Sigmoidoscopy: What is this examination and how to prepare?

Sigmoidoscopy is an endoscopic examination of the rectum and sigmoid colon, allowing for examination of the distal colon, biopsy, and removal of small polyps. This procedure is used to diagnose lower intestinal complaints, monitor inflammatory bowel disease, and serve as a screening option for colorectal cancer. Unlike a full-thickness colonoscopy, sigmoidoscopy examines the left half of the colon and is typically performed without sedation, making it shorter and easier to prepare. [1]

In international screening programs, sigmoidoscopy has been confirmed as a method for reducing colorectal cancer incidence and mortality over many years after a single examination. Long-term randomized trials have shown a sustained reduction in the risk of both incidence and mortality, which is particularly pronounced for the distal colon. [2]

Current screening guidelines recommend sigmoidoscopy as an acceptable strategy for individuals at average risk, along with fecal occult blood immunoassay, full-body colonoscopy, and computed tomography colonography. The choice of method depends on availability, individual preferences, and the patient's readiness for specific preparations. [3]

The method has evolved technologically: the use of carbon dioxide to straighten the lumen and water-based techniques reduces discomfort, while removable attachments and improved optics improve the quality of mucosal examination. However, the basic principle remains the same: safe direct examination of the mucosa with the possibility of immediate, minimally invasive treatment of any small polyps detected. [4]

Table 1. Sigmoidoscopy in the context of other methods

Task	Sigmoidoscopy	Colonoscopy	Computed tomography colonography	Fecal occult blood immunoassay
Inspection area	The left half of the large intestine	The entire colon	The entire colon	No visualization
Treatment of polyps immediately	Yes, small ones	Yes	No	No
Preparation	Enema more often	Complete cleansing	Complete cleansing	No
Sedation	Usually not needed	Often needed	Not needed	Not needed
[5]

Indications

Typical indications include rectal bleeding, changes in bowel habits, lower abdominal pain or discomfort, and monitoring of known inflammatory bowel disease when assessing the distal colon. In outpatient settings, sigmoidoscopy is often the first step due to its speed and reduced preparation, especially if left-sided pathology is clinically suspected. [6]

A separate group of indications is colorectal cancer screening in people at average risk. A single sigmoidoscopy in adulthood demonstrates a long-lasting protective effect and can also be combined with an annual fecal occult blood immunochemical test. This combination improves sensitivity to neoplasms that may develop after the initial examination. [7]

If acute diverticulitis, perforation, or severe pain are suspected, the procedure is postponed until the patient's condition stabilizes. For acute diverticulitis, imaging techniques that do not require endoscopic intervention are preferred due to the increased risk of complications. [8]

If complaints or anamnesis indicate possible damage to the right colon, a total colonoscopy is immediately chosen. This is important, as a sigmoidoscopy examines the left colon and may not reveal pathology beyond the area up to the splenic flexure. [9]

Table 2. Common clinical scenarios and choice of method

Situation	Preferred method	Comment
Rectal bleeding without warning signs	Sigmoidoscopy	Rapid assessment of distal regions
Screening for average risk	Sigmoidoscopy according to the program or colonoscopy	Timing and intervals depend on the strategy
Suspected pathology of the right sections	Colonoscopy	Complete examination of the entire intestine
Suspected acute diverticulitis	Non-endoscopic visualization	Avoid endoscopy in the acute period
[10]

Contraindications and risks: how to minimize complications

Absolute contraindications include severe acute diverticulitis, severe acute colitis, patient refusal, and unstable severe conditions. Relative contraindications include toxic colonic dilatation, suspected ischemic necrosis of the colon wall, recent colon surgery, and severe bleeding disorders. The decision to conduct the study is made by the physician after assessing the benefits and risks. [11]

The perforation rate during sigmoidoscopy is significantly lower than during total colonoscopy, and in modern series is measured in fractions of cases per several thousand procedures. Bleeding occurs primarily after polyp removal; the risk is minimal during diagnostic examinations. These data are confirmed by systematic reviews and large observational studies. [12]

Risk reduction is achieved through careful patient selection and adherence to the appropriate technique: careful device placement, minimally adequate carbon dioxide insufflation, gentle aspiration, and substituting cold loops for hot polyp removal techniques for small lesions. Standard procedures for dealing with emergency complications should be developed by the entire team. [13]

The patient is informed in advance of the warning signs following the procedure: increasing abdominal pain, fever, and persistent rectal bleeding. Such symptoms require immediate medical attention, even if the procedure was performed without intervention. [14]

Table 3. Contraindications and typical risks

Category	Examples
Absolute contraindications	Severe acute diverticulitis, severe acute colitis, patient refusal
Relative contraindications	Toxic colonic dilatation, suspected ischemic necrosis, recent surgery
The most common complications	Bleeding after polyp removal, extremely rare perforation
Prevention	Gentle technique, carbon dioxide, moderate insufflation, cold loop for small polyps
[15]

Preparation

In most centers, a cleansing enema on the day of or the day before a sigmoidoscopy is sufficient to ensure good visibility of the left-sided mucosa. The specific protocol is chosen individually; sometimes a combination of a mild laxative the day before and an enema on the day of the procedure is used. Patients must follow the instructions carefully, otherwise repeated preparation may be necessary. [16]

Some institutions administer enemas in the endoscopy department immediately before the procedure, while other patients are advised to perform them at home using clear, step-by-step instructions. In patients with kidney disease and in the elderly, the choice of enema medication and rehydration require special attention. [17]

Medication discontinuation is discussed in advance. Iron-containing medications are usually discontinued several days in advance, as they impair vision. Antithrombotic and anticoagulant medications are discussed individually depending on the indications and risk of the procedure. Dietary restrictions are usually not imposed unless sedation is planned. [18]

If pregnancy is suspected, endoscopic interventions are postponed whenever possible, and if vital indications arise, the most gentle preparation is chosen. Historically, for a limited examination of the left gastrointestinal tract in pregnant women, the use of a warm water enema has been described under strict indications and with interdisciplinary coordination. [19]

Table 4. Preparation for sigmoidoscopy

Element	What to do
Colon cleansing	Enema at home according to the instructions or in the department before the procedure
Nutrition	Generally, without strict restrictions, unless sedation is planned
Medicines	Stop iron, discuss antithrombotic and anticoagulant medications
Special cases	Pregnancy and Chronic Kidney Disease - An Individual Plan
[20]

How the procedure is performed and how comfort is ensured

The procedure typically takes 5-10 minutes. The patient lies on their left side, and a thin, flexible endoscope is carefully inserted through the anus. The mucosa of the rectum and sigmoid colon is examined, and if possible, it is advanced up to the splenic flexure. If necessary, biopsies are taken and small polyps are removed. After the examination is complete, the endoscope is slowly withdrawn, and the mucosa is re-evaluated. [21]

Sedation is not required for most patients; many tolerate the procedure well with modern methods of reducing discomfort. Nitrous oxide/oxygen inhalation may be used for pain relief, as may minimal sedation in sensitive patients; decisions are made in accordance with sedation guidelines. [22]

The use of carbon dioxide instead of air accelerates gas absorption in the intestinal lumen and reduces bloating and pain after the examination. Water techniques—water infusion and water exchange—help straighten loops, improve visibility, and reduce the need for sedation, as confirmed by randomized trials and technology reviews. [23]

After the procedure, the patient quickly returns to normal activity if sedation was not used. Driving and other activities requiring concentration are avoided for 24 hours after sedation. The team will discuss any red flags and provide a contact information sheet in case of any late complaints. [24]

Table 5. What helps to make sigmoidoscopy comfortable

Reception	For what
Carbon dioxide instead of air	It dissolves faster, there is less bloating and pain.
Water technicians when starting the apparatus	Less discomfort, better loop straightening
Minimal sedation as indicated	For anxious or sensitive patients
Clear instructions after the procedure	Early recognition of rare complications
[25]

Biopsies and removal of polyps

If a small polyp is detected, it is usually removed immediately. For polyps up to 10 millimeters, the current standard is a cold loop, which requires capturing a narrow rim of healthy mucosa to ensure complete removal. This approach combines high resection completeness with minimal risk of bleeding and thermal tissue damage. [26]

Hot forceps are not recommended due to the high rate of incomplete removal and the risk of delayed bleeding. For polyps measuring 10-19 mm, a hot loop with submucosal injection of a solution is acceptable to create a protective cushion. Larger and more complex lesions are referred for endoscopic mucosal dissection or other advanced techniques. [27]

Biopsies are performed with forceps from visually altered areas to clarify the diagnosis of inflammatory bowel disease, ischemic, and neoplastic lesions. The quality of the biopsy specimen depends on the correct selection of the site and careful technique, which is especially important for superficial lesions. [28]

The post-polypectomy surveillance strategy depends on the histology, size, and number of polyps. Small adenomas without dysplasia generally do not require accelerated surveillance; advanced adenomas or those with multiple findings are followed by follow-up according to current guidelines for post-polypectomy surveillance. [29]

Table 6. Tactics for polyps detected by sigmoidoscopy

Polyp size	Recommended technique	Note
Up to 5 mm	Cold loop	Capture 1-2 mm of normal mucosa
6-9 mm	Cold loop	Preferably for safety reasons
10-19 mm	Hot loop with submucosal pad	According to indications, with risk assessment
Larger than 19 mm or complex shapes	Advanced techniques	By referral to a specialized center
[30]

Screening: intervals and choice of strategy

In adults with average risk, sigmoidoscopy is acceptable as a standalone strategy, performed every 5 years, or as a single procedure followed by annual fecal occult blood immunoassays. Alternatively, total colonoscopy every 10 years, as well as noninvasive stool tests, remain. The decision is made based on availability and individual preferences. [31]

Long-term studies have shown that single-use sigmoidoscopy provides decades of protection, particularly for the left sigmoid, reducing the need for more frequent invasive examinations in some people. This is important for public health programs that value the balance between effectiveness, acceptability, and cost. [32]

It's important to remember the limitations of this method: pathology in the right colon may go undetected, so a full colonoscopy is recommended for people with symptoms suggesting right-sided colon involvement or at high risk. If in doubt, a full colonoscopy may be performed after a sigmoidoscopy. [33]

Organized programs set quality standards and targets for population coverage, quality of preparation, and depth of device insertion to the splenic flexure. Quality directly impacts effectiveness: the better the visibility and depth of examination, the greater the preventive effect. [34]

Table 7. Screening in people at average risk: where sigmoidoscopy fits in

Strategy	Interval	Advantages	Restrictions
Sigmoidoscopy	5 years or one time with further stool testing	Fast, often without sedation	Does not examine the right sections
Colonoscopy	10 years	Complete examination and treatment of polyps	Preparation and sedation are often necessary.
Fecal occult blood immunoassay	1 year	Non-invasive	If the result is positive, a colonoscopy is required.
Computed tomography colonography	5 years	Noninvasive Imaging	There is no treatment, preparation is needed
[35]

Quality indicators: what offices focus on

Essential quality indicators include adequate bowel preparation, achievement of the splenic flexure without limiting factors, documentation of device insertion depth, correct examination timing during removal, and the proportion of adenomas detected. Audit standards and external accreditation adapted from colonoscopy are used for quality control. [36]

National program studies indicate an association between longer examination times during extraction and increased adenoma detection rates. The use of water-based techniques and carbon dioxide has also been shown to improve tolerance and may indirectly improve quality indicators. [37]

Staff training and regular feedback on audit results remain key. If quality targets are consistently not met, patient routing, training, and technical protocol elements are reviewed. [38]

Clear pre- and post-procedure instructions, availability of pain relief when indicated, and clear timelines for reporting results are important for the patient experience. These organizational details increase satisfaction and willingness to participate in the screening. [39]

Table 8. Practical quality indicators

Indicator	Targeted aspiration
Achieving the splenic flexure without restrictions	Yes
Adequacy of preparation of left departments	High proportion of adequate studies
The proportion of adenomas detected in the distal regions	Monitor and benchmark against program standards
Documentation of inspection time during extraction	Locally regulated and verifiable
[40]

Complications: frequency and tactics of action

Serious complications following diagnostic sigmoidoscopy are rare. Historical and current estimates indicate an extremely low rate of perforation and clinically significant bleeding, especially if no interventions are performed. Risks increase with therapeutic procedures but remain lower than with total colonoscopy. [41]

Management of bleeding after polyp removal includes local endoscopic techniques, observation, and, if necessary, hospitalization. Prevention is based on the use of a cold loop for small polyps and careful technique. If perforation is suspected, immediate evaluation and referral to a surgical hospital are indicated. [42]

The patient receives written instructions with alert signs and contact information. In the absence of sedation, return to normal activity is possible the same day; after sedation, an accompanying person and 24-hour restrictions are required. Clear communication reduces anxiety and allows for a timely response to rare late events. [43]

Quality programs require practices to record and analyze all adverse events, comparing the data with expected thresholds. This improves safety and allows for protocol adjustments. [44]

Table 9. Frequency of key complications and prevention

Complication	Frequency assessment	Basic prevention
Perforation	Cases for tens of thousands of diagnostic procedures	Careful technique, moderate insufflation with carbon dioxide
Bleeding after polyp removal	Rarely with small polyps	Cold loop, careful visualization
Late pain and bloating	Usually short-term	Carbon dioxide, water techniques
[45]

What to do after a sigmoidoscopy

If biopsies and polyp removals were not performed, most people can immediately return to their normal activities. Mild gas and short-term discomfort are acceptable. Fluids and a normal diet are resumed immediately unless otherwise agreed upon. [46]

After polyp removal, slight bleeding from the rectum may occur during the first 24 hours. Excessive bleeding, increased pain, fever, or increasing weakness are reasons to seek immediate medical attention. The team will provide specific contact information and a time to expect histology results. [47]

If sigmoidoscopy was performed as part of a screening strategy, the patient is explained the subsequent plan: either an annual fecal occult blood immunochemical test or a full colonoscopy based on specific findings or complaints. A structured plan increases the effectiveness of prevention. [48]

If polyps are detected, the follow-up plan is determined by the histology and number of lesions in accordance with current guidelines for post-polypectomy follow-up. It is important for the patient to retain his discharge summary and adhere to the prescribed follow-up schedules. [49]

Table 10. Roadmap after sigmoidoscopy

Situation	Next steps
Nothing suspicious was found.	Return to normal activity; screening plan according to strategy
A biopsy was taken	Wait for the results; if alarming symptoms occur, seek immediate consultation.
A small polyp was removed	Follow the recommendations, monitor for symptoms, and follow the monitoring plan
Signs requiring further evaluation have been identified.	Referral for a full colonoscopy or other methods
[50]

Conclusion

Sigmoidoscopy is a fast and proven effective method for diagnosing and preventing diseases of the left colon. Proper patient selection, simple and straightforward preparation, modern comfort techniques, and safe removal techniques for small polyps make it a valuable alternative in situations where a full examination of the entire colon is not required. For symptoms suggesting right colon involvement or high risk, a total colonoscopy is preferred; as part of screening, the choice of method is discussed with the patient. [51]