RNY Gastric Bypass (Roux en Y) surgery is a restrictive and malabsorptive procedure.  Restriction is accomplished by surgically altering the stomach so it is smaller (1/2 to 1 ounce).  Staples may be used to segregate the upper stomach from the lower, or the stomach may be transected.  Malabsorption is accomplished through surgical bypass of a large portion of the intestinal tract.  The common channel is 500 cm in Proximal RNY and 100-400 cm in Distal RNY.

RNY Gastric Bypass

RNY Gastric Bypass (Roux en Y Gastric) is the most common obesity surgery done in the United States today. The common names for this obesity surgery are “gastric bypass” or “RNY.” Of the 100,000 operations done in 2003 for obesity, 61,000 of them were the RNY Gastric Bypass type. The other types are lap-band, Vertical banded Gastroplasty (VBG), and the Duodenal Switch.

How to do RNY Gastric Bypass surgery

Roux en Y (RNY) Gastric Bypass Surgery…step-by-step

Roux en Y Gastric Bypass – where to cut the stomach



In RNY surgery, the stomach is completely divided into two compartments —an upper part, or pouch, and the lower portion of the stomach.

Where to cut ?

RNY gastric bypass – where the lower half and small bowel is attached


The upper pouch is smaller, and is made to hold one ounce (about the size of an egg) or less.  The small bowel is divided and brought up to the upper stomach where an anastomosis is made between the pouch and the small bowel.  An anastomosis is the term surgeons use for the opening formed when they sew, or staple together, two pieces of bowel, making an opening—or stoma—between them.  The Y-connection allows pancreatic fluid and bile to aid in absorption of nutrients

Roux en Y Gastric Bypass – upper pouch or stomach – stoma – small bowel

The opening between the new pouch and the intestines is called a stoma.

The stoma size keeps food in the pouch, allowing the patient to feel full for several hours on a small amount of food.

RNY Surgery Information…how it works

Roux, my French friends tell me, means road but this surgery was not named after French roads.  Dr. Roux was the name of the surgeon who developed this operation for gastric surgery in 1893.  The anastomosis (surgical connection of two structures) between the pouch and the intestines is made small so that food will leave the pouch slowly, giving a feeling of fullness.  If the stoma is too large, food goes through too quickly and patients don’t feel full. If the stoma is too small, then nausea and vomiting may result.

Rules of the Stoma…

…the opening between the stomach and the small bowel:

  • If the stoma bowel is too large, you won’t feel full
  • If the stoma is too small, you will have heartburn, nausea or vomiting
  • A meal should stay in the pouch for several hours
  • Sip, do not gulp liquids. Gulping can force food out and you will feel hungry sooner
  • For the first 12 weeks, do not eat and drink at the same time

Since the upper pouch only holds an ounce of food, the patient feels full after eating just a few bites. It is an enforced “portion control” diet.  Eating more than the pouch holds can cause nausea, severe discomfort (like you ate all of the Thanksgiving Day turkey) and might lead to vomiting.  Learning portion control of food is a difficult task for anyone, but it becomes a way of life after this surgery.


Some RNY gastric bypass patients, about sixty percent, develop a syndrome called “dumping” if they eat foods too high in sugar or carbohydrates.  Dumping can cause severe diarrhea, cramping, nausea, flatulence, cold sweats, rapid pulse, or a sensation of feeling shaky or faint.  This unpleasant sensation can serve as negative feedback and keep patients from resorting to higher carbohydrate foods.  Dumping is not fun—and patients who have this are not happy.

I had one wonderful patient who came to me weighing over 400 pounds.  After I did the RNY surgery, he did great, followed his diet, and then, over time, stopped following up with me—as many patients do.  He went about enjoying his newer, healthier 155 pound life.  Two years later he returned and requested that I do a colostomy (a bag).  He said he had such severe diarrhea sometimes that he would wake up at night and be unable to get to the bathroom in time.  He had been examined by a gastroenterologist who did a colonoscopy on him and found everything normal.  The doctor couldn’t understand why this guy had this severe, uncontrolled diarrhea.  The mystery was finally solved.  He had a lemon tree on his property, and his wife made some of the best lemonade in the city—with sugar.  Once his wife started making the lemonade with Splenda®, his diarrhea stopped and she was able to sleep with him again.  Neither one of them knew that the sugar in the lemonade was causing the dumping.  Splenda is a sugar substitute that does not cause dumping.

Dumping does not happen with Lap-band or VBG surgery.  Dumping has no relation to weight loss.  You can dump and still absorb sugars and carbohydrates.  Dumping can be quite serious, causing people to black-out and have other severe reactions.

Dumping has no relation to weight loss

All patients experience dumping differently; in the most severe form, some patients find they can never again eat even small amounts of simple carbohydrates like bread, sugar, candy or potatoes.

We have no way of knowing which patients will dump and which patients will not. So before you choose this operation, know that your days of eating sweets may be over completely. For some this is a desired goal, for others, having an occasional sweet sometime in the future for birthdays or special occasions is a nice reward for weight loss.

Now, if you prefer to have the dumping syndrome because you think it will provide a form of behavior modification, you may be one of the forty percent of patients who will not develop it. Jill was a nice lady with five children who decided to have RNY weight loss surgery because her neighbor had the procedure and it was very successful. She underwent a successful RNY but called me late one night, upset that she was able to eat cookies without triggering dumping. I explained that she was probably one of the 40 percent who wouldn’t develop “dumping.” She was quite upset by this, and unfortunately continued to feast on cookies and clean her kids’ plates. She didn’t lose as much weight as her neighbor.

Variations of the RNY

Proximal RNY has 18 to 40 inches bypassed – Distal has more than 120 inches bypassed

Normally the small bowel is a mixture of food and digestive juices. When we bypass a portion of it, some of the small bowel will see food, and some will see the digestive juices, but the percent that sees both is the common channel.  For insurance purposes, a proximal bypass must be less than 100 cm ((39.37 inches).  No small bowel is removed.

Distal RNY Bypass Surgery causes malabsorption

If more intestines are bypassed, another mechanism of weight loss is created called malabsorption.  This means, in addition to portion control, there is less intestine to absorb food.  Some surgeons reserve the distal bypass for patients who have a BMI above 50, also known as the “super morbid obese” patients.  Other surgeons use a distal bypass when patients have, through a food history, revealed that many of their calories come from fat.

After distal bypass RNY surgery, patients do not absorb fat as well but they still absorb simple carbohydrates.  How much small bowel is bypassed will determine how much fat and complex carbohydrates will be absorbed.  Most studies show that a distal bypass can only absorb thirty percent of the fat the patient consumes early on.  The reason patients reach their goal weight is not the malabsorption from the small bowel bypass, but from the restriction, or portion control.  Over time, the common channel will become more efficient and be able to absorb more fat, protein, and carbohydrates.

There are middle grounds where a shorter amount of the small bowel is bypassed.  In these cases less than sixty percent but more than twenty percent is bypassed.  There are no rules here for who gets what.  Some patients believe that if they have more intestines bypassed they will lose weight faster.  But the vast majority of individuals who have gotten to their weight loss goal did it with a proximal RNY bypass.  Some insurance companies will deny patients requests to have a “malabsorptive” procedure, calling this “investigational.”  In 2003 the American Society for Bariatric Surgery, the world experts in weight loss surgery, stated that distal procedures, including the duodenal switch, are acceptable and are not considered experimental or investigational.

As a rule, distal bypass patients have more loose stools, and proximal bypass patients more constipation.  But these rules, unlike constipation, are not hard.  Each patient reacts differently.

Stomal Stenosis

—or, learning to swallow a big scope

The stoma between the pouch and the intestine is made in a very specific way.  Some surgeons use a stapler to make the diameter of the stoma a little less than half an inch in diameter.  Other surgeons sew the bowel and stomach together (or make an anastomosis) over a guide so that the size of the stoma will be precise.  But as the anastomosis heals, scaring may occur that causes the stoma to decrease in size (a stenosis).  When this happens, smaller and smaller amounts of regular food can pass through the stoma and patients develop more vomiting.  Your friendly gastroenterologist, or GI doctor, has the cure for this.  The GI doctor places a scope down your throat and when it get to the stoma, he passes a special balloon through it.  He inflates the balloon that stretches the scar tissue, and this allows the stoma to open up.  Often this needs to be repeated a few times.  This is an outpatient procedure, so it may be a bit inconvenient.

Sometimes an ulcer develops at the stoma…

…resulting in scarring and stenosis (or scarring down in size).  Patients with an ulcer need to be on some acid blocking therapy such as Pepcid™ or Prevacid™, and they will also need to have their stoma opened by the balloon dilation.  If it becomes too damaged from the scar tissue or the ulcer to be taken care of by a scope, it will need to be revised through an operation.  This will require surgical revision, and this means major surgery and hospitalization for a minimum of several days.

How to Defeat RNY Surgery

The three most common ways to regain your weight…

There are three common ways patients who have RNY gastric bypass defeat the surgery.  Defeating RNY surgery means the patients either don’t lose very much weight, or they lose some weight but regain it.  The most common mistake is falling back into old eating habits, the habits that caused them to be overweight in the first place.  The three most common habits are skipping meals, snacking (or grazing), and eating foods that are high in carbohydrates.

Skipping meals…leads to grazing on junk food

In my seminars, I always ask people to raise their hands if they skip meals—most do.  Skipping meals only makes you hungry later and when you become hungry, you will grab the first snack available.  These snacks are rarely nutritious and are commonly filled with lots of calories.  No weight loss surgery has been invented that is a match for grazing on junk food.  Eating a little bit here and there, (grazing) is a great way to get in a lot of calories without feeling full.  Alcohol is another source of calories that is often overlooked.

Stretching the pouch by overeating

The second most common way to defeat RNY surgery is to stretch the pouch.  We expect the pouch to stretch over time.  It will probably stretch to eight or ten ounces after a couple of years, and that is fine.  The pouch works by making you feel full with less food.  If the pouch stretches and becomes too large, you will eat the same amount of food that you did prior to RNY surgery.  That is why it is important to learn what “full” feels like, and why we emphasize measuring your food early in the postoperative process.  Many people don’t really know what “full” feels like.  The feeling of being full (or satiety) often comes thirty minutes after eating (it is kind of a slow reflex).  Remember how, after a large Thanksgiving meal, you notice the discomfort 20-30 minutes after eating?

By measuring your food, eating it slowly, and noticing when you are full, you can avoid both pouch stretch and vomiting.  Retraining your body to notice when you are full, and refraining from eating more food after you feel full, is a goal in the early postoperative period.  The pouch doesn’t typically stretch out after one large meal, but from chronically over filling it.  The only way to make a pouch smaller is with surgery, so learn to measure your food early on.  The first few weeks after RNY surgery, until they get good at “eyeballing” it, I ask patients to measure everything they eat or drink with a shot glass.

Enlarging the stoma

The final way to defeat RNY surgery is by enlarging the stoma—or opening—between the upper pouch and the intestine.  You can cause this by not chewing food well and by forcing large bits of food through the stoma with liquids.  Many patients who are at goal weight will sip some water with their meal, but they will not gulp liquids to force large chunks of food down.  If the stoma enlarges, then food does not remain in the pouch for long and you become hungry.  Making the stoma smaller often requires an operation.  It is a lot easier to learn new habits, like only putting pieces of food in your mouth that are smaller than a pencil eraser and chewing them well.

Don’t forget—certain foods stay in the pouch longer than others do.  These include poultry, meats, and some vegetables. Liquids, soups, yogurt, ice cream, and other soft foods go through the pouch quickly and don’t keep you full for long.  In fact, most liquids stay in the pouch only a few seconds, moving quickly through the stoma and into the intestine.  Some days you can only eat a forkful or two, and other days you can eat more.  That is also normal. Just remember—eat slowly, cut your food into small pieces, chew your food well, and enjoy it.

Carbonated Drinks

—a real problem, or a solution.

Many surgeons do not allow their patients to drink carbonated beverages.  There is a little bit of fact here, and a lot of fiction. The facts are fairly simple: most carbonated beverages are very high in sugar or in carbohydrates.  Many patients find it hard to give them up, however.  I had one lovely lady who underwent RNY surgery and quickly lost weight, but then she stopped losing for a while.  She came back to see me, after having stretched her pouch to over 20 ounces, and wanted a revision.  She admitted to drinking about 40 ounces of Coke® a day.  I told her once she stopped drinking the cola we would reverse the surgery for her. She never returned.

When you drink carbonated beverages, the concern is that the gas from the carbonation will stretch out your pouch.  However, the pouch is NOT an isolated closed bit of stomach.  It has two openings, and if you have some gas it will pass one way or the other.  Nevertheless, for safety sake—if your surgeon says no carbonation—then do not drink carbonated beverages.

No matter what, DO NOT DRINK CARBONATED BEVERAGES for six weeks or longer after your RNY surgery unless instructed by your physician.


—Your cat isn’t the only one with a hair ball

Bezoars are the human equivalent of a hair ball.  After RNY gastric bypass surgery some indigestible items can accumulate in the stomach and form a small ball of material which can cause vomiting, a feeling of satiety, weight loss, nausea, and can lead to ulcers or an obstruction.

Bezoars can grow and grow and grow, and cause further problems. Small bezoars can pass spontaneously, or with the help of some medications, but most of the time a gastroenterologist will need to either put a scope down and pull them out or fracture them into smaller pieces.  Sometimes they are refractory to this therapy and need to be removed surgically.  If you develop a bezoar then you have a high likelihood of developing further bezoars.

Four types of bezoars

The four types of common bezoars are: phytobezoars, which are composed of vegetable material; trichobezoars which are composed of hair; pharmacobezoars, which are composed of medications; and lactobezoars, which are composed of baby formula or whey products.  For RNY gastric bypass patients, phytobezoars are the most common, followed by pharmacobezoars.  Occasionally a bypass patient will develop a lactobezoars, and these are usually patients who are taking whey protein supplements in very concentrated quantities.

Undigested vegetable matter is the most common culprit, which is why a number of surgeons ask their patients who have had RNY not to eat celery, prunes, raisons, beets, persimmons, pumpkins, and grape skins (I like grape skins in the form of wine—they make a Zinfandel a nice red color—unless you are like my dad, who prefers white zinfandel, which is made by leaving the grape skins out of the vat).  There are a few things that are very hard to digest early on – bananas, oranges, pineapples, and other pulp laden fruit.

A number of agents cause pharmacobezoars, the most common culprits are antacids, some fiber laxatives, Cholestyramine®, Sucralfate®, but there are a host of others.  Again—just because one pill is good for you doesn’t mean the whole bottle is better.

What happens to the lower stomach?

—Why your surgeon doesn’t want you to take Motrin

The lower stomach is still an active organ.  It continues to make gastric hormones, acid, enzymes, and mucous. It does not shrink up or go away. It can also develop ulcers.

The effect of aspirin, Motrin®, or a host of other drugs called non-steroidal anti-inflammatories (NSAID), is to break the barrier in the stomach.  This does not bother some people too much, but a fair number of individuals end up with some ulcers.  While having a pill sit on or in the stomach is irritating, the effect of the NSAID is not dependent on direct contact.  This is why a number of surgeons do not like their patients taking these pills (like aspirin, ibuprofen, Naprosyn®, Indomethacin®, and other drugs of this class).  If you develop an ulcer in the lower stomach, there is no easy way to have it treated or even diagnosed.

That lower stomach is physically separate from the upper pouch.  Normally if a patient develops ulcer symptoms, a gastroenterologist can look into the stomach with an endoscope and make the diagnosis of an ulcer.  If that ulcer is bleeding, the gastroenterologist can also treat the ulcer to stop it from bleeding by injecting a drug into it or putting some electric current on the ulcer to coagulate it.  These options are taken away once you have a RNY bypass.  There is no physical way to get to that ulcer. If these medications are important to you, you might wish to consider some other operation instead of the RNY bypass.

Transection vs. Stapling

—how do we separate the stomach?

One other debate among surgeons who do the RNY surgery is whether it is better to physically separate the upper pouch from the lower stomach, or if it is better to staple them off from one anther, but leave them attached.  Those who favor stapling, but leaving them together note that five percent of patients will break through the staple line, and it is a lot easier to have a patient who leaks into the lower stomach than a patient who leaks into the abdomen, which will make them very sick.  Those who transect the stomach into two separate parts state that there is no chance of this leak between upper and lower pouch and that the transected stomach has a lower incidence of leaking than a stapled stomach.

If your RNY surgery is to be done through a laparoscope, your stomach will be transected. If your surgery is done open it might be done through either one of these approaches.

Transected Roux-en-y gastric bypass vs stapled version

Vitamin supplements after the RNY

Appendix Two in the book “Weight Loss Surgery – A Lighter Look” contains more details about vitamins and the tests your doctor should order. I want to mention here, however, that patients who have the RNY are subject to iron, vitamin B12, and Folate deficiencies. For patients with a long limb RNY bypass, vitamins A, D, E, and K might need to be added (often drug stores have a pill with those four vitamins in them).

RecommendedDaily multivitamin Examples include: Flintstones, Centrum, Silver VistaCalcium Daily: Tums, CitracalFor menstruating women 350 mg a day of iron in either Ferrous Gluconate, Ferrous Sulfate, Chromagen Forte