Intestinal obstruction is one of the most common surgical emergencies. 90% of intestinal obstruction occurs in the small intestine, especially in the narrowest part of the ileum, while colonic obstruction occurs most often in the sigmoid colon. The condition of intestinal obstruction is variable, develops rapidly, and can often endanger the patient’s life; according to statistics, the mortality rate of small bowel obstruction in the United States is 10%, and the mortality rate of colonic obstruction is 30%. If intestinal obstruction is not diagnosed and treated timely within 24 hours, the mortality rate will increase; especially strangulated intestinal obstruction, the mortality rate is quite high.
I. Etiology
There are many causes of intestinal obstruction, small intestine obstruction may be caused by inflammation, tumor, adhesion, hernia, intestinal torsion, intussusception, blockage of food mass and narrowing of intestinal lumen caused by external pressure, paralytic intestinal obstruction, mesenteric vascular embolism and hypokalemia can also cause small intestine obstruction, in addition, serious infection can cause intestinal obstruction. 80% of large intestine obstruction is caused by tumor, most of which occurs in sigmoid colon, other Other causes include diverticulitis, ulcerative colitis, history of previous surgical procedures, etc.
According to the cause of intestinal obstruction, it can be divided into mechanical, neurogenic and vascular intestinal obstruction.
1.Mechanical intestinal obstruction
(1) Adhesions: It is the most common cause of large intestine and small intestine obstruction. Adhesions caused by surgical procedures or unknown reasons, especially foreign body stimulation left over from surgical procedures, will cause fibers and scar tissue to form bundles, forming external pressure on the intestinal lumen, or causing the intestinal tube to adhere to other tissues, causing intestinal deformation, angulation, or even becoming the axis of intestinal torsion, causing intestinal obstruction. On the basis of the disease of adhesions, intestinal obstruction can be induced by improper diet, strenuous exercise or sudden change of body position. Intestinal obstruction caused by adhesions accounts for 20-40% of all types of obstruction; multiple adhesions increase the possibility of intestinal obstruction.
(2) Intestinal torsion and intussusception: intestinal torsion is a segment of intestinal tube rotating along the long axis of mesentery and forming closed collaterals of intestinal obstruction, often with tumor or diverticular inflammation of intestinal segment torsion is common, most often occurs in small intestine, followed by sigmoid colon. Small intestine torsion is most common in young adults, often due to strenuous exercise immediately after a full meal; sigmoid colon torsion is most common in elderly men, often with constipation habits. Intestinal torsion can occur within a short period of time due to vascular compression, intestinal strangulation and necrosis, with a mortality rate of 15-40%. Intestinal torsion is due to various reasons that the proximal intestine peristalsis, compression into the distal intestine, commonly seen in infants and children and patients with colorectal tumors, etc.
(3) Tumor: 80% of mechanical intestinal obstruction of the large intestine is caused by tumor, most often occurs in the sigmoid colon. Because of the slow growth of tumor and the wide intestinal lumen of large intestine, the course of intestinal obstruction is induced or aggravated by the blockage of fecal mass in the obstruction site. Although the lumen of small intestine is narrow, because the contents of small intestine are mostly fluid, the obstruction does not appear at the early stage of tumor development.
(4) Other: incarcerated hernia and strangulated hernia often cause intestinal obstruction due to blood flow blockage and loss of function. In addition, congenital intestinal atresia, parasites (roundworms, etc.), fecal masses, stones, foreign bodies, etc. can also cause intestinal obstruction.
2.Blood flow intestinal obstruction
The intestinal blood flow is supplied by the abdominal arterial trunk and the superior and inferior mesenteric arteries, and each branch of blood flow is connected with each other in the head of the pancreas and the transverse colon. Blockage of blood flow can cause partial or complete obstruction. Complete intestinal obstruction is commonly caused by necrosis caused by mesenteric vascular embolism or embolism, with mortality rate up to 75% in acute cases; partial intestinal obstruction is seen in abdominal vascular ischemia, of which arteriosclerosis is the most common cause.
3.Powered intestinal obstruction
The intestinal wall itself has no lesion, but the muscle function of the intestinal wall is disturbed due to neural reflex or toxin stimulation, which prevents normal peristalsis and prevents the normal passage of intestinal contents, and can be divided into paralytic and spastic intestinal obstruction. Paralytic intestinal obstruction can be seen after surgical procedures, where the peritoneum is stimulated and the sympathetic nervous system reacts to make the intestinal peristalsis disappear for up to 72 hours or more. Spastic intestinal obstruction is less common and is caused by abnormal muscle contraction of the intestinal wall and can be seen in acute enterocolitis or chronic lead poisoning.
In addition, according to the presence or absence of blood flow disorders in the intestinal wall when intestinal obstruction occurs, it can be divided into simple intestinal obstruction and strangulatedintestinalobstruction; according to the site of obstruction, it can be divided into high (upper jejunum) and low (end ileum and colon) intestinal obstruction; according to the rapidity of obstruction, it can be divided into acute and chronic intestinal obstruction If a segment of intestinal collaterals is completely obstructed at both ends, such as intestinal torsion, it is called closed-collaterals intestinal obstruction.
Pathophysiology
The pathophysiological changes of various types of intestinal obstruction are not exactly the same.
1.Local pathophysiological changes of intestinal canal
When the intestinal canal is obstructed, it first causes the intestinal peristalsis above the obstruction to increase, trying to overcome the resistance to pass the obstruction; after a few hours, the intestinal peristalsis is weak and the pressure in the intestinal lumen is temporarily reduced. The obstruction causes continuous accumulation of gas and fluid in the intestinal cavity. The accumulation of gas mainly comes from the gas swallowed, partly produced by bacterial decomposition and fermentation of intestinal contents; the accumulation of fluid mainly comes from the endocrine fluid of the gastrointestinal tract, under normal conditions, the small intestine secretes 7-8L of intestinal fluid, and the large intestine mainly secretes mucus. The large amount of accumulated gas and fluid causes the proximal intestinal canal to expand and swell; because the small intestine is narrower and peristalsis is active, this change appears earlier and the small intestine secretes a large amount of intestinal fluid, which has more serious consequences.
2.Systemic pathophysiological changes
When the intestinal lumen is obstructed, part of the intestinal fluid cannot be reabsorbed and is retained in the intestinal canal, while part of it is expelled from the body due to vomiting, resulting in a significant decrease in circulating blood volume, and the patient develops hypotension and hypovolemic shock, with a corresponding decrease in renal blood flow and cerebral blood flow. At the same time, the decrease in body fluids results in a relative increase in blood cells and hemoglobin, a thickening of the blood, and an increased incidence of vascular obstructive diseases such as coronary artery disease, cerebrovascular disease and mesenteric embolism.
High intestinal obstruction patients lose a lot of gastric acid and chloride ions due to severe vomiting, while low intestinal obstruction patients lose even more sodium and potassium ions. Dehydration and hypoxia cause a sharp increase in acidic metabolites, and patients develop serious water and electrolyte disorders and acid-base imbalance.
At the same time, the permeability of the intestinal wall increases, and the intestinal bacteria and toxins seep into the abdominal cavity. The retention of intestinal contents leads to bacterial multiplication and the production of large amounts of toxins, which can cause peritonitis, sepsis, and even systemic infection.
In addition, intestinal distension is an increase in intra-abdominal pressure, the diaphragm rises, abdominal breathing is weakened, and the lung gas exchange function is affected. At the same time, the inferior vena cava reflux is obstructed, exacerbating circulatory dysfunction.
III. Clinical manifestations
1.Symptoms
The clinical manifestations of patients with intestinal obstruction depend on various factors such as the location and scope of the affected intestinal canal, the effect of obstruction on blood flow, whether the obstruction is complete, and the cause of the obstruction.
Abdominal pain varies in different types of intestinal obstruction. Simple mechanical intestinal obstruction, especially small bowel obstruction, is characterized by typical, recurrent, rhythmic, paroxysmal colic, which is caused by intensified peristalsis of the intestine trying to push the intestinal contents past the obstruction site, and increasing abdominal distension is also a cause of pain. The painful areas of small bowel obstruction are usually in the upper and middle abdomen, and the painful areas of colonic obstruction are in the lower abdomen. Strangulated intestinal obstruction may occur when the interval of abdominal pain is shortened and worsened, and then turns into persistent abdominal pain. Paralytic intestinal obstruction manifests as persistent distension and pain.
Vomiting is often reflexive. The timing and nature of vomiting varies depending on the site of obstruction. In high intestinal obstruction, vomiting appears early and frequently, and the vomit is mainly gastric juice, duodenal fluid and bile; later, foul-smelling dark fluid appears due to bacterial multiplication, suggesting a possible increase in infection. In low intestinal obstruction, vomiting appears later, and the vomit is often foul-smelling fecal juice. If the vomit is bloody or brownish fluid, it often indicates blood flow disorders in the intestinal canal. Vomiting in paralytic intestinal obstruction is overflowing.
Abdominal distension usually appears later and its degree is related to the site of obstruction. In high intestinal obstruction, abdominal distension is not obvious because of frequent vomiting; in low or paralytic intestinal obstruction, abdominal distension is obvious throughout the abdomen, mainly because vomiting cannot completely discharge the contents, resulting in pneumatization and fluid accumulation, accumulation of contents, enlargement of the intestinal cavity, and obvious abdominal distension.
Stopping defecation and exhaustion is one of the typical clinical symptoms that must occur in intestinal obstruction. However, in the early stage of obstruction, especially in high intestinal obstruction, the existence of intestinal obstruction cannot be denied when there is a small amount of defecation in the early stage because the residual stool and gas in the intestine below the obstruction can still be expelled. In strangulated intestinal obstruction, bloody mucus-like stools can be excreted.
In the early stage of simple intestinal obstruction, there is no obvious change in the general condition, but in the late stage, there may be signs of dehydration such as dry lips, sunken eyes, poor skin elasticity, and little urination. In severe water shortage or strangulated intestinal obstruction, signs of shock such as fine and rapid pulse, decreased blood pressure, pale face and cold extremities may appear.
2.Signs
Simple mechanical intestinal obstruction can often show abdominal distension, intestinal pattern and peristaltic wave, and abdominal distension is mostly asymmetric in intestinal torsion, and uniform abdominal distension in paralytic intestinal obstruction. Palpation: simple intestinal obstruction may have mild pressure pain but no peritoneal irritation sign, while strangulated intestinal obstruction may have fixed pressure pain and peritoneal irritation sign. Auscultation: In strangulated intestinal obstruction, there is fluid in the abdominal cavity, and there may be mobile turbid sounds. Auscultation: if the sound of air over water or metallic sound is heard, and the intestinal sound is hyperactive, it is a manifestation of mechanical intestinal obstruction; in paralytic intestinal obstruction, the intestinal sound is diminished or disappeared.
Four, auxiliary examination
1.Laboratory examination
In the early stage of simple intestinal obstruction, the changes are not obvious. With the development of the disease, the hemoglobin value and erythrocyte pressure product will increase due to the lack of water and blood concentration. In strangulated intestinal obstruction, there may be obvious increase in white blood cell count and neutrophils. There may be changes in blood sodium, potassium, chloride and blood gas analysis value when there is also electrolyte acid-base imbalance.
2.X-ray examination
Generally, 4-6 hours after the occurrence of intestinal obstruction, X-ray standing plain film can show distended intestinal collaterals and most stepped liquid planes; jejunal distention can be seen as “fish rib spur”-like circular mucosal pattern. In strangulated intestinal obstruction, isolated and protruding distended intestinal collaterals can be seen on X-ray, which do not change position due to time.
3.Finger intestinal finger examination
If the finger stained with blood, strangulated intestinal obstruction should be considered; if a mass is palpated, it may be a rectal tumor, etc.
V. Treatment principles
Relieve the obstruction and correct the systemic physiological disorder caused by the obstruction.
1.Basic treatment
(1) Gastrointestinal decompression is one of the important measures to treat intestinal obstruction. Through gastrointestinal decompression, gas and liquid in the gastrointestinal tract can be sucked out, thus reducing abdominal distension, lowering the pressure in the intestinal cavity, reducing bacteria and toxins in the intestinal cavity, and improving blood transport of the intestinal wall.
(2) Correct the imbalance of water, electrolytes and acid-base balance. The amount and type of fluid infusion should be decided according to the vomiting and dehydration, urine volume and combined with the blood concentration, serum electrolyte value and blood gas analysis results. If intestinal obstruction has existed for several days, high intestinal obstruction and frequent vomiting, potassium supplementation is required. If necessary, transfuse plasma, whole blood or plasma substitutes to compensate for the lost plasma and blood.
(3) Prevent and control infection, use antibiotics against intestinal bacteria to prevent and control infection and reduce the production of toxins.
2.Relief of obstruction
(1) Non-surgical treatment, applicable to simple adhesive intestinal obstruction, dynamic intestinal obstruction, intestinal obstruction caused by blockage of roundworms or fecal masses, can be applied through basic therapy to make the intestinal tube rest, relieve the symptoms and avoid stimulating the intestinal tube movement.
(2) Surgical treatment is applicable to intestinal obstruction caused by strangulated intestinal obstruction, tumor, congenital intestinal malformation, and patients with intestinal obstruction for which surgical treatment is ineffective. The principle is to release the obstruction or restore the patency of the intestinal lumen in the shortest time and by the simplest method. The methods include adhesiolysis, enterotomy to remove foreign bodies, intestinal resection anastomosis, intestinal torsional repositioning, short-circuit surgery and enterostomy, etc.