What is ODS? Obstructive Defecation Syndrome, or ODS, is a very common condition in which there is difficulty in defecation because of certain changes in the pelvic region. ODS is more common in women, with over 60% of the ODS cases being observed in the female population. These numbers can be attributed majorly to pregnancy and childbirth. ODS is also observed to advance as age progresses, due to many other accompanying changes in the body.  In this part of the ODS series, let us look at how and why this uncomfortable condition comes about and how to identify it.  

  What is ODS type of constipation? 

• Constipation is a medical term for a condition wherein there are hard stools and you face difficulty in passing it. Accompanying symptoms are bloating, fullness, and pain when passing stools.  

• There are many types of constipation put into two main groups—primary constipation and secondary constipation.  

• Primary constipation generally happens because of some underlying disorder related to the functioning of the colon (intestine) or the rectum (part where the poop is pushed out from).  

• Secondary constipation is the well-known type, which is related to lifestyle factors like not enough hydration or fibre intake, sedentary activities, or due to the intake of some medications like iron supplements.  

• ODS is a sub-type of primary constipation class where there is a change or obstruction in the functioning of the muscles in the rectum either due to loss of function or some other physical change to their structure. 
  
  

 What causes ODS? 

The main cause which brings about ODS is any obstruction in the rectum or pelvic muscles which prevents them from pushing out the stools completely.  

Please put in side by side pictures of cross sectional view of normal pelvic region as picture A vs rectocele pelvic region as picture B at this location of the article.  

Observe the above pictures closely. 

In picture A, a cross-sectional view of a normal pelvic region is shown.  

-Here the colon (intestine) extends into the rectum (just above the anus), which in turn aligns straight to the anus.  

-The walls of the rectum and vagina are strong and straight, which in turn means passage of the stools through the rectum will also be a straight forward push.  

 In picture B, one of the common causes of ODS is shown.  

-This is called a rectocele (one of the different types of obstructions which cause ODS)—where the wall of the rectum extends or bulges into the vaginal space. 

-The walls of the rectum and vagina in this case also look stretched out and thin. 

-Due to the bulge of the rectal wall, there is a dent created in the passage.  

-The stool movement is different in this situation. Some volume of stools goes out when you use the toilet. But due to the pocket in the wall, and weak rectal muscle strength, not all of it goes out. 

-There is some stool volume which gets stuck in the dent/pocket of the rectal wall, which gets hardened over time, and also causes obstruction in the normal movement of stools.  

This process of difficult defecation is called obstructed defecation, and the condition is called obstructed defecation syndrome.  

 A side note about ODS causes: as explained in part 1 of this series, there are different ways these obstructions can manifest in ODS. 

While obstruction is understood commonly as something blocking the exit of stools, in ODS this obstruction can be in different forms.  

Functional obstructions can cause of a loss of muscle functioning, but the physical structures will be intact. If you have this type of ODS, you will hear terms like anismus, dyssynergic defecation, spastic colon and rectal hyposensation from your doctor.  

 Mechanical or physical obstructions involve changes to the muscle structures. If you have this, you will hear terms like rectocele, internal rectal prolapse, sigmoidocele, and descending perineum syndrome from your colorectal specialist. 
 

To understand how these physical and muscular changes happen in the first place, think of everyday life events which anyone goes through: 

• Pregnancy and Childbirth: The pelvic floor muscles holds all your organs in place. Pregnancy and pushing during a natural delivery can stretch and weaken their strength. Over time, the rectal wall bulges forward, directly causing a rectocele. 

• Chronic Straining and Heavy Lifting: Regularly straining on the toilet due to long-term constipation, or frequently lifting heavy weights at work or the gym can put repeated pressure on your pelvic region. This constant pressure can eventually cause the rectal tissue to sag inward, leading to an internal rectal prolapse. 

• Aging and Menopause: As women age, the body naturally loses muscle tone and elasticity. After menopause, a drop in estrogen further weakens the pelvic tissues, making the walls between the rectum and vagina thin out and become prone to pocketing. 

• Functional loss due to miscommunication: Due to stress, chronic pain, or bad bathroom habits (like rushing or squeezing too hard), the brain forgets how to coordinate the pelvic muscles. Instead of relaxing to pass stools, the muscles might be accidentally clamping shut, creating a functional obstruction. This is called anismus.  

 What foods trigger bowel obstruction? 

• It is natural to assume that foods which trigger constipation like ultra-processed or fried foods also trigger ODS or bowel obstruction. 

• This is just partly true. Foods without fiber do tend to make hard stools which settle down and make it harder for the weak muscles to push.  

• On the other hand, eating foods which create too much bulk also does not work. Bulky stools also require certain muscle strength to be pushed out, which is not there in rectal muscles of ODS patients.   

Keeping in mind the above two criteria, here are some food types which trigger ODS: 

• Insoluble Fiber: These foods do not dissolve in water. They add bulk to your stools, but in ODS, they can sometimes get stuck in rectal dents/pockets. Examples of these foods are: raw kale, broccoli stalks, cauliflower; lentils and kidney beans with tough outer skins; and large amounts of flaxseeds. 
• Pasty foods: These foods create a clay-like stool. Because they are high in starch, they tend to cling to the walls of a rectal pocket than move easily through it.  Examples are: Maida and pizza dough; snacks like Crackers, and thick pastries;  and overcooked white pasta. 
•  Low-Residue foods: These foods lack fiber completely or have compounds which physically slow down the bowel movement. Lack of fiber makes hard stools as these foods which produce very little waste volume. Examples are: Heavy cheeses like cheddar or processed cheese and large amounts of full-fat milk; eating lots of red meat; and  white rice and instant noodles. 

 Is surgery needed for ODS?

ODS like other disorders, progresses in stages. Stage 1 and Stage 2 are considered mild bowel obstructions. At these stages, there are a wide number of options for conservative and holistic treatments. Even if the ODS progresses beyond stage 2, medical advancements have created very minimally invasive surgeries such as the STARR procedure, which can rectify physical obstructions easily.  

The key is early diagnosis, which will allow anyone facing this to regain normal function without needing an operation. Ultimately, surgery is seen as a last resort, used only when structural changes significantly impact a person’s quality of life. 

Most of the time, when anyone faces repeated bouts of constipation, they naturally and for good reason, assume that it is because of dietary choices which make the stools hard and dry. While this is true, it is important to recognise that the causes for the long-term constipation are not just bad diet habits. That is where understanding ODS becomes a turning point. By identifying why you feel blocked,  you can stop the cycle of facing hard toilet times and take the appropriate, targeted steps toward your healing journey. In Part 3 of this series, we will dive into the specific symptoms of ODS and the modern diagnostic tools specialists use to provide a clear answer.