Rectum - Its Role, Conditions and Disorders
Know your Body

Rectum: Its Role and Conditions

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 12 Jun 2014 - 10:57.

The human rectum begins where the pelvic part of the large intestine ends. The rectum is a muscular tube about 5" (12.7 cm) long that connects the large intestine (colon) to the anus. The anus begins where the rectum ends. The anal sphincter is a ring of muscle at the opening of the anus. The sphincter keeps the anus closed until a stool needs to be passed.

The rectum and anus are almost an integral part of the lower end of the large intestines. While stool material collects in the rectum and causes pressure on the walls of the rectum, the resulting pressure causes the anal sphincter to relax allowing the stool to pass out of the body through the anus. In other words the rectum and anus have a synergistic action in the mechanism of defecation.  A muscular ring (anal sphincter) keeps the anus closed. This sphincter is controlled subconsciously by the autonomic nervous system (This system connects the brain stem and spinal cord with internal organs and regulates internal body processes that require no conscious effort).  

The rectal lining red tissue contains mucus glands similar to theintestinal lining. The rectal lining tissue is relatively insensitive to pain. However, the nerves from the anus and the external skin around it is very sensitive to pain.

The rectum is very elastic and has a dual action. First it receives the entire residue from the large intestines and stores it. The moment it is full it causes pressure on its walls opening up the anus for the smooth passage of stool to the exterior. This action is controlled by the rich supply of sensory nerves surrounding the rectum which detect the filling of the rectum with food residues.

This sensation that the rectum is almost full and cannot hold any more, enables us to consciously or unconsciously squeeze the external anal sphincter to prevent involuntary passage until we reach a toilet. There is a limit to squeeze and hold the imminent act of defecation.

Any delay beyond the limits might result in involuntary passage of stools before we reach a toilet. These sphincter muscles also aid in the process of relaxation allowing the smooth passage of stools. Any deviation in the mechanism of holding the stool material leads to involuntary passage of fecal material. This is called as Fecal Incontinence.

Conditions of the Rectum: Normally physiological incontinence occurs in young children who for unknown reasons keep passing stools in their clothes while in bed or sometimes during attending classes or playing in the playgrounds. If this continues beyond 4 to 5 years we should worry about fecal incontinence as the cause.

The most common causes for fecal incontinence are:

  • Weakness of the anal sphincter and its muscles which normally allow us to voluntarily hold back a bowel movement.
  • Loss of sensation that the rectum is full so much so that we cannot even judge when to squeeze the sphincter muscles.
  • If there is constipation the rectum fills up and overflows.
  • When the rectum is stiff the fecal material is forced through so quickly that there is no time to prevent incontinence by squeezing the sphincter muscles.
  • Diarrhea when severe, leads to fecal incontinence.

There are two ways when the sphincter muscles can get weaker. One reason is injuries to the muscles of the pelvic floor. The other reason could be some injury to the nerves supplying these muscles. Delivering a baby in case of females could be the most common cause for the muscles of the pelvic floor becoming weaker and also sustain injury to the nerves. Diseases like Spina bifida and Myasthenia gravis can affect the nerves supplying these muscles. Ulcerative colitis, is where the lining of the intestines and the rectum get inflamed invariably lead to a stiff rectum. Constipation with overflow incontinence is a very common cause of fecal incontinence in children.

Common investigation to detect the cause for fecal incontinence includes rectal manometry study where a tube is passed inside the rectum, the end of which is attached to a balloon. The tube has sensors to measure the pressure in the areas of the sphincter muscles. It also provides information about the rectal sensation and stiffness of the rectal walls including the strength of the sphincter.muscles. Electromyographic test can determine whether there is any damage to the nerves supplying the anal sphincters. An ultrasound study of the rectum can detect the presence of any tears in the sphincter muscles.

Congenital Disorder: There is one common birth defect in the new born which affect the rectum. This disorder called Hirschsprung's disease is a serious condition warranting urgent surgical intervention. The main cause of this disease is congenital absence of innervations of the walls of the intestines and the rectum. If this happens at the level of the rectum, prognosis is very encouraging because the portion of the rectum which has no nerve supply can be resected and the upper end pulled down and stitched at the anal orifice. There are cases on record when infants were required to be operated in the first week of birth itself to save the child from burst abdomen and death.

Another congenital disorder of the rectum is closure of the anal opening after birth. This condition is called Imperforate Anus when the child is born with a closed anus leading to inability to pass even the meconium. The condition needs immediate surgical intervention when the surgeon creates the anus for easy passage of stools. Failure to act immediately may lead to intestinal obstruction and resultant complications including burst abdomen.

Rectal Pain

Some of the common reasons for rectal pain include constipation, diarrhea, or anal itching and scratching. If the rectal pain is caused by these conditions it usually goes away when the problem is solved.

Some other common causes of rectal pain may be due to:

  • Enlargement of rectum, or hemorrhoids
  • Infections of the prostate or STI (Sexually transmitted infection), pilonidal cyst or abcess.
  • Anal fistula and fissures or rectal prolapse.
  • Anal intercourse or anal injury.
  • Liver Cirrhosis, Diabetes, ulcerative colitis or lymphoma.
  • Rectum or prostate cancers.
  • A surgery or radiation therapy to the rectum or pelvis.
  • Rectal spasms
  • Perianal Abscess
  • Pilonidal Disease
  • Proctitis

Cancer Rectum: The worst and most dreaded condition affecting the rectum is Cancer Rectum. It occurs in both men and women and is commonly found amongst people over the age of 50 though it can occur in the younger age group as well. It can also occur during teen age though this is most uncommon. High fat with excess calories and low fiber content in the diet is implicated as a cause for cancer rectum. Therefore, cancer rectum can be prevented by taking low fat and low calorie diet with more fiber contents in the food. When present surgical removal of the affected rectum plus chemotherapy and radiation are the only chances for improving survival rates.

Anal cancer may be caused by certain sexually transmitted diseases. It develops in the area immediately around the anus, or in the area where the rectum transitions into the anus. Typical symptoms of anal cancer may include pain, bowel movements associated with bleeding and itching around the anus. To confirm diagnosis a manual examination and biopsy may be performed. The treatment normally involves a surgery with a combination of radiation and chemotherapy or surgery with radiation therapy.

Anal fissures : Prolonged constipation or  injury caused from a hard or large bowel movement may cause anal fissures. It may also be caused by frequent loose bowel movements. Sometimes they may be caused by anal sex. A doctor’s evaluation can help diagnosis. The doctor may prescribe stool softeners or psyllium, to prevent injury from hard bowels, protective zinc oxide ointments to soften stools. At times sitz bath is also recommended where the anus is soaked in warm water for 10 or 15 minutes after defecating so that it helps blood circulation and heals the anus.

Hemorrhoids: One of the commonest conditions affecting the rectum is hemorrhoids or what we call piles. A person loses lot of blood unless hemorrhoids are dealt with through surgical procedures. Even after surgery it is necessary for the person to avoid spicy food.

Other common conditions affecting the rectum include fissure in ano, Ischirectal Abscess, Fistula in ano (complete or incomplete) and constipation.

Prolapse Rectum is yet another common condition affecting the rectum. In this condition two things play an important role namely weak muscles and sphincter and a concomitant constipation leading to "coming out of the rectum" through the anal opening. The victim can push it back inside only to find it coming out during a severe bout of cough or strain. If neglected it might lead to thrombosis of the rectum and other complications.

Polyps arise as abnormal growth from the lining of the large intestine (colon or rectum) and protrude into the intestinal canal (lumen). Polyps are of two types: some flat and others have a stalk.

About 20 percent of the adult population is affected by Polyps, a common condition of the rectum and colon. Polyps may be benign most often but certain polyps could be cancerous too.

Polyps are more common in the left colon, sigmoid colon, or rectum. Most polyps are asymptomatic and are often found incidentally during an endoscopy or x-ray of the bowel. Some polyps can cause bleeding, discharge of mucus, alteration in bowel function and occasionally abdomen pain too.

Perianal Abcess:The anal region consists of tiny glands which open on the inside of the anus to aid the passage of stools. If any of these glands get blocked, it can lead to an infection. The infection can lead to a pocket of pus formation called abscess. Under local anesthesia the pus is drained out and treated.

Proctitis : This is inflammation of the rectum which is becoming common of late. It is caused due to various reasons like infection, ulcerative colitis, STD, radiation therapy etc. Depending on the cause of the inflammation Proctitis is painful or painless. The doctor can diagnose on examination and provide appropriate treatment. If caused by infection it can be treated by antibiotics.Sometimes proctitis is also caused by impaired  immunity by sexually transmitted diseases like herpes simplex virus.

*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.