutive necrosis;
- intra-abdominal collections (hematoma, abscess, etc.);
- cause of the obstruction left untreated.

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