Lower gastrointestinal disease

Last updated date: 18-Oct-2022

Originally Written in English

Lower gastrointestinal disease

Lower gastrointestinal disease


The lower gastrointestinal (GI) tract begins in the center of the small intestine and extends all the way to the anus. Lower gastrointestinal (GI) illnesses and its symptoms account for a significant number of medical visits each year. Diverticular disease, polyps, irritable bowel syndrome (IBS), cancer, and Crohn's disease are all common disorders linked with the lower GI tract that typically need early clinical care by a gastroenterologist or a colorectal surgeon.


What is Lower gastrointestinal disease?

Lower gastrointestinal disease

The small intestine, large intestine (colon), rectum, and anus comprise the lower GI tract. The small intestine absorbs the majority of the nutrients from our meals; what remains in the small intestine is waste, which flows to the big intestine.

As waste materials pass through our colon, water is absorbed and the particles solidify, resulting in stool. The feces subsequently enters the lower colon, followed by the rectum and anal canal. It then exits the body as a bowel movement.

Symptoms of lower GI tract problems might include diarrhea, constipation, and hemorrhoids. These symptoms can be very painful and should not be overlooked since they may suggest a more serious underlying disease.


Anatomy and Vascular Supply

Anatomy and Vascular Supply

The gastrointestinal tract is made up of three germ layers that are physically split into segments based on arterial blood flow. The mouth cavity, esophagus, stomach, and first portion of the duodenum are all part of the foregut. The liver, biliary tree, and pancreas all develop from foregut buds. The midgut is made up of the remainder of the small intestine as well as the proximal colon up to the proximal transverse colon.

The residual colon, rectum, and upper section of the anal canal comprise the hindgut. The cecum, ascending colon, and proximal two-thirds of the transverse colon get blood flow from branches of the superior mesenteric artery. The colon's remaining section is fed by branches of the inferior mesenteric artery. The superior and middle rectal arteries supply the rectum, and branches of the inferior mesenteric and internal iliac arteries supply the anal canal. The inferior rectal artery supplies the remainder of the rectum.

Lower GI tract problems mostly affect the muscles of the colon, rectum, anus, and pelvic floor. To maintain fecal continence, the anal canal possesses two sphincters:

  1. The internal anal sphincter is just a continuation of the rectum's circular smooth muscle, 
  2. The external sphincter is a voluntary muscle made up of skeletal muscle fibers.

Hemorrhoids are dilated vascular channels in the anal canal that operate as vascular "pads" to assist maintain stool continence in combination with the anal sphincters. These can become engorged, resulting in anal irritation, rectal bleeding, and rectal discomfort.


Physiology of GI tract

Physiology of GI tract

The key functions of the lower GI tract include water absorption, stool lubricating and storage, and waste ejection. The colon receives around 2 L of fluid every day from the small bowel. The colon absorbs around 1.8 L of this, despite considerable electrochemical gradients. Sodium is the primary ion that directs water absorption.

In addition to water absorption, the colon aids in the digestion of components that tiny intestine and pancreatic enzymes cannot absorb. This is performed not by the colon itself, but by the many bacteria that live there. Nonstarch polysaccharides originating from plants, such as cellulose and hemicellulose, are resistant to the activities of small bowel and pancreatic enzymes and would not be digested without the presence of colonic bacteria.

These polysaccharides are converted by bacteria into short-chain fatty acids such as butyrate, propionate, and acetate. These chemicals are subsequently taken up by colonic epithelial cells via active and passive processes. In turn, fatty acid absorption improves salt and chloride absorption.

Colonic absorption of nutrients is limited in a healthy condition. In situations of mild intestinal malabsorption, however, the colon can "save" certain nutrients. The caloric value of short-chain fatty acids produced by intestinal bacterial breakdown is unknown. These products are absorbed by the colon with 90% efficiency. Chronic malabsorption causes adaptive changes in the gut flora, which enhances this process. Short-chain fatty acids can help people maintain a healthy calorie balance.

Here are some of the most common lower gastrointestinal (GI) tract:


Rectal bleeding

Rectal bleeding

Rectal hemorrhage, also known as hematochezia, is a common condition in the outpatient environment. It can indicate a pathology in the proximal lower gastrointestinal tract, but it can also indicate rectal disorders such as hemorrhoids, fissures, proctitis, and anorectal cancer. Unfortunately, it has been reported that less than half of patients experiencing rectal bleeding will seek medical attention.

Rectal hemorrhage appears as open crimson blood draining from the anus. Depending on the cause of the bleeding, the appearance might range from minor to severe. Mild instances may manifest as red blood marking the patient's feces or toilet paper after wiping, but severe cases may manifest as a big volume, rapid hemorrhage.

With any complaint of bleeding, a complete blood count (CBC) should be obtained to determine the severity and guide care. Other vital lab tests to acquire are the international normalized ratio (INR) and the partial thromboplastin time (PTT), which will aid in determining any bleeding tendencies. In situations of severe bleeding, a cross-match test may be required to store blood for transfusion and keep the hemoglobin level above 7gm/dL.

Endoscopies are the gold standard for evaluating rectal bleeding and should be done independently of other clinical symptoms in people over the age of 40. A rigid procto-sigmoidoscope or an anoscope can be used to look for a distant source of bleeding, such as internal hemorrhoids, proctitis, rectal ulcers, malignancies, or varices. If there is a suspicion of proximal lower GIT pathology, a colonoscopy should be performed.

If there is significant bleeding or the patient is too unstable to endure anesthesia for endoscopic intervention, CT angiography may be performed. When there is a high volume of blood in the gut, it may be difficult to pinpoint where the blood is coming from.


Management of Rectal bleeding

Acute, severe rectal bleeding necessitates an initial hemodynamic evaluation and, if necessary, the start of hemostatic resuscitation to regulate the patient's vital signs. In more severe situations, IV fluids or vasopressors may be used to achieve this. Rectal bleeding severe enough to jeopardize the hemodynamic system is uncommon and generally results from significant upper GI bleeding such as bleeding varices, a perforated ulcer, or an aortoenteric fistula, and may necessitate an upper GI endoscopy. Endoscopic cauterization, ligation, or direct injection to the bleeding site with either epinephrine or sclerosing agents can be used to control bleeding if the patient undergoes endoscopy.

Cauterization is the thermal ablation of the bleeding location with a unipolar or bipolar electrical cautery. Sclerosing chemicals are irritants to the tissue that produce vascular thrombosis and can thus be administered during hemostatic endoscopy. Ethanolamine oleate and sodium tetradecyl sulfate are the most widely utilized agents. If the patient has an angiography, arterial embolization may be conducted, especially if the bleeding arteries had already been cut, which makes them clearly visible in imaging. If the patient is hemodynamically stable, they can be examined and treated as an outpatient.


What is Irritable Bowel Syndrome (IBS)?

Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a long-term condition that affects the colon (large intestine). It interferes with the normal operation of the colon, causing discomfort and pain, changes in bowel habits (constipation or diarrhoea), gas, and bloating. Irritable bowel syndrome is not fatal since it does not cause chronic colon damage or major consequences such as cancer.

Irritable bowel syndrome has no known cause, although those who suffer from it frequently report one of the following symptoms:

  • Food passing through the bowel quickly and forcefully, leading to diarrhoea
  • Constipation is caused by food moving slowly through the colon.
  • Sensitive bowel muscles and nerves Excessive contraction of these muscles while eating might cause abdominal cramps (belly)


What are the symptoms of irritable bowel syndrome (IBS)?

Irritable bowel syndrome symptoms might vary widely between individuals. Your symptoms, which can range from moderate to severe, include:

  • Changes to your stools (small hard pellets or loose stools)
  • Changes to your bowel habits (diarrhoea or constipation)
  • Feeling that your bowel doesn’t empty completely
  • Finding mucus in the stools
  • Excess gas and bloating
  • Having pain or cramps in the abdomen

These symptoms are comparable to those of colon cancer, and you should consult your doctor about your situation. Irritable bowel syndrome symptoms include overall weariness, backache, headache, perspiration, nausea, vomiting, and pain while going to the bathroom.


How is irritable bowel syndrome (IBS) treated?

Irritable bowel syndrome has no known treatment. Treatment options include treating your symptoms and avoiding the risk factors that caused your irritable bowel syndrome to develop. Your doctor will recommend a treatment plan that is appropriate for you, which may involve a mix of the following:

  • Activities and medication to keep your stress in check
  • Dietary changes such as:
      • Avoiding alcohol, fatty foods, chocolate and caffeinated drinks
      • Increasing or reducing your intake of fibre, depending on your condition
      • Eating small meals
      • Medication to help alleviate your constipation, diarrhea, or abdominal pain and cramps




Constipation occurs when bowel motions are difficult to evacuate or occur less often than normal. Stool can move too slowly through the digestive tract due to a lack of fiber, dehydration, or certain medications. As a result, the stool becomes hard and dry. Constipation becomes chronic when symptoms linger for many weeks.

Constipation treatment includes gradually increasing fiber in the diet, drinking more water, staying active, and going to the toilet whenever you feel the urge.




Diarrhea is a typical ailment that everyone encounters at some time in their lives. It is the second most prevalent GI symptom that initiates an outpatient clinic visit, behind abdominal discomfort. The majority of diarrhea bouts are brief and self-limiting. However, diarrhea can be fatal at times, especially in immunocompromised people, the elderly, or those with several comorbidities. The majority of acute diarrheal diseases are infectious. Symptoms that linger more than 4 weeks are indicative of subacute to chronic diarrhea, and alternative diagnosis should be investigated. Chronic diarrhea can cause malabsorption, dehydration, and weight loss in the long run.

Diarrhea, like constipation, can be described in various ways by patients depending on their personal perceptions of typical bowel habits. The typical medical definition of diarrhea is three or more bowel motions per day with stool weight more than 200 g. Patients who eat a high-fiber diet can change this.

Diarrhea is categorized into several types, including acute vs chronic, osmotic versus secretory, and watery versus inflammatory. As one might anticipate, not all problems fall cleanly into one group or another, although these broad classifications might give diagnostic hints about the underlying cause. In most cases, infectious pathogens produce acute diarrhea. This form of diarrhea normally disappears on its own or is easily treated with antibiotic medication when necessary. Diarrhea that lasts more than 4 weeks implies a noninfectious cause, such as an underlying inflammatory illness or a side effect of medicine.


Colon polyps

Colon polyps

Colon polyps are quite prevalent, affecting up to 50% of all people! A colon polyp is a tiny mass that grows in the colon lining. Most colon polyps do not cause symptoms, however some patients may have discomfort, rectal bleeding, changes in stool color, and bowel changes.

Though most colon polyps are benign, some might progress to colon cancer. In the United States, colon cancer is the third most frequent kind of cancer. Fortunately, colon cancer may be avoided with frequent colon cancer screenings, often known as colonoscopies.

Laparoscopic surgery, removal of the colon or rectum, and colonoscopies are all options for treating colon polyps. A gastroenterologist examines the walls of the large intestine with a colonoscope, which is a long, flexible tube equipped with a camera and a light. If polyps are discovered during the colonoscopy, the gastroenterologist can remove them. As a result, colonoscopies are the only cancer screening procedure that both prevents and detects cancer. Colonoscopies are advised for those over the age of 45.


Diverticular Disease

Diverticular Disease

Diverticular disease is a group of conditions that include diverticulosis, diverticulitis, and diverticular bleeding.

  • Diverticulosis is the development of diverticula (small pockets that form in the wall of the bowel). Diverticula can occur as a result of increasing strain on vulnerable areas of the intestinal wall. Diverticulosis is usually asymptomatic.
  • Diverticulitis is caused by an infection or inflammation of one or more diverticulum. This is most commonly caused by waste that clogs the diverticula, allowing bacteria to proliferate and get infected. Cramping, especially in the lower left abdomen; discomfort, nausea, and vomiting; fever and chills; constipation; and diarrhea are all indications of diverticulosis.
  • Diverticular bleeding occurs when a tiny artery in a diverticulum ruptures, resulting in rectum bleeding. This might cause maroon or bright crimson blood to appear during bowel movements. Diverticular bleeding is rarely painful.

Treatment of diverticular disease depends on the severity of symptoms.

  • Treatment for mild symptoms includes antibiotics and a clear liquid diet. 
  • Treatment for severe symptoms may include hospital care, intravenous antibiotics, and fluids, or abscess draining. In some cases, surgery may be needed.


Ulcerative Colitis

Ulcerative Colitis

Ulcerative colitis, one of several kinds of colitis, is a chronic inflammatory bowel disease (IBD) that produces inflammation and ulcers in the large intestine. The etiology of ulcerative colitis is uncertain, although evidence suggests that genetics, the environment, and an overactive immune system all have a role. Diarrhea, stomach discomfort or cramping, rectal pain and bleeding, constipation, fever, dehydration, and weight loss are all symptoms of ulcerative colitis.


What is Crohn's disease?

Crohn's disease

Crohn's disease is an inflammatory illness that affects the small and large intestines over time.

Crohn's disease causes digestive tract inflammation, which can cause stomach discomfort, severe diarrhea, exhaustion, weight loss, and malnutrition. The inflammation can affect many sections of the digestive tract and frequently extends deep into the layers of impacted colon tissues. The condition can be excruciatingly painful and incapacitating, and it can lead to significant consequences.

A mix of treatment choices can help you keep your condition under control and live a full and meaningful life. Remember that there is no one-size-fits-all therapy for all patients. Each patient's condition is unique, and treatment must be tailored to their specific needs. Treatment for Crohn's disease and other IBD types may involve medication, dietary and nutritional changes, and, in rare cases, surgical treatments to repair or remove diseased sections of your GI tract.


Rectal Cancer

Rectal Cancer

Rectal cancer is frequently discussed alongside colon cancer, but deserves special attention due to a few epidemiologic differences and treatment considerations. Rectal cancer has a greater recurrence rate following resection than colon cancer. In general, patients with stage II and stage III illness are provided neoadjuvant chemoradiation since it has been demonstrated to reduce local recurrence rates.

The extent of tumor invasion and involvement of neighboring lymph nodes influence treatment options. Rectal endoscopic ultrasonography or magnetic resonance imaging (MRI) can be used to assess these parameters. Complications are lower with preoperative radiation and chemotherapy for locally advanced nonmetastatic cancer.

The surgical excision of rectal lesions is determined by the tumor's location. A surgery known as low anterior resection can be performed in the upper rectum and rectosigmoid area. The distal sigmoid, rectum, and anus are removed, and a permanent sigmoid colostomy is created. Patients who have had radiation therapy prior to or after surgical resection with colo-anal or recto-anal anastomosis are at risk of long-term problems such as chronic radiation proctitis with rectal bleeding, anastomotic strictures, and fecal incontinence.


Anal Fistulas

Anal Fistulas

Anal fistulas are abnormal tiny channels or connections that form between the rectum and the surrounding skin. Patients may experience soreness, redness, or edema around the anus.

Anal fistulas are frequently caused by an acute infection of an anal gland, which is positioned inside the anus opening. An abscess forms as a result of the infection, which eventually develops into a fistula going to the outer skin. Surgery, Crohn's disease, or radiation therapy can potentially create anal fistulas.


Diagnosis of Anal Fistulas

Fistulas must be carefully evaluated to establish their precise position within the anus. CADC physicians typically utilize an anoscope – a tiny tool used to inspect the anal canal – to accomplish this. The checkup is sometimes conducted in the operation room. A colonoscopy or sigmoidoscopy may be performed by the doctor to rule out Crohn's disease or ulcerative colitis.


Fecal Incontinence 

Fecal Incontinence 

The inability to regulate bowel motions is defined by fecal incontinence (bowel incontinence). More than 5.5 million Americans suffer with fecal incontinence, which affects both adults (particularly women and the elderly) and children. It can be caused by a variety of factors, including:

  • An abscess or inflammation in the rectum or anal area
  • Damage to the anal sphincter muscles or pelvic floor muscles from complications of childbirth
  • Nerve damage from childbirth neurologic disorders
  • Complications of a previous operation
  • Damage to nerves that control the anal sphincters resulting from a stroke, diabetes, or multiple sclerosis
  • Hemorrhoid surgery
  • Chronic constipation or diarrhea
  • Radiation treatment and rectal surgery, causing a loss of storage capacity in the rectum


Diagnosis of Fecal Incontinence

To diagnose fecal incontinence, CADC physicians conduct a number of tests, including:

  • Anal manometry, which measures the strength of the anal sphincter muscles and their ability to respond to signals.
  • An MRI and/or an anorectal ultrasound may also be done to visualize the structure of the sphincter.
  • Proctography (also known as defacography) demonstrates how much excrement the rectum can keep, how well it holds it, and how well it empties.
  • Proctosigmoidoscopy allows the doctor to see within the rectum and lower colon to look for illness or other issues that may be causing fecal incontinence, such as inflammation, scar tissue, or tumors.
  • Anal electromyography, which utilizes small needles to evaluate nerve damage, may also be performed to look for nerve damage caused by delivery injury.


Treatment for Fecal Incontinence

Treatment for bowel incontinence may involve medication, dietary modifications, biofeedback, or surgery, depending on the origin and severity of the issue. To treat fecal incontinence, many therapies or procedures are frequently performed.

Surgeons use the patient's tissue or a device to heal sphincter mechanism injuries or to restrict the sphincter. When compared to standard open surgical approaches, minimally invasive surgery may be performed for individuals with rectal prolapse, in which the walls of the rectum protrude through the anus, resulting in less postoperative discomfort, less medication, and faster recovery.


Colon Cancer Screenings

Colon cancer is one of the most preventable kinds of cancer if you have frequent testing for it. A colonoscopy on a regular basis can detect polyps (growths) in your large intestine. Because nearly all colon cancers begin as polyps, this sort of screening is quite efficient at eliminating questionable tissue before cancer develops. It is also critical to undergo frequent colonoscopies because colon cancer seldom causes symptoms. When symptoms do occur, it may indicate that the cancer has already progressed sufficiently.



Lower gastrointestinal symptoms (LGS) are a typical reason for a referral to gastroenterology. Diverticular disease, polyps, irritable bowel syndrome (IBS), cancer, and Crohn's disease are all common disorders linked with the lower GI tract that typically need early clinical care by a gastroenterologist or a colorectal surgeon.