Constipation After Weight Loss Surgery

Constipation After Weight Loss Surgery: Causes and Treatments

March 16, 2018

Constipation is a very common symptom in the general population, we have ALL suffered from it at some point in our lives. It usually resolves with minimal intervention. Even though a minority of people seek medical attention, it continues to account for about 8 million physician visits a year. Symptoms vary individually, however, most of the people complain of infrequent bowel movements (less than three times per week) and difficult or unsatisfactory defecation.

Generally speaking, medications are the main culprits in causing constipation, especially opioid analgesics. Other drugs used for hypertension, allergies, bloating (medications like Gas-X may help with the bloating sensation but it will do so by slowing your bowels), and heartburn may also lead to constipation. Furthermore, neurological diseases and metabolic disturbances which may lead to constipation. As one can see, the potential causes for constipation are diverse and careful workup is needed.

Chronic constipation is thought to be caused by neurophysiological dysfunction of the colon and/or the ano-rectum muscle complex, which is involved in coordinating defecation.

One very worrying sign, for which you MUST seek immediate medical attention, is an unprovoked and rapid constipation. Especially if it is associated with other symptoms such as bleeding, change in stool caliber, or weight loss especially if there is a family history of gastrointestinal cancers.

In such cases, a thorough workup for colorectal cancer needs to be done before addressing the constipation symptoms.

Bariatric Surgery and Bowel Habit Changes

Any manipulation of the gastrointestinal tract will lead to anatomical and physiological changes. The gastrointestinal tract is a very dynamic system and organs are in constant communication with each other and with other systems. The brain also plays a key role in the entire equilibrium as I explain in my previous article.

The nature of this change is determined by the type of surgery which is performed (i.e. vertical sleeve gastrectomy, roux-en-Y gastric bypass, biliopancreatic diversion with duodenal switch BPD/DS, etc), each procedure has a different effect because the anatomical and metabolic changes are different.

Generally, ‘malabsorbtive procedures’ such as the roux-en-y gastric bypass and the BPD/DS lead to loose bowel movements and even diarrhea initially. Patients also complain of foul smelling gas and stools. Whereas, the sleeve gastrectomy (VSG) leads to constipation. Given that the VSG is the commonest procedure performed, we will focus on constipation, since this is becoming a very common complaint post weight loss surgery.

Causes of Constipation After Weight Loss Surgery

Constipation is very common in the first 1-6 months post bariatric surgery, and it’s not unusual for it to recur intermittently later on. There are multiple factors that contribute to constipation in the immediate and short-term post-procedure.

Anesthetic agents and analgesics are the main culprits in the short-term. Also, most surgeons will have the patient start a low carbohydrate and high protein diet, many patients struggle with consuming enough fiber to match the amount of fiber, which they used to get from carbohydrate containing meals (i.e bread, pasta, rice, etc). They also are not able to consume enough water, thus leaving them dehydrated prior to their surgery.

During the post-operative period, dehydration is usually exacerbated, leading to dry hard stools and constipation. When there is a lack of fluid intake, the colon will attempt to absorb as much fluid as possible from your food to replenish your low fluid status.

Consequently, your stool will become very dry, making it very difficult to move through the colon. This will lead to bloating, crampy abdominal pain excessive straining and pain on defecation due to lack of lubrication. If you suffer from hemorrhoids, or even if you never had them, you may develop them if your constipation is severe and/or prolonged.

Treatment Modalities for Constipation Post-Bariatric Surgery

After ruling out potential complications of surgery and other significant pathology. The mainstay of treatment is increasing fiber and water for a successful long-term resolution of symptoms. However, initially, you may need medications to help regulate your bowel movements.

There are four broad classes of laxatives and they are usually used in a step-up fashion or in combination for more persistent cases.

Classes of Laxatives

The first are bulk-forming laxatives. This includes psyllium (Metamucil, Perdiem), methylcellulose (Citrucel), calcium polycarbophil (Fiber-Lax, Fibercon), and dextrin (Benefiber). You must consume a large quantity of water with bulk-forming laxatives to facilitate their transit through the bowel. They can help with crampy gas pain.

Hyperosmolar and saline laxatives work through a similar mechanism, but the later is more effective. Examples of hyperosmolar laxatives include; polyethylene glycol (Miralax, Glycolax), Lactulose (Generalac, Enulose) and sorbitol. All of these are fairly effective but they can cause bloating and gas pain.

Saline laxatives include magnesium citrate and magnesium hydroxide (Milk of Magnesium). You have to be careful with either of these laxatives if you have renal insufficiency. However, you shouldn’t be taking them more than twice a week under any circumstance without consulting with your physician.

Stimulant laxatives are used either on their own or in combination with the other forms of laxatives to improve their efficacy. These include senna (Senokot, Ex-Lax) and bisacodyl (Dulcolax).

There are new classes of laxatives which are only available in prescription form. These are lubiprostone (Amitiza) and linaclutide (Linzess), they are used in a very specific group of the patient population with specific symptoms.

How I Usually Address Constipation in My Bariatric Patients

Usually, I try to educate the patients about good toilet habits. These include the following:

  • If you get an urge to move your bowels then MAKE time to use the toilet, delaying and withholding this urge will cause hardening of the stools and disruption of the natural defecation reflex.
  • If you are having a bowel movement at a certain time of the day or after a certain meal, then make sure you MAKE TIME for it to happen.
  • When you are sitting on the toilet, you should focus on moving your bowels!
  • Reading, looking at your emails, playing with your phone, trying to do work while sitting on the toilet is an ABSOLUTELY TERRIBLE HABIT! If you suffer from this you have to QUIT now.
  • Once you are done with your business, get off the basin and leave (after washing your hands, of course!)

If the above instructions fail, then I start with increasing the fluid intake and ask my patients to record the exact amount they are drinking (it must be more than 64 ounces of fluid), they are started on one tablespoon of Metamucil every morning. In the meantime, I have them follow-up with our bariatric dietician to review their diet and make sure they are consuming enough fibers in their diet.

I usually do not like to prescribe tablets in the immediate post-procedure period. Thus, I tend to rely on laxatives in liquid forms and enemas. A second agent which I add is lactulose/polyethelyne glycol/or sorbitol, a combination of these laxatives usually works very well in regulating bowel movement.

Occasionally there are hard stools in the rectum and despite straining, the patient finds it very difficult to have a satisfactory bowel movement. In these instances, I will add an emollient suppository such as a mineral oil/fleet enema. This will increase the amount of water in the rectum and make the stool softer as well as provide lubrication for an easier defecation.

These agents are then decreased over time and stopped. You may have to take them occasionally but, I strongly advise against taking them on a routine basis for more than 2-4 weeks. If your constipation persists then you will need a further workup to rule out other significant pathology such as malignancy or narrowing of your colon/rectum.


Dr. Husain Abbas of Memorial Advanced Surgery, is a Board Certified surgeon trained in Minimally Invasive Surgery. After his surgical residency at St. Mary's, a Yale University affiliated hospital, Dr. Abbas completed a fellowship in Minimally Invasive Gastroesophageal & Bariatric Surgery at the University of Florida, Gainesville. Dr. Abbas' expertise extends to a wide array of gastroesophageal disorders, anti-reflux surgery, complex hernia repairs, endocrine, oncology and bariatric procedures.

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