Dr. Mohammad Masoud Andalib is a laparoscopic and laser surgeon specializing in gastrointestinal diseases and cancers. He provides advanced medical and surgical care in the following areas:
Hemorrhoids occur when the hemorrhoidal cushions in the anal canal become enlarged or prolapsed, leading to bleeding, pain, or a sensation of a lump. Under normal conditions, these cushions help keep the anal opening closed, but when their shape or position changes, symptoms can develop.
Hemorrhoids are very common and become even more frequent with age and during pregnancy. Contributing factors include constipation and straining during bowel movements, prolonged sitting, obesity, pregnancy, chronic coughing, and medical conditions that increase venous pressure, such as liver failure.
An anal fissure is a tear or longitudinal crack in the delicate skin lining the anal canal, causing sharp pain and bright red bleeding during bowel movements. It may be acute (short-term) or chronic (lasting more than 6–8 weeks, often with indurated edges or a skin tag).
Anal fissures are most common in adults aged 20 to 45, and 70–90% of cases occur in the posterior midline. In women—especially after childbirth—anterior fissures are more likely.
Fissures that occur off the midline, are multiple, or fail to heal with standard treatment may indicate an underlying condition and require further evaluation.
An anal fistula is an abnormal tract connecting the inside of the anal canal to the skin around the anus, most commonly developing after an abscess. It typically presents with purulent discharge, pain, or skin irritation. The goal of treatment is to close the tract while preserving sphincter function.
Anal fistulas occur most often in middle-aged adults and are slightly more common in men. The most common underlying factor is a history of perianal abscess. Conditions such as Crohn’s disease, uncontrolled diabetes, prior surgeries or trauma, pelvic radiotherapy, and immunocompromised states (such as HIV) increase the risk of fistula formation or complications.
In Crohn’s disease, fistulas tend to be more complex and resistant to treatment, often requiring combined medical therapy and staged surgical management.
A perianal or anorectal abscess is a localized collection of pus that forms near the anus or within the anal canal due to infection of the anal glands. It typically presents with severe, constant pain, swelling, redness, and warmth around the anal area, and may be accompanied by fever or malaise.
Abscesses are classified based on their location—perianal, ischiorectal, intersphincteric, or supralevator—with perianal abscesses being the most common type. They usually develop when the small glands inside the anal canal become blocked and infected.
Risk factors include Crohn’s disease, diabetes, immunosuppression (such as HIV or corticosteroid use), previous anorectal infections, and trauma or procedures in the anorectal region.
Early diagnosis and surgical drainage are essential, as delayed treatment can lead to complications. A significant number of patients—up to 30–50%—may develop an anal fistula after an abscess, requiring further evaluation and management.
Rectal prolapse is the abnormal protrusion of part of the rectum through the anal canal. The prolapse may involve only the mucosal layer or the full thickness of the rectal wall, and in some cases presents as internal intussusception where the tissue folds into itself without visibly exiting the anus.
Rectal prolapse may begin intermittently but can gradually progress to a persistent condition that significantly affects quality of life. It is more common in women, especially middle-aged and elderly individuals. The two main high-risk groups are young children and adults over 50 years of age, particularly women with multiple or complicated childbirths.
Contributing factors include neurological disorders affecting the pelvic floor, connective tissue abnormalities, a history of pelvic or anorectal surgery, and long-standing constipation. However, the presence of these factors does not necessarily mean that prolapse will occur.
Anal warts are skin or mucosal growths in the genital and perianal region, most commonly caused by infection with the human papillomavirus (HPV). The lesions may appear as single or multiple growths, either small and cauliflower-like or flat and smooth. Their appearance, associated pain, and treatment vary depending on their location—whether on the external skin or the mucosal lining inside the anal canal.
Genital HPV warts are very common, and anyone who is sexually active may be exposed to HPV. The peak incidence occurs in young adults at the beginning of their sexual activity. The risk of infection increases in individuals with multiple sexual partners, early initiation of sexual intercourse, or a weakened immune system.
A colon polyp is a growth on the lining of the large intestine that is often asymptomatic and typically detected during colonoscopy. Some polyps can become cancerous over the course of several years; therefore, identifying and removing polyps is the most important strategy for preventing colorectal cancer.
The risk of developing polyps increases with age, a family history of colorectal cancer or polyps, certain genetic syndromes, unhealthy lifestyle habits (such as a low-fiber, high-fat diet, obesity, smoking, and alcohol consumption), and long-standing inflammatory bowel disease.
Crohn’s disease is a chronic inflammatory condition of the gastrointestinal tract that can affect any part from the mouth to the anus, but it most commonly involves the small intestine and the colon. The inflammation typically occurs in a patchy pattern and extends through all layers of the bowel wall, which can lead to deep ulcers, strictures, and fistula formation.
The disease usually begins between the ages of 20 and 35, although it can occur at any age, and its prevalence is nearly equal in men and women. The rising incidence in recent years—especially in countries that previously had low rates—highlights the important role of environmental and lifestyle factors.
Ulcerative colitis is a chronic inflammatory condition of the large intestine that affects only the superficial mucosal layer. It typically begins in the rectum and extends continuously through the colon. Unlike Crohn’s disease, it is limited to the colon and does not involve the full thickness of the bowel wall.
The disease most commonly appears between the ages of 20 and 40, although it can occur at any age, and its prevalence is nearly equal among men and women. In recent decades, the incidence has increased in some countries, likely due to environmental and lifestyle factors.
Diverticulosis refers to the presence of multiple small pouches that protrude from the wall of the colon. When these pouches become inflamed or infected, the condition is called diverticulitis.
The prevalence of diverticulosis increases with age and affects a large portion of the population after the age of 60. Historically, the pattern of colonic involvement varied among populations—for example, the sigmoid colon was more commonly affected in Western countries, whereas right-sided involvement was more frequent in some Asian populations. However, these differences have decreased with lifestyle changes.
Diet, physical activity, and obesity are major factors influencing the development of the condition.
Cecal cancer is a malignant tumor that originates from the cells of the cecum—the initial segment of the large intestine located in the lower right abdomen where the ileum connects to the colon. The tumor may invade deeper layers of the bowel wall, spread to adjacent tissues, or metastasize to distant organs through the blood and lymphatic system.
Cecal cancer accounts for approximately 10–15% of all colorectal cancer cases, is more common in older adults, and is often diagnosed due to iron-deficiency anemia or occult gastrointestinal bleeding.
Colorectal cancer has more than 1.9 million new cases annually worldwide, and in Iran it represents about 9–10% of all cancers, making it one of the most common malignancies. The proportion of cecal cancer in Iran generally aligns with global patterns.
Ascending colon cancer is a malignant growth of cells in the ascending colon, the portion of the large intestine located on the lower right side of the abdomen, extending upward from the cecum. The cancer typically begins in the mucosal lining and may invade deeper layers of the bowel wall, nearby lymph nodes, or metastasize to the liver and lungs through the bloodstream.
This type of cancer accounts for approximately 20% of all colorectal cancer cases. It often produces late or subtle symptoms, which means many patients are diagnosed at more advanced stages.
Globally, its incidence is increasing with aging populations and the adoption of Western lifestyle factors. In Iran as well, according to national cancer registry data, the rate has been rising—particularly in urban areas—and is believed to be associated with dietary changes and reduced physical activity.
Transverse colon cancer is a malignant growth of cells in the horizontal, central portion of the large intestine, which extends from right to left across the upper abdomen. The cancer typically originates in the mucosal lining and may invade deeper layers of the colon wall, spread to regional lymph nodes, or metastasize to distant organs.
It accounts for about 10% of all colorectal cancers and is less common than right-sided colon cancer or sigmoid colon cancer. However, due to its vague symptoms—such as diffuse abdominal pain or mild changes in bowel habits—it is often diagnosed at a later stage.
Globally, its share has remained relatively stable, while in recent years a slight increase has been reported in Iran, although it still remains less common than cancers arising in other parts of the colon.
Descending colon cancer is a malignant tumor that arises from the inner mucosal lining of the descending colon—the segment of the large intestine located on the left side of the abdomen. In its early stages, the tumor may grow silently without causing pain or noticeable symptoms, which is why many cases remain undetected until the disease progresses.
As the cancer enlarges, it can invade deeper layers of the bowel wall and eventually spread to nearby lymph nodes. If left untreated, cancer cells may enter the bloodstream and metastasize to distant organs, most commonly the liver and lungs.
Symptoms often appear gradually and may include left-sided abdominal pain, changes in bowel habits (such as constipation or narrowing of stool), visible or occult blood in the stool, unexplained weight loss, and anemia
Sigmoid colon cancer is a malignant tumor that originates from the mucosal lining of the sigmoid colon—the section of the large intestine located near the rectum. The tumor may spread into deeper layers of the bowel wall, extend to regional lymph nodes, or metastasize to distant organs such as the liver or lungs through the bloodstream or lymphatic system.
This type of cancer accounts for approximately 25–30% of all colorectal cancer cases. Due to its proximity to the rectum, it is often diagnosed earlier, typically presenting with symptoms such as bleeding, changes in bowel habits, or a sensation of incomplete evacuation.
Globally and in Iran, the sigmoid colon is one of the most common sites of colorectal cancer involvement. Notably, the average age of affected patients in Iran is reported to be younger compared to Western countries.
The rectum is the final segment of the large intestine, located approximately 10 to 15 centimeters above the anus. Rectal cancer refers to the malignant growth of cells in this region. Because of its position within the pelvis and its proximity to nerves, the bladder, and reproductive organs, treatment is often more complex and typically involves a combination of surgery, chemotherapy, and radiotherapy.
Rectal cancer accounts for about 30–35% of all colorectal cancer cases. Its incidence has decreased in Western countries due to widespread screening programs, but continues to rise in developing nations, including Iran. In Iran, its overall proportion is similar to global statistics; however, patients tend to be younger, with a significant number diagnosed before the age of 50.
Anal cancer is a malignant growth of cells in the anal canal or the surrounding perianal area. The most common type is squamous cell carcinoma, which originates from the surface epithelial cells lining the anus. The disease typically presents with a mass, a non-healing ulcer, or bleeding, and is most often treated with a combination of radiotherapy and chemotherapy.
Risk is increased in individuals with persistent high-risk HPV infection, men who have sex with men, patients with HIV or other immunodeficiencies, and those with multiple sexual partners.
Anal cancer accounts for less than 2% of lower gastrointestinal malignancies worldwide, but its global incidence is rising. In Iran, the reported number of cases is lower, though its prevalence may increase with rising rates of HPV infection.
Fecal incontinence is the inability to control the passage of gas, mucus, or stool in a way that causes distress or functional problems for the patient—ranging from minor staining of underwear to complete loss of control. In addition to its physical impact, it carries significant psychological and social burdens, and the primary goal of treatment is to improve quality of life.
The condition is more common than often assumed, largely because many patients feel too embarrassed to report it. It is more frequently seen in women—especially after vaginal childbirth—and in older adults, with mild cases often going unnoticed.
Functional constipation, also known as obstructed defecation syndrome (ODS), refers to the inability to completely empty the bowels despite having the urge to defecate. Its main symptoms include excessive straining, a sensation of incomplete evacuation, and in some cases, the need for digital assistance.
The condition may result from pelvic floor muscle dysfunction or structural abnormalities such as rectocele or internal intussusception. ODS is one of the important causes of chronic constipation and is reported in 20–30% of constipated patients in some populations.
It is more common in women—particularly after childbirth—and in middle-aged and older adults.
Rectal prolapse is the abnormal protrusion of the rectum through the anus, which may involve only the mucosal layer or the full thickness of the rectal wall. A milder form, known as internal intussusception, occurs when the rectal wall folds inward without visibly exiting the anus.
This condition is more commonly seen in middle-aged and elderly women as well as in young children. Predisposing factors include multiple or complicated childbirths, chronic constipation, pelvic floor neurological disorders, connective tissue abnormalities, and a history of pelvic or anorectal surgery.
Rectal prolapse can lead to difficulties with bowel movements and significantly impact quality of life.
A rectocele is a bulging of a portion of the rectum into the vagina caused by weakening of the rectovaginal septum—the wall separating the rectum and the vagina—and it occurs only in women. It is more common in middle age and after menopause. Many women have some degree of rectocele, but it does not always produce symptoms.
Risk factors include multiple vaginal deliveries, chronic constipation, obesity, and long-standing chronic coughing, all of which increase pressure on the pelvic floor and contribute to the development of a rectocele.
Cystocele is the descent or bulging of part of the bladder into the vagina caused by weakening of the anterior vaginal wall. It is common in women and becomes more frequent with aging and vaginal childbirth.
Many cases are detected during examination but do not always produce symptoms, and some patients may remain entirely asymptomatic.
Uterine and vaginal prolapse refers to the descent of the uterus or the vaginal apex into or outside the vaginal canal due to weakening of the pelvic support structures. It may also occur together with bladder (cystocele) or rectal (rectocele) prolapse.
This condition can affect sexual function, urination, and bowel movements, leading to a reduced quality of life. Prolapse is more common in women, especially after the age of 40–50, and many have mild degrees of it without noticeable symptoms.
Risk factors include vaginal childbirth, obesity, chronic constipation, and genetically weaker connective tissue.
Perineal descent refers to excessive downward movement of the pelvic floor (the area between the anus and the genitals) during straining, in which the anorectal region drops below its normal position. This condition can lead to difficulty with bowel movements, a sensation of incomplete evacuation, excessive straining, leakage of stool or gas, and a feeling of pelvic heaviness or bulging. It may also affect urinary function or sexual activity in some patients.
Perineal descent is more commonly seen in middle-aged and older adults and occurs more frequently in women, particularly after vaginal childbirth. Other risk factors include chronic constipation and straining, obesity, long-term coughing, connective tissue disorders, and nerve injury or previous pelvic surgeries.
