An ostomy is a surgical opening (stoma) created in the body to divert waste when the natural pathway is compromised. The stoma connects an internal organ to the surface of the abdomen, allowing waste products to be collected in an external pouch. While both ileostomy and colostomy serve this function, they differ significantly in their anatomical origin and subsequent care requirements. The distinction between using the small or large intestine affects the consistency of the output and the daily management routine.
Anatomy and Surgical Placement
An ileostomy involves creating a stoma from the ileum (small intestine). This portion of the bowel is brought through the abdominal wall, typically resulting in a stoma situated on the lower right side of the abdomen. The ileostomy stoma often includes a slight protrusion or “spout,” designed to direct the highly liquid output away from the surrounding skin.
A colostomy is a procedure where a section of the colon (large intestine) is brought to the surface of the abdomen to form the stoma. The location is more variable than an ileostomy, depending on the segment used for diversion. Colostomies are most commonly placed on the left side of the abdomen, such as the lower left quadrant for a sigmoid colostomy.
The specific site dictates the nature of the waste, as it depends on how much of the colon remains active. For example, a colostomy in the ascending colon would be located on the right side, while a descending colostomy would be on the left. Surgeons select the precise placement based on the affected segment and the segment healthy enough to be exteriorized. The colostomy stoma can often be flatter to the skin compared to an ileostomy, especially when created from the descending or sigmoid colon.
Output Consistency and Management Implications
The primary difference between the two procedures is the consistency and nature of the waste output. An ileostomy bypasses the large intestine, which is primarily responsible for absorbing water and electrolytes. Consequently, the output from an ileostomy is typically liquid or semi-liquid and continuous throughout the day.
The output from the ileum contains highly acidic and corrosive digestive enzymes, making it irritating to the peristomal skin. This requires diligent skin care and the continuous use of a well-fitting, drainable pouching system to collect the frequent output. Individuals with an ileostomy face a risk of dehydration and electrolyte imbalance due to the large volume of water lost, with typical daily output ranging between 200 and 700 milliliters.
In contrast, a colostomy allows the remaining colon to continue water reabsorption. Therefore, the output is generally more formed, ranging from paste-like to solid, especially when the stoma is created from the descending or sigmoid colon. Since the waste is more solid and less chemically irritating, colostomates may experience fewer issues with skin breakdown.
The predictable and formed output means some colostomates can use a closed-end pouch that is disposed of after use, rather than a drainable one. Some individuals may also manage their function through irrigation, which allows for controlled emptying and may eliminate the need to wear a pouch for periods of time. The reduced frequency and less corrosive nature of the output lead to a different management approach, often allowing for longer wear time of the adhesive skin barrier.
Clinical Reasons for Selection
The choice between an ileostomy and a colostomy is determined by the underlying medical condition and the extent of the diseased bowel. An ileostomy is typically selected when the entire colon or rectum must be bypassed or removed due to widespread disease. Conditions commonly necessitating an ileostomy include severe inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis, that affect the large intestine.
It is also the chosen procedure when the surgeon intends to remove the entire colon (total colectomy). The ileostomy allows the digestive tract to function when waste must be permanently diverted away from the anal sphincter. In some instances, it may be created temporarily to allow a surgical connection lower in the bowel to heal completely.
A colostomy, conversely, is generally performed when the problem is isolated to the rectum or a lower section of the colon. This procedure is frequently used to manage conditions like colorectal cancer, diverticulitis, or trauma affecting the lower bowel. Diverting the waste higher up allows the diseased or injured segment of the colon or rectum to rest and heal.
Depending on the medical situation, a colostomy may be temporary, with the bowel reconnected later, or permanent. A permanent colostomy often results from procedures like an abdominoperineal resection, where the rectum and anus are completely removed, making the natural route of excretion impossible.