Intestinal bypass is a

bariatric surgery Bariatric surgery (also known as metabolic surgery or weight loss surgery) is a surgical procedure used to manage obesity and obesity-related conditions. Long term weight loss with bariatric surgery may be achieved through alteration of gut ho ...

performed on patients with morbid

obesity Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...

to create an irreversible weight loss, when implementing harsh restrictions on the

diets The Low Countries comprise the coastal Rhine–Meuse–Scheldt delta region in Western Europe, whose definition usually includes the modern countries of Luxembourg, Belgium, the Netherlands and parts of Northern France. Both Belgium and the ...

have failed. Jejunocolic anastomosis was firstly employed. Nonetheless, it led to some unexpected complications such as severe

electrolyte imbalance Electrolyte imbalance, or water-electrolyte imbalance, is an abnormality in the concentration of electrolytes in the body. Electrolytes play a vital role in maintaining homeostasis in the body. They help to regulate heart and neurological function ...

and

liver failure Liver failure is the inability of the liver to perform its normal synthetic and metabolic functions as part of normal physiology. Two forms are recognised, acute and chronic (cirrhosis). Recently, a third form of liver failure known as acute- ...

. It was then modified to jejunoileal techniques. Viewed as a novel form of treatment for obesity, many intestinal bypass operations were carried out in the 1960s and 1980s. Significant weight loss was observed in patients, but this surgery also resulted in several complications, for instance, nutritional deficiencies and metabolic problems. Due to the presence of surgical alternatives and anti-obesity medications, intestinal bypass is now rarely used.

Anatomy of human digestive system

In the human digestive system, the stomach is responsible for mechanical and chemical

digestion Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into th ...

s. The small intestine is involved in both the absorption and digestion of nutrients, whereas the large intestine is responsible for the elimination of wastes (

defecation Defecation (or defaecation) follows digestion and is the necessary biological process by which organisms eliminate a solid, semisolid, or liquid metabolic waste, waste material known as feces (or faeces) from the digestive tract via the anus o ...

). The small intestine consists of 3 parts:

duodenum The duodenum is the first section of the small intestine in most vertebrates, including mammals, reptiles, and birds. In mammals, it may be the principal site for iron absorption. The duodenum precedes the jejunum and ileum and is the shortest p ...

jejunum The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been pr ...

and

ileum The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may ...

. The duodenum is the first part of the small intestine and is connected to the stomach via the

pyloric valve The pylorus ( or ) connects the stomach to the duodenum. The pylorus is considered as having two parts, the ''pyloric antrum'' (opening to the body of the stomach) and the ''pyloric canal'' (opening to the duodenum). The ''pyloric canal'' ends a ...

. The jejunum is the second and middle part of the small intestine. The ileum is the last part of the small intestine and is connected to the cecum, a part of the large intestine, via the

ileocecal valve In many Animalia, including humans, an ileocolic structure or problem is something that concerns the region of the gastrointestinal tract from the ileum to the large intestine, colon. In Animalia that have cecum, ceca, the ileocecal region is a sub ...

Types of intestinal bypass

Procedures of intestinal bypass surgery

The intestinal bypass surgery, as the name suggests, anastomoses 14 inches of the proximal duodenum, the part of the small intestine closest to the stomach, to the 4 inches of the distal ileum, the part of the small intestine closest to large intestines. This creates a blind loop and bypasses nearly 85-90 % of the small intestine. As a corollary, the absorption of nutrients is greatly reduced, and thus lead to apparent weight reduction. There are four variations of intestinal bypass. They are jejunocolic bypass, end-to-side jejunoileal bypass, end-to-end jejunoileal bypass, and biliopancreatic diversion, respectively.

Jejunocolic bypass

First performed in 1963, the jejunocolic bypass is regarded as the first type of intestinal bypass surgery. This surgery anastomoses the proximal duodenum to the

transverse colon In human anatomy, the transverse colon is the longest and most movable part of the Large intestine#Structure, colon. Anatomical position It crosses the abdomen from the ascending colon at the right colic flexure (hepatic flexure) with a downward ...

(a part of the large intestine). The surgery, nevertheless, turned out to be a huge failure as patients suffered from severe electrolyte imbalance and metabolic disturbance after it.

End-to-side jejunoileal bypass

This type of surgery was designed to overcome the shortcomings of jejunocolic bypass. First performed in 1969, it anastomoses the end of the proximal duodenum to the side of the distal ileum. However, owing to the possibility of reflux of ileal content to the blind loop, some surgeons doubted the effectiveness of this surgery.

End-to-end jejunoileal bypass

This type of surgery appeared at the same time as end-to-side jejunoileal bypass. Some surgeons regarded this as a better option than end-to-side jejunoileal bypass because it prevented the reflux of ileal content to the blind loop. In order to achieve this, the end of the proximal duodenum is anastomosed to the distal ileum. The blind loop is drained to the

. However, two studies revealed that both end-to-side and end-to-end jejunoileal bypass had similar weight loss effect.

Biliopancreatic diversion

First appeared in 1980, biliopancreatic diversion involves two parts: gastrectomy and intestinal bypass. Firstly,

gastrectomy A gastrectomy is a partial or total surgical removal of the stomach. Indications Gastrectomies are performed to treat stomach cancer and perforations of the stomach wall. For severe duodenal ulcers, it may be necessary to remove the lower ...

removes a large portion of the

stomach The stomach is a muscular, hollow organ in the upper gastrointestinal tract of Human, humans and many other animals, including several invertebrates. The Ancient Greek name for the stomach is ''gaster'' which is used as ''gastric'' in medical t ...

. Reduction in stomach capacity decreases the appetite of patients. Secondly, intestinal bypass anastomoses the proximal duodenum and the distal ileum. This intestinal bypass is different from the above three bypasses in the way that the blind loop carrying

bile Bile (from Latin ''bilis''), also known as gall, is a yellow-green/misty green fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is primarily composed of water, is pro ...

and

digestive enzymes Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes ...

will drain into the distal portion of the small intestine. With this technique, the absorption of nutrients, in particular, fat, can be reduced tremendously.

Mechanisms of weight reduction

This surgery acts in the following ways to help patients reduce their body weight:

Induction of malabsorption

Induction of

malabsorption Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal (GI) tract. Impairment can be of single or multiple nutrients depending on the abnormality. This may lead to malnutrition and a varie ...

is the most prominent effect of the surgery. The small intestines are responsible for most of the absorption of nutrients. By bypassing a considerable length of the small intestines, this type of surgery greatly reduces the absorption capacity of the digestive system.

Malabsorption Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal (GI) tract. Impairment can be of single or multiple nutrients depending on the abnormality. This may lead to malnutrition and a varie ...

is especially prominent in biliopancreatic diversion. Not only does it reduce the length of the small intestine for absorption, but it also drains the bile and digestive enzymes only to the distal ileum. Bile is essential for fat absorption, while digestive enzymes facilitate the intake of proteins. Draining them to only the distal ileum further reduces the efficiency of intestinal absorption, hence achieving the goal of weight reduction.

Conditioning of appetite

If the patients take excessive food after the surgery, they will experience abdominal discomforts such as

steatorrhea Steatorrhea (or steatorrhoea) is the presence of excess fat in Human feces, feces. Stools may be bulky and difficult to flush, have a pale and oily appearance, and can be especially foul-smelling. An oily anal leakage or some level of fecal incon ...

and

abdominal pain Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues. Since the abdomen contains most of the body's vital organs, it can be an indicator of a wide variety of diseases. Given th ...

, as patients' digestive system capacity has been reduced drastically.

Selection Criteria

Intestinal bypass, in spite of its highly effectiveness in weight reduction, is a risky and irreversible. Thus, it requires rigorous assessment and selection before the surgery is carried out. The following are the normal selection criteria: * Overweight for more than 100 lbs. * Readiness to accept the side effects and hence all the follow-up procedures. * Evidence of failure in all previous attempts in weight reduction. * Stable mental health status. * Psychiatric evaluation showing the obese state. * An absence of all types of endocrinopathies that are correctable. This surgery serves as the LAST approach to lose weight when all other weight-losing methods have failed and at the same time,

morbid obesity Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...

remains a life-threatening problem. It is crucial for patients to understand all the pros and cons of this surgery, despite the weight loss they aimed for.

Health impacts

Intestinal bypass surgery can lead to loss of weight effectively, but it can also lead to various complications that should not be neglected. About half of the patients who received this surgery need rehospitalization to manage the complications. The expected outcomes and possible risks of the intestinal bypass surgery are shown as follows:

Expected surgical outcomes

Weight loss

It is estimated that the absorptive surface area in the small intestine can be reduced by 85% after the surgery. This results in continuous malabsorption, and thus sustainable weight loss.

Metabolic benefits

* Blood

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

level is significantly reduced. In patients with

hyperglycaemia Hyperglycemia is a condition where unusually high amount of glucose is present in blood. It is defined as blood glucose level exceeding 6.9 mmol/L (125 mg/dL) after fasting for 8 hours or 10 mmol/L (180 mg/dL) 2 hours after eating. Blood gluco ...

, a normal blood glucose level and a significant decline of insulin resistance are observed after the surgery, except for the cases of patients with

type I diabetes Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that occurs when the body's immune system destroys pancreatic cells (beta cells). In healthy persons, beta cells produce insulin. Insulin is a hormone required ...

. * Serum

cholesterol Cholesterol is the principal sterol of all higher animals, distributed in body Tissue (biology), tissues, especially the brain and spinal cord, and in Animal fat, animal fats and oils. Cholesterol is biosynthesis, biosynthesized by all anima ...

and

lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...

levels decrease, which lower the risks of developing cardiovascular diseases such as atherosclerosis.

Risks of the intestinal bypass

Adverse metabolic effects

Diarrhoea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

is observed in almost all patients undertaking this surgery. The daily frequency of defecations can be up to 20. This will usually affect the patients for three to six months. Electrolyte imbalance is very likely to occur owing to

diarrhoea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

. Low serum level of potassium, magnesium and zinc were reported. *

Metabolic bone disease Metabolic bone disease is an abnormality of bones caused by a broad spectrum of disorders. Most commonly these disorders are caused by deficiencies of minerals such as calcium, phosphorus, magnesium or vitamin D leading to dramatic clinical disor ...

is more likely to occur in patients with

Vitamin D deficiency Vitamin D deficiency or hypovitaminosis D is a vitamin D level that is below normal. It most commonly occurs in people when they have inadequate exposure to sunlight, particularly sunlight with adequate ultraviolet B rays (UVB). Vitamin D def ...

before the surgery. A few cases of

osteomalacia Osteomalacia is a disease characterized by the softening of the bones caused by impaired bone metabolism primarily due to inadequate levels of available phosphate, calcium, and vitamin D, or because of resorption of calcium. The impairment of b ...

were reported.

Physical weakness

Fatigue Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself. Fatigue (in the medical sense) is sometimes associated wit ...

is common after the surgery due to the malabsorption of nutrients.

Complications

Kidney stone Kidney stone disease (known as nephrolithiasis, renal calculus disease, or urolithiasis) is a crystallopathy and occurs when there are too many minerals in the urine and not enough liquid or hydration. This imbalance causes tiny pieces of cr ...

is also an associated risk of the intestinal bypass surgery. This is mainly due to enteric

hyperoxaluria Hyperoxaluria is an excessive urinary excretion of oxalate. Individuals with hyperoxaluria often have calcium oxalate kidney stones. It is sometimes called Bird's disease, after Golding Bird, who first described the condition. Presentation Caus ...

. Increased absorption of

oxalate Oxalate (systematic IUPAC name: ethanedioate) is an anion with the chemical formula . This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (), and several esters such as ...

in colons rises the risk of the formation of kidney stones. *

Arthritis Arthritis is a general medical term used to describe a disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, Joint effusion, swelling, and decreased range of motion of ...

may appear after the surgery in morbid obesity patients due to excessive

immune In biology, immunity is the state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease. Immunity may occur naturally or be produced by prior exposure or immunization. Innate and adaptive ...

responses to the

gut bacteria Gut microbiota, gut microbiome, or gut flora are the microorganisms, including bacteria, archaea, fungi, and viruses, that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the g ...

. The symptoms can last for three to six months. However, symptoms of arthritis are not severe.

Dysfunctions in GI tracts

Flatulence Flatulence is the expulsion of gas from the Gastrointestinal tract, intestines via the anus, commonly referred to as farting. "Flatus" is the medical word for gas generated in the stomach or bowels. A proportion of intestinal gas may be swal ...

is observed even after years of surgery. Patients may suffer from persisted problems of producing

flatus Flatulence is the expulsion of gas from the intestines via the anus, commonly referred to as farting. "Flatus" is the medical word for gas generated in the stomach or bowels. A proportion of intestinal gas may be swallowed environmental air, ...

with foul-smell due to the accumulation of gas in the gastrointestinal tract. There can also be problems of abnormal distension of the abdomen after meals.

Long-term health issues

Long-term negative health effects were reported. Chronic diarrhoea is a common and frequent complication, and further leading to higher risk of proctologic diseases such as

haemorrhoids Hemorrhoids (or haemorrhoids), also known as piles, are vascular structures in the anal canal. In their normal state, they are cushions that help with stool control. They become a disease when swollen or inflamed; the unqualified term ''he ...

. More seriously, the risks of developing

nephrolithiasis Kidney stone disease (known as nephrolithiasis, renal calculus disease, or urolithiasis) is a crystallopathy and occurs when there are too many minerals in the urine and not enough liquid or hydration. This imbalance causes tiny pieces of cr ...

and

chronic kidney disease Chronic kidney disease (CKD) is a type of long-term kidney disease, defined by the sustained presence of abnormal kidney function and/or abnormal kidney structure. To meet criteria for CKD, the abnormalities must be present for at least three mo ...

are 28.7% and 9.0% respectively in the long term.

Nutritional deficiencies and solutions

Nutritional deficiencies are often seen in patients after the surgery due to malabsorption. They include:

Loss of appetite

Anorexia Anorexia nervosa (AN), often referred to simply as anorexia, is an eating disorder characterized by Calorie restriction, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. Individuals wit ...

is considered to be a normal response found after the first few weeks of the surgery but after four to six weeks, most patients gain back their initial appetite before receiving the surgery.

Electrolyte imbalance

Hypokalaemia Hypokalemia is a low level of potassium (K+) in the blood serum. Mild low potassium does not typically cause symptoms. Symptoms may include feeling tired, leg cramps, weakness, and constipation. Low potassium also increases the risk of an ...

is also considered to be a normal response after the intestinal bypass surgery. Without the supply of potassium supplements, hypokalaemia is seen in almost all patients. Therefore, patients are usually prescribed with six months of tablet or liquid form of potassium supplements postoperatively. *

Hypocalcaemia Hypocalcemia is a medical condition characterized by low calcium levels in the blood serum. The normal range of blood calcium is typically between 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L), while levels less than 2.1 mm ...

is also observed in some patients. Symptoms resulting from this electrolyte imbalance include anxiety, muscle

cramping A cramp is a sudden, involuntary, painful skeletal muscle contraction or overshortening associated with electrical activity. While generally temporary and non-damaging, they can cause significant pain and a paralysis-like immobility of the affe ...

and

paraesthesia Paresthesia is a sensation of the skin that may feel like numbness (''hypoesthesia''), tingling, pricking, chilling, or burning. It can be temporary or chronic and has many possible underlying causes. Paresthesia is usually painless and can oc ...

. Calcium supplements are administered to patients when serum calcium levels are lower than normal.

Lack of vitamins

Low serum levels of

Vitamin B12 Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. One of eight B vitamins, it serves as a vital cofactor (biochemistry), cofactor in DNA synthesis and both fatty acid metabolism, fatty acid and amino a ...

Vitamin A Vitamin A is a fat-soluble vitamin that is an essential nutrient. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinyl esters, and several provitamin (precursor) carotenoids, most not ...

Vitamin D Vitamin D is a group of structurally related, fat-soluble compounds responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, along with numerous other biological functions. In humans, the most important compo ...

Vitamin E Vitamin E is a group of eight compounds related in molecular structure that includes four tocopherols and four tocotrienols. The tocopherols function as fat-soluble antioxidants which may help protect cell membranes from reactive oxygen speci ...

, and

Vitamin K Vitamin K is a family of structurally similar, fat-soluble vitamers found in foods and marketed as dietary supplements. The human body requires vitamin K for post-translational modification, post-synthesis modification of certain proteins ...

are common nutritional deficiencies after the surgery. 1000 mg of Vitamin B12 is recommended monthly, and supplements of vitamins and minerals are also recommended for the first half to full year after the surgery until the rapid weight loss period has passed.

Damages to organs

Hepatic damage results from the inadequacy in nutritional supply and

steatosis Steatosis, also called fatty change, is abnormal retention of fat (lipids) within a cell or organ. Steatosis most often affects the liver – the primary organ of lipid metabolism – where the condition is commonly referred to as fatty liver dis ...

, where it remains as the most serious, and possibly lethal, side effect. Patients may show symptoms like

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...

and

emesis Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteritis, pregna ...

. Intake of

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

is intolerable as it increases the tendency for the liver to become impaired. Incidents of death due to

have also been reported. By applying

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

replacement orally right after the surgery, prevention of these liver problems may be achieved.

Alternatives to intestinal bypass

Alternative surgical treatments

Due to the aforementioned complications, instead of performing the intestinal bypass surgery,

gastric bypass surgery Gastric bypass surgery refers to a technique in which the stomach is divided into a small upper pouch and a much larger lower "remnant" pouch, where the small intestine is rearranged to connect to both. Surgeons have developed several differen ...

is a more commonly used

nowadays. Intestinal bypass surgery induces malabsorption by anastomosing proximal and distal small intestine. Yet, the small intestine has an important role in performing a wide range of important physiological and metabolic functions, such as the metabolism of lipids. Stomach, on the contrary, has a less significant role in the physiological and metabolic functions. The most prominent physiological function of the stomach is digestion, but the small intestine is also capable of digestion. Thus, gastric bypass surgery does less harm to the overall metabolism of nutrients. Gastric bypass leads to weight loss by controlling the appetite of the patients, instead of inducing malabsorption. As a result, the intestinal bypass is now replaced by an alternative of gastric bypass.

Anti-obesity medications

Anti-obesity medication Anti-obesity medication or weight loss medications are pharmacological agents that reduce or control excess body fat. These medications alter one of the fundamental processes of the human body, weight regulation, by: reducing appetite and con ...

s is also a possible solution. Examples of such medications include the

Orlistat Orlistat, sold under the brand name Xenical among others, is a medication used to treat obesity. Its primary function is preventing the absorption of fats from the human diet by acting as a lipase inhibitor, thereby reducing caloric intake. It ...

, which was first prescribed in 1998. In 2009, it became an

over-the-counter drug Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid pres ...

after obtaining consent from the

European Medicines Agency The European Medicines Agency (EMA) is an agency of the European Union (EU) in charge of the evaluation and supervision of pharmaceutical products. Prior to 2004, it was known as the European Agency for the Evaluation of Medicinal Products ...

. In clinical trials, patients prescribed with Orlistat (120 mg) showed better weight loss than those without (8.76 kg vs 5.81 kg) in one year. With effective medications, the obese can better control their weight without the need of undergoing a relatively high-risk surgery.

References

{{reflist Surgery Obesity